>Hello all,any body got a single 4cx1600b going yet??
I have heard from those who are having grief. Some free advice: If you
aren't intending to use the 4CX1600B as a VHF oscillator, it is important
that the 50 ohm grid termination R NOT be connected in series with an
inductor. I have seen diagrams floating about that advised connecting an
inductor in series with the grid termination R to semi-cancel the
capacitive reactance of the grid at 15m to 10m. Such an inductor will
not cause fundamental instability---however, it increases anode-to-grid
feedback at the anode circuit's VHF-resonance. A better method of
cancelling grid-C in grid-driven amplifiers is by connecting a small
roller-coil between the grid and a C-divider from the anode to
chassis-ground. When the ratio of the C-divider equals the ratio of the
grid-anode C divided by the grid-C, the amplifier will be in
neutralization whenever the roller coil is tuned for a one-to-one input
SWR. The bottom-line is that engineering shortcuts are virtually
certain to have an engineering trade-off.
Another precaution is to use a zener-string shunt regulator on tubes
that use less than about 1000 screen volts.
Details:
http://www.vcnet.com/measures
see *Amplifiers*.
Rich---
R. L. Measures, 805-386-3734, AG6K
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