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By
Steve Katz WB2WIK
October 23, 2002
Overview
Antennas, antennas, antennas! They are our transducers to the ether, and are
what make our wireless equipment work. Yet, for various reasons, many hams seem
unconcerned about them.
Deed restrictions (CC&Rs) are probably a leading cause of hams having
poor antennas, although plain old apathy seems at least as big a problem. Budget
should never be the problem; since so many excellent antennas are available as
used items either very cheaply or free, and of course some great designs can be
homebrewed for almost nothing. And we find that often times, the ham with no
antenna had enough of a budget to buy a $1000 radio. Hmph.
This subject is too vast to address in a brief article, so I'll focus on a
single, popular design: HF Vertical Antennas. Even more specifically,
inexpensive HF vertical antennas, which are typically base-fed, trapped or
loaded designs requiring a counterpoise or image plane in order to function
properly. Among all the commercial designs on the market, the Hustler
4BTV-5BTV-6BTV are likely the best bang for the buck products currently out
there, although Butternut HF6V-HF9V, Hy-Gain 12AVQ-14AVQ-18VS and DX88, and
others can be good deals, too.
The products listed, and other popular commercial models, have one thing in
common: They are not ground-independent, and have no factory-supplied
counterpoise. They are trapped or loaded, base-fed antennas that not only work
better with radials, they work only with radials.
Any antenna can make contacts. Good ones make stronger, longer-distance
contacts more reliably. With a 100W transmitter and a good antenna, many of the
signal reports you receive should be `Wow, great signal - very, very strong, S9+
here.' If you don't commonly get such reports, you're definitely missing out on
a lot of stuff that could be worked, but you're not going to hear it, and it's
not going to hear you, either. A simple, inexpensive vertical antenna can
produce such reports, repeatedly. The difference between a vertical that does
get the `you're blowing me out of my chair' reports and one that doesn't is
simple deployment.
50 Million Frenchmen Can't Be Wrong
That's a really old phrase, and I'm not even sure where it started - but it
fits the situation. If you use modern antenna modeling software, you'll see that
any current-fed vertical fed at its base, which usually means it’s, or t image
plane, usually made from wire radials, in order to reduce its vertical angle of
radiation and reduce ground losses. When one installs such a vertical, say a
5BTV for example, on the ground without any radial system, it will generally
demonstrate a good impedance match (to 50 Ohm coax), and nice, smooth, low curve
plotting VSWR against frequency. That's a sure sign that it stinks.
In reality, this antenna should have a feedpoint impedance of about 30 Ohms
(VSWR = 1.7 or so), and have sharp, narrow resonance curves if you plot VSWR
against frequency. If the vertical has VSWR < 2.0 across the whole 40 meter
band, you've got a problem, because the antenna's incapable of that. What's
making the VSWR nice and low is ground loss, which appears in series with the
antenna current and directly reduces antenna efficiency (both transmitting and
receiving). My 6BTV is resonant at 7150 kHz, and VSWR climbs to about 3:1 at
7000 and 7300 kHz, which is about right. That's because my installation has very
little ground loss - and that's because I have radials that work.
How much difference does this really make? That's a really interesting
question, and although computer modeling shows the effects of radials with
regard to feedpoint impedance and radiation angle, it doesn't demonstrate the
real-world difference in what can be heard and worked. Simply using the antenna
with easily added or removed radials (using alligator clips to attach them) is
more demonstrative.
Having a battery-powered, portable HF receiver is very cool, if you're
experimenting with antennas. This is because you can bring the “rig” pretty
close to the antenna, and instantly assess whether a change you've made is for
the better, or not. I sometimes use my little Ten-Tec SCOUT for this, but any
short-wave receiver with an S-meter and an external antenna jack works. I also
have an MFJ-259B Antenna Analyzer, as do, evidently, thousands of others -
almost everybody I chat with seems to have one. It's a good investment.
Reality Check
Here's what I did, and have done many times. It's very interesting, and it
yields great results:
-First, I installed a 6BTV vertical on my lawn, in the back yard, on a 4 feet
long, 1-1/2 inch diameter pipe driven into the ground. That leaves about 3' of
mast remaining above the ground, and is exactly what the Hustler assembly
instructions recommend for a “no radial” installation. (In my opinion, Hustler
makes good vertical antennas and gives lousy advice. Under no conditions should
these antennas be used without radials, if you want to work DX.)
-I connect a short piece (about six feet) of coax to the feedpoint, and using
the MFJ-259B, plot impedance data (R+jX or R-jX) vs. frequency across all bands,
80-40-30-20-15-10 meters (which is all this particular antenna covers).
-Then, I roll out four 32' long insulated wire radials, tying off the ends
with plastic insulators and string to support them in position so they are laid
out like sloping spokes of a wheel, spaced about 90 degrees apart from each
other. I line the radials up so they can all be connected to the base of the
antenna (aluminum mounting bracket), and install an alligator clip at the
“antenna” end of each radial, so they can be quickly connected, or disconnected.
