[R-390] R-390 Digest, Vol 74, Issue 18

[Jim Green]

Interesting question,

I have heard there is a quiet zone around the NSA and Langly. That  
those that live there must sign a covenant that prevents them from  
using any EMI emitting devices of any sort. I don't know if it's true  
or not, but it makes sense. Also, I have google earthed several  
elephant cage antanna farms that are located well away from noise  
centers. Therefore, perhaps the low noise floor of a R-390 is still of  
value.

Just guessing. I really don't know what the H*** I'm talking about.

Jim
On Jun 17, 2010, at 11:00 AM, r-390-request at mailman.qth.net wrote:

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>   1. Re: NSA True or False (Shoppa, Tim)
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> Message: 1
> Date: Thu, 17 Jun 2010 11:49:14 -0400
> From: "Shoppa, Tim" <tshoppa at wmata.com>
> Subject: Re: [R-390] NSA True or False
> To: "wa4aos at aol.com" <wa4aos at aol.com>, "r-390 at mailman.qth.net"
> 	<r-390 at mailman.qth.net>
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> 	<B136EDE3DF5EC441B6F08E0A7AB872450AC5DF3C42 at EX2K7-CMS-1.wmata.local>
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> 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
>
>
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> End of R-390 Digest, Vol 74, Issue 18
> *************************************