>
>OK, another question. I'm designing the output network for my amp, and I'm
>facing the issue of getting a reasonable Q on 10 meters with practical
>parts.
>The 1999 ARRL handbook has a discussion of this, and they mention putting a
>small inductance in series with the plate of the tube, before the pi-net
>input
>capacitor. This has the effect of transforming the plate load impedance to a
>much lower value (in their example, from 2200 to 1200 ohms), so that the
>pi-net can be designed with a more practical value of input capacity on the
higher
>bands. The effect of this inductance decreases with frequency, of course, so
>you can ignore it on the lower bands. Sort of a "L-Pi" (or L-Pi-L) network!
>
>Recently I was looking at a 30S-1, and I noticed that the plate tuning
>capacitor was a big air variable, right next to the shielding. "Collins
should know
>better", I thought, until I saw the little coil in the anode compartment!
>
>I know this was discussed a few months or a year ago, and I recall that KE9NA
>used this in his amp. My question is: what is the downside of doing
>this? It
>looks too much like a free lunch to me.
>
? Murphy said that things are more complicated than they look. In my
opinion, this is prime example of what he was talking about.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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