I clip the radials to the antenna-mounting bracket. (The radials slope gently
away from the base of the antenna, towards the ground, but never actually touch
the ground. This is an important note.)
-Next, I tune through the 40-meter band once again, using the MFJ-259B, and
once again plotting impedance vs. frequency. Note the curve is much sharper,
now, although the resonant frequency (where X = 0) usually doesn't change much.
Also, the R is now lower.
-Then, I disconnect the MFJ-259B and replace it with the HF receiver, tuned
to 7335 kHz. That's a “beacon” signal, so to speak, generated by station CHU in
Ottawa, Ontario, almost exactly 3000 miles from my home. It's weak during the
day, and strong at night, but can almost always be heard unless there's been a
huge solar flare or other incident that just wipes out the ionosphere. I tune in
CHU, and note the S-meter reading.
-Next, I disconnect the radials by unclipping them from the antenna base. If
I can still hear CHU, I log its signal strength. Note, often times,
disconnecting the radials causes me to lose the CHU signal altogether, making
this test rather dramatic. On a typical evening, around gray line when CHU
starts `pounding in' at S9+, disconnecting the radials can cause the signal
strength to drop almost into the noise - a 9 S-unit change. Umm, how many dB is
that? A lot. I re-connect the radials by clipping them back on to the antenna
base bracket.
-Reconnecting the MFJ-259B, I tune it to 7150 kHz and observe the indication,
then walk around in a circle, making each radial 2' longer, by clipping another
2' length of wire (Radio Shack clip lead) onto the end of each one. I go back to
the MFJ-259B and observe the indication. Quite a difference! Resonant frequency
of the antenna has dropped from 7150 kHz to 6940 kHz, completely out of the
band! Well, that's about right. This verifies that the radials are tuning the
antenna, and capable of changing its resonance, and the proportion change is
about correct for the radial length change. Golly, does this mean that the
radials are, quite literally, half the antenna? You bet it does.
I unclip the extra 2' long leads, which were an experiment only to verify
that the radials were affecting resonance. Now, I roll out four insulated
radials cut to 16-1/2' long each, and perform the same set of tests on 20
meters, again using the MFJ-259B, but this time using the WWV signal at 15.000
MHz as the test beacon. This is impressive, but since I only live about 850
miles from WWV, this reception test is not a good indicator of `low angle'
antenna performance: Even a very high-angle antenna will hear WWV quite well
here. So, if possible, I do this test between 4:00 and 6:00pm local time during
a weekday, when the ARRL CW practice and bulletins are broadcast on 14.047 MHz.
The W1AW signal is strong and steady, and there for nearly two hours, so this
gives me plenty of time to experiment. And, W1AW is nearly 2700 miles from me,
so it's a better `low angle' signal.
-Note the differences, once again, using the MFJ-259B and the beacon signal
received, this time using 20 meters. Holy cow. W1AW is S9+30 with the radials,
and only S6 without them. How could that be? Of course it can be. The radials
bring down the antenna's vertical angle of radiation (and also reception) to a
useful angle for W1AW's signal. That means, the angle should now be low enough
for working DX, too.
Try it. It's quite a test, and if you haven't actually performed a test just
like this, you're doing your vertical quite a disservice.
Real Life
I couldn't leave my 6BTV mounted to a pipe on the lawn, in the back yard. The
radials would eventually get tripped over and mowed down. Kids, dogs and other
organisms would cause the demise of the whole system in pretty short order,
here. Plus, even though I don't mind the way antennas look, this installation
was pretty ugly, even to me. I scanned the horizon and found a better place: The
roof of the house.
My personal solution was to install an 8' tall Glen Martin Engineering
4-legged roof tower at the peak of the roof of our single-story home; although,
frankly, a cheap 3' Radio Shack tripod probably would have sufficed. I used the
stronger GME roof tower to provide for the future, when I might want to put
something larger and heavier up there. Then, I made multi-band radials using
combinations of heavy-duty 300 Ohm twin lead and other conductors, until I had
two radials for 80m; four radials for 40m; two radials for 30m; four radials for
20m; and four radials for 10m. I don't have separate 15m radials because the
quarter-wavelength radials for 40m seem to work well as three-quarter-wavelength
radials on 15m. (I did try, with and without separate 15m radials, and even as
nitpicky as I am, could hardly tell any difference.)
Photo B: Close-up view of the 6BTV base
connections, viewed looking up from the roof. I used the `radial attachment
point' mounting holes in the horizontal part of the 6BTV aluminum base bracket
assembly, as well as additional holes in the vertical part of the same bracket.
Here you can see what appears to be nine (9) terminals making radial wire
connections; in reality, those nine terminals are carrying 16 total conductors.
So, my current system has 16 radials, four per band for
40-20-10m, and two per band for 80-30m. This isn't ideal, but works pretty well
and doesn't look too crazy up there on the roof. (I did, at one time, have 24
radials on the same vertical. I took eight down, selectively, and now have the
`minimum' configuration that actually works.) My current radial system uses 405
feet of insulated wire. At about $.12/foot, that's a $48.60 investment to make a
$200 vertical antenna actually work properly. A very wise investment, indeed.
