ANTENNA Q&A
Choosing A VHF/UHF Antenna
Choosing A Shortwave
Antenna MFJ 1020C Tuned Indoor
Active Antenna
AOR SA-7000 ICOM AH-7000 H-800 SkyMatch /
H-900 SkyMatch Super Stealth
Grove Omni II Scantenna Scanner Beam
Diamond Discone WinRadio
PAR Create Log Periodic 5130-1N Create
Log Periodic 5130-2N AOR DA-3000
Antennas
There are several factors that weigh in so far as the distance an antenna can hear, including:
Height of the antenna; Presence of obstructions; Length and losses of the transmission line; Gain of the antenna; Direction in which a gain antenna is pointing; Frequency of the signal; Sensitivity of the receiver; Presence of interference Power of the transmitted signal; Bandwidth of the signal Solar effects (day/night, sunspots, flares); Weather and humidity; Electrical storm presence.
That said, under normal circumstances, and using the non-directional AX12B with good coax, good locations and a good receiver, the following could be expected: (1) HF reception (under 30 MHz): Thousands of miles for broadcasters, two-way communicators. (2) VHF (30-300 MHz): Up to 100 miles for broadcasters and two-way communications. (3) UHF (300-500 MHz): Up to 75 miles. (4) Microwave (800-2000 MHz): 25-50 miles. Naturally, these are only approximations due to the numbers of variables pointed out above, but should give you an average expectation. Naturally, if you're looking for a simple, low-power device like a bug or cell phone, we're talking feet, not miles.
Loose BNC whip? There's a quick and simple fix for those annoying desktop scanner whips with the right-angle BNC connectors that keep falling over. (1) Disconnect the antenna and observe the seam where the shell of the BNC twists back and forth; (2) Reattach the antenna firmly into place on the scanner's antenna jack and set it upright as it should be; (3) Place a small drop of quick-setting glue right on that seam found in step 1 and let it set. The antenna is now anchored on the BNC connector so it won't slip, yet it's easy to remove. If you are reluctant to do anything so permanent (although acetone or nail polish remover will dissolve the glue), you can wrap a small piece of PVC electrical tape or even a thin strip of duct tape around that same joint instead of gluing it.
Reception seems weak or goes in and out? Try this. Disconnect the antenna. Look inside the BNC connector on the radio. Locate where the center pin of the antenna inserts and see if the connection looks too wide. if so, take a pair of tweezers and gently squeeze them together. Now, on the antenna. Find the center pin and place your finger on it and slightly wiggle. If the center pin seems loose it needs to be repaired or the antenna replaced.
Is it possible to operate two radios
from one antenna? Yes. Is it possible to connect two
antennas to one radio? Yes. But there are catches. Two radios from one
antenna. This is the easiest task. Purchase a two-way TV splitter from Radio
Shack, Wal-Mart, Grove, or any other source; just be sure it is wideband (they
are typically marked 5-900 MHz, but operate beyond those limits as well). You
will need adapters and short cable runs (RG59/U or RG6/U is fine for this) for
the F connectors to attach to your receiver(s) or scanner(s). Naturally, the
antenna you attach to the input of the splitter determines the ultimate
performance; use the same antenna you would choose for just one radio. Since
the signal is divided in half, there will be at least a 3 dB drop in strength
at each output port, but for most purposes you won’t notice the difference.
Two antennas into one radio? This is the toughest challenge because, unless they are properly spaced, they can actually reduce signal strengths! Even when you add a second identical antenna, no matter how superb they are, only a 3 dB improvement is possible. But other factors besides gain come indirectivity and noise reduction, for example. At shortwave it is usually better to erect two antennas pointing in different directions, selecting between them with a common antenna switch (CB, TV, or even a video game switch works well for this). It is still possible to use two antennas simultaneously, however. If they are highly directional and point in different directions, or of two entirely different frequency ranges, so that signal cancellation is unlikely, you can use a splitter again, but "upside down." Instead of a signal splitter, it is now a signal combiner. As with any new antenna system, plan ahead and test the results before permanently mounting everything in place. If all goes well, you will have improved reception; if it doesn’t, it’s summertime, and you got good exercise!
General Antenna Questions
The little plug-in antennas that come with desktop scanners are simple whips that work best in the 150-960 MHz range, but they are too short to work well on lower frequencies. Let's review some simple theory. Virtually all antennas are fed at or near their electrical center. Even base-fed verticals use something to emulate the lower "half" of the antenna, often ground radials if earth-mounted, or metal ("ground plane") radials if elevated. For mobile mount, the car body becomes the missing portion of the center-fed antenna, and even on a hand-held radio, your body is capacitively-coupled to the radio to substitute (usually poorly) for the missing lower element. A desktop scanner with a plug-in antenna uses the mass of the chassis metal as the missing portion. Now to your more specific question. Any length of metal has a specific frequency to which it is "resonant;" that is, it has a feed impedance which matches that of the feedline, typically 50-70 ohms. If you make it longer, its feedpoint impedance rises; if made shorter, that impedance lowers.
It's a cyclical phenomenon -- once the antenna length doubles the original resonant length, the impedance is several thousand ohms, quite a mismatch to your 50-70 ohm coax! Standing voltage waves (high SWR) may dissipate the useable signal as heat rather than deliver it to and from the radio receiver or transmitter. But as the length increases further, approaching three times the resonant length for that frequency, the impedance lowers again toward 50-70 ohms. That's why center-fed antennas are often used on their odd harmonics. For example, a 50 MHz (six meter amateur) antenna will work well at 150 MHz (the third harmonic), but a 150 (or in your case, 144 MHz) antenna won't work as well at 1/3 its frequency range (50 MHz), and its reduced length also means less signal-voltage capture. An antenna designed for hamming on a particular frequency will work great for reception only; after all, it was designed to transmit AND receive on that frequency!
Q. For scanner listening, I have a magnetic base mounted on top of a filing cabinet with the scanner's original rubber duckie antenna plugged into it, but signals are weaker. What could be wrong? (Gary Kinsman, email)
A. Although the magnetic base, cable or connector could be defective, it's also possible that there is a directional effect or signal acquisition problem at the location. Try putting the duckie back on your scanner and placing the scanner on the filing cabinet. Are the signals stronger? If so, try the following tests with an ohmmeter: With the antenna removed from the magnetic base, set the meter to low ohms and touch one prod to the shell of the BNC connector, the other to the BNC center pin; the meter should not move (infinite resistance). If you are using adaptors, keep them in place, too; mismatched connectors are often problematic. Next, touch one prod to the center pin of the male cable connector, and the other to the center hole of the BNC on the mount; it should show a short (perhaps an ohm or two). Repeat between the shell of the male connector and the shell of the connector on the magnet base. Both of these tests should confirm continuity of the shield and the center conductor from one end of the cable to the other. If it passes, repeat the tests while wiggling the connector and also the cable at the mount to see if there is a loose connection. You may need an extra pair of hands for this! Finally, check the center hole in the magnetic base to see if the leaves have somehow spread too far to touch the center pin of the antenna when it's inserted. The leaves can be easily pressed closer by pushing a pin behind each leaf and the insulation surrounding it.
Q. I am going to browse the 6 meter band -receive only, no transmitting. Because of the perpetual lightning hazards I have elected
hang an antenna in the attic. Could you tell me what kind of antenna loop, dipole, or what -is the best idea for an antenna in the attic, for receiving only? Thanks in advance. Pat
A. The location has no bearing on the type of antenna you choose. If you want omni directional performance, a vertical is mandatory. Since there's rarely enough headroom for a 9-foot vertical dipole, you will
probably opt for a ground plane. The vertical element should be about 4.5 feet long, and you should have three radials running out from the base, each of which is also 4.5 feet long.
Try to keep the vertical element a good 5-6 feet away from large, parallel metal surfaces like heating and air ducts that would interact and absorb/reflect signals. Be sure the insulation in the walls isn't metallized mylar and you don't have sheet-metal roofing and you should be
OK. Thanks for the warning. The central air is up there. Pat
Q. I know with cable TV the RG6 cabling is one of
the better types. I noticed that both the AOR and ICOM antennas come with
50 feet of RG-58/U which I though was not that great. Is it better to
replace the included cables with say RG6 or RG8 or LMR240? You only carry
the RG6 type cables, correct? Is it worth spending the $$ for the better
cables? My run from antenna to receiver should be under 75' but probably
over 50', I need to measure it.
A.
RG-58/U is not a good choice at VHF/UHF. RG-6/U is much better, especially for
longer runs at the higher frequencies. RG-58/U is fine for shortwave.
Q. I know TV antennas used to have a ground wire
running to a copper rod. Should scanner antennas be grounded the same way?
Does the receiver itself need to be grounded? I do plan on purchasing your
lightning arrestor that you sell along with whatever antenna I purchase from
you.
A.
Grounding an antenna or receiver does not improve signal strengths, it only
guards against shock hazard and sometimes may reduce electrical noise
interference, especially at shortwave and long wave frequencies. It is easiest
to run a ground from the receiver.
Q. Many (???) years ago, I was advised that Radio
Shack made a small, portable (Battery & A/C adapter) TV amplified antenna by the
stock number 15-1607. It was a small black box about the size of a pack of
playing cards with two telescoping antennas attached to one end. The "box"
contained the electronics for amplification as well as space for batteries.
