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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