Of course, I encourage others to scrounge, and it should be possible to come
up with radial wire that costs absolutely nothing!
Alternative
For those having sufficient real estate to effectively ground-mount such a
vertical, I've found the proper way to do this is to sink the base of the
vertical nearly to earth, e.g., have the feedpoint within a few inches of the
ground, and use lots and lots of wire radials either laying on, or buried
beneath (doesn't matter) the soil. In this situation, the radials need not be
resonant, but merely need to be plentiful.
Experimenting several years ago with a very large piece of property in
upstate New York, and feeding a vertical against a ground-mounted radial field,
I found the first few radials did virtually nothing. The next few helped. The
next few helped more. And so it went, until we reached about 64 radials. After
that, adding more radials didn't have much effect. In our case, we used VSWR
measurement as an indication of whether the radials were actually doing their
job: After about 64 radials, adding more hardly changed the antenna feedpoint
impedance, indicating that we probably had enough.
Using that particular vertical, we could work global DX on 160 meters, which
was the idea. Without the radial field, we couldn't hear any global DX, so it
wouldn't matter if they heard us, or not.
I've found, both experimentally and also by researching others' data, that a
lot of wire radials 20' long each is sufficient for amateur-band work with a
ground-mounted vertical. 64 such radials would be 1280 feet of wire. I can buy a
50 lb. spool of #14 ga copper wire for about $100, and such a spool contains
3160' of wire. Thus, 1280' is about $40.50 worth. Not bad.
Summary
I have a tower and beams, too. But the vertical is a great go-to antenna, for
when the beam's aimed the wrong way, or for use in a `round table' QSO. And I
currently have no beams for 30-40-80 meters, so this vertical, and one or two
simple wire doublets, is all I have. The vertical almost always outperforms any
sort of doublet: G5RV, Windom, dipole - whatever - when working DX. Last night
(August 7, 2002), I worked A71MA in Qatar `first call' on 20-meter phone, using
the vertical and a barefoot TS850S. That's not `works great,' that's getting
through on the first call, in a small pileup of perhaps 3-4 dozen stations I
could hear calling Mohammad. With a vertical. and 100 Watts. And, oh yes: He did
give me a `59+, very strong signal' report. I know he meant it, since he gave
others `56,' `57' and `58' reports, right after me.
Photo C: Here is a close-up side view of the 6BTV base and some of the
radial wires and attachments. I use Scotch 88 electrical tape to securely attach
all the insulated radial wires to the 2-inch diameter support pipe below the
antenna's base, so the tape, rather than the lug terminals supports the
mechanical strain of the wires. The lugs and attachments last much longer this
way.
(In the background, a bit of my tower can be seen - it's about 50 feet
away.)
Radials. They make verticals really work.
WB2WIK/6
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20 dB for $48.60 |
By KV7X on October 23, 2002 |
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A timely article, since I am installing a 4-BTV
this weekend. I won't be putting mine on the roof so will follow your advice on
the ground radials. Hustler recommends 14-ga wires for the radials - any
thoughts on the importance of wire gauge for a ground-mounted installation?
Also, what are your thoughts on the importance of a 1:1 isolation transformer
between the antenna & feed line? Hustler suggests 10 turns of coax on a 6"
diameter form. Thanks.
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20 dB for $48.60
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By KG6AMW on October 23, 2002
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Hi Steve. Very interesting and informative. The
photos really help to understand. I came to the assumption months ago, that
radials are key to performance. The other variable is antenna location, having
the antenna up and away from houses and other metal objects that may hurt
performance. You didn't comment on ground independent verticals like GAP and the
Force 12 Sigma series. How would you rate the ground independent vertical
against a vertical with radials? I would assume they would perform about the
same. Thanks for the well-written article.
Merrill
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RE: 20 dB for $48.60
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By KC8SBV on October 23, 2002
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Great article! Timely as well. Going to put up a
4BTV soon. Question on long radials that cannot be run straight on the roof: The
instructions from Hustler show placing the radial in an L, straight from the
antenna to the edge of the roof, then turn 90 and follow edge and attach to
roof. Any thoughts on this? Also your "multi-band radials" made out of 300-ohm
twin lead: Was one lead cut for a different band than the other?
TNX ES 73,
Ed kc8sbv
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20 dB for $48.60
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By WB2WIK on October 23, 2002
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I recommend using radial wires that are strong
enough and won't break! I'm sure Hustler recommends #14AWG because thinner
gauges, if pure copper, are too weak to survive the application (like walking on
them). If your radials will be installed such that it would be impossible to
ever walk on or trip over them, smaller gauge wires will work fine.
Re the "coaxial choke balun" discussed as a 1:1
transformer, I've never found the need, with a matched antenna. The 1/4-wave
vertical discussed is not balanced, it's unbalanced, just like its feed-line,
and so a balun is not indicated. A choke would be helpful to reduce line
radiation during mismatch conditions, but I don't use the antenna under mismatch
conditions, as that's a great way to blow a trap. I don't use the choke balun,
although I cannot imagine it could hurt anything.
