|[AMRadio] Safe Metering for Blind Operators|
Mike Duke, K5XU
k5xu at jam.rr.com
Mon Jan 3 13:43:25 EST 2005
"In my homebrew rigs with triode finals, I place the plate meters between
common point for grid leak/bias supply and PA filament, and ground. The
Gates BC1-T does it the same way, with no HV on the meter."
I've been reading the discussion of safe metering with great interest, as
perhaps explained by my subject line and signature.
I would love to find a good plate modulated transmitter in the power class
of a DX100 or Valiant, in which the plate meter would not have the full
plate voltage across its terminals. Is anyone aware of a commercial or
surplus transmitter with this design feature?
I could easily and safely tune such a transmitter by connecting an audible
meter-reading device across the meter terminals. I still have the circuit
which I used successfully with a DX60, and very cautiously with a Viking
Ranger from 1969 - 1974. I learned quickly that the ranger meter is at full
plate potential. The good news is that I lived to tell about the experience.
I also recall reading somewhere of using a voltage divider in order to
obtain a safe potential level in the external audible reader. If anyone on
this list has ever encountered a transmitter which was modified in this way,
I'd like to know more about how it was done, since I'd love to put a Ranger
on the air in order to re-create my first station.
The point can be made that the easiest route is to put a rice box and linear
combination on the air. Yes, that would be the easiest thing for anyone,
but, not nearly as much fun!
Mike Duke, K5XU
American Council of Blind Radio Amateurs
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