[R-390] Call for measurements - 100dB carrier reading

[Barry]

>Hi David,
>
>I disagree with one earlier comment kinda ripping this AGC discussion.  I 
>find this much more interesting than many of the topics that appear through 
>the R390 threads....however, I do have a rather simplifying question:  Why 
>not just use a 10-turn precision pot to solve the carrier meter zero issue? 
>I made that change and it is now easy has heck to zero and the adjustment 
>has not moved since.
>
>Keep up the great tech discussions...I learn a lot from them all!
>
>73 de Mike
>K7PI
>Mercer Island, WA
>www.k7pi.com

I may have mentioned this before, but the 100-ohm pot can also be replaced with a 20-ohm pot and discard the parallel resistance originally used with the 100-ohm pot.  I used the 20-ohm pot (first image at the top left) on the following page:

http://www.surplussales.com/Potentiometers/PBM-SlotAdj/PBM-SlotAdj-1.html

(Ideally, the replacement pot should be 18 ohms, but I could not find one.)

The shaft on this one has a smaller diameter than the original and I considered making a bushing to center it in the existing hole, but ended up just using some 1/4" washers on both sides.  It works well.

Barry - N4BUQ