Re the GAP and F-12 verticals, they're quite
different animals and I've found the ones I've used (various models from GAP and
F-12) work well, but they are substantially more expensive than the simple 6BTV.
This was a "For less than $50 you can really make your $195 vertical work"
article. For those who don't mind spending $300+ (in some cases, a lot "+") for
a ground-independent vertical, often times the whole radial requirement goes
away.
Re radials "L" shaped, this is surely better than
not using them. I'd do it, if faced with the space limitation.
Re the twin lead radials, this is something I've
done for many years, and it's not so simple. The proximity of the parallel
conductors changes resonant length, so without a dip meter or some other way to
"tune" the radials to the correct electrical length, I wouldn't use the twin
lead approach at all -- I'm just used to it, and do have a good grid dip meter.
WB2WIK/6
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20 dB for $48.60
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By ZS1DX on October 23, 2002
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Thanks for a great article Steve.
I picked up a used 4BTV for 25US$. It is mounted on
top of my house. The metal roof serves as ground plane. I joined many of the
metal sheets together on the inside with coax braid, and connected it to the
antenna ground. This system works well, and I regularly get 59 reports from all
over the world.
But it is no mono-bander at 100" HI. I can
recommend Steve's setup 100%.
73, Chris ZS1DX
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20 dB for $48.60
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By N9BDF on October 23, 2002
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Steve,
I agree with everything you have said. And, any
good book on antennas (like the ARRL Antenna Book) will also support what you
have said. The bottom line is that verticals are viable HF antennas IF you use
an appropriate ground radial SYSTEM with them.
Your experiments with and without the ground radial
system demonstrate just how much of a difference an appropriate ground radial
system makes.
73, Michael N9BDF
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RE: 20 dB for $48.60
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By W0FM on October 23, 2002 |
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Great article Steve. I always said that my 6BTV
"worked just fine" without the radials because of the great soil conductivity we
have in my area. (And in contests, EVERYONE is 5-9). With your efforts in "A/B"
testing you've proven that those of us who subscribe to that theory (maybe even
Hustler) are only fooling ourselves.
I had convinced myself that, if I made contacts, I
was doing OK. Fact is, I didn't know what I was missing because I had never
taken the time to do the tests that you did.
I can't imagine using a Yagi with all the left side
elements cut off. Why would I use half a vertical? You've made a believer out of
me.
73,
Terry, WØFM
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RE: 20 dB for $48.60
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By WB2WIK on October 23, 2002
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Hi Terry (W0FM),
Thanks.
BTW, I don't know what you're using on 12m, but I
heard you work ZL7C Chatham Is. on 24 MHz CW the other night, and your sig was
the one that alerted me he was on the band.
I worked him right after you!
73,
Steve WB2WIK/6
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20 dB for $48.60
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By NI0C on October 23, 2002
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Good jobs, Steve, of consolidating in one place
much of the practical advice you have provided to so many hams regarding
vertical antennas. "Our transducers to the ether" -- so true and yet poetic--
well said! And thanks for the paragraph concerning your experience with adding
(and adding and adding) radials to a ground-mounted vertical. So far, I've
managed to string 20 radials ranging in length from 30 ft. to 90 ft. at the base
of my Butternut HF-2V (some of them had to be bent in order to stay within the
property line). However, as long as there's wire left on the spool I don't think
I'll be satisfied.
73,
Chuck NI0C
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20 dB for $48.60
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By VE7LFN on October 23, 2002
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Good article!
I am just putting together a homemade vertical and
have been doing a bit of research. Folks might want to check out the "Tech
Notes" at http://www.bencher.com/pdf_download.html
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RE: 20 dB for $48.60
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By WB2WIK on October 23, 2002
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I've read all the notes at the Bencher/Butternut
website since they've been posted there, and while they're interesting reading,
they, too, contain misconceptions.
It's interesting that the Bencher "Dirty Little
Secrets," "Tech Notes" and "Why Radials?" publications are neither credited nor
annotated, and seem simply to target the "half-wave, ground-independent"
vertical products as poor performers; but many are actually excellent
performers, and they're getting better all the time.
My article didn't focus on these, at all, but for
those who have the budget and the space, some of the GAP, Cushcraft, Hy-Gain and
Force-12 "ground independent" products are great. The F-12 top & bottom
loaded, conjugate-matched products like the Sigma-5 are revolutionary.
