[R-390] RF deck alignment

[David Wise]

Charles already said that the RF is wide enough not to cut into the IF passband.

I'll add that the R-390 and R-390A are not short on gain, _and_ that I think it's a very bad idea.  The cams were built linear, and the coils specially wound so _they_ were linear.  If the system law is not linear and the cams aren't worn, it points to deterioration of a coil or a manufacturing defect therein.  I can't imagine rewinding one and getting it better than before.  Also, one cam affects several coils.  Unless they're all off the same way... even then, I'd never mess with a cam except to replace one that was obviously off.

Overall, if you're in the mood, it would be an interesting exercise to map out the RF response, but an extremely frustrating one to attempt to change it by any means other than the approved trims.

Dave Wise
SWL in Hillsboro Oregon

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Tisha Hayes
Sent: Sunday, August 04, 2013 2:23 PM
To: R390A
Subject: [R-390] RF deck alignment

I know that this generally falls under the "leave it alone" category but
has anyone ever gone through the process of aligning the RF deck stages and
bands for linearity?

Generally I know that we pick a few spots on each band and peak through the
RF stages for performance but what happens when a slug has been replaced,
repaired or the spring was accidentally stretched? That one slug will have
a different peak than the other in the string when the band selector switch
is lined up that way.

The only way I could think to do it would be to inject a known RF signal
level and to use a RF microvoltmeter (like a Boonton 92) at test points to
walk through the stages.

Am I wrong-headed to think that the more selective the RF stages are the
better the desired response would be at the IF?

Ideas?

-- 
Ms. Tisha Hayes/ AA4HA

"Objective considerations of contemporary phenomena compel the conclusion
that success or failure in competitive activities exhibits no tendency to
be commensurate with innate capacity, but that a considerable element of
the unpredictable must invariably be taken into account." -- George Orwell
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