[Elecraft] 2 radios, 1 antenna... finally a prototype!

[Vic K2VCO]

JEAN-FRANCOIS MENARD wrote:

> I finally did a first prototype of an interface to link two K2/KPA100  
> on one multi-band HF antenna using Don W3FPR schematic. For my first  
> "from scratch" project, it is not too bad. 
<snip>
> Take a look... http://homepage.mac.com/jfmenard/PhotoAlbum55.html

The only thing that bothers me about this circuit is that if the Amp Key 
output from either K2 is disconnected for any reason, transmitting on 
the other one will put RF into the front end of the first one.

I thought of several ways to make the circuit fail-safe with a few logic 
gates, but I'll leave it to the real circuit designers to suggest the 
best way.  I would suggest using the 8r signals from the K2s in addition 
to the amp-key output.  The 8r is on in receive mode, and you could 
arrange things so that unless either an 8r signal or amp-key ground is 
present, that K2 will always be connected to the dummy load.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco