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 The $4 Special Antenna by Joe Tyburczy, W1GFH (Used with his kind permission) Sure, you can find "all-band wire antennas" for sale in the back pages of Ham magazines costing $150 or more. But beware: Marconi spins in his grave every time a ham buys an aerial instead of building it. The plain and simple truth is that wire antennas for the HF bands were intended to be hand-made and not store-bought. Untold generations of intrepid Radio Hams have fashioned their own equipment out of spit and bailing wire. Do you think the spark-gap dudes of the 1920's just went out and bought ready-built G5RV's from HRO or AES? No way! They slapped together aerials out of bedsprings, chewing gum, and frozen cow poop. For them, every day was Field Day. I think that home-built antennas should be awarded 10 db of "honorary gain" simply by virtue of their ingenuity. And in this world of microprocessor controlled micro-rigs, constructing one may be your only chance to build something and actually see it work on the air. Think about it. RadioWorks, Alpha-Delta, MFJ, B&W, Van Gordon,
W9INN, and W7FG...nothing wrong with the wire antennas they sell. But
buying one is no substitute for "rolling your own". Don't be overawed by
their advertising rhetoric. You can make an antenna every bit as good as
theirs, and even better in many
cases. Just Do It Don't be intimidated by SWR, either. Your rig will not blow up and kill you. Most modern rigs will politely refuse to transmit into a really bad match. A perfect 1:1 SWR is for sissies, anyway. All *real* hams have conducted perfectly good QSO's at 3:1 (or more) at some time or another. You may be surprised to know that the vast majority of hams didn't fret about SWR until after WWII when coax cable and SWR meters ("SWR Bridges" as they were first known) became available on the commercial market. Before that time, you simply cut your antenna to frequency, loaded the transmitter final for best output according to the plate current meter, and that was that. I am a big fan of "balanced line" (twinlead, open wire line, etc.) vs. coax. By using balanced line and a tuner you can have one, single-element antenna that works well on all bands. You can't do that as easily with coax. The basic "W1GFH $4 SPECIAL" shown below is a variation on the type of versatile skyhook I've been using for years. Now at this point, some of you may be looking at the
diagram and muttering, "Jeez Joe, that's just a dipole fed with twinlead
and used with a tuner". Well of course it is. Virtually all antennas are
"di-poles" (i.e. "two sides") in some form or another. This one just
happens to be made from low-cost
materials. I won't go into the theory here, but trust me:
balanced feedline, properly used, does not "leak" RF and is less lossy
than coax. I've tried the commercial 450-ohm ladder line, but prefer
300-ohm TV twinlead, and the cheaper the better. Radio Shack TV twinlead
is ideal. Home Depot has some good stuff, too. Forget all the obsessive
junk about standing waves, impedance and velocity factor. What you really
need to concentrate on is getting an interesting set of antenna
insulators.  Hang It Up Back during the disco era when I first got on the
air, I got a pair of really cool antique pyrex antenna insulators
from a flea market table in Derry, NH for 25 cents each. They looked like
the kind Hiram Percy Maxim used in 1910, and seemed able to pull in exotic
DX all by themselves. The other day I found out that Radio Shack wants $5
apiece for insulators made from some kind of white plastic crap. So I
improvised my own by sawing up pieces of an acrylic adjusting rod from a
discarded miniblind. I think Hiram would've been proud of
me. Hang the center of the antenna from a tree limb, or
use a support as pictured. The exact height of the antenna's feedpoint is
not crucial. The higher, the better. 20 feet might be considered the
minimum. 60 feet is ideal. However, in the real world, 30-50 feet is
average. For the antenna wire itself, virtually anything will
work, but something close to #18 stranded/insulated is ideal. My favorite
stealth antenna material is magnet wire. You can dig this out of an old
transformer or even a busted loudspeaker's coil. This ultra-thin stuff is
truly INVISIBLE to neighbors and wives alike, and it'll handle 100 watts,
no sweat. If you need to keep a low profile, try it as a long longwire,
end-fed from your tuner's "wire" terminal. (Be sure and ground everything
in the shack like crazy) No trees in your yard? Use a sock filled with
sand for a weight and hurl the far end of the wire onto a NEIGHBORS roof
or tree. (I would advise doing this at night. If you are caught, claim you
are "trying out an old FARMERS ALMANAC recipe to keep bats away". People
universally hate bats, and love farmers) If you can't possibly scheme to
get your wire more than a dozen feet off the ground, try flinging a few
hundred feet of the magnet wire all around the yard in a big loop (find
out measurements in the ARRL Handbook or Google "80 meter loop antenna").
