> arcing with up to a few thousand volts across a few
millimeters. I
> suggested a different relay configuration that doesn't put
high voltage
> across close-spaced contacts.
I don't follow that John. There is still high voltage across
contact gaps.
On 160 you'd have this:
Ant
160 coil top--NO-C-------NC---jmp
160 coil bot--NO-C-------NC---jmp
Coax
If the jumper had negligible self-capacitance, voltage
across the coil would divide equally between two C to NC
gaps, making voltage across each gap half of coil end-to-end
voltage. That is not zero volts.
In the real world the upper contact gap to the NC contact
would have significantly higher gap voltage than the lower
open gap.
I'm not saying that's a bad system or it won't work, only
that there is still significant voltage across gaps. In many
relays applying full HV to the moving upper contact support
bar, as the circuit above does, could be a problem.
The ideal relay would be a form X or double-make
double-break relay that pulls a shorting bar between
contacts, wired like this:
ANT
160 coil top --------NC----X-NO
160 coil bottom ----NC----X-NO
Coax
In this case when bar X moves to normal, the coil is
shorted. When energized full voltage appears only on the top
NC contact post that is now floating, and two gaps are in
series with (again) uneven division causing the upper gap to
have the highest voltage.
My main point is we are always, no matter what we do, stuck
with nearly full voltage across a gap.
This is a particularly common problem in relay switched tube
amplifier tanks. With a SPDT relay it should be wired like
this:
ANT and 160 coil top--NC------com--160 coil bot and coax
NO just floats
NC and NO can be swapped to reverse logic.
73 Tom
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