>Lane,
>
>Are you looking to run these guys as a linear, or as plate modulated am?
>
>If the latter, then you'll be pushing the vacuum variables if you run
>5KV on the plates, since at full modulation, the plate volts hits 10KV.
>
True, Peter. However, since the RF peak V rating of vacuum variable
capacitors is 60% of the DC/60Hz rating, the 12kV rating is actually a
7200 RF peak V rating. IMO, breakdown of such a capacitor would be
likely during 100% modulation crests.
>If you run it as a linear, then you'll only get about 1KW to 1.2KW of
>carrier - the PEP is 4 times the carrier for AM.
>If you are plate modulating,(and running, I guess Class C) then getting
>the screen supply from the plate by a dropping resistor is probabaly the
>best approach, unless you can get a modulation xfmr with an extra
>winding for the screen. For plate and screen modulation, you'll need a
>hefty mod. xfmr., and a modulator capable of 2500 watts or so of audio.
>
>Straight screen or grid modulation is another approach. They're more
>tricky to set up, and usually run about 30% efficiency on the carrier,
>but need less audio.
>
>In Class C, plate modulated, a pair of 4-1000's will run 2780 watts
>carrier output, which with plate and screen modulation will be 11.12KW
>PEP. That needs 3KV on the plate at 1.2Amps, and 500 volts at 290mA for
>the screens.
>
>As a linear, grid driven AB2, you'll get 3KW PEP, or 750watts of carrier
>if you 100% modulate. ...
In the Eimac technical specifications for the 4-1000A/8166 there is no
information about Class AB2 "linear" operation. According to what I see
in the 8166's constant-current curves, grid-driven linear operation is
feasable with zero grid current (Class AB1), and 1000v on the screen. A
screen potential of 500v would reduce the power output by about 2/3. In
the grid-driven configuration, grid current clearly equals non-linearity.
Rich---
R. L. Measures, 805-386-3734, AG6K
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