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Re: [Amps] Relays

To: 'Amps' <>
Subject: Re: [Amps] Relays
From: Paul Kelley N1BUG <>
Date: Sun, 30 Mar 2008 14:09:43 -0400
List-post: <">>
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 

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
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