[AMPS] Amplifier Experiments!

[Jon Ogden]

OK...

This morning I did some experiments with stability on 10 meters on my 
4-1000A amp.

First I put in my original supressor design.  This consisted of 3 3watt 
metal film resistors in parallel with about 70 Ohms or so total 
resistance.  The inductor was one turn of #18 magnet wire with about 42 
nH inductance.  I had earlier tried more than one turn, but the resistors 
kept burning up.  The rest of the anode circuitry was brass plate stock 
about 1" wide.

Anyhow, on 10 meters, I was able to get out about 1200 watts with about 
95 watts in.

Then I decided to key the amp but provide no input signal.  I then varied 
the tune and load controls to see if I could make the amp oscillate.  As 
I decreased tune C down close to its minimum value, plate and grid 
current took off.  I had made an oscillator!  So obviously my supressor 
design did not work!

The anode circuit had a nice big dip in my GDO right around 80 MHz.

Next I took replaced my supressor design with supressors I had built from 
an AG6K kit.  Put them in.  Power out was not about 1050 Watts.  So I did 
have about 150 watts of loss in the supressors.  And I am using 3 runs of 
nichrome wire after the supressors to the blocking caps.  Anyhow, the GDO 
dipped at 80 MHz, but much, much less dip.  I put the dip coil in 
*exactly* the same place as previously.  Then I did the same zero signal 
experiment.  No oscillations occured regardless of the tune and load C 
combinations.  The amp was completely stable.

So Rich's supressors work far better then mine.  Am I concerned about 150 
Watts?  Well, it's less than 1.5 dB so  probably not.  And actually I 
think I can get more power out on 10 m if I could get a little more load 
C.  It's fully meshed when I tune up and pretty much stays that way.

OK...while I am experimenting on this nice holiday weekend here, anyone 
else got any good, quick supressor ideas that I could try out?

I am thinking of trying one of Rich's supressors by itself with my old 
anode circuitry.  Just experimenting that's all.

And I am not trying to start a war here.  Just reporting back real life 
experiments and asking for any comments.

73,

Jon
KE9NA


-------------------------------------
Jon Ogden
KE9NA

http://www.qsl.net/ke9na


"A life lived in fear is a life half lived."


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