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[AMPS] Is screen potential important?

To: <amps@contesting.com>
Subject: [AMPS] Is screen potential important?
From: rfamps@ic24.net (Steve Thompson)
Date: Sun, 26 Mar 2000 08:34:26 +0100

-----Original Message-----
From: measures <2@vc.net>
To: AMPS <amps@contesting.com>
To: <amps@contesting.com>
Date: 25 March 2000 11:54
Subject: [AMPS] Is screen potential important?


>
>In a G2DAF amplifier, screen potential wanders from zero to approx. max.


It doesn't wander. It follows the rf envelope.

>Some say that screen potential can wander about with no serious
>consequences.  Please consider the constant-current curves for the 8171
>posted at the beginning of my Web site.  One set of curves is for a
>screen potential of 500v.  The other set is for 1500v on the screen.
>Assuming a peak grid potential of +10v, with1500v on the screen, peak
>anode current is c. 12a.  However, with +10v on the grid and 500v on the
>screen, .peak anode current is 3a.

But screen voltage is set by rf (=grid) voltage. If +10 grid gives +1500
screen it won't suddenly or randomly give 500V screen instead. The time
constant in the screen system is in the order of usecs, the fastest edge in
a SSB signal is in the order of 100us - to all intents and purposes, the
screen will follow the rf envelope.
I don't think you could get +10 grid and 500 screen at the same time with a
normal SSB drive signal.

Steve


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