It's a great thing to have a waterfall display on a radio. Even better, if it's from a second receiver, that can be used independently. That way, one station can be worked, while simultaneously exploring different signals on the band. Also, turning the dial can become touching the screen. Not the way to go for everyone, but I love it...
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QMX+ has an I/Q mode, that uses the soundcard as interface, allowing for a panadapter. A perfect solution for CW operation: Everything you need. Not-so-perfect for digimodes or future SSB, though: Those modes do need the soundcard for the audio data, so the current implementation does not allow for the use of the I/Q mode in the same way you can do in CW (this sentence may contain wrong assumptions as I do not have QMX at hand, yet). Also, the manual states, that the I/Q data delivered over the soundcard is not suitable for decoding digimodes. I remember having read thoughts about a? possible future implementation of a different type, maybe QMX+ will have that feature out-of-the-box some day, but while Hans is busy on ticking the SSB-To-Do-List, maybe it's not the right time to propose even more features...?
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So I'd like to come up with a different approach:
On my analog TRXes I had the same no-waterfall-issue. It could be solved relatively easy, by tapping the intermediate-frequency (using a buffer board like iface2 from tspelettronica) and feeding that signal into an SDR-receiver. The frequency syncing is done by polling the working freq via CAT from the TRX and feeding it into the SDR-software. That should be possible with QMX+, too, shouldn't it? Unfortunately my knowledge is very limited, so maybe the forum can help?
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* What I like to obtain is the analog input signal from the antenna (or intermediate frequency, if there is one) - to be able to feed that in a second SDR-receiver. The signal should be taken from at a point after the LNA , but before any narrow filters are applied. Thus, the antenna signal should not be worsened for the receivers and the second RX should get a broadband signal.
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* Also, the signal should be taken at best at a point that will never see the TX signal, so that my SDR receiver will have a long an peaceful live. If that's not possible, the buffer board mentioned above takes a 12V signal for PTT, that will isolate the circuit, while sending. In that case, I would need to know, where I can get the RX/TX switching from the QMX board.?
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Maybe someone could point out a suitable tap-point for the freq-out (and, if needed TX-detection) on the circuit board of the QMX+?
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* Tapping the signal directly would draw power and that would probably interfere with the inner-workings of the QMX. That's what the iface2 buffer board is for. It copies the signal without drawing significant power. The delay introduced is negligible, the software delay from the subsequent software processing is much greater. That buffer circuit worked great on my analog TRX, it should on QMX+, too, shouldn't it?
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* Am I on the right track? Maybe there's a different / better approach to get that panadapter feature. Any suggestions?
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P.S: My QMX+ is still climbing up the assembly-list (making good progress!), so this question is purely theoretical for me, right now. It will become more relevant in the near future, though and I might order that interface patine, which also has some delivery time in order to have everything ready when QMX arrives. I sure will post the results here, it just may take some time.
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Any help is appreciated!
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Yours Joe, DJ0CHE
