Antennas currently in use at VA7ST
antenna farm: Figured I should provide an update on which
antennas are currently in use, as they do tend to be changed from
time to time. Right now I am using the following:
17M, 15M, 12M, 10M -- SteppIR
3-element yagi on a 47' crankup tower
-- SteppIR 30M/40M dipole
-- Hybrid 2-element: SteppIR
40M dipole + fixed wire element
-- twin half-square array (EU/ZL)
-- twin elevated verticals, switchable
East or West (US/JA)
-- Inverted-L, 70' vert., 65' horiz. sloping 30 degrees, due East
80M -- 260' long Beverage,
unterminated, hears East and West. It's fed with RG58 coax, and
uses a small transformer at the feedpoint, wound on a binocular
core BN-73-202 toroid.
advantage in the terrain
SteppIR yagi is usually at 25 to 30 feet in height (tower cranked
down) but can be cranked up to 47 feet. When I point toward Europe,
the antenna performs as well as -- and in some cases better
than -- an identical antenna on a 120' tower, due to beneficial
surrounding terrain that drops off sharply in that direction.
I said 45' here compares favorably to 120' on a flat landscape (say,
prairie country), if you believe in terrain advantages.
benefits are found when working Africa, Canada, the U.S., and South
America. In fact, working Canada and the U.S., I no longer crank
up the tower and still get great results due to the higher take-off
angle combined with the much lower far-field topography at this
the terrain analysis
choke for a tribander -- random or solenoid winding?
I was plagued by odd SWR issues with my Mosley Classic-33 for a
couple of years, ever since installing a randomly-wound coax choke
at the feedpoint.
included working a lot of stations off the back of the beam -- for
example, working W4s while beaming Asia, or working W6s while beaming
when using higher power -- say 600 watts or more on RTTY or high-rate
CW -- the amplifier would occasionally reduce its output (plate
current would rise and output power would fall) and SWR would shift
a bit. If I stopped transmitting or lowered power for a while, everything
returned to normal.
was using about 8 turns of RG213 taped together in a loop about
6" in diameter. People who know a lot more about these chokes
than I do advise using such a bunch-wrapped device only at lower
HF frequencies, such as 30M, 40M and below.
my opinion, Ed Gilbert WA2SRQ, has really nailed down the data on
which kind of coax coil "air wound" balun or choke to
use. Of course, you can use ferrite core baluns, bead baluns and
other types of choking devices, but air-wound coax chokes -- in
a close-spaced linear coil, not in a scramble-wound bunch
-- appear to work as well as any, and they cost only as much as
a few extra feet of coax cable. ANYONE can build one.
WA2SRQ's coax choke testing
WA2SRQ's advice, in Nov. 2008, I replaced the 8-turn randomly wound
loop of coax with a solenoid-wound coax choke. The turns are wrapped
side-by-side, 7.5 turns on a 4.25" form (made out of an old
white plastic canister).
testing showed a restored front-to-back performance, but the power-handling
problem reappeared during Sweepstakes Phone and CQWW CW later in
April 2009, I replaced the Classic-33 antenna with a SteppIR 3-element
yagi. I also replaced the coax up the tower. Although the old coax
appeared to be fine, I now suspect that it had water inside the
jacket, which would have caused problems after running higher power
for a while. The new coax and SteppIR antenna handle all the power
I have every thrown at it.
about SWR on the Mosley Classic-33 tribander
Classic-33 is a truly great triband yagi. Yes, it has traps and
it's a design from the 1950s, but it has great forward gain thanks
to the 18-foot boom and Mosley's little-known balanced capacitive
matching system which runs wires inside the radiating driven element.
downside of the Classic-33 is its very narrow SWR bandwidth on 20M.
Using the factory-specified CW settings, the antenna offers a very
competent 1.5:1 or better SWR over most of 15M and 10M, but on 20M
the SWR is 1:1 at the bottom of the band (great) but 2:1 only 150
khz away at 14.150 Mhz. At the top of the Phone band, 14.300, the
SWR is beyond 4:1 and totally unusable.
asked Bill K1XT, a former owner of a Classic-33, about his experience
tweaking the 20M SWR by adjusting the driver's tips. He confirmed
that a small adjustment can move the useful SWR bandwidth to where
you need it most. The antenna's sadly narrow bandwidth doesn't change,
but you can move the sweetspot around.
more comfortably operate in Sweepstakes Phone 2008, my plan is to
tweak the 20M SWR by shortening the tips (outboard from the 10M
and 15M traps) by 1.5" -- essentially moving the lowest SWR
point up the band by 100 khz.
the existing SWR sweep (using the factory's CW settings):
a look at the SWR chart showing before-and-after under-2:1 SWR bandwidths:
image for larger view
is the current configuration of the half-squares, my 40M EU raised
vertical array, and the location of my new dual 80M verticals in
image to view full-size in a new window)
vertical array: I have built a simple two-element
80M vertical array. It works even better than I had hoped to
the US/VE and Asia.
