The 80M elevated wire vertical array
25, 2008 (updated Aug. 26, 2010)
new "keeper" 80M antenna is a pair of raised 1/4-wave
(68') verticals in the pine woods on our sloping lower property.
verticals, each is 68' of 16-gauge aluminum fence wire
(Princess Auto farm section, $30 for 1,300' roll)
elevated 66'-long radials for each vertical
control box switches for NE, SW or broadside signal
one SPDT relay to switch for end-fire patterns, and if you want
a second SPDT to short the phasing line for broadside bidirectional
at 1 dB gain over a single vertical.
up to 5 S-units of front-to-back between endfire
samples of antenna doing its thing
Note: an SPDT relay is all you need... I had a DPDT on hand
but only use one side of it.
pole 3 pos
view of vertical array control box
The 71-degree phasing line (on the left, partly hidden under the
pine needles) is now connected to the E and W feedpoints directly.
For broadside firing, a second relay shorts across the two antennas,
so both 84-degree feedlines are fed at the same time, without the
71-degree phasing line.
schematic for end-fire in two directions
This diagram does not show a second relay used to create a broadside
pattern (simply shorts across the A and B terminals).
the past four years, I have sought a good DX and contesting antenna
for 80M. The best I found was the venerable delta loop -- about
90 feet on each side, it is a giant. Once, I had two of them in
the air, spaced about 50 feet apart and working as a driver and
passive reflector. Worked well to the U.S. and Canada, but was large,
hard to keep in the air, and the support rope was not in a useful
line on the property (it ran above my tower and yagi, which always
made me worry about a rope failure).
studying Google Earth views
of our property, I saw how I could raise a pair of 1/4-wave
80M verticals from pine trees. Took a day to get ropes into the
right trees at the necessary height, but when I was done the two
68' wire verticals were hanging from 75' high or higher branches.
Vertical bases were about 5' off the ground, and about 70' apart
-- close enough to 1/4-wave spacing for a good endfire pattern in
with 84-degree and 71-degree Coax Lines
an antenna book (Low Band DXing, I think), I ran across a suggestion
for "from the book" Christman phasing that could work
for typical two-vertical arrays spaced 1/4-wavelength apart.
every antenna installation varies, the suggestion I followed said
that if you have 1/4-wave verticals on 80M, each with a self-impedance
at the feedpoint of about 50 ohms (a reasonable assumption if you
have less than ideal radials), the mutual impedance of
such an array could lend itself nicely to feeding each antenna with
an 84-degree line of 50-ohm coax, and connecting
the two feedpoints with a 71-degree piece of coax
-- the "phasing" line. (This is a replacement for the
typical "90-degree" lines to each antenna, and a 90-degree
shorting the 71-degree phasing line with a relay, the pair of antennas
becomes a broadside array.
a 40M version of this antenna, be sure to read N4JTE's very good
(and illustrated) article on eHam "Verticals...
Got Two?" about how to wire the relay. Also, see notes
on my 40M two-element array.
and Cutting the Coax: 84- and 71-degree lines
Aug. 2010: I have created an
easy calculator to figure out the proper lengths, and the
frequency for your RF analyzer so you end up with 71 or 84 degrees
at your operating freqency.
those who want to know the inside details, here's how I manually
determined the proper lengths:
a cheap-o ham, rather than using pricey RG213 for an experiment
that might not work, I bought a bunch of the cheapest RG58 I could
find (30-cents a foot) with a velocity factor of .66.
a design frequency of 3.550 Mhz, I cut two 42'8" lengths
to feed the antennas (that's 84-degrees at .66 vf) and one
36' length for the 71-degree phasing line.
got lucky because the lengths I calculated worked out very well
for the particular brand of RG58 I used. To check that I was indeed
getting 84 degrees and 71 degrees for 3.550 Mhz, I calculated the
frequency for which I expected each piece of coax to be 1/4-wavelength
(90 degrees), and checked for a null there using a Palomar RX Noise
specs for velocity factor aren't always what you get. Coax ain't
cheap, so before cutting, borrow an antenna analyzer or RX noise
bridge and test a piece of coax to confirm its velocity factor.
Then, before cutting your feedlines, check calculations for the
intended frequency, think it over twice more, and cut carefully.
figure out 84 degrees: VA7ST's
custom Christman calculator
out 360 degrees (1 wavelength) in feet
(3.550 mhz = 277.06 ft).
