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B- on RF Amp

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March 15th 05, 11:07 PM

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On Tue, 15 Mar 2005 15:11:40 +0000 (UTC),
(Chuck Hanavin) wrote:

In article ,
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On Mon, 14 Mar 2005 18:37:26 +0000 (UTC),
(Chuck Hanavin) wrote:

I was wondering what the advantges are of having B- on RF amplifer
instead of just grounding it? I think it may be that the plate meter
doesn't have a huge voltage across it, that can arc to ground. But what
if you are using a triode and just have a cathode meter, no plate meter
is the B- necessary? Any comments are appreciated.

thanks-Chuck (W3FJJ)

What kind of circuit? Is the B- applied to the grid? What class of
operation? You mention meters so this is the final stage of a
transmitter?

Class B linear, 3cx3000A7, Can be a final stage or used as
an exciter for 3cx1000000, hi hi, the B- doesn't not go to the grid but to
the centertap of the filimnet tranformer. well throught a cathode DC amp
meter...

On most modern amplifiers schematics they all seem to
use a b- lead which is basically the negative lead of the high voltage
lifted abouve ground by low ohm resister (10 ohms, 25w ). Im sure this is
done for a reason. Im looking for input on way this matters,
thanks-Chuck

I think Roger has your answer. I thought you were seeing a B- power
supply - which is sometimes used in Class C finals for CW ops. What
you are dealing with is just a sampling point to sample current
without the high voltage insulation problem you would see with a B+
inserted current meter.

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