With the antennas completely collapsed (perhaps 4" long) and pointing opposite
each other...almost in a straight line, the amplification on 800MHz is
fantastic. The antenna is equipped with a connecting cable (perhaps 3'
long) and an on/off switch. I contacted Radio Shack approximately a year
ago and they explained that they had discontinued the product....no hope for
return... I bought mine with the A/C adapter and it actually sits on one of the
5 or 6 scanners I've purchased from Grove.
With such a GREAT product, I'm amazed that someone else hasn't introduced
something equally as small and as good a performer.... Any ideas?
Thanks - Steve
A. I think there are several reasons why you don't
see amplified, indoor, pre-amplified TV antennas any anymore:
(1) With the emergency of so many RF-generating consumer appliances, the
likelihood of encouraging interference is much greater now;
(2) Transmitters are everywhere now so that even outdoors preamplifiers are
likely to suffer from strong-signal overload resulting in poor reception;
(3) Satellite TV and cable are usually the answer for people in the boonies who
used to be too far from TV stations to get good reception;
(4) Consumers now are of a plug-and-play mentality, no longer interesting in
fiddling with accessories to make their reception better.
(5) If cable, satellite and VHF/UHF TV are not available, consumers have
Internet, email, chat rooms, on-line video, DVD's and even multi-screen theaters
for alternative entertainment.
Q. We use an A.M. radio in a steel roof bldg, near St
Paul, MN, so am signal strength is good. But the interference from the ceiling
fans with an adjustable rheostat and fluorescent lights is very bad. The
adjustable fan produces the most static. Any solutions?
A. Electrical interference on the AM radio band
from fluorescent lights and speed-controlled fans as well as dimmer controls on
lights is severe and well documented. It's also difficult to get rid of, or even
reduce. If you are using commercial wall speed control/dimmers, you can
often reduce some of the interference by installing a capacitor, typically 0.47
(0.05) microfarad at 600 working volts (600 WV) across the control terminals
that feed the fan or lights.
So far as the fluorescent ceiling lights, this may be due to improper grounding
of the lights and the presence of the sheet-metal roof which acts like a giant
transmitting antenna for the noise! Since I don't know what kind of radio and
antenna you are using, I will assume it's a little AM/FM job with a built-in
loop.
If you can't run coax from it to an outdoor antenna, you might be able to
improve things with a passive, tuned loop antenna like our very popular and very
effective Select-A-Tenna.
You position this loop near the radio, tune in your favorite station, then
carefully tune the loop the that frequency. By moving the radio to a position
that minimizes the interference, then doing the same thing with the loop, you
may be able to reach a happy compromise in good listening.
Q. Is it ok to paint my antenna and mast? Will the
signal be "lossy"? Steve
A. It all depends upon the contents of the paint.
The solvent is no problem--it evaporates. But if the pigment contains lead (some
whites) or other metallic components, or carbon (some blacks), it is absorptive
to the signal and is, thus, lossy. The same caveat applies to encapsulates
like plastics and other resins
that are pigmented.
One way to test the different pigments before applying them is to put them on
something dry and non-metallic and put them into a microwave for a few seconds
to see if they heat up; if they do, they are lossy to RF. I should further
clarify: Virtually anything will heat up in a microwave; this should be a
comparative test among several samples to compare degrees of heating. I'd
suggest putting them on white paper and let them dry first. You could even coax
them to dry with the microwave, but let them cool off first before the next zap
to test for loss!
Q.
How do I ground scanner antennas? I have an 8 foot ground rod already in the
ground, and will use 4 gauge bare copper wire. Would it ground with a clamp at
the antennae mast (provided I scrape off paint there with a wire brush?), or
does it have to be grounded on the co-ax outside connector? I have some of those
ground blocks (I am using RG 6 with F connectors), but the hole is too small for
# 4 wire, plus I understand that the more connectors in the line, you lose some
signal gain). Any advice you give me would be greatly appreciated. I have
three antennas, two already up, and the other shortly. I understand I can run
the ground to each antennae with one wire to the rod. W. Mitchell
A. Grounding may do
three things:
(1) Reduce the hazard of electrical shock to the operator who may come in
contact with an ungrounded, "hot" accessory;
(2) In some instances reduce local electrical interference to AM and shortwave
broadcasts; and
(3) Provide an alternative path to ground for nearby lightning-induced voltage
transients, rather than destroying the equipment. But keep in mind, nothing you
can install will prevent damage from a direct lightning hit.
That said, a good ground consists of two eight-foot rods
about 10 feet apart driven into moist, conductive (not sandy) soil. All ground
leads from your equipment should come down one heavy cable (like your #4 wire)
attached between the two rods with a clamp, or heavily soldered. Your one ground
rod may be adequate if the soil is quite moist.
When your coax lead-in is attached to your receiver(s) or
scanner(s), the braided shield is already directed to ground by the chassis of
the equipment. You don't need separate wires to each antenna mast. Depending on
the type of antenna, grounding the mast may be of no use if the antenna elements
are insulated from the mast. The the cable shield will always be connected to
some part of the antenna and will always provide the ground you need for the
three reasons cited above.
Q.
I skimmed thru the questions and answers on your web-link. Didn't find a
solution for me. I need an external antenna to clearly pick up the station
about 100 miles away. I don't have the luxury of accommodation for a long
wire approach. Any recommendation on one that I can mount on my current
VHF/UHF/AM antenna mast? Thanks, Dave
A. You're right; I
don't remember any discussions of that sort in my column. Essentially, in order
to M broadcasters, you need one of these approaches: 1. A longer antenna 2. A directional outdoor antenna like
a Beverage 3. An active antenna like our H800
Sky-Match 4. An indoor loop antenna with or
without an amplifier like the Select-A-Tenna
In your case, if it's a clear-channel station so you don't
need directivity on the antenna, I'd recommend either solution 3 or 4. An active
antenna is omni-directional, so it will amplify everything (signals and noise)
from all directions.
The indoor loop can be adjusted for maximum signal from a
direction, or to minimize interference from co channel broadcasters or
electrical appliances from other directions. But an indoor antenna of any type
is vulnerable to both signal reduction because of indoor shielding (especially
metalized Mylar insulation as well as aluminum siding) and wiring.
Q.
What makes a better shortwave receiving antenna; A half wave dipole wire antenna
designed to be approximately resonant in the middle of the shortwave band,
whose length is 30 ft. used along with a "MFJ Deluxe Versa Turner"
antenna tuner? A random wire antenna whose length is
60 ft or longer? S.J.
A. I will take the random wire antenna at 60 feet
since I have more capture area than the 30 foot. Using a tuner in a receive only
situation is a big hassle and can not make up for the 30 foot difference in wire
length. Larry Van Horn, N5FPW
Q. I already
have one of your above antennas in my attic which feeds an old Radio Shack PRO
2004.I was thinking of trying to boost the signals in the 45-140 MHZ range.
Rather than going to a preamp ,which would also increase noise, I thought of
buying another antenna & combining them for more gain. The question is How
far apart should they be and how should they be connected for maximum gain.
Brian M Moyse
A. Any
time you double your antennas (using the same make and model), you add only 3 dB
gain, and that's only in its favored direction; you also reduce gain in its
other directions. Essentially, then you are making a directional antenna. To
prevent too much interaction between the antennas, they should be separated by
at least a quarter wavelength at the lowest frequency of interest. In your case,
that would be about 6 feet at 40 MHz; for high band and above, you would
separate them only about 3 feet. Don't expect miracles, however; 3 dB gain is
only noticeable on very weak signals which are experiencing hiss, and you will
reduce, somewhat, reception off the sides. The best bet is always choose the
best single antenna for the job and use low-loss coax.
The only reason for
using a balun or transmatch is to protect the transmitter output from high
voltages that may appear due to mismatch. Because of this potential damage,
modern solid-state transmitters have an automatic shut-down circuit that lowers
power if a mismatch greater than 3:1 is sensed.
A half-wave dipole works well without a balun or
transmatch on the frequency for which is it cut; it also works well on odd
harmonics. Thus, a 7 MHz dipole performs well on 21 MHz without a balun or
transmatch.
It's when you try to operate a dipole on multiple frequency
ranges that you need to match the system with an external device. But for
receiving purposes, you don't. A badly-matched dipole may have slightly reduced
signal strengths as shown on a meter, but the signal will still be above the
noise. If the system was perfectly matched, the S meter would read higher, but
the signal and the noise would both have come up, thus the signal would still be
the same amount above the noise. No real improvement in audibility.
Q. Mobile Roof Mount
antennas-scanner-2m/440. Will mounting antennas there lessen
my signal quality? R. Martinez
A. Unfortunately, most luggage rack mounting bars are
either too small for an NMO mount, non-metallic so they won't work at all, or
too high to maintain an appropriate impedance match with the car
roof. I guess you could get a mag-mount adaptor; our NMO version of the
Nil-Jon Super M would fit an NMO mag-mount.
I currently have a long-wire
antenna mounted at one end (with required cable/insulator) to a TV antenna
tower. I presently run a coaxial cable out through a window and attach the
center conductor to one end of the long-wire, the braid to the metal tower
(mediocre ground, but it does reduce noise). I'm looking to set this up
properly. What would you suggest for:
Q. Hooking the coax to the long-wire
A. How long is the wire? This guides the answer
as to where to hook the coax. If it is 40-150 feet (approximately), you should
put your insulator at or near the center, then the shield to one side of the
insulator and the coax center conductor to the other side. If it is shorter than
40 feet, you attach the coax center conductor to the near end of the wire,
leaving the shield floating, or to a ground if that reduces noise.
