> To: amps@contesting.com
> From: km1h@juno.com (km1h @ juno.com)
> Subject: Re: [AMPS] Yet more parasitics
To: <amps@contesting.com>
> Date: Tue, 11 Nov 97 20:31:08 +0000
Hi Carl,
> That is assuming the manufacturers even use bias John!
> The lack of adequate bias circuits for linear operation of the majority
> of VHF-UHF brick amps is a sore point with many users. It appears that
> only Teletec is using an active circuit that holds up under all drive
> conditions.
That's right Carl, using a series resistance and a shunt diode for
bias is just plain dumb.
It makes a great bias system for a CB "linear" or low power stage,
but the bias wanders all over the place when any base current
appears.
IMHO, QST ought to make most VHF amplifier manufacturers stop
claiming they are "linear amps".
The "bias" systems often do have LF parasitic paths, but then the VHF
stabilty is also poor in many designs. Quite frankly, most are junk.
73, Tom W8JI
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