[Elecraft] OT: Relays for antenna switching

[Phil & Debbie Salas]

I've built a lot of HF relay-switched projects, including a relay-based QSK
switch for my ALS-600 amplifier.  I've found that virtually any relay works
well at HF as long as the contact rating and voltage breakdown are
sufficient.

Since Power = I-squared R, at 100 watts and 50 ohms, you will have 1.414
amps RMS of RF current.  And since Power = V-squared/R, at 100 watts you are
looking at 70.7Vrms contact-to-contact voltage breakdown.  Multiply these
values by the square root of SWR if the relay will be used in a system with
an SWR greater than 1:1 (worst case value).

My favorite relays are the high speed OMRON signal relays available from
Mouser (653-G6A-274P40-DC12), or Panasonic DS2E-M-DC12V relays available
from Allied (788-1053).  These are DPDT relays with contacts rated at 3-amps
and 1000Vrms breakdown.  These relays switch in 3-5ms typical, which is
about as fast as vacuum relays.  I paralleled the DPDT contacts to give a
6-amp rating for my ALS-600 QSK switch.  These relays only cost about $3
each and plug into a 16-pin IC socket.

Phil - AD5X