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".
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 cm
).
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,
Joe Speroni, AH0A/7J1AAA
Ex-Technical Adviser TIARA
1 April 1997