[Amps] Pi-L Network

[Peter Voelpel]

Hi Tom,

The output impedance of the tubes are 1000-1500/3000 respectively.
The corresponding mid impedances are 600-800/1200 ohms.
Yes, I avoid that on my bandswitched homebrew amps for the mentioned reason
(arcs at the bandswitch).
I use 1/4 wl stubs in addition behind the amps and band pass filter on the
input.

73
Peter

-----Original Message-----
From: Tom W8JI [mailto:w8ji at w8ji.com] 


Are you saying the mid-impedance of the network, or the impedance across the
loading capacitor, is 1000-1500 ohms? 
Or 3000 ohms at that point on 160?

If so, I agree with you. You could get 6dB or more additional harmonic
suppression.

The problem is the loading capacitor has 3000 volts peak voltage at 1500
watts using a 3000 ohm mid impedance, and 2100 volts peak using 1500 ohms at
1500 watts

So while you might gain 6dB or more harmonic suppression into a 50 ohm
resistor load with a good layout, you now have to deal with 3000 volts where
most amplifiers only have 700 volts peak. This is OK in a monobander but not
easy to handle with components in a production bandswitched amplifier.