160M inverted-L has been moved. I was feeding the bottom
of the wire hanging down in the middle of the back lawn, with an
SO-239 feedpoint mounted on the same post that supported my now-dismantled
ground-mounted all-band vertical.
the 160M coax feedpoint (SO-239) is attached to the top rail of
my chainlink fence. Will be pulling up all the old radials on the
back lawn, so I can mow properly without constantly stopping to
fix or move errant radial wires. Will arrange a few raised 160M
1/4-wave radials for the 160M antenna.
SWR is high at over 2:1 right now, but expect to fine-tune over
the summer in plenty of time for fall's top-band contesting.
wires for low bands: Just relocated my 40M EU/ZL half-square
so it doesn't have to fire through the US/JA half-square to get
to Europe. Works really, really well now.
recorded a few seconds of VP5/W5CW working stations on 40M around
0340Z on March 26, 2008. Switching between the two half-squares,
you can hear his signal rise on one half-square and, at times, almost
disappear on the other half-square (about 90 degrees off his bearing
in the Turks and Caicos Islands, 3,200 miles away).
to audio (MP3, 400kb)
also recorded CM6RCR in Cuba, showing an even more dramatic difference
between the two half-squares.
to audio (MP3, 727kb)
is one issue with the new EU half-square location -- the horizontal
wire runs over part of the house, so if I run high power, the RF
gets into one of our TVs (the kids use an old 26" TV to play
almost as old classic Nintendo video games in one of their bedrooms...
Go figure, they have XBox 360 on a 52" HDTV in the family room.
Kids these days, I tell ya).
I have discovered that the forgotten 40M 2-element raised vertical
array I have hanging in the woods (now nicely tucked in between
the 80M verticals) works really well for EU paths. It's a passive
array, fed at the north element, with the south element cut 5 percent
longer and spaced 30 feet or so a bit southwest, so the signal fires
a bit northeast, almost perfectly at Europe (a bearing of 30 degrees).
for Low Bands: We have been at the "new" QTH
for three years now, allowing time to consider many options for
wire antennas. Wires for the low bands have included delta loops
for 40 and 80, 2- and 3-element wire yagis, vertical arrays for
40, and an inverted-L for 160.
current setup is:
a 160M Inverted-L (65' tall and 65' horizonal)
ground-mounted all-band vertical
(started out with 36 radials of aluminum wire, now needs re-doing
as many radials have broken or otherwise failed due to corrosion)
2-element 40M vertical array with 3/4-wave
(intended to point at EU, but has never really shown much gain
over the single vertical)
40M half-squares, one fires E-W, the other N-S
about the current antennas:
40M, I have now put up two half-squares -- one for E-W (slightly
south-east facing) and one for N-S (just slightly north-east facing).
Broadside patterns are nice and wide, with strong end-nulls. Often,
these antennas give me 4 s-units between signals when switching.
For example, if listening to a W6 on the antenna facing W6, I can
switch to the antenna facing E-W and an S9 signal drops to S-4 or
S-5. It's great.
horizontal wires on these are about 70', and the vertical legs about
35' -- just added a bit length to each to get the SWR down. It's
1.1:1 from 7.000 to 7.070 on my EU/W6, and a bit higher on my JA/US-VE-Caribbean
summer (August 2006), I installed the 18AVT/WB ground-mounted vertical
in the back lawn (see below for details).
The update is: aluminum fence wire began disintegrating in the lawn
by spring 2007, about nine months after installation, and it all
has to be replaced. I continue to scrounge insulated copper wire,
most of it very light guage telephone-wire (22ga or so). Sad to
think how many days I spent running the 36 radials, all now to be
re-done with insulated copper. The hope is this wire will have a
much longer lifespan.
have reported great success with pinning wire on top of the lawn,
and I can verify that the lawn does, indeed, grow over and draw
the wire into the mulch layer. The aluminum was invisible after
a few weeks -- at least, where I could get lawn staples into the
radial system also serves the wire 160M inverted-L. This wire is
actually clipped into the base of the Hy-Gain trapped vertical,
which has allowed me to basically use that vertical on 160M. It's
a touchy feed SWR-wise... and has never been as good as when, originally,
I fed the 160M L with its own coax (even with a much lesser radial
plans: Today (took Friday as a vacation day to prep for WPX CW this
afternoon) I am adding an SO-239 to the vertical base, to which
I will attach the 160M inverted-V wire and a new standalone 80M
vertical wire of 67'. Will feed them from a new coax run to the
base in the lawn, and run as many replacement radials as I can manage
(even temporarily till I can do a proper stapling job).
