[Amps] suppressors

[Karl-Arne Markström]

Even in smaller transmitters, similar metods had to be used.

The very "temperamental" 5 kW PEP Granger 172-2 MF/HF transmitters
had several Morganite 100 ohm resistors placed around the anode cooler of
the P-290A final, with one end grounded. 

They damped out VHF parasitic resonances
in both the tube mounting and its connecting leads.

Without them, a VHF power oscillator resulted at certain settings of 
the tune and load controls.

73/

Karl-Arne
SM0AOM




----- Original Message ----- 
From: "Peter Chadwick" <g3rzp at g3rzp.wanadoo.co.uk>
To: <amps at contesting.com>
Sent: Saturday, July 14, 2007 11:00 AM
Subject: Re: [Amps] suppressors


> Carl said:
> >However there are instances, for whatever reason, that a resistive material 
> solves the problem.<
> 
> Very definitely. There's a book now out of print called 'Radio Transmitters' by Brown of Marconi. He has quite a lot on parasitic suppression in big transmitters - and points out that the box can be a VHF resonant cavity (we're talking 50 -100kW transmitters or more) and resistive loading by having such a thing as an 80 ohm carbon resistor - Globar type, 12 inches long, 1 inch diameter -  with one end connected to the anode and the otehr in free space can privide enough resistive loading to kill a VHF parasitic. Or even several of them at various angles.
> Rather out of our legal power levels.......
> 
> 73
> Peter G3RZP
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