Q. Grounding of the coax braid (perhaps
covered above in #1)
A. Suitable ground consists of two 8' metal rods separated by
about 10' and fed by heavy braided cable. Keep in mind, however, that this will
only protect you from electric shock, and may reduce noise; it won't make
signals stronger.
Q. Lightning protection at the junction between
coax and antenna
A. We recommend a gas-discharge type device, not
a spark gap, anywhere between the antenna and the radio. We sell a suitable
device that attaches to the back of your radio and you can connect a ground wire
to it. Remember, however, that nothing survives a direct lightning strike. It is
better to disconnect the antenna cable from the radio during a severe electric
storm where lightning is popping all around you.
Q. Direction of coax into house (tower/antenna)
is adjacent to window of listening room
A. It's better to run the coax as close to a
right angle to the wire for as far as you can, at least 10-20 feet, if you want
to keep the pattern uniform. If that is not the case, you can bend it closer
than that, but try not to run it parallel to the wire for a long distance.
Q. Ease of disconnection of system during
electrical storm (plenty of them out on the prairie where I live); if
disconnection at radio, hazards of leaving "tag end" of coaxial
unattended?
A. Old-timers would drape the removed cable and
connector into a glass beverage tumbler to add the increased insulation of the
glass.
Q. Requirement for grounding of receiver; perhaps
a moot point if ground is established at junction of coax/antenna
A. As above. It's absolutely not necessary
to have a ground for signal improvement.
You can see our lightning arrestor on our web site at http://www.grove-ent.com/LAR.html;
we also have adaptors suitable for your requirements.
Q. I have about 50ft of heavy copper wire in the
air and the center of coax solder to it. What I want to know is, should
you use a balun on it for noise? Dave
A. No, if you don't have the shield attached to
something, a balun won't work. A balun is a transformer with two windings, (or a
winding with a tap). Even if you do cut the antenna wire and insert a strain
insulator to make a dipole, and attach the coax shield and center conductor to
the input of the balun, this would only be for impedance matching; it won't
affect noise.
Q. I recently ordered 100' of
coax and installed an outdoor antenna for my scanner. Is it necessary to have a
ground wire attached to the antenna mast? I noticed you carry something called a
lightning arrestor which attaches between the scanner and the coax, would you
recommend that I install that? D. Boyle
A. A ground is absolutely unnecessary for scanner
reception, and even on lower frequency ( long and short wave) radios, all a
ground does is prevent electrical shock from faulty AC installations, and
occasionally reduce background electrical noise.
So far as the lightning arrestor goes, yes, it's a good idea. I have on on each
of my personal scanners, transceivers, and shortwave receivers, and have never
had a problem from nearby lightning strikes.
Q. I am writing this letter in the hope that I can
contact someone who could give me recommendations - including part numbers and
costs - for equipment to improve my Short Wave Radio listening. I have been using a Radio Shack
DX-392 portable shortwave radio with a Radio Shack Antenna Tuner for about many
years now. I have been a short wave radio listener for about more than 40
years, and have been successful in hearing
such stations as Mongolia, Namibia, Vanuatu etc. on my portable recently.
I typically take my radio with me when I travel to the Adirondack Mountains and
reception is good. I live in New York City - Manhattan -
in a five story brownstone. I live on the second floor and have 70 foot
copper wire kit spread across my roof and connected to my radio by a 100 foot
lead-in of covered copper wire only. This is the equipment I use when I go the
the mountains, but I would very much like to be able to enjoy my hobby here in
New York City - noise and all.
I have just brought two antenna kits
from Grove in the last month and sent them to Florida and California, where I
typically go to visit. I was in Florida and set up my radio, but realized
I needed a coaxial cable connection and know nothing about electronics and was
hoping someone at Grove could suggest or offer me some information on a coaxial
cable and how to connect it to my radio, which doesn't have a port for a coaxial
connection. I would buy it immediately and try it out. Beyond that, I would like to update
my equipment. I still like the 70 foot wire on the roof of my building,
but you might suggest a better antenna system and I would very much like some
information on that. The need for a coaxial cable connection and how can I
get a length of 100 feet shipped to me. I have no ground for my radio. Is
that important and how would I connect it and could you recommend something that
Grove sells. I like the antenna tuner and could recommend and updated type
of equipment and how could I connect it to my DX-392 radio? T. Sliva
A. I'll be happy to answer your questions;
fortunately for you, the answer is pretty easy--and cheap! First of all, the
wire antenna should be as far from nearby wiring and masses of metal as
possible, even on your roof. For shortwave listening, any coaxial cable will
work just fine. Its advantage is its shielding which prevents nearby electrical
interference from getting into the cable (although it can still radiate far
enough to be picked up by the antenna!). You insert the cable anywhere near the
center of the wire, and it can be off by a good number of feet without affecting
reception. As a matter of fact, if the antenna is only 30-40 feet long, you can
feed it at one end just by connecting the center conductor of the coax to either
end of the wire antenna. Ideally, you need an antenna about 40-80 feet long, cut at
the center; there you wrap the wires around the ends of a glass, plastic, or
porcelain insulator. You attach the coax shield to one side and the center
conductor to the other; it doesn't matter which goes to which, even if you're
feeding it off-center. The coax goes down to the proper plug or connector for
your radio, the shield connected to the outside barrel of the connector and the
center conductor to the center pin of the connector.
Be sure all connections are tightly soldered to prevent static and poor
reception from corrosion. So use the wire you have and put together the parts
from Radio Shack, Wal-Mart, or whatever. Of course, you can buy the whole thing
from us as
our ANT-2 Skywire and our CBL-100
coaxial cable. We ask what kind of connector you want, and that's what it's
shipped with.
Q. I live in a poor radio reception
area.. Mountainous.. In N. Idaho. I'm in need of a radio and antenna system that
will pull in AM radio broadcasts, primarily. FM reception would be secondary. I
don't have much interest in short-wave. We have poor reception with standard
radios with built-in antennas. Do you have any suggestions? D. Egerb
A. I'll be glad to help. Any radio
that has an external antenna connection will work, but some cheaper radios
suffer strong-signal overload when an amplifier is used; this manifests itself
as a splattering of signals repeated all over the dial and is called
intermodulation ("intermod").
We sell quite a variety of shortwave
radios, from portables to desktop communications receivers. I would
recommend first of all, if you have the outside room, to erect a simple wire
antenna, say, 50 feet or so. It should be as high as possible, and as distant
from your house an power lines as practical to reduce interference from
electrical accessories and appliances. For best reception, the side of the wire (not the long axis)
should face the direction of the desired stations; this isn't sharply critical,
but the general direction should be favored since signals will be minimized off
the ends of the wire. Feed the antenna from one end by a length of coaxial cable
(and kind) with only the center conductor of the cable connected to the wire
antenna. At the radio end of the cable, however, the shield of the cable is
grounded to the chassis of the radio by the connector. We can, of course, supply everything you need, or you may
wish to put it together yourself from Radio Shack and Wal-Mart! If you buy from
us, it would be our ANT-2 Skywire
antenna and one of our cables (CBL-50
or CBL-100 ) to run from the
antenna to your radio receiver.
And now about that receiver....
We have new and used receivers that would do the job well.
Decide what your spending cap should be, then get the best receiver that you can
afford. While the little portables will certainly work, the bigger radios do
work better from a standpoint of selectivity (reducing adjacent-frequency signal
interference) and dynamic range (not overloading from strong signals).
The Skywire does not have a matching transformer because it is intended for receiving, but for transmitting it will have an impedance mismatch which is easily corrected by the insertion of a transmatch (antenna tuner) between the transceiver and the coax. If the antenna is only 15 feet off the ground, considerable upward reflection from the ground will occur, and the returning reflected wave ("skip") will be fairly close, limiting the long distance reception a bit. At HF, getting a horizontal up at least 30-40 feet is important to optimize distant communications. This doesn't mean it won't hear things, or even transmit to distant locations, only that it will work better higher.
Q.
I would like to know if your 'Grove Sky-Wire antenna' (ANT02) contains an
impedance matching transformer where the coax connects to the feed-point
of the antenna? If not, how is the coax matched to the antenna's feed-point
impedance over the range of 500 KHz to 30 MHz?
Ed Dubinsky
A. There is no balun
transformer, nor would one work over the entire frequency range. As with any
simple dipole, the Sky-wire has high and low impedance characteristics
periodically throughout its effective range. A balun transformer would face the
same challenge, maintaining a close match only periodically when feedpoint
impedance is high. For receiving purposes, this is unnecessary. For
transmitting, a transmatch at the rig takes care of the mismatch to avoid damage
to the transmitter.
We select an off-center feed-point
which is a useful compromise between high and low impedance excursions. The
length of the Sky-wire is enough to capture even weak signals adequately,
compensating for any perceived mismatch loss, which is minimal at these low
frequencies.
Q. Hey folks, I mistakenly
picked up a Grove Skywire from your website, thinking it would be suitable for
FM use. Having read the manual and noticing the large UHF connector, it's
not going to work. Which of your products would be a good match for my needs?
