[Heathkit] SB-220 & TS-940S

[G. Beat]

Irv -

Many of the older linear amplifiers before 1985, use high voltage (110 volts 
or greater) and current (1 amp or more) -- 
that modern solid-state transceivers can not handle this voltage or current 
to "switch on" your amplifier.

A properly sized external relay in a protective enclosure (due to the 
voltages present) will work.

The Harbach mod places a high voltage/high current switching transistor 
inside the SB-220 ... and only
provides a safe low voltage and current for the transceiver (TS-940)
http://www.harbachelectronics.com/

Mike Bryce offers an external unit for those individuals who do not wish to 
internally modify
the SB-220 amplifier or do not have the proper electronic skills to install 
the Harbach mod or build their own interface.
http://www.theheathkitshop.com/ampkeyer.html

Your TS-940 Owner's Manual will also have specific details (cabling,  ACC 
jack wiring) for interfacing the rig to a non-QSK amplifier.

73 de Greg
w9gb

> From: irvingf
> Subject: [Heathkit] connection
> To: heathkit at mailman.qth.net
> Message-ID: <000001c48561$e39dd470$2602a8c0 at arvin4g5clavba>
> Content-Type: text/plain; charset=us-ascii
>
> Hi,
>
> I own a Kenwood 940s transceiver and just picked up a Heathkit SB220 
> amplifier.
> I was told that told that I would need an isolation relay in order not to 
> "fry" the radio.
>
> I found the Soft key 220 interface by Harbach Electronics on the Internet.
> Is this what i need for an interface?  Is it the best?
>
> I was told of an Icom interface, but this does not fit the TS-940 
> transceiver.
> Any help is appreciated.
>
> Irv, ka2zje
>