WB2WIK/6
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20 dB for $48.60
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By K5YY on October 23, 2002
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I have been around as a ham since 1957 and before
that an SWL. Steve's article is simple to understand and just what we need to
read once in a while on antenna theory and design. Most major points about
verticals were touched on and actual "on air" results recorded. Nice job of
putting theory and actual results down on paper in simple terms. My DXpedition
experiences have proven that even ONE insulated wire cut to resonance for each
band in use, laid on the ground and held down with a concrete block at the end
will improve performance. If you can elevate the radials and feedpoint 4-6 feet
the results are even better. If one uses a "bare wire" radial system on the
ground, you need several, as Steve said. If in doubt or using small number of
radials, go insulated route for a little more money. Also, slightly larger
radial wire works better overall. In simplest of terms, use your vertical
elevated 6 feet with one radial per band and you are going to work a lot of low
angle contacts. If you go to 4 radials per band (elevated) you will have better
current return, slightly changed resonant frequency. If you go ground mounted,
be prepared for a LOT of radial work, preferably insulated wire and many
headaches! Good job , Steve. San K5YY |
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20 dB for $48.60
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By WA7NDD on October 23, 2002
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I took 3 weeks to install my elevated 6BTV and
lots of pictures. It is mounted a few inches above a steel roof, and tuned
radials to the east side for all bands. The vertical was designed to tilt over
for tuning. I never had to remove it from the mast to tune. The radials were
designed for quick release, for tilt over but yet a solid connection. I also
installed an isolator at the base of the vertical from Radio Works and one in
the shack. The 6BTV has been up for about two months and works DX very will. For
really long hall DX the vertical is about 2db better then my dipoles, which are
separate, cut and tuned for 80,40,20, and 10 meters. The dipole is quite
compared to the vertical, but the vertical is hearing 360 degrees. A big secret
I use is the Clear Speech base unit with my FT-920. I like it better then the
920's DSP noise reduction. Turn it on, noise goes away, and singles pop out. On
side band the voices sound a little like talking through water with weak
signals, but I could not have heard them through the noise before at all. The
Hustler 6BTV is a good price for what I received. I like it very much. My 6BTV
is tuned on all bands, very narrow on 80, so I set it in the DX slot. If anyone
is interested in pictures I can Email them, and my SWR chart that I have since
redone by some more tuning, but you will get an idea.
Jim,WA7NDD
griffithj@byui.edu
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20 dB for $48.60
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By KA5S on October 23, 2002
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Good article! Back in the 1970's, while stationed
at Fort Hood, Texas, I put up a ground-mounted Hustler 4BTV. My _mobile_ worked
better. It took 48 radials before the 4BTV worked as well as a mobile antenna on
my van. Of course, "ground" there was ninety percent limestone -- laterite is no
ground at all! But at least it gripped the mounting stake; I had to pound that
into the dirt when I was transferred. It sure wouldn't come out.
Cortland, KA5S
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RE: 20 dB for $48.60
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By NZ5L on October 23, 2002
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Isn't 20 Db exaggerating things a bit? Actually,
past articles along this line made more modest claims - 3 to 6 Db. That having
been said, I enjoyed the article. Most hams don't realize the importance
(necessity, really) of a good counterpoise for a vertical antenna. Several years
ago my set-up was an HF6V, roof mounted on a 3' Radio Shack tripod with 2 sets
of Butternut Stub-Tuned Radials. Signal wise, it was awfully close to the
Cushcraft A4 at 27' (no F/B of course) and a whole lot easier to maintain. At
XYL's insistence ("Please take that giant spider off the roof") I switched to a
GAP Titan. What genuinely surprised me was that my STR kit evinced absolutely no
interest at the local 'fest! Articles like this may help folks become aware of
just how important the ground is in radio communications. Keep up the good work!
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RE: 20 dB for $48.60
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By KL7IPV on October 24, 2002
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Good article, Steve. There is another way to get
the radials you need. Find, buy, or borrow a piece of 26 pair, any gauge
telephone cable about 36 feet long. Strip about 2 inches from one end and make
all the wires bare and twist them together. The 2 inches of bare wire will be
attached to the grounded base of the antenna in whatever fashion works for you.
Leave about 8 inches of outside sheath on the cable and remove all the rest of
the remaining 35+ feet of covering. Leave each of the longer exposed wire
insulated. Separate each of the paired wires and then fan them around the
antenna. It they are fanned around a roof, trim them even with the roof edges.
The wires should provide almost a metal ground plane to that antenna. The
longest wire left should be trimmed to match the portion of the 40-meter band
that interests you. Trimming the rest for each band should give an approximate
match for all the remaining bands of the 5BTV/6BTV antenna. Cheap and it works.
The 8 inches of cable sheath will allow you to fasten that to the
antenna-mounting pipe.
73
Frank
KL7IPV
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20 dB for $48.60
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By NX5W on October 24, 2002
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Good Morning, Gentlemen, Try this one out, "Dirty
Little Secrets" from the "Antenna Designers Notebook". Or www.bencher.com. or
"AC6V.com" and type in "Dirty Little Secrets". By the way go also to reviews on
Butternut HF6V's here at eham.net, look at what "KB5QNO" my previous call sign,
had to say about these antennas. 3000 sq. ft. of a sheet Iron Roof, doesn’t do
too bad either, when you have the whole roof grounded any way. I have had this
HF6V up in 5 different locations, all I do is put some "Noalox" ( Get this at
Home Depot ) on the connections about every 2-3 years. This antenna has a 75 ohm
11' 6" tune stub on it, and a barrel connector to your 50-ohm lead. She sure
works Great! After having it for 12 years. I guess I better go catch that guy
out of Tel-Aviv. I might just use this HF6V instead of my monobander. Ya'll keep
on sittin' around now, ya hear? Just Kidding!
