Re: Multiband QCX


John VA7JBE
 

There are a few people who've tried to multband the QCX before, and it seems to be pretty easy.  In regards to the receive chain, T1 and the bandpass filter are the crux.  Some people have gotten around it by switching in more capacitance as needed to change the BPF peak (my favorite example of this is a varactor diode with a trimpot to really dial it in.)  Others have replaced the iron powder core with ferrite and a simple trifilar winding to maintain the balanced input but eliminate the BPF.  Still others have unbalanced the input entirely (like Guido PE1NNZ did: https://groups.io/g/QRPLabs/message/38064).  I seem to recall somebody else adding a socket to T1 so they could plug in different modules, but I'm afraid I can't find a reference.  Most approaches seem to work reasonably well and nobody has reported a significant degradation of performance so far.

Good luck!
John VA7JBE

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