The knife switch is cool, but I think using ordinary household 120V
wall-installed electric light switches is better.
First, you can use switches installed on opposite walls to provide
considerable isolation, and promote a healthy life by considerable exercise.
T/R time might increase to 10-15 seconds, but whatever the other guy says
for the first 10 seconds or so usually isn't important.
Next, in a contest situation you'll get a great deal of exercise, but all
indoors so weather won't be a factor as it might be with climbing towers.
Then, the house wiring will radiate some, to give you a more evenly
distributed radiation pattern to be enjoyed by other household members and
possibly even neighbors. I think if you load up all the house wiring, and
the right amount is vertical, and horizontal, you can eventually achieve the
long-sought after "isotropic" radiation pattern. And they said it couldn't
be done.
-WB2WIK/6
"Success is the ability to go from failure to failure with no loss of
enthusiasm." -Winston Churchill
> -----Original Message-----
> From: W0YR@aol.com [SMTP:W0YR@aol.com]
> Sent: Thursday, March 06, 2003 4:09 AM
> To: amps@contesting.com
> Subject: [Amps] Use of Manual T/R Switches
>
> After several failures of Dow-Key T/R switches and unsatisfactory results
> from open-frame relays, I have decided to use an old, tried but true
> technology: A knife switch.
>
> I have three here: one is about 2" X 4 1/2" , DPDT. The other two are
> larger, about 3 1/2 X 5 1/2", one on a phenolic base and the other on a
> ceramic base. I assume the ceramic base would be the best for 1,500 w.
> r.f.
> applications at h.f. My concern is the apparent lack of isolation
> between
> the input switch and the output switch, since the switch bars are only
> about
> 1 1/2" apart on the big switches. The amp is a pair of 4CX1500Bs, grid
> driven in AB1 and only 8 w. is needed to excite the tubes to produce legal
>
> limit output. While experimenting last week I got the worst r.f. burn I
> have
> ever gotten, but have now wrapped the switch bars in Saran Wrap and I wear
>
> rubber gloves when operating the amp. Feed back caused by coupling
> between
> the switch sections is a big, big problem and it has to be eliminated. I
>
> have put an upright piece of aluminum (about 4" X 2" between the switch
> bars
> but now I can't throw the switch. Anyone have any ideas. Also, my T/R
> switching time has gone from 18 ms. to something just under 4 seconds,
> unless
> I stand up all the time.
>
> Thoughts????
>
> P.S. Thanks to all those who helped me solve the knob orientation dilemma.
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
|