I need FM capabilities with a standard coax connector to plug into my receiver
(not sure of the
official name, whatever the standard connectors that cable TV uses). Basically
I'm looking for an improvement over those lousy Terk amplified antennas, since
my area gets poor reception. M. Volpi
A. I think our OMNI-II would be
ideal. Although made for scanners, it has outstanding FM broadcast performance.
You can keep the cable and simply remove the adaptor(s) since the OMNI and your
receiver both have TV-style F connectors.
The AOR DA3000 is a very sturdy antenna and performs well throughout its advertised range. Keep in mind, however, that discones have no gain over a cut-to-frequency ground plane anywhere in their frequency range. There are better receiving antennas out there because they have gain over a discone; however, they are usually not as sturdy (although they survive for years under adverse conditions). From a pure reception standpoint, the ScanTenna hears the best because it has more gain than a discone, but it's nowhere nearly as sturdy against strong winds as the discone.
Create Log Periodic 5130-1N Create Log Periodic 5130-2N
Q. First, is there provision for mounting this antenna vertically, and attaching the rear of the antenna to the mast, as opposed to the center of the antenna?
Q. Also, when mounted vertically,
what sort of pattern or lobe of directivity in the azimuth can be
expected...20, or 30 degrees, or ?
A. This all depends upon the frequency range and, if it's in
front of a metal mast, how that affects the pattern at various frequencies.
Q. Does it have to be mounted on a non-metallic mast, as some
other log periodic devices do?
A. Actually, a non-metallic mast would be better to avoid
unpredictable lobing from reflections at various wavelengths, but I have
mine on a metal mast and it works very well.
Thank you for any assistance with this information, as it will help me to decide whether or not to purchase this antenna. My pleasure. I've had my 5130N for many years and it's survived a hurricane that spawned winds that twisted and broke my tower, but the antenna merely need a slight bend back into place for a couple of elements--it's been working fine every since!
Q. I am new to shortwave listening and want
an antenna outside to optimize the signal but I don't want to break
the bank with the cost. I was looking at the WinRadio long wire
antenna (ADP35) and was wondering if the Balun needed to be outside or
in and I already have a Grove scanner beam for scanning on a mast. Can
I run the long wire around the mast to get it as high as possible
without it affecting the performance of the beam or the long wire. I
was originally looking at the H800 Sky-Match antenna but was afraid it
would overload my Alinco DJ-X10T. Could you please let me know what
direction I should go? Thank you Steve
A.
Effective shortwave antennas can actually be pretty simple--and
cheap--to achieve. With modern, sensitive receivers, the length of the
wire need not be great; typically, 20-70 feet is plenty. Any longer
and your likely to overload the receiver, and even the weak signals
don't get any stronger above the background noise since it rises as
well.
Just follow these rules:
(1) Outdoors, away from the house to avoid home-generated electrical
and electronic interference;
(2) If a horizontal antenna, as high as practical--at least 20 feet or
so. If vertical, the lower end can be very near the ground (just above
the grass!);
(3) Feed it either at the end or at or near the center with coax
(virtually any kind except teensy RG-174/U which is too lossy) which
is run to your radio.
(4) You can use absolutely any kind of copper wire--insulated or uninsulated-- for the antenna so long as it is strong enough to endure
wind and tension.
(5) Try to make it as straight as practical, although a few bends of
less than 90 degrees from straight are just fine.
Q. I am interested in the
PAR End Fed Z EF-SWL antenna. I was wondering how it compares in
performance to the Eavesdropper trapped dipole (center fed, 11- 60
meter, about 42 feet in length)?
A. The PAR will perform equally well, but probably have slightly better noise
immunity. Even better, since trap dipoles favor specific frequency ranges,
the performance of the PAR should be more uniform over the entire
spectrum.
Q. I'm
currently using a random length of wire on the floor!
A. Anything will probably work better than that!
Q. Location: Carlsbad
, California - about 3
miles east of the Pacific Ocean.
A.
We constantly hear from the west coast about their poor shortwave reception
due to the propagation distances.
Q. Grounding - the
receiver ground terminal isn't connected to a ground at this time. My
house has 3 wire style outlets (hot, neutral, ground) though.
A.
Grounding doesn't help signal strengths; in some cases it might reduce
electrical noise.
Q. Coax lead in length -
would be about 75 feet for the PAR antenna and about 100 feet for the
Eavesdropper.
A.
No problem, even using RG-58/U
Q. Concerns - corrosion
due to close proximity to ocean
A. Always a concern, but it can be reduced by using insulated wire and by
coating all metal parts with a silicone grease.
Q. With an end fed S/W receiving antenna, what is the best
pickup direction? In line, or at right angles to length? Can directivity be
changed by having one end higher than the other? B. Crewe
A. The radiation
(receiver or transmit) pattern of a dipole does not change as you relocate the
feedpoint, so an end-fed dipole of a specific length has the same pattern
as a center-fed dipole. Yes, the pattern will change slightly as you lower one
end, looking more like a sloper. The pattern will favor the sloped direction.
Q. We have two of your
Winradio VHF/UHF AX-71C wide band discone antennas mounted on top of our
building. The antennas are 23 ft apart and approximately 8 ft above the
building roof. Each antenna is mounted on the manufacturer provided mounting
tube. The mounting tube is clamped to a mast of 1 inch RGS conduit. Mounted
on top of the conduit mast is a lightning protection rod the protrudes about 6
inches above the antenna. Will this type of mounting method have any effect
at all on the transmitting/receiving capabilities of the antenna?
A. Any metallic mast that comes
within 1/4 wavelength at the operating frequency of the antenna, and is
parallel with the active portion (top spokes and radial elements), will have
an effect on the directivity and gain. It is like a reflector or director on a
Yagi antenna.
Q. Will the WinRadio AX-37 work for television reception, or should I
keep using my rabbit ears?
A.
While rabbit ears work just fine for strong, local signals,
they provide no "gain;" this is accessible only with multiple
elements in parallel (a beam). However, such a small antenna as the
WiNRADiO AX-37 is only usable above 200 MHz or so; that is, only the
upper VHF and the UHF TV channels; you'd not get good reception on
channels 2-10 or so. For those, the rabbit ears would work just fine
for local signals. Keep in mind, however, that NO indoor antenna
will work as well as an outdoor antenna.
Q. Hello, I spoke with you yesterday by phone about the AX-71C
antenna I purchased early this week. I'd like to mount the antenna but,
before I do I'd like to ask a question. I don't think it working correctly so,
I did a continuity check from the cable end to the antenna and all the
lower elements check but the upper elements do not. Is this
normal or should I reassemble?
Thank you,
M. Ellison
A. In all Discone antennas, the top "disc" elements are attached to the coax
center conductor, and the lower drooping radials are connected to the
shield. Thus, with an ohmmeter, you should show a short between the top
elements and the center conductor of the coax, and another short between the
lower radials and the coax shield. There should be an "open" between the
shield and the center conductor.
Although problems with WiNRADiO products are few and far
between, the most common complaint is "poor sensitivity." Before reporting
this, be sure you have checked the following on your WiNRADiO receiver:
(1) Are you using the wire test antenna that may have been included with your
receiver? Don't! It's for initial checkout only.
(2) Is your antenna appropriate for the frequency range you have tuned, and is
it mounted outdoors?
(3) Are you using low-loss coax (RG-6/U, RG-8 or similar) to your antenna?
(4) Are all connectors and adaptors tight and making contact?
(5) Is the receiver "DX/LOCAL" option set on "DX?"
(6) Was there a lightning storm prior to your noticing low sensitivity?
(7) Was the radio working satisfactorily prior to your loading some additional
software?
(8) Have you tested your antenna system on another radio for comparison?
These hints usually solve the problem!
Antenna Selection: There are several factors that weigh in so far as the distance an antenna can hear, including:
Height of the antenna; Presence of obstructions; Length and losses of the transmission line; Gain of the antenna; Direction in which a gain antenna is pointing; Frequency of the signal; Sensitivity of the receiver; Presence of interference; Power of the transmitted signal; Bandwidth of the signal; Solar effects (day/night, sunspots, flares); Weather and humidity; Electrical storm presence That said, under normal circumstances, and using the non-directional AX12B with good coax, good locations and a good receiver, the following could be expected: (1) HF reception (under 30 MHz): Thousands of miles for broadcasters and two-way communicators. (2) VHF (30-300 MHz): Up to 100 miles for broadcasters and two-way communications. (3) UHF (300-500 MHz): Up to 75 miles. (4) Microwave (800-2000 MHz): 25-50 miles.
Naturally, these are only approximations due to the numbers of variables pointed out above, but should give you an average expectation. Naturally, if you're looking for a simple, low-power device like a bug or cell phone, we're talking feet, not miles.
Q. Will the WinRadio AX-37 work for television
reception, or should I keep using my rabbit ears?
A. While rabbit ears work just fine for strong,
local signals, they provide no "gain;" this is accessible only with multiple
elements in parallel (a beam). However, such a small antenna as the WiNRADiO
AX-37 is only usable above 200 MHz or so; that is, only the upper VHF and the
UHF TV channels; you'd not get good reception on channels 2-10 or so. For
those, the rabbit ears would work just fine for local signals. Keep in mind,
however, that NO indoor antenna will work as well as an outdoor antenna.
