[R-390] Ending The Moment Of Silence

[Cecil Acuff]

You have found a way to eliminate the only internal self test besides the 
Xtal Calibrator the R-390A possesses?

I'll have to think about that one....

Cecil...
----- Original Message ----- 
From: "David Wise" <David_Wise at Phoenix.com>
To: <r-390 at mailman.qth.net>
Sent: Thursday, January 20, 2005 6:19 PM
Subject: [R-390] Ending The Moment Of Silence


I did it!

I have perfected a mod that eliminates the carrier level
disturbance when switching the R-390/391/390A AGC rate.
Only the front panel wiring changes.  It is 100% compatible
with standard IF decks and those with the Lankford AGC mod.
This is how Collins should have done it, it would have cost
them next to nothing.  Like the carrier level pot, the
engineer just didn't think it through.

The mod I posted earlier had side effects that ultimately
caused me to reject it, although it was very compact and
easy to do.  This mod borrows an idea, but otherwise it's
totally new.  I have tested it extensively, and the
ergonomic improvement is just fantastic.  You'll never
realize how obnoxious and fatiguing the stock AGC switch
is until you try this.

Pros:
No more "Moment Of Silence" (SLOW to MED)
No more blasting (MED to SLOW)
Same time constants as before, or season to taste
Compatible with existing modules
Reversible (no holes)
No "box on the side", it's all internal
Works with decks that have a bad C551

Cons:
Needs a new AGC switch (2-pole vs 1-pole)
Needs a piece of sheet metal (if you want it to be neat)

Performance:
OLD
FAST-MED: Dip, Nothing, or Surge, depending on signal levels
MED-SLOW: Severe Overload for 1-2 seconds
SLOW-MED: No Signal for 1-2 seconds
MED-FAST: Nothing

NEW
FAST-MED: Nothing!
MED-SLOW: Nothing!
SLOW-MED: Nothing!
MED-FAST: Nothing

(Lest someone accuse me of advertising hype, I will qualify the above claims
to the extent that at very high signal levels (over 80dB), you may detect
a slight surge on MED-SLOW and SLOW-MED, but it's barely perceptible except
under artificial laboratory conditions, where it becomes merely 
"perceptible".)

Cost: About $15 and a couple of hours.

Well?

Dave Wise
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