Re: QMX RX BPF troubleshooting, a new clue
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Roger that, Hans. It is an amazing circuit!
The question of "is filtering before-or-after the switches?" is sort of meaningless I think. The switches and integrating capacitors are married rather inseparably.?
The question might take on some merit if the input signal was so large that the channel resistance of the mux switches underwent modulation by that signal: a major nonlinearity.
That would require a rather *Yuge* input signal! Hundreds of millivolts, probably, to be meaningful.
We enjoy the benefits of this nearly unbreakable design every day as it has become a clear winner in cellphones. Kudos to the genius of Dan Tayloe!
JZ
Hello JZ
Yes but does it really move the filtering effect to BEFORE the multiplexer switch... or is it a filtering effect BEHIND the multiplexer switch, as would occur in the thought-experiment diode mixer?+ op-amp low pass filter (for example)... hmm... Anyway, regardless of the theoreticals, I love the QSD which is why I have used it so much for everything, fantastic circuit, unrivaled performance:price ratio.?
It's not magical, actually. It is a direct consequence of the switched-capacitor tracking filter origins of this circuit.
JZ
? I have had a diode ring DC receiver and a QSD Tayloe detector running
side by side. There is simply no comparison. The diode ring will serve
up plenty of news and music along with your CW or SSB. Not so much
with the Tayloe circuit.
Yes, I agree completely, it's an EXCELLENT mixer... I'm just not able to convince myself of the inbuilt pre-selector thing, and no benefit in any BPF at all ahead of it... I'm feeling the large IP3 is what makes it so good, not any magical pre-selection... could be I'm wrong though.
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