As a monitoring officer with the Radio Intelligence Division (RID) of the
FCC in Hawaii during WW2 I was privy to some interesting situations. Our State
Department was of course aware of the operations occurring in the Pacific
Theater. The people there were also aware of the propaganda being spewed by the
Japanese short-wave broadcasters. But State was curious concerning what the
Japanese living on the homeland were being told-were they being told the truth,
or the same propaganda as told on the short-wave broadcasts, or a totally
different story. State asked the RID to determine whether we could obtain such
information.
We cruised the AM broadcast band and found several nighttime signals from
Japanese mainland stations, but most were too weak to copy. However, JOAK,
Tokyo, on 650 KHz was S9, but there was a problem in copying it. KFI, Los
Angeles, was also on 650 KHz with an S9 signal-copying intelligence from JOAK
was impossible. How can we eliminate, or reduce KFI's signal level. A Beverage
Wave antenna, perhaps?
We then proceeded to the northern portion of Oahu and constructed a
Beverage one-half mile long, five feet above ground, aimed at Tokyo, and
terminated with a 1000-ohm pot resistor to ground at the Tokyo end. We
discovered that by varying the pot resistance we could null the KFI signal to
almost zero. The resistance terminating the Beverage that produced the null was
around 600 ohms. Because the matching resistive termination rendered the
Beverage a traveling-wave antenna with no standing wave, the signal from JOAK
was terminated by the input of our receiver, while the signal from KFI was
dissipated in the matched resistance at the Tokyo end of the Beverage-no KFI
signal reflected toward the receiver. Voila-JOAK was perfectly readable for
recording!
We sent the first recording to Washington, and State was
delighted-requesting that we continue recording JOAK continuously. Consequently,
our recordings were flown daily to Washington from Hickam Field in Honolulu. We
were left in the dark concerning the information on the recordings, and how it
affected the War effort, because State didn't share it with us. But it must have
been pretty good, because State was on our case every day to make sure we sent
them the recordings.

Walt, W2DU