CW doesn't have a lot of 80M activity, so the trap vertical would
probably be sufficient, but I want to see what a half-decent radial
field and a true 1/4-wave vertical can do at the bottom of the solar
cycle. We are smack-dab in the minimum -- today, zero sunspots again.
But by the fall contest season, I'll be thankful to have sorted
out a useful antenna for this often valuable band in both DX and
for Low Bands: After two years of experimenting, I now
use several wire antennas suspended from a rope over the back yard.
The rope is up 80' on the East end, and 55' on the West end, about
150' between ends.
a 160M Inverted-L
80M Inverted-V and reflector,
40M Inverted-V reflector with directors 20' East and West of the
the support rope actually runs above part of my HF yagi, I have
decided to re-route it to another tree in the yard -- but it will
be just 40' high to the West, and only 70' from the tall pine to
the East. I will be able to keep the 160M Inverted-L, though the
horizontal portion will slope downward.
may be able to keep the 40M two-element beam, but it will point
slightly NE now.
80M two-elements never really worked as a beam, so I may go back
to a delta loop -- one I had last winter worked very nicely (Worked
Senegal the night before CQWW CW!). At 80' apex, the delta will
fit all right on a slight diagonal NE-SW. As it's only slightly
directional, I should still have good omni coverage and very nice
low-angle (but low-gain) performance.
UPDATE May 2007: no longer have the 80M delta loops, wire yagis
or the overhead rope to support such antennas. I have run a steel
rope into one tall pine, and use that to support the tops of verticals
only -- no catenary wires any longer, as they always had to run
above the tower and yagi, and that made me leery about them ever
breaking and perhaps pulling the yagi apart, or worse.
40M Verticals: In the forest on the slope below our back
yard, I used to have two 40M verticals suspended from a rope between
about the 40M wire vertical array
Tribander: My primary 10M-20M antenna is a three-element
Mosley Classic 33 (CL33) on a 40' tubular crankup, tilt-over tower.
The yagi is at about 45' when the tower's fully extended, and the
mast continues 10' up to a 40M rotary dipole.
Vertical: In early August 2006, I took an old HyGain 18AVT/WB
vertical off the chainlink fence where it was useless, and put it
on the ground in the middle of the large back lawn. I spent a couple
of vacation days putting down about 1,500 feet of aluminum fence
wire on the lawn in 36 radials of varying lengths (averaging over
The radial system under my HyGain 18AVT/WB vertical. (Click
for larger view).
the vertical is directly below the rope supporting all my wire antennas,
I will be able to tie the 160M Inverted-L base to the same radial
field -- have never had any real radials for that antenna and look
forward to seeing how it plays this winter.
I am limited to hanging wires from the trees --
as high as I can get them.
highest wires are the 80m and 40m full-size dipoles at about 65',
running from east to west. I have a 20m dipole up there, too, which
works very nicely into Europe.
wires form a catenary above the backyard lawn. I admit that the
sky above our yard looks like a crazy person lives here.
Click for larger image
have a half-size G5RV (52' is the space between available trees)
at about 45' in the air, running roughly north to south. This is
my primary antenna for working Japan and most of North America.
Even tunes on 80m in a pinch. I also use a fence-mounted HyGain
18AVT/wb vertical to fill in on 80m when the high E-W dipole is
in the wrong orientation.
the July NAQP RTTY test, I rigged up my old 2-element wire tribander,
which slopes from one tree at 45' or so down to 15'. Supposed to
work well like that. Will know in an hour or so how it plays in
couple of weeks after we moved, and my first wires were up, the
neighbor asked my father-in-law "how did he get those up so
high?" They were astonished to learn that I had used a slingshot
and fishing line.
Wire Vertical Phased Array Project
Simple "from the book" phasing lines, a relay switching
box, and two easy 68' wire verticals with raised radials gives me
a competitive contest signal covering most of the horizon on 80M
Rotatable Dipole Project
Using two fiberglass fishing poles (Crappie poles), some wire and
a few feet of TV twinlead, this linear-loaded dipole is less than
40' from tip to tip, cheap and works well for its size.
Hex Beam Project
Read the construction details for a homebrew hex-style beam. This
is a super performer -- if you want all five upper HF bands, or
don't have the wingspan room for a spider beam or other large-format
Beam Group on Yahoo
A spider beam hot spot. See what other homebrewers
(and spider beam kit builders) are doing to get great signals on
20m, 15m and 10m.
Spider Beam Site
Information about the spider beam from its inventor, Con DF4SA.
See how he has used this outstanding antenna to win CQWW contests
from Portugal. The
spider beam is a serious antenna that, in my opinion, is destined
to be one of the most popular homebrewed tribanders.