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Two Radios, One Antenna

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sprocket(at)vx-aviation.c
Guest

Posted: Sun Sep 18, 2011 8:07 am Post subject: Two Radios, One Antenna

Hi Bob.



I like this design.  One suggestion that I have is to provide an interlock 

on the PTT function.  For example, tie the common pole of the #2  PTT switch 

(currently tied to ground) to the top pole of the #1 PTT switch (currently 

not connected).  This makes the #1 PTT the 'master'.  This will prevent both 

transmitters from attempting to transmit simultaneously.



Your switch makes it easy to add a portable comm into an existing 

installation.



Vern



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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Sep 18, 2011 9:35 am Post subject: Two Radios, One Antenna

At 11:02 AM 9/18/2011, you wrote:

 	  Quote: 	
		  

<sprocket(at)vx-aviation.com>



Hi Bob.



I like this design.  One suggestion that I have is to provide an 

interlock on the PTT function.  For example, tie the common pole of 

the #2  PTT switch (currently tied to ground) to the top pole of the 

#1 PTT switch (currently not connected).  This makes the #1 PTT the 

'master'.  This will prevent both transmitters from attempting to 

transmit simultaneously.



Your switch makes it easy to add a portable comm into an existing 

installation.


	


   Yeah, I'm debating whether or not to productionize

   this design. It's really a really-quick-n-simple.

   But I've got a lot of more important projects on

   the back burners already . . .



   Not sure about the portable comm . . . you'd need

   to extend a ptt line to the antenna switch. It's certainly

   applicable to dual panel-comms but a pain in

   the you-know-what for a hand-held.



   I toyed with a solid-state, pin-diode switch

   that would switch by extended ptt lines . . .or

   perhaps one channel could do it with a transmit

   power detector. There's a number of amateur radio

   boosters for hand-helds that simply hook into the

   antenna feedline. In the receive mode, the booster

   offers front end filtering and pre-amp to improve

   receive functions . . . when you hit the hand-held's

   ptt, the booster detects the strong RF and switches

   to a transmitter boost mode.



   A similar technique could be applied to either a

   hard-contact relay version or a pin-diode version.

   I have the equipment to develop and test a solid

   state version but time to market for that task

   is much longer. I think I'd stay with relays for

   the quick-turn project.



   Bob . . .





   Bob . . .

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