[Elecraft] K3 with a Kenwood TL-922A

[Paul Christensen]

For folks not wanting to modify their amps, a solid-state amp buffer can be 
placed between the K3 and TL-922.  I like the Jackson Harbor "Keyall" 
circuit since it can switch up to 500V AC/DC at several amps and it 
optically isolates the K3's switching transistor from the amp.

http://wb9kzy.com/keyall.pdf

The Keyall is sold as a kit through Jackson Harbor Press, although Andy, 
W8CNZ is providing an assembled plug-'n-play device for about USD $25.

Paul, W9AC


----- Original Message ----- 
From: "Joe Subich, W4TV" <lists at subich.com>
To: <elecraft at mailman.qth.net>
Sent: Friday, September 02, 2011 9:38 PM
Subject: Re: [Elecraft] K3 with a Kenwood TL-922A


>
>
> > Anything I need to know before I hook the K3 up to it.
>
> Don't do it!  The TL-922 has a high voltage PTT line with *no* current
> limiting and no reverse EMF diode across the relay coils.  The relay
> current is rather high and the "spike" when releasing PTT is quite
> high.  You will need to add a Harbach engineering "soft key" board -
>   www.harbachelectronics.com/main/page_products_kenwood_tl922a.html -
> in order to keep from blowing the K3's keying FET and potentially
> causing other damage to the K3 due to the spike.
>
> Even if you add the soft key board, I would recommend adding "back
> diodes" across the T/R relay coils and adding a series resistor in
> the relay line to keep the current down and minimize the potential
> for a spike.
>
> 73,
>
>    ... Joe, W4TV
>
>
> On 9/2/2011 8:57 PM, Chris Hembree wrote:
>> I am buying a Kenwood TL-922A Amp. Anything I need to know before I hook 
>> the K3 up to it.
>>
>> Thanks
>> Chris W7CTH
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