Please explain why varying the VSWR on the driver "causes grief"?
John ZS5JF
----------
> From: Rich Measures <measures@vc.net>
> To: John Fielding <johnf@futurenet.co.za>; Amps Contesting
<amps@contesting.com>
> Subject: Re: Fw: [AMPS] tuning capacitor & insulator
To: <amps@contesting.com>
> Date: 18 December 1998 06:56
>
> >
> >Eimac short form catalog gives typical operation in AB1 as 300W o/p with
> >2000Va and 400Vg2. Seems to me (and I have used a lot of 4CX250 types)
> >that 600W from a pair is all you can really expect and maintain
linearity.
> >Of course if linear operation is not required - eg for CW - then the
tubes
> >can be driven harder, more towards Class C, and then you can expect a
> >little more out. But the maximum grid dissipation is only 2 Watts so
that
> >could be a bit risky!
> >
> True enough, John, however when the grid is driven from zero grid current
> in AB1 to substantial grid current in Class C, input SWR rises abruptly -
> and that causes grief for the radio that is used to drive the amplifier.
> Compared to Class C, Class AB1 costs one about 1/5 of one "S" unit on the
> "S" meter. In my mind the bottom-line is that Class C has too many
> trade-offs. . If one needs more suds, 'tis better to use a larger tube
> in AB1 than to beat up a less-capable tube in Class C.
> - later, John
>
>
> Rich...
>
> R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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