73's, Darryl
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RE: 20 dB for $48.60
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By WB2WIK on October 24, 2002
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NZ5L, 20 dB isn't exaggerating in the slightest.
I actually see far more difference than that,
typically, on low-angle signals (3000+ miles), if I disconnect the radial system
on my vertical.
As stated in the article, CHU on 7335 kHz at 0000
UTC is 20dB/S9 here this time of year. If I remove my 40m radials, it literally
drops to the noise level. That's a lot more than 20 dB.
WB2WIK/6
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RE: 20 dB for $48.60
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By WA2KWP on October 24, 2002
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Hi Steve,
You have been very careful not to use the word
"gain" in any of your comments. What you have described is an improvement in
performance in a vertical antenna equivalent to 20db in signal strength
received. Actually and unfortunately a vertical antenna works equally poorly in
all directions with a "gain" of nothing. So if you want to get all you can in
terms of performance out of the vertical that is a great idea, but you will get
no gain, unless you use two, three or four verticals and feed them in and out of
phase. (See the excellent series of articles on vertical antennas by Jerry
Sevick, written about 30 years ago in QST)
I was forced to use a vertical antenna at my QTH in
New York City. Fortunately luck came into play. The antenna is mounted 35
stories above the ground and the roof is solid sheet copper (a common roofing
material on tall buildings in New York City). The roof is "grounded" to the
Water Tank Piping system (the water tank itself is wood!!). I was the first in
every pileup until I lost permission to use the installation (The landlord is a
Neanderthal).
Thanks for an informative point of view!!!
David
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20 dB for $48.60
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By W6TH on October 24, 2002
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Someone wanted to know the gain of Steve's
antenna roof mounted. The gain is approximately 2,736 dbi with a low angle or
radiation plus an additional 3 db for ground reflections, for a total of 5+db
gain. A beam would have to be up 3/4 wavelength with 3 elements to equal this.
Steve achieved the proper match by running the radials 45 degrees for a 50-ohm
match.
I may add that the mounted post should be down 4
feet and 18 inches above ground for proper ground mounting the 4, 5, or 6BTV.
Nice work Steve, sounds like you are talking about
my Hustler.
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RE: 20 dB for $48.60
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By W4AN on October 24, 2002
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Re: W6TH
In my tests with a ground-mounted vertical with
excellent ground system (i.e., 60+ radials) on 20 meters... a dipole up 40 feet
was always as good and mostly better than the vertical. Don't kid yourself in to
thinking that an all band vertical will be better than a dipole. Unless you live
next to salt water.
I'm currently in the process of laying more than 60
radials per vertical under my now raised radial 4-square for 80M. It is a lot of
work, but I'm sure it will pay off. FWIW, W8JI beats me by 1 s-unit or better to
Europe with his flat top dipole at 140'. That is equiv to 70' on 40M or 35' on
20M. And, this is a full sized system, which provides gain (phased verticals).
73
Bill
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20 dB for $48.60
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By W6TH on October 25, 2002
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Hello Bill, w4an,
Steve wb2wik/6 was mostly interested in the
comparison of more costly vertical antennas then the Hustler 4, 5, or 6 Band
trap vertical. He chose to install and demonstrate a test of the Hustler antenna
and the means to install the antenna with radials and how the radials do perform
to improve the radiation efficiency and performance of this particular vertical
antenna. Which by the way has done a magnificent job in the explanation of this
particular vertical.
My point of view was to say that for a certain
angle of radiation will also be less costly as to installing a tower, rotator,
guy wires, concrete, etc.
Many Amateurs of today do not have the finances,
property etc., to go the full extent. Therefore a vertical antenna with radials
may be just what the doctor ordered.
73, Vito W6th
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RE: 20 dB for $48.60
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By K9KJM on October 25, 2002
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My .02 cents worth...... Great article! The
bottom line is: 3 or 4 TUNED elevated radials will make your vertical work. Once
the radials come in close contact with the earth, they are no longer "tuned"
(Even a slight difference in soil moisture can detune) And MANY more radials are
required for the same "performance" The only point I want to make is, If you
(like me) can not have a bunch of "elevated" wire 6-10 feet above the ground all
over the yard, and must bury, Use BARE copper wire (No reason for insulated, as
close proximity to earth detunes anyhow) And use a heavy enough gauge close to
the tower mast that it will ALSO be an addition to your lightning protection
ground. When the soil is moist after a rainfall, take a shovel and just "lay"
the sod back, insert the radial wire in the slit, and "stomp" the sod back. It
is easy to do over 100 feet an hour in normal soil. As others have indicated,
They do not need to all be in a perfect straight line. I have been burying
copper wire for many many years now, and is seems the more I get in, the better
things seem to work. |
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RE: 20 dB for $48.60
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By WB2WIK on October 25, 2002
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Interesting observations, Bill (W4AN) but very
much in conflict with my experience here.