Loops can perform satisfactorily at low heights. And remember, don't fuss
too much about SWR. A little mismatch is good for you and builds
character. The ends of the antenna will be "hot" with RF, so it's a good idea to keep them out of reach of people and pets, say, at least 10 feet above ground. However the antenna will still function if you bring the ends down closer to the ground.  Love Your Tuner An antenna tuner with a balanced output (internal or external balun) is a must. Using one is a simple matter of adjusting capacitance and inductance for the lowest SWR on a given frequency. Always begin your adjustments at low power, increasing to full power only when you have a reasonable match. At first, you may think it's inconvenient and old-fashioned to manually tune your antenna every time you change frequency, but you soon discover the unique satisfaction of tweaking the variable caps and watching the reflected power dip lower as the received signals grow a bit louder in your receiver. It's "real radio". My first tuner was a 1980's wood-grain cabinet style
MFJ-941 I got at a swap meet for $15 a long time ago and featured an
internal balun and connections for balanced lines on the back. Make sure
YOUR tuner is an outboard manual type antenna tuner such as this, and not
an "automatic" or internal tuner that is a pushbutton feature on many
modern rigs. Because they must use small, light-duty components, these
built-in tuners are typically limited to handling mis-matches of 10:1. The
mis-matches YOUR feedline will be seeing can be as high as 100:1. But
don't worry. The he-man sized coils and air-variable caps in a typical
outboard tuner will handle it just
fine. Don't believe the folklore about MFJ tuners being
junk. It's true, they are cheaply made and their Quality Control is
spotty, but the majority of them work perfectly OK if they aren't abused.
So do old Dentron's, Drake, Vectronics, Nye Viking, etc. A link-coupled
balanced tuner arrangement like the Johnson Matchbox would be even better,
but use what you have. Or make one. Ham radio (unlike some other hobbies)
isn't a competition to see who can own the best or most expensive gear.
The idea is to get on the air with what you have or
can afford, enjoy your self making contacts, and as time and money
permits, try something
else. I had a 65ft. per leg version of this antenna working in Massachusetts, and it'd tune up on all bands 80-10. At my Burbank, California QTH, I used a 35 ft. per leg version, and it tuned up on 40-10. By the way, you'll notice it's an inverted vee --- a real advantage if you don't have room for a full-sized dipole in your yard. If you still don't have room, bend and angle the legs to fit the space you've got. Antennas gently bent into Z-shapes still work fine!
The uncut feedline comes straight in thru a clever window sash arrangement first used by hams in the 1920's. (See drawing below) Alternately, you can attach the wires to feed-through bushings (which can be anything from two steel bolts...to a pair of banana jacks end-to-end) set into holes in the wood sash or a glass pane (or a plexiglass panel). 300 ohm twinlead only needs about 2" separation from metal objects in its path. Unlike coax, its "gotta be free" -- don't coil it up, kink it, bury it, or lay it on the ground. Gently brushing against tree limbs or tied to non-conductive surfaces like wood or plastic is OK. The 100 watt output of most transceivers makes TV twinlead a safe and practical choice, but a number of hams have used it successfully with power ranges up to 1KW PEP. You can obtain or construct an external 4:1 balun to make the transition from your twinlead feedline to a short length of coax, then bring the coax into the house via a single feedthrough hole if you'd like. |
Ham
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