[R-390] ER article for R390A SS regulator

[Roger Ruszkowski]

Are there solid-state (FET, etc.) replacements for the oscillator tubes that would eliminate the need to regulate any filament voltages?

Thanks,
Barry - N4BUQ

Barry, there once was a fellow in San Francisco ( 20 years ago) who claimed any tube (R390 size) could be built
as a plug in solid state device. He did a 6DC6 for me. Compared to a real tube in the front end of a receiver my one 
off device did not have the gain. A real tube was hearing more signals than the solid state device. 
The noise floor was up as there was more in the band pass to hear.
If you can not hear the signal noise floor means nothing. 

But for an oscillator a solid state device could be a real possibility.

Perry was looking for some 7 pin male plugs as was I. 
This is the current limit in experiments.


Tish put up a link to a PDF on the once offered device to replace the ballast tube.

Read the fine print. 
Playing with the line voltage / current / power in the lab only produced a 12 hertz VFO frequency shift.
There is a thermal lag in the ballast tube.

Some lag also comes from the filaments of the VFO and BFO themselves.

The solid state device looks to even regulate this 12 hertz oscillator shift.

Just the idea of running the two oscillators in tubes with filtered DC filaments sound like a step
forward in lowering the noise from the oscillators into the receivers signal path mix. 
An then get voltage regulation on top of that.

But now we have to remember the whole VFO stability drift topic is over a shift of just 12 hertz.
The Doctor said so. He did the definitive testing. 

Solid stating the oscillators has got to offer more than 12 hertz stability. Some thing has to come
in better noise floor. Possible a different signal level being presented to the mixer thus yielding
a better stronger, less noise output from the mixer tube whit out other modification beyond just swapping in a solid state VFO  and BFO device.
You will want both as the filament string goes open with just one device. 
Drive up the part count to sell a few more to dive down cost. 
Both VFO and BFO would be useful.

Roger Ruszkowski