This schematic is a bit hard to read but it looks like the screens of the
tubes are grounded. If this is the case, then the cathode has to be above
ground
for d.c. by the screen voltage value. RF is another matter and appropriate
bypass capacitors will take care of that.
When the cathode is above ground for d.c. rf chokes are needed to help
isolate the rf from the power supplies (all three, grid, screen and plate). The
cathode bypass C does most of this but an rf choke only helps.
73,
Gerald K5GW
In a message dated 1/30/2006 10:14:38 A.M. Central Standard Time,
Chuck_Partain@maxtor.com writes:
ya
<http://www.angelfire.com/nb/ni4l/gu84b.html>
http://www.angelfire.com/nb/ni4l/gu84b.html
Look down at the ONE tube schematic.
This is the only one I have seen for HF so far that's not too convoluted.
-----Original Message-----
From: Bill Turner [mailto:dezrat1242@ispwest.com]
Sent: Monday, January 30, 2006 11:11 AM
To: Partain, Chuck; amps@contesting.com
Subject: Re: [Amps] cathode to ground in tetrode amp
ORIGINAL MESSAGE:
At 07:14 AM 1/30/2006, Partain, Chuck wrote:
OK, getting into this more and more every day and learning. Looking at some
designs on this GU-84b
amp, I see a lot if not most of the cathodes have resistance, some a
lot(30k) some little (.7) to ground.
The screen grid and control grids are not grounded and have respectively
~350 and -150v on them.
Why wouldn't it just essentially go to ground? what does the R do in series?
thanks as always.
KA1MWP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Is there a schematic we could look at?
73, Bill W6WRT
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