Semi-Heath-related ?s...

[mike bryce]

John..

Hold the phone!

what you want to do is very simple. You need a good high impedance switch
that will then switch to ground yet won't load down the other two rigs..

a transistor?

nope!

try a power MOSFET!


to use the very common "N" channel types, you'll need to build a small
transistor level converter to switch the fet. This level converter is simple
and is just a pair of transistors, one pnp and one npn.. the fet needs to
see at least +10 volts on its gate to be fully enhanced and then zero volts
to turn off.

since the gate drive current  is just about nil, you just parallel any
number of fets. since each one will switch to ground, all your muting,
keying and other problems are gone.

now, just to make things interesting.. you could easily add on an internal
sidetone generator, a multiplex the outputs using a 4016 or even a T/R
antenna relay switch.
--


sniff!?


I smell a QST article here!


Mike Bryce WB8VGE
SunLight Energy Systems
"Electricity at the speed of light"

> From: John Clifford <johnclif at ix.netcom.com>
> Reply-To: johnclif at ix.netcom.com
> Date: Sat, 21 Oct 2000 06:26:25 -0700
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Semi-Heath-related ?s...
>
> Greetings,
>
> I'm trying to use my MFJ memory keyer to both key my HW-9, and mute my Drake
> R8A.
>

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