> Just plain-Jane open frame, unsealed type - actually 5, 12 or 24 VDC coils
> are fine.
>
> -Mike
Did you say if transmitting, receiving, and how much voltage you
might expect to have or the frequency range??
What works well for receiving are normal DPDT dip package relays,
I have many dozens in use with some being used for at least 15
years!
Many control relays are suitable for transmitting applications, no
need to buy anything exotic for HF applications using low or
modest impedance lines. Loss in any relay will be immeasurable at
HF, so the only real concern is the SWR bump they add and the
voltage and current ratings.
I use Magnecraft W389CX-7 DPDT relays for most switching
applications not handled by RCS-8V relay boxes or vacuum relays
(where speed is required).
That Magnecraft W389 relay is rated for 1HP 600VAC motor
control applications. Since that relay easily handles 10kW into
matched loads, it has a lot of headroom for SWR or operator
errors... like hot switching at a kilowatt or two. I pay under $10 new
for them, and they last forever. They not only reasonable in price,
they have a plastic dust cover with mounting tabs.
If you want a single-pole double-throw relay, especially one for
VHF, look at form-X contacts. This style contact pulls a shorting
bar between stationary contacts, so they have the advantage of
almost zero lead length through the relay. Since no thin long wires
carry RF, they are generally usable to a few hundred MHz.
When picking a relay you want to look at physical spacing
between contacts and the swinger's metal armature. Make sure the
relay has thick (16 ga or larger) but very flexible leads, and wide
contacts and contact support bars and terminals.
This is generally satisfied by relays used for motor control and
ballast operation. You can bet if the insulation passes UL testing
for 300-600VAC switching operation, and if contacts are rated at an
AC switching current of 15 amperes or higher at any voltage (that
rating is the actual hot-switching rating, which you will hopefully
never do), the relay will be an excellent transmitting relay.
73, Tom W8JI
W8JI@contesting.com
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