Apache PTT Relay

[Stu Lyon]

Glen and Larry;
Running AC down the mic cable seems to me to be a real "hum" maker. Also the
life of the PTT switch in the mic would be comprised. It would seem a better
approach would be what every manufacturer does and that is buffer the PTT
switch with an active device such as a triode or hexfet.  I would steal a
design from a SB-101 or -401 -- both which use a triode.

Another possibility is the Harbach SoftKey which is designed to key a SB-200
amplifier and a low cost option. The problem there is that the Harbach site
is not showing their catalog pages at the moment.
http://www.harbachelectronics.com/

The convention in Heathkit mic connectors is pin1 is the mic audio, pin2 is
a PTT switch-to-ground. The connector shield is the return for both
circuits. The relays in both Heath rigs are around 2Kohms.

73, Stu W6CUX
Winnetka, CA
W6CUX at earthlink.net

----- Original Message -----
From: "Glen Zook" <gzook at YAHOO.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Wednesday, July 14, 2004 9:58 AM
Subject: Re: Apache PTT Relay


> Just use a relay with a 6.3 VAC coil.  Run the "hot"
> side of the heater ("filament") string to one side of
> the relay coil.  Then run the other side to the pin on
> the microphone jack that is used for push-to-talk.
>
> Grounding this pin through the microphone will "key"
> the relay.
>
> It might be better to install a silicon diode (i.e.
> 1N4001, etc.) and add a good sized capacitor (like
> maybe 1000 mfd or even higher @ 25 volts) to make the
> relay run off of DC.  This should eliminate any "hum"
> from being introduced into the microphone preamplifier
> due to the wiring in the microphone itself.
>
> If you use DC, then make sure and add a diode across
> the coil in the reverse direction (cathode end of the
> diode to the positive voltage and anode end to the
> negative voltage source).  This is to prevent an
> inductive "kick" when the coil is disenergized when
> the microphone PTT switch is opened.
>
> Glen, K9STH
>
>
> --- lgrindel <lgrindel at MAIL.EV1.NET> wrote:
>
> I would like to change the original "single pin" mike
> plug for the "two pin" type used in the rest of my
> Heath gear. I would also like to add a PTT relay.
> Wiring the relay across the plate switch is pretty
> straight forward, however I am confused as to how to
> energize the relay using this two pin plug.
>
> =====
>

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