Q.
My WR doesn't seem to have the sensitivity of
my regular scanner, what could be the problem?
A. Even though
the WR receivers have excellent sensitivity, this is a common complaint
because there are many possible reasons. Most likely, the host
computer—especially the CRT monitor--is generating electrical "hash" which
raises the general noise floor of the receiver, inhibiting reception of weak
signals. Other household electronic appliances can produce interfering signals
as well. One way to confirm this is to unplug the antenna cable while
listening to the background hiss or noise between stations and see if the
noise diminishes significantly. If it does, that's a sure sign of external
interference. The small wire antenna that may have accompanied your WR is
merely to try it out; it doesn't come close to the performance a
properly-designed antenna. Ideally, your antenna should be cut to frequency,
high, outdoors, away from power lines, and distant from your operating point.
That's a tall order, but it's the best order. For each of those specifications
you compromise, your reception will be degraded. A long wire antenna works
well for shortwave reception, but is next to worthless for the VHF/UHF scanner
bands; similarly, a short whip is a poor choice for shortwave reception. Use
separate antennas and a switch to choose, or connect the two antennas to a
standard TV VHF/UHF splitter, combining the two into one input for the
receiver. There are wideband antennas available on the Grove web site
which are suitable.
About that noise
"Ground loops" allow buzzes and hum to come
through well-shielded antenna systems. The best fix is to find a toroid
(donut-shaped) ferrite ring or square core (Radio shack 273-104) and wind
several turns of the coax through it close to the radio; a conventional
radio-frequency-interference (RFI) bead (Radio Shack 273-105) may work as
well. Since CRT monitors are especially strong radiators, LCD screens are
recommended. All cords should have ferrite-bead RFI (radio frequency
interference) suppressors mounted on them as close to the chassis as possible.
Q. Hello, I recently purchased a WinRadio WR-LWA-0130 long wire antenna
adapter (balun) from you as well as 100 feet of RG-6/U antenna feed coax for my
long wire shortwave antenna. Order invoice # 37756. I have just come to
realize that the RG-6/U coax cable is 75 ohms and my Grundig Satellit receiver
has a coax input connector for 50 ohms!! This is written next to the
connector. My question is: Is it wrong or will I have a problem using 75 ohm
coax antenna feed instead of the 50 ohm type? Will this hinder my SW.
reception? Should I have used 100 ft. of 50 ohm coax? I see that you do not
carry 100 ft. of 50 ohm coax. I really would appreciate any help or advise
about this. I am trying to get the best reception that I can with the 70 ft.
long wire antenna I just completed. It is a 70 foot bare copper wire connected
to the balun with 10 feet of insulated wire. The RG-6/U cable runs from the
above balun to my receiver. I am now worried that I should have used 50 ohm
coax instead of 75 ohms. Can you help or advise me on this please??
Thank you for your time and help..73's. Harvey Bell
A. For shortwave receiving purposes,
the impedance you use for coax is of no importance; you won't notice a bit of
difference between signal levels on 50 vs. 75 ohm line. We use the RG-6/U 75 ohm
cable because it has lower loss than RG-58/U 50 ohm coax. At VHF/UHF ranges (not
so much at HF), the low loss can mean the difference between hearing and not
hearing a weak signal with long lengths of coax. It's much more important the
impedance; that's why we carry only the RG-6/U
Q. Building a new home in the country, and I would like to
install an old wideband Radioshack UHF/VHF scanner I have,
along with a UHF/VHF transceiver. Would it be possible to use your ant
9 as a single antenna for both applications, or what would you suggest?
A. Yes, it's a popular scanner antenna and also has good
impedance matching for transmitting as well. You might wish to
consider the WiNRADiO AX-71C as well. Keep in mind that a discone
has no gain above that of a simple ground plane, but it would be
reliable for local coverage.
Q. Would you suggest a switch
or a splitter?
A. A switch will provide more
isolation between the ports than a splitter, thus creating less likelihood of
front-end burnout of your scanner. I'd recommend for typical UHF power our
low-cost SWC01 antenna switch which is rated all the way to 2000 MHz. It has
female F connectors, so you will need adaptors which we carry.
Q. Do you have an inline surge suppressor (Lighting
Protection) that I should use in the application?
A. Yes, our LAR1F is excellent for this. It comes fitted with F
male/F female connectors since it's designed for TV applications,
but we carry the proper adaptors.
Q. The run from the
radios to the mast would be approx. 40', what cable spec would you suggestion?
A. For only 40 feet, you could
use RG-8/M or RG-8/X mini RG-8 with foam dielectric. It's low loss, and easy
to affix connectors to. Even easier, order our CBL-50, a 50 foot length of
low-loss RG-6/U and you get the adaptors to fit its F connectors free! Even
though it's 70 ohm cable instead of 50 ohms, you won't notice the difference
in actual on-air performance between it and the pricey RG-8/U or Belden coax.
Q. Scanner has a BNC connector,
the UHF/VHF Transceiver needs a PL259 Can you help me configure solution?
A. If you want to use our
RG-6/U cable with its F connectors, simply order the appropriate adaptors for
you configuration.
Q. Do you have to have all the antennas screwed into the Discone for
it to work on 154-155 MHz? is no, you don't.
A. You can eliminate the top vertical which is the low-band
resonator (40-50 MHz range).
However, if you have only one short disk radial (the upper spokes) and
one longer sloping radio beneath it (the bottom elements), it may exhibit some
unpredictable directivity and a poor impedance match. I'd use all of the disc
elements and sloping radials. If you can't, then put in at least four pairs
(upper and lower) evenly spaced (every 90 degrees).
Q. Can you
provide me with the following information for one Diamond D130J with an
appropriate adapter cable to convert the connector to SMA? More detailed specs
than are listed on the site. I need to verify that it is a passive antenna
and need more detailed frequency response characteristics.
A.
Yes, it is a passive antenna of the classical Discone design, but with one added
refinement: It has a low-band (30-50 MHz) element on the top to favor that band
as well, otherwise the frequency range would cut off sharply below about 100 MHz
or so. Realistically, then, the impedance-matched (50 ohms nom.) frequency range for transmitting is more like
80-1300 MHz, with the low-band element cut for transmitting in the amateur
six-meter (50-54) MHz band; it is adjustable.
Q.
I was
wondering if I took two of your scanner beams and set them
up side by side, like the old 3 element beams we called
stacked 3s, would this give me more gain than 1 beam say
one beam has 20 db gain would it now have 40 db gain or
would it not work at all? R Lashbrook
A. While it would sound logical
that two 20 dB antennas in parallel should add their gain
to produce 40 dB total, it doesn't work that way. Two
identical antennas hooked in phase for maximum signal
improvement will add a mere 3 dB to the one antenna!
The reason for this is that doubling
the capture of the signal is only a 3 dB voltage gain.
Q. I'm currently using
your Scantenna, but want to improve reception on 463 MHz from repeaters on the
other side of a mountain range. The Scantenna picks them up, but with a lot of
hash. My questions are: Should I expect much improvement from the Beam? Would I need any additional hardware to install it using the Scantenna's
existing cable run? Many thanks, L. Masterman
A. There is only a small difference in gain between
the Scantenna and the Scanner Beam; the Scanner Beam has better forward
directivity, but I think the answer is probably yes, you should point the beam
toward the desired signal and rotate it for best reception.
Q. I would like to mount my Grove Scanner Beam in my attic but it has a low
ceiling. Am I able to cut the longest elements at the back of the
beam? My main interest is 161 Mhz.
Thanks for the help. Hank
A. Since that rearmost, longest element is
primarily for low band (50 MHz), he can cut it off with virtually no change in
performance at the higher frequencies.
Q. I am not able to tell a big difference between
the ScanTenna and the Scanner Beam when I switch antennas with the A-B switch.
All these stations are the 50-65 mile range in the 450-470 MHz band. Since I am
used to the difference between a CB ground plane and a beam antenna for
comparison. I can only assume that the difference is the ScannerBeam being a
wide-band antenna does not have the same amount of gain when compared to a
narrow-band antenna like a Moon Raker or Wilson beam antenna. Would a 7 element
Yagi 800 MHz antenna mounted above the Scanner Beam allow me to listen to
trucking systems 35 miles north of me? The Scanner Beam is 35 feet above ground
level. The Yagi beam could be mounted 5 feet above the ScannerBeam if it would
pull in the 800 MHz signal. I have access to Belden R11 coax for the 800 MHZ
beam if necessary. Your opinion or recommendation please. John Cowan
A. Yes, the ScanTenna is excellent, and the Scanner
Beam will only show slight improvements on some frequencies in its forward
direction. What kind of coax are you using to it? Ours (RG-6/U)? That's good
stuff. Yes, you might try that 800 MHz beam. You might try coupling it to the
main coax from the scanner beam with a two-way splitter, or run it separately.
Depending on the length of the line, the low-loss, foam dielectric RG-11/U may
work better than the RG-6/U, but probably only in runs approaching 100 feet or
so.
