[R-390] NSA True or False

[Shoppa, Tim]

Glenn writes:
> Now for my question. I have heard for years that the NSA still uses
> R 390A's for weak signal work because of it's very quiet front end and
> sensitivity. I can attest to the fact that many of the receivers I
> have tested in my Electronics lab do not define very weal signals,
> under 1/10th of a microvolt. well.
> [...]
> I would not be surprised if the NSA would choose an R 390A for weak
> signal surveillance  but I guess the real question is if there are
> signals of interest on the HF band in these days of Sat phones,
> Internet and Cell phones.

Just from ham band experience: from 160M to 20M there are few to no applications for a "low noise high gain" receiver. Even the simplest receivers have more than enough gain to turn band noise into intolerable loudness. Band noise is not in the 1/10 microvolt range but in the tens of microvolt range. Intermodulation from strong signals is the problem... and on many solid state receivers the way you deal with that is to put an attenuator in front of the front end in fact. The R-390A's tracking preselectors can eliminate a lot of intermod that many modern radios (even those fancy pants ones with servo-controlled slug-tracked preselectors) have trouble with.

On 15M, or 10M: there I can appreciate, especially with a really kick-ass directional antenna, the weak signal sensitivity and low noise. 15M had some really good openings this past winter.

Tim N3QE