The Large, Powerful Spider Beam
written in May 2003
Update: August 2003
Update: March 2004
in time for WPX CW 2003, I finally got my new homebrew spider beam
up in the air.
antenna offers full-size yagis (with directors and reflectors in
V configuration) interlaced on a 32-foot boom. You get 3 elements
on 20m, 3 elements on 15m, and 4 elements on 10m. It's a powerful
construction method for this antenna was identical to the way I
built my hex-style beam last summer -- a PVC pipe serves as the
center post, which runs up through the middle of a circle of plywood.
The spreaders are U-bolted to the plywood.
everything I needed, except the fishing poles, from Home Depot.
-- 16.5-foot-long Classic Crappie Poles from Cabelas.com
1 -- round 1-foot diameter piece of 1" plywood
1 -- can of black acrylic "plastic' spray paint
1 -- roll of 3-conductor "Romex" house wire
insulation stripped off with a utility knife
1 -- roll of 30lb-test nylon monofilament fishing line
1 -- roll of bright white nylon cord (mason line)
8 -- stainless steel U-bolts (1.75-inch)
4 -- steel "L"-shaped shelving brackets
1 -- 4-foot long piece of 1.5-inch PVC tubing
4 -- stainess steel screw-in eyebolts
2 -- brass machine screws, plus a nut and wing nut for each
miscellaneous bits -- some crazy glue, doweling, old broom handles,
The Cabelas fishing poles are great -- five pieces that nest down
into the largest 3.5-foot section. I found the smallest two sections
too whippy to hold a straight line, so I took them out. To make
up for one of those removed sections, I built 3-foot add-ons of
1" PVC pipe reinforced with old broom handles (they fit perfectly).
extensions were inserted into the butt-ends of the fishing poles,
and also into the hub. They take the compression of the hub's U-bolts
the end result was that I had spreaders of just 13.5 feet, not the
16.5 feet called for in Con's very wonderful design.
great news is that all the elements still fit into this shorter
design, except for the 20M driven (dipole). I decided that, for
me, an acceptable trade-off of size vs. performance would be to
linear load the 20M dipole. This was done by winding about 1 meter
(OK, 3 feet or so) of each side into a coil wrapped around 3-inch-long
pieces of 1" PVC (visible in photos 2 and 3).
used a bead of 5-minute epoxy to keep the wire nicely shaped on
the forms. This made the 20M driven element fit my spreader "wingspan"
perfectly. Again, every other element was cut exactly to Con's measurements.
experimented with element spacings to accommodate the shorter spreader
lengths, looking for best SWR and best perceived receive strength.
Not scientific at all, but I am happy with what I ended up with.
the updates below for information about how I extended the spreaders
and removed the loading coils in August 2003).
I don't yet have a tower (one day...) and can only get my antennas
up about 27-30 feet. Too low to really get much from a yagi (or
a dipole for that matter), but I have had a 5-band hex-style beam
on that same pole from October 2002 to May 2003 and was able to
compare it to the spider on the back lawn (3 feet high in the test
hex and spider were very close, but now that the spider is at 27
feet, I am already hearing stations I've never heard before from
design had me hooked from the second I saw it on his Web site. I
waited anxiously for the day that he would release his design specs,
and when they arrived I started gathering all the parts to build
one. For the past four weeks I puttered around, building the thing
and adjusting, etc.
after work, it took my wife and I over an hour to get the antenna
up off the lawn and onto the steel pole I use, bolted to a lower
eve of the house.
moment it was up, I ran to the shack to compare signals with my
G5RV. Heard a KH7 station at 20 over S9... and down at S5 with the
doublet. Other signals confirmed the differential between antennas.
No comparison, and nor should there be -- this cheap, simple wire
beam is doing its thing. Can't wait for WPX to start at 0000z tomorrow
to see what I can hear, and what I can work.
Here's how I fared
WW WPX CW Contest results
Qs Mults Antenna
63 45 G5RV at 30'
2003 268,348 412 233
Spider beam <30'
my writeup about the 2003 contest
thank you for dreaming up this design -- and sharing it with us!
Although I had to modify my version to suit the parts I had available,
I think many, many hams will enjoy building a spider beam yagi as
the A-index at 65 or so, and a severe solar event under way, I
thought it would be a good time to update my spider beam story.
built the all-homebrew antenna and put it up in late May. Last
week, I took it down and made some modifications.
I used 13.5-foot spreaders (made from fiberglass "Crappie rod"
arms from Cabelas.com) instead of the full-length 16.5-foot spreaders
in Con's design. That meant shortening the 20M driven
element by several feet, and using closer-than-recommended element
make the 20M dipole short enough to fit the spreaders, I installed
coils on PVC forms just out from the feedpoints. I thought it was
a good trade-off between size and performance. I was wrong. The
20M performance was not very good, even compared to my G5RV at the
same height of just under 30 feet (10M).
that original configuration, both 15M and 10M were very good, with
great forward gain and good side and front-to-back rejection. On
20M, despite a 1.5:1 SWR from 14.000 to 14.100, signals were clearly
attenuated -- and the loading coils were my prime suspects.
the help of my wife and sons (7 and 9 yrs.), I eventually managed
to take down the antenna and get it into a WorkMate on the back
lawn to work on it.
experience of putting it up, taking it down and putting it up again
proved to me just how resilient this design really is -- it snagged
on maple brances, snagged on the cedar roof shakes, snagged on the
eavestroughs, balanced almost vertically resting on just one spreader...
and nothing broke! I think it's the German engineering, hi.
it was down, my first task was to extend the lateral (driven element)
spreaders. I am using telescoping fiberglass rods, which initially
came in five nesting sections. The very thinnest 5th section (.4
inch diameter) was removed at the start, and the 4th section was
simply pushed into the other sections.
the lateral spreaders only, I fished out that 4th section and used
it to extend the spreaders to the full 16.5-foot length. That allowed
me to uncoil the 20M driven element wire so it returned to a full-
result of this extension? A big, very noticeable improvement --
the antenna really shows up the G5RV in many instances.
using the spider beam, my contest scores have gone up slightly over
last year, despite declining conditions. My station is still a peanut
whistle (100W max, and no tower yet), and I am limited by a huge
RF filter (mountain) blocking quite a bit of eastern horizon from
our back yard, but every dB of gain helps to overcome the QTH deficiencies.
I now have 13.5-foot boom spreaders, and 16.5-foot lateral spreaders
for the driven elements. The element spacings are still shorter
than Con's design, but not too short to be effective.
time the antenna is down, I will make the 15M element a bit longer
as it has 3:1 SWR in the CW portion of the band (although the tuner
easily tunes it down to 1.2:1 or so). The 15M resonant frequency
appears to be about 400 khz too high.
week I will take down the spider beam in preparation for moving
to a new QTH. On an unseasonably balmy day in December, I took the
antenna down and completely re-did the element spacing to conform
almost exactly to Con's original design dimensions. Even used the
proper guy string layout.
fiberglass spreaders are a bit too whippy for the guying to work
properly, but the antenna is still solid. Flexing allowed the 20m
reflector to tangle a bit in the end of the 15m reflector's fishing
line, but it's nothing major.
will do some additional work to the entire antenna (a stiffer post,
for example) before putting it up at the new house. Will use the
same pole for now. Will probably leave the spider beam up even after
the MA40 crank-up, tilt-over tower is installed for the Mosley CL-33.
A roundup look at the antennas currently in use at the
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.