[Johnson] Ranger VFO chirp on 40 Meters

[WQ9E at btsnetworks.net]

Jim,

Eddy correctly identified the problem.  It is from RF entering the VFO on 40M where it is operating on the same frequency as the final.  This problem is even more common with the higher power Valiant although my even higher power Viking 500 shows no sign of this problem and I have never heard of anyone having it with the 500.  In really severe cases it will also cause some FM when operating AM.

The only instance where I had to go beyond tightening all of the VFO mounting screws properly (surface oxidation causes poor contact with age) was in an early Valiant which had a long factory slot cut into the case where the VFO shaft enters.  I had to add some metallic shielding tape to this one and it cured the problem.

I expect the problem doesn't show up on 160 since it takes a bigger "leak" in the shielding to let this lower frequency radiation into the VFO.

It can be successfully cured, I have a Ranger 1, Ranger 2, Valiant 1, Valiant 2, Viking 500, Navigator, and Pacemaker and none chirp on 40 CW.

Rodger WQ9E

> 
> Dear OM,
> 
> Is the chirp the ABSOLUTE worse on 40-meters, than on the other high bands...?
> 
> I had a similar situation here with my Ranger years ago, that I traced back to feedback into the VFO from the rest of the rig. Keep in mind that on 40-meters, the VFO frequency operates "straight through" to the final PA stage: no doubling / tripling. 
> 
> Why I never had the same troubles on 160-meters is a mystery to me---perhaps the fundamental 1.8-MHz signal frequency is low enough that it was somehow "immune"...?---not so on 7-MHz, however...
> 
> ~73~ de Eddy VE3CUI - VE3XZ
> 
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