[R-390] Ending The Moment Of Silence

[John Schmitz]

Piece of sheet metal

Got any pictures?

John


-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]On
Behalf Of David Wise
Sent: Thursday, January 20, 2005 6:20 PM
To: r-390 at mailman.qth.net
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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