Topband: Antenna relays

[Tom W8JI]

DC or low frequency AC is an almost meaningless test, although field life is 
a good data point.

The only valid bench  tests for a relay in these applications are RF heating 
with high current, and voltage breakdown. Some relays even run current or 
voltage through the coil pole center, making a "capacitor" to the control 
pins. The relay has to be opened and inspected, or measured for stray 
capacitances.

Almost always the heating is in the contact bar or wire to the contact bar. 
Heating there is aggravated by RF current and skin effect, so it must be 
tested at radio frequencies.

Contact materials should be gold overlay and ideally have a small contact 
area, otherwise they develop receiving issues more frequently. The larger 
and more robust the hot switching, the less reliable the receiving becomes.

I find relays that can reliably carry 20-30 amps or more at 60Hz that heat 
and fail at 4-5 amps at 10 MHz.

73 Tom