Topband: More clicks with QSK?

[Tom Rauch]

> Hmm, what would have been the cause of the blackened, pitted contacts
> on the antenna relay on my AL1200, which I had to replace, before I
> caught on to the delay settings in my MP.

The relay should have had the output normally open contact bent up so the
output contact makes connection solidly before the input contact and bias
contact closes. That insures the high power contact is seated before drive
is applied, and always releases AFTER the input contact is open.

If someone failed to do that at the factory then the relay is subject to
contact damage from hot switching, and the tank circuit (mostly bandswitch
and tuning cap) is also likely to have arcing problems.

If the relay is properly sequenced, the relay can be hot switched thousands
of times without problems. The most damaging hotswitch is always the opening
of the contacts, not the closing. That's because the arc is sustained longer
and has significantly higher voltage on opening. Arc duration on closing is
only measured in fractions of a millisecond, and only occurs with minimal
voltage (a few volts) across the contact gap.

The effect is much like striking an arc with a welder. The heat is on pull
back, not closure. Virtually all timing problems are closure related, not
opening.

But neither opening nor closing is a damage problem with solid state
100-200W radios driving amps unless the output relay contact opens before or
closes after the input contact. The input just isn't under that much stress.

73 Tom