Roger and Rich,
Okay, I've got the hot-switching bit figured out. What's the impact? I'd
guess that if the Kenwood is producing full output when the relay goes that
for a moment the SWR will go crazy causing the TS450 to cut back on power.
I doubt the rig would be harmed, but what about the antenna relay in the
SB-200?
Other than the QSK mod is there anything else that can be done? I looked
at Rich's homepage, but this appears quite complicated.
73 de Tom, K4NR
----------
> From: Roger D. Johnson <n1rj@ime.net>
> To: Tom Branch <k4nr@earthlink.net>
> Cc: Amplifier Reflector <amps@contesting.com>
> Subject: Re: [AMPS] Kenwood TS450 & SB-200??
To: <amps@contesting.com>
> Date: Friday, August 14, 1998 7:01 PM
>
>
> 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!!!
>
> Another interesting thing I found was that the
> switching voltage to the TR relay in the 940 was
> delayed 3ms from key down. It took another 2ms for
> the TR relay to switch. So with the
> stock radio, the TR relay barely made contact
> before the 940 started producing output! To
> help the situation, I found a voltage that went
> high right at key down and used that to drive
> a power FET to switch the amp relay. That gained
> 5ms but as you can see by the times
> above, still not good enough for QSK. I replaced
> the old 2 pole "clacker" relay in the L-7
> with a vacuum relay on the output and a fast
> acting 2 pole relay for switching the input and
> bias. I was motivated to do this by Rich's fine
> article on QSKing the TL-922. I did not
> follow his scheme exactly but it worked out well.
>
> 73, Roger
>
>
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