Q. I just purchased a Grove scanner beam. What kind
of gain can I expect from my Scantenna to the beam? I have noticed that the
Grove scanner beam is mounted with the aerials vertical. I seen Amateur antennas
around here mounted with the aerials horizontal. What is the difference mounting
them vertical as opposed to horizontal? John Cowan
A. Most of the improvement you will notice between
the Scanner Beam and the Scantenna will be at UHF since that's where the highest
gain and directivity are. An antenna increases gain in one direction by
redirecting it from other directions. Thus, you will probably notice that some
formerly-weak signals will be much stronger in one direction, but some signals
that are not in the favored direction will be weaker. That's why beam antennas
are rotated toward their targets. Since virtually all mobile communications at
VHF and UHF are using vertical antennas, that's why the base receiving antennas
are vertical as well; this is especially important for line-of-sight
communications. For DX (long distance) communications, the signals have become
bent and reflected enough that the horizontal or vertical matching of the
antennas is no longer as important; that's why you often see amateur beams with
their elements in the horizontal directions, even if they are talking to mobile
stations hundreds or even thousands of miles away that are using vertical whips.
Q. If I get another Scanner Beam from you to go
with the one I have now, how far apart would they have to be in order to stack
them?
Would stacking them narrow the directivity by half what it is now for a more
narrow beam? If my memory is correct stacking them will increase the signal by
about 3 db? J Cowan
A. Right about the 3 dB. Keep them about a
half-wavelength apart at the lowest critical frequency; that's usually about
three feet or so (VHF hi band).
Q. Does the Scanner Beam
II have a "standoff" mount for vertical mounting included? This kind
of mount would position the antenna away from the mounting mast by a distance
that would help the mast not affect the performance of the antenna. Bill
A. Right, and yes it
does. While I suspect there would still be interaction from the separation at
low band (it doesn't stick out THAT far!), at those low frequencies we don't see
much directivity anyway. But at VHF-high and above, the offset appears to be
quite satisfactory
Q. The manager
of my local Radio Shack insist that a TV antenna turned on it's side,
specifically the VU-190 XR, will work better than your scanner beam because it
has more elements and is tuned to the same range. And the RS antenna at
$49.95, is on sale, I am looking for a VHF-UHF band directional to be used with
a rotator to supplement my Discone. Why do you think yours is better? H.
Eddleston
A. Your Radio
Shack dealer has good knowledge of radio; believe it or not, our original
Scanner Beam was fashioned from a TV antenna turned on its side! But over time,
we gradually improved four versions of this, and the latest is, of course, our
best. It's still made out of TV aluminum, and is made by the same company that
makes RS's TV antennas (Antenna Craft), but it's custom designed to our
proprietary specifications to have its best performance in the land mobile
spectrum, not the TV spectrum. This means a slight adjustment in element
length and spacing. Now the final question: Will our Scanner Beam be superior to
RS's highest-price VHF/UHF antenna, rotated over on its side? I suspect they
would be about the same. But because ours is specific to the scanner
frequencies, it's shorter, lighter, and less costly. Plus, you don't have to
drill any new holes!
Q. I bought one of your "Scanner
Beams" about 10 years ago. Used it for a while then removed and stored it
when I needed extra space on my rotor. I would like to put it back up but this
time I want to buy another and stack the 2 of them. Your antenna looks just like
the ones made by Antennacraft in Burlington Iowa...or at least your
"OLD" model did. What are the changes made to this "NEW"
improved version. I want to
eliminate any "unforeseen" problems in stacking antennas with
different characteristics cant understate the importance of having 2 identical
antennas if I want to stack them. Can an old one be stacked with a
"new" one??? By any chance would you know the distances between the 2
for optimal Bandwidth and/or Gain??. I at least need to know if they are
similar enough to stack without problems due to differences either mechanical or
electrical. R. Yurek
A. The new Scanner Beam has virtually identical
characteristics except for directivity; that's why we developed the new model.
The old one had two main lobes displaced off center from the front of the
boom by about 45 degrees so that aiming the antenna between 100-200 MHz gave
false bearings. I wouldn't stack two different versions, so if you're stacking
two Scanner Beams, they should be the new model. This isn't just to sell you a
second antenna, but to prevent destructive interference from trying to phase two
antennas with different patterns. But keep in mind, under perfect conditions,
you will only gain 3 dB (1/2 an S unit) when you stack two identical antennas,
but the pair will provide sharper directivity.
The Scantenna does a very good job on 800 MHz reception, so if you are using low-loss coax and have the antenna properly mounted with all elements moved to their open positions, it should work. But at 800 MHz there are other considerations in an indoor location. If you have wiring or heating/air conditioning ducts near the antenna, the reflections can be a real problem. Another possibility is metalized Mylar insulation in the walls, or even signal-absorbing materials in the roof shingles (I hope you don't have metal roofing!). If you are still receiving other signals (150 MHz range) clear from up to 100 miles, then the antenna is probably working properly. Be sure you have pulled out ALL the elements, including the flat "wings" on the sides of the elements. Make sure you have the antenna vertically, not horizontally, positioned. Another experiment to see if it's the location would be to temporarily place the antenna outside and high to see if now you can receive that 800 MHz signals.
If you can't get the 800 MHz signal on your scanner outside with its own antenna, then signal strengths are very weak and you will need to do whatever you can to capture those signals. The Scantenna is an excellent antenna, and the RG-6/U is what I would recommend. You are losing several dB of signal in the line, but that's inevitable if it has to be that long. One possibility is to try our Scanner Beam which has gain above the Scantenna at the higher frequencies. Another possibility is to try a preamplifier like the Ramsey that we carry; I think that would help, but it is best placed up close to the antenna. Do you have an AC outlet in the attic? My recommendation, then, would be to run a short length of cable to the preamp, then the main down lead to your scanner. I suspect that would help things a lot.
Q.
According to your advertisement, the Scantenna is omni-directional
(non-directional):
http://www.grove-ent.com/ANT7.html . However, when I mounted it on a
mast pipe, I found that when I turned it in different directions, some signal
levels changed. How can this be?
A.
The antenna is omni-directional--there's no false advertising about that.
However, anytime you place an antenna alongside a metal mast, or even its own
cable, there is some reflectivity that occurs. If you were to put the antenna
on a wooden or plastic/PVC mast, and run the coax at right angles to it, you
would see a substantial difference in its non-directional pattern.
Antennas are called directional or omni-directional (non-directional) based upon
the antenna alone, un-mounted.
For example, discones and ground planes are non-directional because they are
mounted at the top of, not alongside, the metal mast pipe. However, if you put
one of those non-directional antennas alongside a metal mast pipe, you would
find the same directivity as you have with the ScanTenna.
Q. I'm currently using
your Scantenna, but want to improve reception on 463 MHz from repeaters on the
other side of a mountain range. The Scantenna picks them up, but with a lot of
hash. My questions are: Should I expect much improvement from the Beam? Would I need any additional hardware to install it using the Scantenna's
existing cable run? Many thanks, L. Masterman
A. There is only a small difference in gain between
the Scantenna and the Scanner Beam; the Scanner Beam has better forward
directivity, but I think the answer is probably yes, you should point the beam
toward the desired signal and rotate it for best reception.
Q. I am not able to tell a big difference between
the ScanTenna and the Scanner Beam when I switch antennas with the A-B switch.
All these stations are the 50-65 mile range in the 450-470 MHz band. Since I am
used to the difference between a CB ground plane and a beam antenna for
comparison. I can only assume that the difference is the ScannerBeam being a
wide-band antenna does not have the same amount of gain when compared to a
narrow-band antenna like a Moon Raker or Wilson beam antenna. Would a 7 element
Yagi 800 MHz antenna mounted above the Scanner Beam allow me to listen to
trucking systems 35 miles north of me? The Scanner Beam is 35 feet above ground
level. The Yagi beam could be mounted 5 feet above the ScannerBeam if it would
pull in the 800 MHz signal. I have access to Belden R11 coax for the 800 MHZ
beam if necessary. Your opinion or recommendation please. John Cowan
A. Yes, the ScanTenna is excellent, and the Scanner
Beam will only show slight improvements on some frequencies in its forward
direction. What kind of coax are you using to it? Ours (RG-6/U)? That's good
stuff. Yes, you might try that 800 MHz beam. You might try coupling it to the
main coax from the scanner beam with a two-way splitter, or run it separately.
Depending on the length of the line, the low-loss, foam dielectric RG-11/U may
work better than the RG-6/U, but probably only in runs approaching 100 feet or
so.
Q. I just purchased a Grove scanner beam. What kind
of gain can I expect from my Scantenna to the beam? I have noticed that the
Grove scanner beam is mounted with the aerials vertical. I seen Amateur antennas
around here mounted with the aerials horizontal. What is the difference mounting
them vertical as opposed to horizontal? John Cowan
A. Most of the improvement you will notice between
the Scanner Beam and the Scantenna will be at UHF since that's where the highest
gain and directivity are. An antenna increases gain in one direction by
redirecting it from other directions. Thus, you will probably notice that some
formerly-weak signals will be much stronger in one direction, but some signals
that are not in the favored direction will be weaker. That's why beam antennas
are rotated toward their targets. Since virtually all mobile communications at
VHF and UHF are using vertical antennas, that's why the base receiving antennas
are vertical as well; this is especially important for line-of-sight
communications. For DX (long distance) communications, the signals have become
bent and reflected enough that the horizontal or vertical matching of the
antennas is no longer as important; that's why you often see amateur beams with
their elements in the horizontal directions, even if they are talking to mobile
stations hundreds or even thousands of miles away that are using vertical whips.
