Re: QCX for 2m VHF? #chat #qcx #vhf #mods

Jim Allyn - N7JA

You seem to be assuming that Dick was asking about a transverter.  I don't think he was.  I think he was asking about a 2 meter QCX.  Dick, the limiting factor on receiving would be how fast the FST3253 can switch on and off, and a quick glance at the specs suggests it probably won't work well if at all at 2 meters.  According to Dan Tayloe in his paper, "Ultra Low Noise, High Performance, Zero IF Quadrature Product Detector and Preamplifier":

"The product detector’s upper frequency limit is set by the ability of a FET to be turned on for only a quarter cycle of the incoming RF being converted to baseband."

I don't think the FST3253 is fast enough for 2 meters.  It seems to me I read that somebody used one at 6 meters, and I think that is pretty much the upper limit.  However, if you have some fast switching FETs, the sky's the limit!

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