I'm trying to think of a modern Ten-Tec radio that doesn't use a relay for
T/R switching, and can't think of one!
Their reed relays are plenty fast enough and I see no real benefit over PIN
diode switching except for longevity. Still, few relays fail in these rigs
even after 20+ years.
I did replace the T/R relay in my Omni VII with a Matsushita/Aromat RS-12D
reed relay, made specifically for RF switching. While the stock Omni VII
relay is reasonably quiet, it's possible to take the slight ticking noise to
zero with the RS-12D.
Ten Tec used an ingenious scheme to isolate the T/R relay. They mounted it
on a very small PCB and cushioned it with foam. I took their idea a step
further and replaced the solid conductor wire with ultra-fine strand,
silicone jacketed wire from a robotics company.
http://www.trossenrobotics.com/store/p/5224-22AWG-High-Strand-Count-Silicone-Wire-Combo-Pack-25-ft-.aspx
The new wire is super flexible and does not acoustically transmit the
armature noise back to the PCB. Totally silent QSK now even when placing
the ear on the cabinet.
Paul, W9AC
|