I was interested in the same topic a few years ago and I made a bunch of
measurements on some Icom radios.
Look at http://www.bnk.com/W0QE/Radio_Measurements/amplifier_timing.html
Bottom line was for all the all the radios I measured I never saw
anything like 3mS on relay closure. However both the IC-706 and IC-7000
have a negative holdover on the relay release in the full QSK mode which
is quite scary.
Tim Duffy K3LR wrote:
> Hello Paul!
> The rig delay of only 3 Ms could be a real problem.
> We never run QSK, so I am sure that helps prolong the life of the relays in
> use at K3LR. The K3LR Icom radios and computer CW keyers and voice keyers
> all have small delays that allow the amplifier relays to close properly
> before RF is applied, so I am sure that helps as well.
> As you point out, radio + amplifier "handshaking is important.
> Tim K3LR
> -----Original Message-----
> From: firstname.lastname@example.org [mailto:email@example.com] On
> Behalf Of Paul Kelley N1BUG
> Sent: Sunday, March 30, 2008 1:10 PM
> To: 'Amps'
> Subject: Re: [Amps] Relays
> 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
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