[AMPS] Neutralising tetrode HF amplifiers

[Chris W Tran]

Saturday 10th October 1998

Hello all

I enjoyed a visit to Rich Measures AG6K web-site - thanks for
the interesting info. Rich. (I also enjoy this reflector when
you guys can't agree on something!)

Thinking about neutralising a tetrode for 1.8-30MHz use, I
noted the method proposed by Rich (disconnect the tank cct.
and terminate with non-inductive R equal to the load impedance,etc)
- I was wondering if the simpler method (which I've only used
once with a 2 x 4CX250B amp. for 144MHz) would give as accurate
a setting ?  
The method is to feed 2-3W of, say, 21MHz RF, INTO the 'RF output' 
connector (with the HV and G2 supplies off, but filament and G1 bias 
'on' and the T/R coax relays activated), then adjust the 
'Neutralising' variable capacitor for minimum RF voltage developed 
across the input (grid) tuned circuit ?
(I'm not sure if the G1 bias should be 'off' or 'on')

Any thoughts ?

73    Chris GM3WOJ/GM8V
<chris.tran@zetnet.co.uk>



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