This thread brought back many good memories over the years of some
really big antennas that I was fortunate enough to see and even design a few.
The one that really comes to mind the most is the very impressive and gigantic
NP4A 80 Meter 3 element Yagi that was designed and built in the
1980s. Pedro Piza, NP4A, is one of my best and closest friends, and we
worked on this together back then. I did the electrical design using some
brute force optimizers put together with NEC-2 and MiniNEC. This was quite
primitive compared to the way things are done today, and I believe I used
an IBM XT computer for this. I remember having to do quite a bit of work
to make sure the tapered diameters were computed properly with the problems
that NEC and MiniNEC had with frequency shifts and stepped-diameter
elements. NEC-4 and Leeson algorithms were not around back then like we
use now.
Pedro did the mechanical design and we both really had a great time working
on this project together back then. Pedro wanted this antenna to
last through the many hurricanes that hit Puerto Rico, and he really
incorporated some extra features, still unique to antennas like this.
The boom was made out of AB-105 tower sections and was split in the middle.
Each half would pivot about the center with a cleverly devised system of
gears and chains. These two boom halves would then be rotated and rest
against the tower when a hurricane was coming. The parasitic elements at
the ends of the boom sections each had their own rotators, and these could
also be rotated to rest against the tower as well. The driven element was
also split and could also pivot so each half would rest against the tower
too. When it was all nested, it looked like an umbrella that was closed
against the tower.
I think the whole thing must have weighed around 2500 to 3000 lbs, or so,
and it was truly a marvel to be seen on Pedro's huge 4 legged 160 foot high
tower
on top of the mountaintop QTH.
This antenna really worked and had some amazing Front-to-Sidelobe
level. It was used by Pedro in a CQWW SSB 80M Single Band effort as I
remember, but he lost power and didn't operate the whole time. The other
amazing effort with this antenna was by Jeff, K1ZM, who operated CQWW CW
80M Single Band back in the 80s and his log was truly amazing, especially
the huge number of JAs that he worked.
It is unfortunate that this antenna was short-lived since Hurricane Hugo
took it all down, including the tower, over the side of the mountain. It
appears that a defective guy anchor let go, and that was the end of this
effort and a life-long
dream to put up such an immense antenna.
I also had the great fortune to visit Frank, W6KPC, mentioned by others, on
a trip as a consultant on another large antenna at the VOA in Delano,
CA. I was hired by the California Dept. of Health to look into the
possibility that the RF from VOA was or was not causing childhood luekemias
in the area. Our findings were that the energy from VOA was way below the
standards of the time and could not be the cause. On the way back, my good
friend, Dick Adler, K3CXZ (a really great antenna engineer) and I sniffed
out the huge 20M array of W6KPC. We drove into Frank's farm and visited
with him for the next several hours. It was like we knew each other all
our lives with Frank's hospitality and knowledge of antennas. He was also
quite interested about what we were doing with the development of NEC and
we were amazed at what he and Simon, OH8OS, were doing with these 20M
arrays at that time. This was truly a visit I will never forget and an
antenna that was absolutely fantastic to see.
Nathan Miller, NW3Z, and I have also built some pretty large antennas at
the station in Central Pennsylvania where we have used the K3CR call over
the years. Out of the host of towers at this station, there are three 185
foot towers with 3-stacks of 6 element OWA Yagis for 20M and 15M and the
4-stack of 7 element OWA Yagis for 10M. The towers are probably more
amazing than the antennas from a mechanical viewpoint since they are
government surplus (were actually brand new) from the Ground Wave Emergency
Network (GWEN). They are solid-round members and are actually specified to
take the force of an atomic blast at some distance from the ground-zero
center. That was what the GWEN system was for when the atomic blasts
burned out the ionosphere and satellites and all that was left was
groundwave at 70 kHz.
The largest 20M antennas that I think anyone probably ever used was when
several of us were able to get government permission to use the VOA curtain
array at Bethany, Ohio for a day before it was shut down and dismantled. I
will still never forget the most amazing signals with a QSO with Robert,
GI0KOW on
40M with this array. I also remember working EA3OT on this array on 20M
and you can imagine what that was like.
What clearly has to be the largest antenna used on 20M has to be the time
Rey Velez, KP4REY, and I put the Arecibo, Puerto Rico, 1000 foot dish on
that band back in the 70s when there was a full-size 3 to 12 MHz crossed
log-periodic antenna at the feedpoint. The signal was beaming straight up
but I was able to work stations with a lot of weird multiple bounces and
echo effects. I was using a Collins 30-L1 and the antenna had a gain of
about 30 dBi at this frequency. That is over half a megawatt of
ERP. Pretty amazing!!!
I guess I love big antennas as you can tell, and this whole thread has
brought back a lot of nostalgia. It is interesting to see all the comments
on big antennas that people have used and know about.
73 Jim WA3FET
James K. Breakall
Professor, Electrical Engineering
225 Electrical Engineering East
Penn State University
University Park, PA 16802
Tel: 814-865-2228
Fax: 814-863-8457
Cell: 814-883-6521
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