Q. Can you transmit on the ScanTenna? L. Larsen
A. Yes, up to about 50 watts.
Grove Omni-II VHF-UHF Receiving Antenna
Q. Hi, I live in area where no antennas can be put
on the roof. It appeared to me that your omni 11 could be attached to the side
of my house unnoticed.. I have an Icom T90A and an old standard #528 both
handheld for transmitting. I just purchased a mirage amplifier that puts out 45
watts on vhf and 35 watts on uhf. From what I understand the balun that comes
with the antenna can handle only 10 to 20 watts. Can I upgrade the balun and
what wattage should I use? Will I still be able to transmit. Are the baluns easy
to install? I am not very hip when it comes to electronics. The antenna will be
arriving 3/23 and I would like to be prepared.
Thanks for your help, Jerry
A. Yes, you can probably use the OMNI II for transmitting with the balun
provided, but only with the barefoot transceivers. If you go to the
higher-powered amplifier, you might want to test it first by running the the
transmitting setup on the ground so you can feel and smell the little balun. If
it gets noticeably warm, most of you power is going into heating the coils.
I've been asked before where to find transmitting baluns for VHF and UHF, but so
far I haven't found an answer. Most hams "roll their own."
Is there any way you could mount the Nil-Jon base antenna? It's not terribly
conspicuous, and it's a good performer on VHF and UHF.
Q. I have an old Grove Omni dipole antenna.
The elements are equal length, 48 inches long. I recall that the top
element should be shortened for best reception, but I don't recall how much to
cut off. What length should the top element be? P. Vieth
A. 18" for the top element.
Actually, you can turn it upside down; there may be some erratic pattern
differences depending on distance from the pole and coax, but it's essentially
the same whether you cut the bottom or top to 18".
Q. Hey folks, I mistakenly
picked up a Grove Skywire from your website, thinking it would be suitable for
FM use. Having read the manual and noticing the large UHF connector, it's
not going to work. Which of your products would be a good match for my needs?
I need FM capabilities with a standard coax connector to plug into my receiver
(not sure of the
official name, whatever the standard connectors that cable TV uses). Basically
I'm looking for an improvement over those lousy Terk amplified antennas, since
my area gets poor reception. M. Volpi
A. I think our OMNI-II would be
ideal. Although made for scanners, it has outstanding FM broadcast performance.
You can keep the cable and simply remove the adaptor(s) since the OMNI and your
receiver both have TV-style F connectors.
H-800 SkyMatch Active Antenna H-900 SkyMatch Active Antenna
Q. In December of last year (2005) we exchanged a few
emails regarding shortwave antennas. The best alternative you recommended me at
that time was the H-900 Gain Probe ANT27 which is priced at U.S. Dollars 189.00.
However, you also recommended the H-800 Sky-Match ANT15 saying that the H900 had
additional gain for weak signal reception, and increased dynamic range to
withstand strong-signal overload, etc, which would explain the price
difference with the H-800. At that time, I explained that what I needed was a
more " professional " type antenna with high gain, to be able to target the HF
SSB air traffic (and maritime) in the North Atlantic, North and South Pacific,
Europe, etc, from Santiago (Chile) where I am located and where HF signals are
extremely weak around my dwelling. What I would like to know is if the H-800
also has " sufficient " gain (obviously not as much as the H-900) to
"bring in" the long-distance weak HF signals from the Northern Hemisphere to a
listenable level. I appreciate that my question is not an easy one for you to
answer due to the many factors that affect shortwave reception, but I would
still wish to know your opinion as to whether the H-800 would (or would not) be
suitable for reception of weak HF signals from the above areas of the world. I
would remind you that my rig is an ICOM IC-R75 communications receiver. I. Moir
A.
There is no question that the H-800 is a perfectly suitable antenna for the
vast majority of shortwave requirements. The limiting factor at those
frequencies is atmospheric noise, so once you bring the signal level up
above the atmospheric noise, you've got it and can receive it. The H-800 does
this.
The main advantage of the H-900 is its slightly better immunity to overload and
attendant intermod problems. All amplifiers (including amplified antenna
systems) have a breaking point above which strong signals generate spurious
responses.
While the H-900 also has slightly higher gain than the H-800, all this means is
that it amplifies the atmospheric noise right along with the signal. The S
meter may read a little higher with the H-900, but you won't hear signals any
better; they will still be the same level above the noise.
Q. I
am using a Grundig Sat 800 with a EMF Electro-Magnetic Field passive wire
antenna (16ft.) string in my screened porch. Reception is slightly better than
the receivers whip antenna. I am not allowed an outside antenna. Do you have any
suggestions for an improvement over the antenna system I am using? Thank you,
Edward Boynton
A. Is it possible for you to mount, say, a 3'
whip outdoors? If so, go for the H800 Sky-Match--it's a killer shortwave
antenna! It's an active antenna that behave like a 100' wire. Other possibilities include running a wire antenna that has a
cover (insulation) that would be neutral to its surroundings (brown against
brick, slate great against the sky, etc.) either from your window to another on
the building, or out to a tree or porch, etc. Finally, can you get into an attic crawl space? Suspend it
from rafters, away from wiring, from end to end of the opening. An important
thing to remember is to get the antenna as far as practical from wiring and
appliances so that it doesn't pick up electrical interference; that's the
reason that the distant antenna should be fed with coax, which is shielded.
Q. I will be purchasing one of your sw antennas
and am considering AOR SA-7000 or H-800 with the below data, which antenna do
you recommend? I live in N. Central W.A., 26 miles south of the Canadian border,
elevation 3200' with adjacent mountain ranges of 4200'. My house has a metal
roof and I want to elevate the antenna above the roof line. Do you have mounting
posts suitable for attachment on cross beam to elevate antenna? The antenna will
be mounted facing north (side of roof line). B. Ronson
A. Since I don't know what kind of receiver you
are using, I am somewhat limited in my response. I'm going to assume that you
are interested only in frequencies below 30 MHz. While we don't have any
additional hardware (you can get that from Radio Shack), I would recommend the
H800; it has considerably more gain than the SA7000 which is a passive antenna
intended for use with super-wide-frequency-coverage receivers (typically 100 kHz
or below all the way up to 2000 MHz.)
If you are interested in the best shortwave performance, and don't have room to
put up an elevated dipole wire antenna, I'd go with the H-The SA7000 is a
passive antenna, but works very well. Performance exceeds
that of a Discone, but unfortunately, I've been unable to get any actual
gain figures. We've sold quite a number of these, and none has ever come back.
Q. I just purchased a dual band Kenwood TM-733A
VHF/UHF mobile that is capable of transmitting in the business bands as well. I
am studying to get my HAM license but am authorized to transmit in the emergency
service bands as I am a 9-1-1 employee in Iredell Co. NC. I was looking at
the SUPER STEALTH MOBILE ANTENNA and was wondering if this would work for dual
band transmission in the frequency ranges of 150-170 MHz and 450-470 MHz? Also
this particular radio has a PL-259 connector for VHF and a separate PL-259
connector for UHF. I am looking for a dual band splitter adapter to connect out
to both of these connectors and in from one single dual band antenna. Do
you offer this? Thanks M. Pruitt
A.
Yes, I've used my Stealth mobile antenna for that very purpose with my
FT-100 transceiver. Since the FT-100 also has dual PL-259s on it, I simply
used adaptors and a Tee connector to combine the two into into one coax
line.
Good luck on the ham test.
Icom AH-7000 Discone
Q. A friend recommended the Icom AH-7000 Discone antenna
to me. It believe it is fairly large and bulky though.
A.
Discones are fine for local-area VHF/UHF reception, but they have no gain. Our
Grove Scanner Beam outperforms it at lower cost, and you can buy the needed
length of RG-6/U coax from our inventory.
AOR SA7000 Full-Frequency Base/Portable Antenna
Q I know larger is better for reception but I was
looking at the AOR SA-7000 that you carry as it looks more stealthy (which would
make the wife happier). Is one design better than the other? I
will actually need a second antenna (at some point) for the shortwave
frequencies as the Icom receiver needs two types of antennas for full receiver
coverage. I am looking for suggestions in that area to.
A.
The SA-7000 is an excellent, all-band antenna. We sell these to the government
and they are quite happy with its performance. Its quite compact which would,
indeed, make your wife much happier!
Q. I am considering purchasing the AOR SA7000
antenna for scanning purposes. Have you experience with it and how does it
compare to the
WINRADiO AX-71C Discone antenna and other antennae? I use a JRC NRD 545
DSP receiver and I have installed the CHE-199 wide
band converter unit for use on the 30 kHz-2 GHz frequency range. R. Hamilton
A. The AOR SA7000 is an excellent antenna, both for
receiving and low-power transmitting. It is compact and sturdy making it ideal
for portable as well as long-term base installations. It has some gain in the
VHF and UHF ranges. Any discone has the same advantages and disadvantages. The
advantages are flat VSWR over a wide frequency range (typically 8:1 octaves or
more), and they accept more power than most scanner antennas. The downside is
that they have no gain, so their best use is for wide-frequency-coverage,
relatively-local applications. They also roll off quickly in performance below
their lowest stated frequency. Since you are using the one antenna for HF as
well as VHF/UHF, I'd definitely opt for the SA7000. It's a popular favorite with
our serious listeners.
