on 5/28/01 4:55 AM, Jim Barber at N7CXI@SiliconPixels.com wrote:
>> ? The high-speed switching circuit shown in Fig, 7B on my web site
>> switches in under 2mS and it supplies adjustable bias for g-g operation.
>> It switches so fast that sequencing is obviated.
>
> I took a look, thanks. I don't know what flavor the existing
> output vacuum relay is, but the printing on it is "TCR1G N/O 7404" .
> It doesn't look like a Jennings, but I've made larger mistakes.
> Anyway, your bias switch design looks fine, and would fit on a
> board the size of the existing one. Even 18 or so 3A diodes,
> (tapped down) although I've heard stories of temperature
> instability going that route? (A question, not a challenge.
> Haven't done it that way before)
Rich's switching circuitry works absolutely outstandingly well! Your vacuum
variable in the amp is probably sufficient or better than an RJ1-A.
One minor correction that I would add to Rich's circuit would be to put a
bleeder resistor across the large cap in the "transformerless" supply
portion of the circuit. That's a large cap and you can still end up keying
the amp for a bit after switching it to standby mode.
Overall, an excellent design.
73,
Jon
NA9D
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)
Member: ARRL, AMSAT, DXCC, NRA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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