RaDAR – QCX Recovery

The QCX is an awesome kit using modern technologies to achieve it’s excellent results. Mine was successfully built but had an audio problem and comments on the QRP Lab forum led me to believe the problems may lie around the receive transformer T1.

The QCX’s PC Board is very finely designed and doesn’t easily stand up to anything more than the initial soldering of components. Removing T1 for a rewind was a recipe for disaster which became reality. My rig was reduced to that of an intelligent QRP beacon … the transmitter still worked.

I built up the courage over a week or two to make a plan to wire in an alternative transformer. I used a T80-2 and even then winding the four coils was a mission. I used veroboard and soldered the coil’s four start’s and finishes in a sequence I could implement within the remaining PCB contact points …. those that weren’t damaged through removal of T1.

I had to connect directly to a Surface Mounted IC, pin 7, in one case. I actually used the wire itself as an extension to my soldering iron bit by strippinng the wire, soldering leaving a little excess solder, touching the IC pin with the wire and heating the wire till the blob of solder at the end melted and flowed between the wire and the IC pin.

Success …………

Peaking of the Band Pass Filter – C1. Also presently fully un-meshed at the peak which requires removal of a few turns on T1 but easier to do now ….. next week’s task but peaked sufficiently I think to use this weekend!

I simply tucked the receive coil under the chopping board and fixed it in place with double sided tape. The QCX was saved.

I still have a bug in the QCX’s audio section but I at this stage don’t want to try desoldering again causing inevitable damage to the PC board so I’m still using my workaround by connecting a 49er board’s audio section to the QCX’s volume control. It works well enough.

Looking forward to making some new contacts with the QCX again this weekend!!!

73 de Eddie ZS6BNE

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