I think this didn't get out earlier. if you get this e-mail twice please
accept my apologies.
Gerard
> N1RJ wrote:
> Hi Tom...
>
> I know you addressed this to Rich but can't resist
> putting in my two cents worth. When I
> was planning to QSK my Drake L-7 amp for use with
> my TS-940, I used a scope with
> triggered sweep to take some measurements. These
> times may not be exact as I don't
> have the info right at hand and am going by
> memory.
>
> Key down.....scope triggers
> 5 milliseconds....940 starts producing output
> 6 milliseconds...940 at full output
> 15 milliseconds...L-7 relay starts to switch
> 20 milliseconds.. L-7 relay switched after some
> contact bounce.
>
> As you can see, the 940 was producing full output
> BEFORE the amp relay had even started
> to move! That is HOT switching!!!
>
> I did some similar measurements on a IC709 some time ago to use it
> with a QSK amplifier. Used the key line to trigger the scope. From
> memory it took a few ms for the amplifier key line to switch, and the
> 709 started producing power a few ms after that. No problems with hot
> switching the amplifier there, provided the QSK circuit used in the
> amp is fast enough. The problem I found was on key up. The amplifier
> switch line went high some 10 ms (again from memory) BEFORE the 709
> stopped producing RF! With a fast QSK switch (especially when using
> PIN diode QSK) you will be hot switching the amp on key up, not key
> down. I e-mailed ICOM tech support here in GB with my findings, and
> after a couple of reminders I was told that the switching times I
> found were 'typical for other ICOM equipment as well'. Beware.
>
> If somebody has done these type of measurement on other ICOM equipment
> I would like to here of the findings.
>
> Cheers
>
> Gerard, MoAIU / AA3ES
>
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