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OK... I'll bite. What exactly is Orr's... "super cathode driven"
circuit all about ?? Is this simply semi floating the grids on a
3-500Z.... or something else ?

25 years ago.... there was this circuit for a 4CX-1000.... and I
thought it was called "super cathode driven".... might be wrong...
believe it was in either cq or 73 rag. If I remember correctly...
Drive was applied to both the cathode and the control grid at the
same time... and the screen grid was grndned for RF. I still know
of two of those 4CX-1000 amps that are still round.. within 200
miles of me. The kicker was.... it required 160 watts to drive
it to 1200 w out. At the time it was no big deal... since the
xcvr's used were FT-DX-400/401's.

### a local across town from me in the 80's built one.... took
out 100 khz of 20m with it.... not imd... but shot noise. My
Drake R4C noise-blanker took it right out on RX... and I could then
get real close to him... within 15 khz. We both had yagi's up
70'.... and only 2500' apart. He subsequently found the problem...
never was told what the problem actually was. His xcvr at the
time was a 101ZD...with 6146W finals.

## The guy's with the FT-DX-400/401 xcvr's had clean sigs on
75m... so the concept worked... albeit... not a lot of gain ...
8.75db

Later... Jim VE7RF

On Nov 9, 2006, at 1:48 PM, pentalab wrote:

OK... I'll bite. What exactly is Orr's... "super cathode driven"
circuit all about ??

The driving signal is applied between the cathode and the screen instead of between the cathode and the grid, and the control grid is connected to the cathode. Thus, the gain is c. the same as the screen amplification factor.

Is this simply semi floating the grids on a
3-500Z.... or something else ?

25 years ago.... there was this circuit for a 4CX-1000.... and I
thought it was called "super cathode driven".... might be wrong...
believe it was in either cq or 73 rag. If I remember correctly...
Drive was applied to both the cathode and the control grid at the
same time... and the screen grid was grndned for RF.

Correct. ...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org