[R-390] HSR-2 vs 390a

[Roy Morgan]

At 12:42 PM 1/27/04 -0500, Vic/Johanna Culver wrote:
>Interesting question, Dan.  ... I'm looking forward to some 'speculation' on
>this issue.  Vic
...a recent article I
>read in Electric Radio,  Jan 2004 issue having to do with performance of
>an apparently pretty simple homebrew receiver vs. R-390a.

Vic, et al:

Here is my reply to Dan:

Almost certainly his IF gain is set too high, and/or his first rf amplifier 
tube is noisy.  The noise contributed by the front end of a properly 
working R-390A is very likely way below the QRM and QRN of the 40 meter band.

If his home brewed radio gives him more signal and less noise than the 
R-390A on the same received signal, then the R-390A needs attention.

With respect to measured sensitivity in the R-390A:

My belief is that there are some discrepancies in the methods used in the 
R-390A manuals to measure sensitivity.  They will tend to produce 
over-optimistic results.  Briefly, they involve receiver input matching and 
generator load and attenuator performance.  The sensitivity measurement 
methods in the manuals are perfectly fine for system performance testing 
and were good for the military maintenance and checking processes.  They 
did not result in accurate measurement of receiver sensitivity.

Nevertheless, I would be most interested in any manual-based measurement of 
the R-390A mentioned in the ER article.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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