[Collins] 30L-1 with Kenwood TS830 Advise??

[Dr. Gerald N. Johnson, electrical engineer]

The easiest interface would use a relay with adequate contacts for 200
volts and half an amp, perhaps driven by a transistor turned on by a TX
voltage from the exciter. Mods internal to the 30L-1 would be a bother
because the key line keys both the TR relay and the PA blocking bias
circuit. Since the tubes get a significant negative voltage to cut them
off, that's a bother to make solid state, though not impossible. An
optoisolator with 4 to 8 volts of photovoltaic output driving the gate
of a P type power MOSFET would work. Actually with the optoisolator a
more common N type power MOSFET would work. Like an IR PVI1050 and a
IRF820. Probably needs a 10K resistor from gate to source to be sure it
turns off, perhaps a .001 capacitor to be sure it doesn't latch up with
RF. IRF820 source to the 30L1 key line, drain to ground. Isolator
outputs in series and then connected with negative to IRF820 source,
positive to IRF820 gate. Makes the IRF820 work upside down but the
optoisolator makes that work good. Then the optoisolator needs 10 to 50
ma drive at a few volts that should be controlled with an external
resistor while checking the gate to source voltage on the IRF820 that
needs 7 or 8 volts to reliably turn on. It could be that simple.
Digi-Key carries the parts. Probably costs $5 in parts, extra for making
a small order.

73, Jerry, K0CQ, Technical Advisor to the CRA
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.