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[linrad] re use of Motorola Micor's

>Since I like to rob Motorola Micors, I will also be using helical filters robbed
>from them to produce needed selectivity in the 144 Mhz RF path.

Interesting, I have just become familiar with the Motorola Micor product Line. Here I am using a 132-142 MHz version re-tuned to 144 Mhz with a Hi Side LO injection. I find the local oscillator string to be exceedingly clean and the Mixer is just excellent. Since these were intended for repeater service the receivers front end performance is just excellent under large signal conditons. I padded C118 to bring the L106 coil assembly down to 5.3 MHz.

Specifically the Mixer Q101 is as good as any I have ever seen. I take the output from C120 into a short coax that feeds a crystal filter. The crystal filter is the 5.3 MHz IF filter from a Low Band, Master Progress Line Executive Series radio by GE. I mounted this filter in a small Pamona cast metal box, paint removed, and the filter output goes to a 2N5109 biased for 100Ma of current at 12V. A 2n5109 is a somewhat tamed 2n3866 and is
extensively used in the CATV amplifier industry.

Even though I live in the sticks out here, I have very RF unfriendly Paging transmitters both just above and just below 144-148 Mhz within 6 miles, line of sight. The previous RX's here, TR751, ICOM 271, IC-706 have all had strong reactions to these noisy paging transmitters, the Micor does not show any indication of seeing them at all.

I feed this into a Time Machine demodulator and it works excellently. The GE 5.3 MHz filter is somewhat unusual in that
it has minimal envelope delay distortion and gives me excellent performance.

Last but not least the LO multiplier chain in the Micor is also excellent and very easy to drive with an external signal in
place of the usual channel unit.

The Micor is a really great basic RX, designed for excellent performance under hostile conditions and for me it is
the best I have seen yet as a 144 MHz front end and converter.

Hope this is of interest to others.