Q.
I am still trying to decide what antenna I need for my AOR 8200 Mk III I
purchased fro Grove. You recommended the Scantenna as an option. If
I want to pick up the AM bands along with short-wave and the rest, would I want
to use a long wire antenna such as the PAR with the Scantenna or would I better
off buying the AOR SA7000. If I would go with two antennas, would I have
to run two leads into the radio or can the two antennas be tied together
somehow?
Rich Widga
A. Since you have only
one antenna jack on the scanner, you need either one continuous-coverage,
wideband antenna or a combination shortwave antenna and VHF/UHF antenna
interconnected through a combiner (a splitter like our SBL-1 connected in
reverse).
For shortwave, you don't want too long an antenna or you will overload the
scanner, resulting in intermod and images--phantom repeated signals appearing
throughout the tuning range.
The AOR SA7000 is an excellent, passive, all-band antenna for
this receiver. You could also use an antenna like our ANT-7 Scantenna which
provides excellent VHF/UHF coverage, and some limited shortwave coverage as
well. If you wanted to use the splitter for better shortwave reception, you
could try any combination of shortwave antenna (like our ANT-2 Skywire or the
H800 Skymatch) with a VHF/UHF antenna like the Scantenna or any other scanner
antenna in our catalog.
Q. I will be purchasing one of your sw antennas
and am considering AOR SA-7000 or H-800 with the below data, which antenna do
you recommend? I live in N. Central W.A., 26 miles south of the Canadian border,
elevation 3200' with adjacent mountain ranges of 4200'. My house has a metal
roof and I want to elevate the antenna above the roof line. Do you have mounting
posts suitable for attachment on cross beam to elevate antenna? The antenna will
be mounted facing north (side of roof line). B. Ronson
A. Since I don't know what kind of receiver you
are using, I am somewhat limited in my response. I'm going to assume that you
are interested only in frequencies below 30 MHz. While we don't have any
additional hardware (you can get that from Radio Shack), I would recommend the
H800; it has considerably more gain than the SA7000 which is a passive antenna
intended for use with super-wide-frequency-coverage receivers (typically 100 kHz
or below all the way up to 2000 MHz.)
If you are interested in the best shortwave performance, and don't have room to
put up an elevated dipole wire antenna, I'd go with the H-The SA7000 is a
passive antenna, but works very well. Performance exceeds
that of a Discone, but unfortunately, I've been unable to get any actual
gain figures. We've sold quite a number of these, and none has ever come back.
Q. Is there a wide band amp on
the AOR SA700 antenna? What is the gain over the Diamond Discone ? D. Mac
A. The SA7000 is a passive antenna,
but works very well. Performance exceeds that of a Discone, but unfortunately,
I've been unable to get any actual gain figures. We've sold quite a number of
these, and none has ever come back.
MFJ 1020C Tuned Indoor Active Antenna
Q. Would the MFJ 1020
active antenna do my ATS 818 shortwave radio any good? What else would I need
beside the PL-259 3' jumper cable to hook it up?
A. Only if you cannot put up any sort of external
wire antenna, say, 20-30 feet long. Remember, any indoor antenna, no matter how
good it is, will be more vulnerable to interference from household electronics
than a more distant outdoor antenna with shielded (coaxial) cable lead-in.
Nothing but 12 VDC from the AC adaptor.
Q. Would it work by just placing it on my kitchen table
with the ATS818? I already have a high performance am radio from radio shack
near the window
for better reception. So I am somewhat limited on what I can put near the
window.
A. Within the limits discussed above.
Choosing a Shortwave Antenna
Whichever antenna you choose, it's best put outside, reasonably high, and away from power lines and your dwelling. Next best bet is an attic crawl space, as close to the roof peak as possible. Always use coaxial cable from the antenna to the receiver; its shielding prevents electrical noise pickup from your environment, although the antenna itself remains vulnerable to nearby electrical noise.
The choice of antenna isn't really all that critical--typically, a random, 20-60 feet of wire is entirely adequate for listening between 1-30 MHz, and the coax may be attached anywhere along its length. While larger antennas with better impedance matching may provide more signal, they also provide more noise, so the net result of signal above noise is about the same.
One final note: If you are using a long antenna wire, chances are very good you will get signal overloading on your portable radio; such receivers typically have poorer dynamic range than the more professional desktop receivers, resulting in phantom signals appearing all over the spectrum. Try listening with your attenuator (DX/LOCAL) switch activated.
Our Skywire ANT02 dipole has been a favorite, serious, budget-priced, shortwave listener's antenna for decades. It can be mounted horizontally, vertically, as a sloper, or even at an obtuse angle and still provide reliable reception throughout the entire shortwave spectrum, even down to 100 kHz. As with any horizontal wire antenna, it should be erected as high above ground as practical, although elevations of only 15 feet or so have proven very satisfactory.
The PAR "END FEDZ" ANT08 is a superb listener's antenna with superior construction materials. Since it's end-fed, the coax can be shorter, attached to the close end of the wire. Its 9:1 impedance-matching transformer brings higher signal levels to your receiver.
Want to "roll your own?" The WiNRADiO WR-LWA-0130 ADP35 adapter is a weatherproof matching transformer that allows you to attach a long wire of your choice, and still have better signal transfer to your receiver.
Cramped for outside space? Don't want the neighbors to know you have an antenna? The H800 Skymatch ANT15 is an outstanding active antenna that embodies a booster amplifier to make its short (3') length sound like a 100' dipole! It is powered by a wall transformer or, for total isolation from power lines, you may install two 9-volt batteries. Its high performance is the widest frequency range of all--10 kHz through 54 MHz. The H-900 Gain Probe ANT27 has all of the features of the H-800 Skymatch but with additional gain for weak signal reception, and increased dynamic range to withstand strong-signal overload and avoid desensitization from close-by transmitting antennas
Is an indoor or radio-room antenna a necessity? Then try the MFJ 1020C ANT19 active antenna which is a handy accessory, allowing sharp signal-peaking from 300 kHz-40 MHz. It can also be used as a preselector/preamplifer for outdoor shortwave antennas.
The AOR WL500 ANT24 amplified window antenna provides 3.5-30 MHz reception when mounted either in a window or suspended. It is powered either by a nine-volt battery or an external power supply (neither included), and its 2' diamond shape is easily accommodated in convenient locations.
Want to null out that indoor interference? The AOR LA380 ANT44DS loop offers professional performance it features an internal high-gain amplifier (20dB for 10kHz-250MHz) and excellent overall strong signal handling (high IP3 +10dBm) ,and a sturdy, tunable loop which can be rotated to reduce indoor electrical noise sources.
Full-Spectrum Antenna Looking for extremely wide frequency coverage in one antenna? The low-profile AOR SA-7000 ANT39 vertical covers 30 kHz through 2000 MHz to match the new breed of wide-spectrum receivers, and it does it well.
Choosing a VHF/UHF Antenna
VHF/UHF are more critical than shortwave antennas. Their more size required more attention to design details to increase signal capture. The more gain an antenna has, the more directional it is, since gain comes from "shaping" the response pattern of the antenna to incoming signals.
The Grove Scanner Beam ANT18 has been through several minor iterations over the decades, and is now revered as "the" scanner antenna for serious monitoring. Although it's assembled with conventional TV-antenna, rolled-aluminum elements, this cost saving doesn't compromise its high performance which matches that of professional beams costing many hundreds of dollars. Use it for continuous-spectrum monitoring from 30-900 MHz at least. In the clear, its range approaches 100 miles radius.
Need higher gain? Planning to transmit? The rugged design of the Create log-periodic beam invites power to at least 100 watts, and the durable elements withstand high wind load. This is a professional antenna with a typical gain in the 10-12 dB range and a choice of 50-1300 MHz (CLP-5130 -1N) ANT16 or 100-1300 MHz (CLP-5130-2N) ANT17.
A popular favorite with scanner monitors and two-way users (up to 100 watts transmit) is the Nil-Jon ANT10MBS multiband base antenna. Designed for transmitting in the 140-174, 216-225 and 406-512 MHz bands, it also provides reception from 25-1300 MHz.
The Scantenna ANT07 has set itself apart from the others with its excellent, omnidirectional performance. If maximum range, all-around, and no rotating beam are your requirements, you won't do better than this 25-1300 MHz scanner antenna.
For casual scanner monitoring over metropolitan areas, the Grove Omni ANT05 can't be beat for price vs. performance. A 50 mile range isn't unusual on several scanner bands between 30 and 960 MHz.
Discones have their place. While they don't offer the gain of other designs, they do offer uniform response in all directions, and on all frequencies continuously through their design spectrum--and, because of their constant impedance over their design bandwidth, they can transmit as well as receive throughout the design frequency range. Choose the Winradio AX-71C ANT01 for reception from 30 MHz right up through 3 GHz, the AOR DA3000 ANT11 for 30-2000 MHz, or the Diamond D130J ANT09 for more conventional 30-1300 MHz coverage.
Transmitting as well as receiving?
Full-Spectrum Antenna Looking for extremely wide frequency coverage in one antenna? The low-profile AOR SA-7000 ANT39 vertical covers 30 kHz through 2000 MHz to match the new breed of wide-spectrum receivers, and it does it well