In addition to the 6BTV on the roof tower with the
sloping radials shown, I have the option of two 20m beams, and usually use the
Tennadyne LPDA at 55', which is 15' higher than the 20m dipole you discussed and
surely better than a dipole...and on many paths, the vertical will outperform
the LPDA (or the 203BA), just depends on the path, and the propagation at the
moment.
I could never say, at my location, that a 40' high
dipole would consistently outperform the vertical on low-angle paths. It just
doesn't, at least not here.
However, my vertical is not ground mounted, it's
elevated and has its feedpoint sitting about 28' above ground. I agree this
seems to work better than the same vertical ground-mounted with _any_ quantity
of radials -- I've tried that and was disappointed.
As I'm sure you know, one can never have too many
antennas and the more antennas you have per band, the longer that band works. At
the contest station I usually operate, K2XR in NJ (#7 in the Top Ten ARRL Phone
'02, results just published in Nov QST), we have about 15 beams up and it's
definitely not enough -- all our 20m antennas are too high for the short paths
into the Caribbean and western EU, and we get clobbered there.
Time for more aluminum.
73 de Steve, WB2WIK/6
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RE: 20 dB for $48.60
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By KC8SBV on October 25, 2002
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Steve,
Did you resonate your radials on the roof in the
installed position? It seems to me to be the only way to insure that the
installation doesn't change the resonate freq.
Thanks,
Ed
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20 dB for $48.60
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By K3ZD on October 25, 2002
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A fine article but why not just put up a dipole?
They are more efficient than verticals and horizontal polarization is better
anyway because it is not so ground dependent.
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RE: 20 dB for $48.60
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By WB2WIK on October 25, 2002
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Ed: Yes, of course I did. I use the MFJ-259B to
tune the radials as part of the "system," and it goes very quickly. The
older-fashioned way works, too, but takes longer!
Re the "dipole," I have dipoles. No dipole works as
well as a properly deployed vertical for low-angle DX, and mine are no
exception, but they occupy worthwhile positions on my antenna switch
nonetheless. I also have a tower and three beams, and use them, too (as shown in
one of the photographs). You can never have too many antennas, but I would not
want to be without one good vertical in the arsenal.
WB2WIK/6
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20 dB for $48.60
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By K3DML on October 25, 2002
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Super article. Another wonderful solution to a
good and cheap low angle DX antenna is a full wave square loop fed in the center
of a VERTICAL side.
I can't mount a vertical on my roof but am
considering suspending one from a very tall tree and adding elevated radials
about 10' above the ground. Any thoughts on whether this is a lousy idea?
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20 dB for $48.60
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by N4ZOU on October 26, 2002
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I use the aluminum electric fence wire for
radials under a Butternut HF2V vertical. A 1/4-mile roll runs about $14 and is
available at any building or hardware supply store. As the wire is a silver
color it's very hard to see when it's mounted above ground. Don't use it for in
the ground radials, the soil will "eat" it quickly. While your looking at the
wire check out the nice selection insulators available for use with the wire. I
love the nail up insulators for stringing out 1/4-wave 160-meter radials through
the trees. |
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20 dB for $48.60
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By K2UOD on October 26, 2002 |
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I have spent the last year experimenting with a
ground-mounted 6BVT. The first installation was in an area with 6" of topsoil
and then clay. I mounted the antenna on a 4' pipe with about 2'6" buried, no
radials. It worked fine across all bands, with good success on DX.
In March, I moved the antenna to the Adirondacks.
Digging through the 3 - 5' of snow, I erected the vertical without radials. It
worked fine on 40, 20, 15 and 10. The best SWR on 40 was about 2:1, with a
usable bandwidth of about 40 KHZ. (I use a Kenwood TS830s w/o a tuner-- as long
as I can tune the finals and the SWR isn't to high, I'm OK).
As we got into Spring - Summer, the antenna's
performance and my ability to get a match dropped dramatically. The soil is
essentially pure sand and we had an extremely dry year. Performance would
improve after a soaking rain.
I started to add radials-- cut to resonant
frequencies as suggested by Hustler. My approach was to use insulated two-lead
AC power cord wire, with each lead cut to a different band-- two for each band.
Performance improved dramatically. I laid the radials on the ground (the ground
cover was brown, and we don't mow--so to me I was golden-- then the XYL saw the
radial snaking though her flower bed.) I then read (probably on this board) that
cutting to resonance was not essential for ground mounted antenna radials. So I
added about 8 more radials, cut for 40m (CW portion). Overall performance of the
antenna improved dramatically. I then buried the radials.
SWR is 1:1 on 10-15 and 20. I cannot get 30 to
tune. SWR on 40 is below 2:1 in the CW portion; off the charts on 7.255 (I have
since added a 40 meter dipole for regional phone use).
