[Johnson] My Viking II

Climber _ [email protected]
Fri, 21 Mar 2003 08:31:41 -0700


Concerning your apparent low modulation levels: I am not sure what the 
problem is in your specific rig, but be advised that the Viking IIs had a 
serious shortcoming: There was just no way to 100 percent modulate the 
things. This is because � even though Johnson CLAIMED the 807s modulators 
were running in AB2, the fact is that if you ever tried to drive them into 
grid current, the whole system would fall into distortion. Hence, they are 
capable of AB1 only. I discovered this on my own, but I later saw a copy of 
Electric Radio where the author had made the same determination.

Sadly, over the years there were many attempts by hams to rebuild the speech 
amp in the rig to correct the problem, but it was my experience four or five 
years ago that the very best way to improve the modulation in the Viking IIs 
is to throw in some VR rubes to regulate the 807 screens, and to build a 
regulated bias supply for the 807 grids. Then � once the tubes have the 
headroom to properly modulate the transmitter at full output � you will have 
a much better radio.

There are other improvements that can be made, too. For example, the 
transformer driving the grids of the 807s is not the best. But the fact is 
this: The Viking II is incapable of 100 percent modulation as it was shipped 
from the factory. Don�t ask me why they did this, but they did it.

Interestingly, I have a Ranger II, and it does not have this problem, And my 
Ranger II, combined with my Johnson Desk, is one of the nicest sounding rigs 
around � but don�t ask me why the engineers did such a marginal job on the 
Viking II modulator section. And don�t ask me why the engineers claimed the 
circuit ran in AB2, which it positively could not and would not.  That�s a 
question for the historians.

By the way, if you load the finals to only about 80 watts of carrier, the 
modulation section can get by. If you go any higher, be prepared for audio 
reports that are not the best.

� Richard, WB5NEN







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