[ARC5] Solved: Where'd the Harmonic Come From?

[J Mcvey]

 What is the pate voltage and current you need? 
There is a 6as7 triode that can be had for $20 NOSI was also wondering if you could use a power pentode by running  a limiting resistor  to the plate for the G2 supply and a larger than usual bypass cap at the grid ?  Hokey, but might work?
Also, they make mosfets that can take 600 volts or more. Even though they are designed for pulse operation, they can be coaxed into working analog. You would want to have a limiting resistor in the source circuit because these thing will go to just about zero ohms when saturated. The threshold bias is very low too. The gate can take +/- 20v .Maybe this suggestion is sacrilege, though...??? 

    On Sunday, April 7, 2019, 6:51:26 PM EDT, David Stinson <arc5 at ix.netcom.com> wrote:  
 
 Figured it out.
Set the bias wrong in the Master Oscillator.
Can't just tweak it for "maximum smoke."  It was
driving the PA grid too hard and pushing the 6S4 
waaaay deep into Class C, making it act like
a frequency multiplier.  Was pushing nearly twice
the grid current (4 mills) needed ( 2 mills ).
Tweaked the MO grid leak value down and the output
waveform at the 50 Ohm non-reactive load 
cleaned right up.  Making good headway with the
modulators as well.

Looks like in AM, the 6S4 tubes are going to
be good for just over 4W carrier, a little better
than 12W PEP.  If we're biasing just for CW,
you can get about 6.5W carrier.  You can push
the PA grid current and get more, but the output
waveform suffers.

TNX ES 73 DE Dave AB5S


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