I am pleased with this setup. I may be adding
another vertical at the original location-- If I do, it will be the 4BVT-- with
radials!
73,
Keith, K2UOD
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RE: 20 dB for $48.60
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By K2WH on October 27, 2002
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Great article! Steve and absolutely correct. I
don't know how many times I have tried to convince hams of the necessity of
radials. Their reply "But the add says you don't need them". Anyway, I built a
monoband 1/4 wave vertical for 80 meters with 52 radials on the ground. Works
wonderfully. Got WAC on 80, WAS on 80 and almost there on DXCC on 80. Radials -
can't live without em.
K2WH
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RE: 20 dB for $48.60
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By ZC4BS on October 27, 2002
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What an excellent article - I'm over the moon
reading this and other comments.
Having just purchased a 5BTV and awaiting the
roofers to sort out the soffets and fascia boards I will be putting it up.
After reading this I realized just how much I had
forgotten/didn't know, so thank you Steve for the "wakeup call" lol
I am not fortunate enough to have the antenna
raised as my neighbors would have a sense of humo(u)r failure. But a 5' pole
buried 4' deep seems to be the best solution - and of course as many "un-tuned"
radials I can muster!!!
Thanks once again Steve - it was a pleasure
reading.
Steve ZC4BS ZC40BS G4KIV
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20 dB for $48.60
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By W3DCG on October 27, 2002
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Thanks for this, Steve... you're turning into nearly an Elmer
for me at this point, you answered a question re CCRs, PB & J, and BLT I had
a while back and then you do this article.
Complete with pictures. You know, at least for me, pictures are
worth a thousand words at least. I would have gotten the whole gist with the
picture and your statement of:
Four radials per band except for 2 per band 30 & 80.
The reason why it almost seems like you're becoming some sort of
Elmer is that, the evening before this article posted, I received my used 5btv I
got for a fair deal.
Before I can even open the box here is this article.
Awesome timing at least for me, thanks for the info-
73 w3dcg.
These are the life's coincidences that lead me to calling you
something of an oracle. And it did turn out that my "Windom" really is just an
OCF low dipole, too! Ha! And so I have succumbed to the pressure of low angle
radiation, and am going to give a vertical a whirl, despite all the hype of it's
inefficiency compared to a dipole. My dipole height is maxed, at 35 feet.
TTFN.
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GP radials, how many?
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By W3DCG on October 27, 2002
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Thanks for this, Steve... you're turning into nearly an elmer
for me at this point, you answered a question re CCRs, PB & J, and BLT I had
a while back and then you do this article.
Complete with pictures. You know, at least for me, pictures are
worth a thousand words at least. I would have gotten the whole gist with the
picture and your statement of:
Four radials per band except for 2 per band 30 & 80.
The reason why it almost seems like you're becoming some sort of
Elmer is that, the evening before this article posted, I received my used 5btv I
got for a fair deal.
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RE: GP radials, how many?
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By WB2WIK on October 28, 2002 |
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K3DML: It's not crazy to hang a vertical from a tree and attach
sloping radials to its feed point hanging 10 feet above ground. I've seen others
do this, and the same setup has been the subject of a few good QST articles.
Seems to work just fine, provided the radials don't strangle anybody!
K2UOD: If your 6BTV as you described won't load up on 30 meters,
either you've got the length of tubing between the 20m and 30m traps set
incorrectly or you've got a malfunctioning 30m trap. Since 30m is a very narrow
band (50 kHz total bandwidth), the 30m tuning on the 6BTV is very critical -- if
you miss the dimension by 1/4", it will resonate out of the band. If you can
reach that section of tubing, try making an adjustment. If you adjust it and
cannot achieve resonance in 30m no matter what you do, chances are the 30m trap
is damaged. The Hustler traps are easy to damage because the aluminum "cover" is
actually the trap capacitor. Any dents or dings in the covers can grossly throw
off the trap tuning.
WB2WIK/6
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RE: GP radials, how many?
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By WB2WIK on October 28, 2002
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W3DCG, the word "inefficiency" is really misplaced when
describing most antennas, and most all vertical antennas.
Energy applied to an antenna must be radiated or dissipated, or
converted to light, sound or motion, which I don't think any antenna can do. So,
it's pretty much radiated or dissipated. If it's dissipated, the energy is
converted to heat. How hot does your antenna get? Mine don't even get slightly
warm, no matter how much power I run (even 1500 Watts RMS), so I think the
"dissipation" thing is out.
The energy is radiated -- virtually all of it. Thus, most
antennas, and surely the kinds discussed here, are nearly 100% efficient. The
difference between an "efficient" 1/2-wave antenna and an "inefficient" 1/2-wave
antenna is found in positive signal reinforcement created by ground reflection,
or pattern arrangement, which can be altered, by design and deployment.
This article focused on proper deployment only; there are lots of
other variables. But I think most all antennas not containing resistors (and
some do!) are close to 100% efficient.
WB2WIK/6 |
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. Samir Popaja
7S7V (SM7VZX)
Malmö
Sweden
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