I used an online
wavelength calculator to get the 1-wave length
this by 360 degrees (to get the length of 1 degree)
277/360 = 0.77 feet per degree
this by 84 degrees
84 x 0.77 = 64.63 feet for 84 degrees
this by your coax's velocity factor
64.63 feet x 0.66 vf (RG58) = cut the coax at 42.66
figure out 71 degrees: VA7ST's
custom Christman calculator
0.77 feet per degree x 71 degrees = 54.67 feet
this by 0.66 vf = 36.08 feet (the length to cut
yes, it works very fine business, and thank you for asking. So far,
I can happily report that the cheap-o RG58 lines and the 5-amp Mode
relay, which I worried wouldn't handle much power, seem to handle
500-700 watts just fine!
SWR, which the book predicts will be 2.4:1 or so, is actually very
low -- under 1.5:1 in either end-fire direction. That low SWR indicates
either: less than ideal efficiency (ground losses, due to having
just four raised radials for each vertical), or the mutual impedance
due to sloping raised radials just works well with this feeding
have the system working and exhibiting all the right characteristics
I'd hoped for, so I'll tweak later with more raised radials and
just enjoy playing with the thing for a while first.
first time I tried out the antenna (April 10, 2008), I heard Peter,
ZS1JX, calling CQ on 3.501. I have never heard ZS on 80M before.
I turned on the amp and worked him (received a paltry 349 report,
but I got a report!).
Africa is on a heading of 60 degrees from here, quite a long way
off the vertical array's prime heading of 120 degrees -- so I was
fortunate to hear him or be heard there. Over the next week, every
night between 0330Z and 0430Z I heard Peter calling CQ, sometimes
peaking at S5!
guess what? Peter was trying out his own new 80M antenna. A two-element
bands have been dismal since then, with flux in the 68 to 70 range,
but I've also worked V63JQ and FG5FR.
(North American) Performance
Eastern and Southeastern stations pound into British Columbia even
better than they did with the big old delta loop, which was a pretty
strong performer for that range. I worried that the array would
not do so well for close-in stations (WA, OR, CA, ID, CO, WY, ND),
but they have been just as plentiful during the regular Thursday
night Northern California Contest Club (NCCC) ladder CW sprints.
night, a few minutes after the first NCCC ladder sprint using the
new verticals, I heard the NCCC Net fellas on 3.610 SSB commenting
that they'd never heard VA7ST that loud before. Nothing different
here except the new verticals!
have not found the broadside pattern very useful. The two higher-gain
end-fire lobes are so broad that they cover big sections of the
horizon to the SE and NW from here. Broadside should point right
at Europe and W6, but I have not heard any Europe on the antenna.
Nov. 14, 2008.... Yes I have! Heard F5IN (France) and CT3FT
(Madeira Is.) tonight just before midnight local (0800z), both about
559 down low in the CW band.
Recordings of 80M Antenna in Action
are not yet back to normal (may take a few more
years) but I've added a few 80M audio recordings to illustrate the
difference in signals when switching between endfire patterns. The
difference is at least as prominent as the
difference between my 40M single half-squares.
was calling CQ on 3.510 mhz around 0330Z on April 29, 2008. I recorded
four brief samples of his signal, switching the vertical array from
East to West and back again. You'll hear the difference when it's
aiming his direction.
Recordings of 40M vertical array in Action
how the 40M version of this vertical array sounds
ES3AX (Estonia) on 7.010 mhz at around 0140z on Feb. 17, 2010. You'll
hear him clearly with the 40M array switched to the Northeast (about
30 degrees) then fade away when I switch the array to aim Southwest.
HK1KRY on 7.010 mhz at around 0150z on Feb. 17, 2010. You'll hear
him clearly with the 40M array switched to the Southwest then disappear
into the noise when I switch the array to aim Northeast toward Europe.
There is some fading on the signal, so the rear null comes in and
goes out enough to notice.
I have constant broadband B.C. Hydro power line noise from a faulty
(diagnosed but unrepaired) power distribution substation about 1
mile from home, due East. While the noise isn't nearly as bad on
80M as it is on 20M and 15M, it's still there. That's why this antenna
sounds a bit noisier pointing East and quieter pointing West. I
heard JAs rather well in the mornings when the band was actually
30M Bonus Antenna!
and I have discovered that this 80M vertical array also tunes to
below 1.5:1 on 30M (10.1 Mhz). Since April 10, 2008, I've picked
up 20 countries on 30M just casually tuning around. These include:
ZF, LU, PJ2, CO, HP, KP4, TI, TG, FG, SM, LY, UA3, 4A3, ES, V31,
T32, KH6, 9M6 and, of course, W. Not bad for a bonus band, hi.
A roundup look at the antennas currently in use at the
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.