ARLA/CLUSTER: Querem esta Antena ?

[Carlos Nora]

The Antenna
Bert Thompson, KG6SL
Dear Bert,

I received this letter from an old friend, Joe Speroni AH0A/7J1AAA,
who has been living and working in Japan for many years. He is also
the author of the well-known MORSE ACADEMY software for teaching Morse
code. Anyway, it was such an exciting letter that I thought it would
be of interest to others here on "the Web".



Best 73 de Sandy, W7BX

Dear Sandy, W7BX

Greetings from Tokyo and all the members of TIARA (Tokyo International
Amateur Radio Association). I know I promised you a series of articles
on Japanese amateur radio, but there is something so exciting I just
have to take a break and tell you about it.
It all started with the work that Ed Coan (AH7L/7J1AAE) did on antenna
pattern plotting using his personal computer and the A-to-D converter
in his FT-1000. The circular, and even backward antenna patterns of
some of our local TIARA club members brought home the point that what
a good station needs is a good antenna. Ed's antenna looks great and
the results verify it. He works regular schedules into Colorado and
Maine, just like sunspots don't mean anything. My mini-beam just could
not compare.
Well, I got to thinking about what we Tokyo apartment dwellers could
do and realized that space is THE problem. How do you fit a full-sized
beam on a balcony? Loading coils are the answer and the problem at the
same time - the antenna radiation resistance drops as reactance is
substituted for length. High current loops develop and the power is
dissipated in the antenna instead of being radiated. If only the
antenna didn't dissipate the power. Hmmm....let's see, P=E2 /R; now if
R were 0 then...
>From my work, I have some contacts in research groups over at Tokyo
University. Better yet, I knew a Japanese ham that is a graduate
student there. The thought running through my head was to build a
super-conducting antenna. This requires cryogenics, i.e. temperatures
around minus 279 degrees Centigrade. I was able get the university
folks interested in the project and we built a 10-meter dipole test
silicon wafer. They put together a lot of serial coils by "re-work" on
the wafer; they were able to connect them so we had a super-conducting
yagi. I took my TS-930 transceiver down to the lab for the first
tests, but before we could test it, actual measurements showed it was
resonant on 3.126 MHz. It seems that the normal equations for
inductance don't work with super-conducting materials -- you need a
lot fewer turns to get the same results compared to room temperature.
Many measurements and trials later, we had a ten-meter resonant wafer.
This time we put a 40-element beam on each wafer and stacked 4 wafers
in the same assembly. That made a 160-element array on 10-meters in
less than a half-foot cube (15 cm3).
The first test didn't go too well. I connected my TS-930 to the
super-conducting wafer antenna and tuned it for 10 meters. At room
temperature, we couldn't hear anything. Using a heat pump, the lab
technicians started lowering the antenna's temperature toward the
super-conducting region. I was really impressed by how small the
equipment is, and started thinking it might all fit in the shack. Just
then, the TS-930 froze solid, which had a negative effect on its
operating characteristics. This wouldn't be so easy after all; the
coax connection would need some study!
We reworked the wafers to put inductive coupling on them, but I could
find no way to efficiently couple to it from the conducting array.
Fortunately the lab technicians came up with a new ceramic material
that passed RF but not heat. Probably, something that Kyocera invented
just for this use. I sent the TS-930 to the ham shop in Akihabara and
asked them to touch it up for me. My friend Suzuki-San, JH1WWC (store
manager at the ham shop), asked exactly how the paint had been peeled
off around the coax connector -- lightning maybe? No, I assured him --
just low temperature exposure, without saying how low the temperatures
were. The project had to stay secret and besides, Suzuki-San can
repair anything!
Since it looked like it might be a while before the TS-930 would be
repaired, I brought out my TS-940. I had already placed an order for a
Yaesu FT-1000 anyway. After verifying that in the super-conducting
range the antenna was resonant on 10-meters, we connected the TS-940.
The ceramic material worked and the rig operated well as we began the
cooling cycle. The band seemed dead even with the antenna at -150
degrees C. It took another 10 minutes to get to the super-conducting
range - then the TS-940 blew up. It seems our antenna had a bit more
gain than the TS-940 front-end could take. Later measurements showed
500 volts coming out of the coax. A little hard to believe, but then
what do I know about cryogenic LSI antenna technology? The TS-940 was
also returned to Suzuki-San, but this time he frowned a bit -- the
front-end board did look like it had been hit by lightning. Not to
worry, Suzuki-San can repair anything!
The FT-1000 arrived just in time to be able to continue experiments.
We built a QSK attenuator to protect the receiver. With the LSI wafer
antenna still inside the lab, we decided to try to make a contact on
10-meters. What a shock when we got it working! The first thing we
heard was a couple of W2's talking locally on 10 meters and that was
with 80 dB of attenuation. We had the antenna array on a rotatable
mount; I moved it about a half-degree and the W2's disappeared. What
beam width! We tuned them in again, and they were just about to sign
off, so we thought we would try to work them. The rig was tuned up at
50 watts on a dummy load; we switched in the wafer antenna and gave
N2BA a call. The noise was unbelievable -- an ionized ray shot out
from the antenna and hit the wall of the building. Before we knocked a
hole in the band, we took a piece out of the lab wall! Ever wonder
what an antenna pattern looks like in three dimensions? There was a
oval hole in the wall of the lab -- about 1-cm high by 2-cm wide. We
cut power quickly. N2BA came back on frequency a few minutes later and
said he was using his back-up rig; something had taken his main rig
off the air. For some reason, the station he was talking to never came
back, so we decided not to transmit again until we knew for sure what
was going on.
As near as we can tell, the antenna array has 620-dB gain over a
dipole, but with a beamwidth of 0.75 degrees using the 60-dB points.
With 50 watts output, the effective radiated power is 55 quadrillion
watts at the center of the beam (5.5 with 13 zeroes). As soon as the
University realized what we had built, the entire project was taken
away from us and turned over to the Japanese Self-Defense Force.
Amateur radio "tinkering" has contributed to something, but I am not
exactly sure what. I haven't the slightest idea what was in those
wafers or how to build another set. Do you think someone may be
interested in this idea for Star Wars/SDI?? What I'd give to use a
much smaller set in the next CQ World Wide Contest!
A few months later, the University contacted all of us and asked just
how close we had been to the antenna when operating. As best as I can
figure, we were in the null behind the array. From what has been said
so far, it looks like a secondary use for our antenna may be as a mass
sterilizer, but confirmation will have to await the results of our
medical tests. If our antenna ever hits the market, it looks like
remote operation may be desirable.
As I am writing this, I have been informed that my friend Suzuki-San
can't fix everything after all. He's written off the TS-930 and
TS-940, and I just found out that before the university terminated the
project, they tried one more time with my FT-1000, but without the
100-dB attenuator to protect the receiver. Its front-end now matches
the 940's and it looks like it will be a while before I am on the air
again.

Best 73,



-- 
73 e Obrigado , Carlos Nora - CT1END
NNNN
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