[NLRS] Wanted:Modification Info for Lowband Motorola Maxar for 6 mtrs; Bandpass Filter

[Dr. Gerald N. Johnson, electrical engineer]

Probably the main thing will be raising the cutoff frequency of the low
pass filter, but then only if you want to use it up in the 53 or 54 MHz
range. Its sure that the cutoff isn't going to be so sharp as to allow
it to run on 49.990 and not just as well on 50.067... The same applies
to the tuned circuits in the multipliers, though for optimum noise
bandwidth one would like to take a turn or two off each coil so a higher
than normal capacitance value could tune each for a higher loaded Q.

One of these days you should have the Maxar 80 manual that I've sent so
you can see the details.

The PA and low pass filter of the Maxar are somewhat narrow banded. In
my manual collection, I noticed that Mitrek low band units cover 30 to
50 in one unit, no subbands and the PA is matched with toroidal
transformers (as in HF solid state PA) without the band sensitive
matching of the Maxar family. I was interested in using a few Mitrek PA
decks with appropriate power splitters and combiners for a 6m buffer
stage (waiting for me to build something with a few tubes and lots of
power) but I found the 100 watt Mitreks tended to have excessive asking
prices and when I found a Mirage on ebay, I bought that instead.

The output of a Motorola FM crystal radio as a beacon should be very
clean, but I doubt the ICE style filter would help clean any noise from
in band operation. I don't think its sharp enough to pass 50.067 and
stop 50.1 and up.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.