[Amps] coaxial stub on amplifier output

[Carl]

Those are fairly common for multi TX stations to knock down harmonics and 
phase noise. I use stubs on the feedlines of all the monoband yagis and 
typical rejection is 25+ dB using CATV RG-11. On 80M I add a short length 
for CW. I often run 2 stations and at othertimes it keeps area hams happy 
since with a negative horizon my groundwave signal travels a long way.

And no, I havent used them for amplifier tuning except for an old 6&2M PP 
4CX250B amp I built ages ago.

Carl
KM1H



----- Original Message ----- 
From: "John Lyles" <jtml at losalamos.com>
To: <amps at contesting.com>
Sent: Monday, March 29, 2010 11:28 PM
Subject: [Amps] coaxial stub on amplifier output


> Has anyone seen anything in print about using a lambda/4 (Quarter
> wavelength) stub on the output of an amplifier with a tube. Its a nice
> way to bring water, tuning mechanisms into an output circuit, without
> looking like a short circuit for the primary frequency. This same stub
> is a half wavelength at second harmonic, so it reflects a short right
> across the output at F2. This should cause some plate current waveform
> modification, depending on where it is located physically with respect
> to the plate, i.e., similar to Tyler circuits.
>
> 73
> K5PRO
> John
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