> I am home brewing a coax switch for the shack. I want it
to handle 1500
> watts of power, but not to "hot" switch. I am looking at
PCB relays and
> found many that handle 10 amps, but only a few that
specify a high
> dielectric voltage. What kind of voltage should be
expected out of a
> legal-limit amplifier such as an Alpha or Ameritron? TIA
Keith,
Having been involved in this since the 80's, my advice would
be to NOT use DC or LF amperes, and you actually can't use
DC or LF AC voltage either. To pick a relay you'd have to
test through dozens of relays. In some cases they handle
more voltage and/or current than the DC ratings, in many
cases MUCH less.
I can show you nice looking large 30A relays that have
terrible current capacity at HF, some actually smoke at 1000
watts at 30MHz. Others rated at 2kV will have dielectric
failure at voltages produced by a thousand watts or less
into a 50 ohm load. Some very small relays can handle over
10kW!!
I normally spend days or weeks testing new relays from
vendors. Unfortunately that time is paid for by others so I
can't publicize results. I can tell you what to watch for.
The things you have to watch for are:
The RF path must NOT be through braided or woven conductors,
or through contact materials that are exceptionally lossy at
radio frequencies. Beryllium copper is good, but watch out
for plated steels that look like copper or silver.
RF current and voltage must not be through the coil, or have
a connection to the pole piece of the coil
Watch out for small area conductors, you need wide smooth
surface areas carrying currents.
Most of the engineering time (cost/investment) is spent on
picking a good relay, and doing a good board layout. That
care is why some switches like the DXE switch or the RCS8V
will blow away other switches that look like they have nice
jumbo relays. If you just pick a relay based on size or DC
ratings, you likely won't do well. Same for a board layout.
DON'T, whatever you do, make the common mistake of trying to
use 50 ohm traces over a groundplane on a double sided
board. You'll wind up with a horrible switch.
73 Tom
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