...(Rich)
>>However, with Rich's approach, no grid current can flow, and, for Class
>>AB1, that is not an option - - like it or not.
>
>Sure - provided you proportioned everything so that the exciter can't
>radically over drive. F'r instance, take a 4CX1000 with -60v on the grid,
>and a 100 watt driver. Then we have 18 ohms of shunt resistor.
18 ohms is not convenient to match to 50 ohms. 12.5 ohms is, using a 4
to 1 bifilar input transformer. 144w of drive would produce 120v peak at
the input of the input transformer, and 60v peak at the grid. With c.
320 screen V, all would be well.
>If we
>change to a 200 watt driver, we'll have 170 volts peak to peak, ...
I calculate the potential of 200w-rms and 50 ohms at 141V-pk. The grid
would see half that, or 70.5V-pk, so the grid-bias would need to be
increased to -71v and the screen potential increased to c. 385v. Since
the max. rating of the screen is 400v, no problema.
...
>>- The advantage of resistance-wire suppressors is that, at 100MHz,
>>they exhibit about 40% less Rp than do otherwise similar, conventional
>>suppressors made from copper-wire.
>
>Is this 40% less Rp than the 'conventional' parasitic suppressor i.e.
>coil and shunt resistor, or just 40% less Rp than the coil alone?
The comparison involved similar, complete Ls/Rs VHF suppressor
assemblies. One was a W8JI/C.T. Rauch, Jr. design the other suppressor
was essentially identical except that resistance-wire was used for Ls
instead of copper-wire. N7WS' Rp measurements are published at:
http://www.vcnet.com/measures/Rp_comp.html
...snip...
Rich---
R. L. Measures, 805-386-3734, AG6K
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