archiv~1: SETI "The Antenna" ;-)

SETI "The Antenna" ;-)

willcox@voicenet.com
Tue, 10 Nov 1998 12:43:21 +0500

Definately off-topic ;-)
Apologies if this is too long.

"The Antenna"

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 120-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
would 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, Joe Speroni, AH0A/7J1AAA
Ex-Technical Adviser - TIARA
1 April 1997

This story has been reprinted and edited from the April 1985 issue of the
Tokyo International Amateur Radio
Association's (TIARA) newsletter. Permission is hereby granted to reprint
all or any portion of the material, provided
credit is given to both TIARA NEWS and the author - Joe Speroni,
AH0A/7J1AAA.