Thursday, December 4, 2014

Seperate Receive and transmit paths for the Elecraft K3 Internal K144XV Transverter

When using the Internal K144XV  2m transverter in my Elecraft K3, it has a single BNC connector on the back panel for receive and transmit signals. Having obtained an HA8ET 2m mast head preamp I needed to separate the two signal paths to avoid putting RF up the back of the preamp.

Elecraft in the past have said it is possible to connect a separate RX antenna to transverter but nothing has ever been documented! The only clues have been the comment  in the K144XV manual about not removing links P2 and P3 inside the transverter. Time to investigate!

I took the cover off the K3 and the K144XV transverter and found that if the link between pins 1 and 2 of P3 was removed the receiver went deaf.  Pin 3 was ground.  I connected a coax cable with centre conductor to pin 2 and the braid to pin 3 the GB3VHF beacon could be heard on my collinear. The radio still produced the normal 9W out of the BNC connector on the back panel.
I did not want to solder to the header so I found a 3 pin female header (previously used for arduino shields) and soldered a piece of RG174 with a BNC socket on the other end, which hung out of the back of the lid panel. I did look at tidying up the cabling by using the AUX RX BNC connector but this would mean taking the K3 apart and removing the sub receiver every time I wanted to change between internal and external 2m antenna switching.
For reference P2 link allows the Receive IF output to be diverted from going to the KXV3A module. P8 link enables the DC voltage on transmit on the centre pin of the Transmit port.


I have written up the "Seperate  Receive and transmit paths for the Elecraft K3  Internal K144XV Transverter" modifications with pictures at http://g4fre.com/kx144_split.htm


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