[Milsurplus] LO radiation

[J. Forster]

Mike Feher wrote:

> Bob -
>
> I am in total agreement with your calculations, on a rough order of
> magnitude basis. As had been mentioned previously we discussed this at
> length years ago and I mentioned then that it is still a problem. In the
> 80's I ran a group at Melpar designing surveillance receivers, mainly for
> aircraft, where the LO re-radiation numbers were specified and almost
> impossible to meet.

I was on a tour of a nuclear sub briefly in the late 1960s and they had a rack
of ACL GLR-9s or SR-209s for ELINT activities. To keep stealthy, they had
Avantek FET preamps near the top of the periscope, near the antennas. These
amplifiers had a BNC input that 'gated' them on and off. I don't know if this is
true, but I was told that the gate essentially shut off the amp to prevent LO
retardation.

As I remember, the band of one of these amps was 1 to 2.6 GHz, and the other was
higher. I know the SR-209 has plug-ins that go from at least 30 MHz to 12 GHz.

Apparently, the USN used this stuff to sneak up on opposition ports and listen
to what was happening, all very quietly.

-John