Thanks Tim,
That is reassuring. I have been using RJ1A relays in my HF single
4CX1500B for some time and have yet to experience a failure. I run
QSK CW frequently. I am also using them on my new 6m 4CX1500B amp
where I realize I'm probably pushing my luck... time will tell.
Recently I was asked to repair an amp using RJ1A relays that had
suffered contact failures. It wasn't all that much power, about 1
kW. I became curious as to why the relays had failed. The owner had
controlled the amp by a simple cable from the rig's amp T/R control
line to the amp. Unfortunately that rig only had a delay around 3 ms
after closure of the amp T/R contacts to the start of RF output in
both CW and SSB. The new RJ1A relays I installed needed 5 ms
(measured) to close and stop bouncing, so they would be hot switched
by that setup. Not good. I wonder if this sort of thing might
explain some of the vacuum relay failures we hear about?
I would add that fast relays can in some cases actually be slowed
down by the nature of the power supply or the circuit controlling
them. I always verify actual timing of the relays in an amp with the
RF output delay of the radio(s) it is to be used with unless there
is provision for 'RF hold off' handshaking between the amp and
transceiver.
73,
Paul N1BUG
Tim Duffy K3LR wrote:
> I have been using single Kilovac HC-1 and Jennings RJ1A relays for input and
> output T/R switching on all of my single 8877 amplifiers for the past 25
> years.
>
> Even in heavy contest operating, I have had no problems at 1500 watts output
> up through 50 MHz.
>
> 73!
> Tim K3LR
> http://www.k3lr.com
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