[R-390] R-390A RF Intermod?

[Roy Morgan]

At 06:47 PM 9/2/02 +0000, you wrote:
>   high IMD on the BCB band when tuned close to my two local stations,

... This is the same
>set that "seems" to have somewhat lower gain in the IF section,

Low gain in the IF would mean that the AGC has got the front end at higher 
gain..even maybe well up toward wide open.  This would certainly lead to 
more intermod.  Having proper "gain distribution" in this radio (any, for 
that matter) is the key to getting best performance in such areas as 
intermodulation.


There are two very quick ways to spoil this:

1) Put a "HOT" tube in the front end (or other places).
2) Mess up the IF gain by setting it too high or too low.

It might be interesting to compare the AGC voltage in this radio with 
others on the same station and antenna.  If you find the AGC voltage is 
lower, it's a clue that your front end is at a higher than needed gain setting.

An interesting problem.. :-)

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
roy.morgan@nist.gov --