[amsat-bb] Conifer Update

["Gary \"Joe\" Mayfield" <gary_mayfield@xxxxxxxxxxx>]

I finally got a chance to play with the Conifer down converter a little more
last night.  Some of my previous statements were wrong.  Here is what I
believe to be the straight scoop.  The real designed for frequencies are as
follows:

Input  2150 MHz  (MDS Channel 1 not MMDS Channel 1 like I reported earlier)
Output 54 MHz  (At least I had that one right!)

My base LO frequency measured at 122.780 MHz this results in a final stage
LO frequency of 2087.263 MHz..
I believe the actual design was for a base LO of 123.294 MHz yielding a
final LO of 2096.000 MHz.

The 2087.263 LO frequency resulted in fairly accurate test results.

2155.000 MHz in yielded 67.737 MHz out
2152.500 MHz in yielded 65.237 MHz out
2150.625 MHz in yielded 63.362 MHz out

My test set consisted of the following:

Yaesu FT470 Hand-Held feeding a home brew frequency multiplier as my signal
source.
The Conifer downconverter connected to the 50 MHz port of a Yaesu FT847.
Pyramid 13.8 Volt power supply.

I have modified the Conifer making the second 'F' connector a power feed.  I
am using a .25 wavelength probe for an antenna on the dowconverter.
Separation distance from the down converter to the frequency multiplier is 2
inches.  I am using no other coupling between the two.  Signals on the 847
are quite strong S7 to S9.

My next step is to call my favorite Crystal company and see if the can make
a 138.235 MHz crystal for me.  This should yield a final LO of around 2350
MHz (i.e. 2400 in yields 50 Mhz out).  There are some "hair pin" filters on
the board that may need to be altered, and I know with the diode mixer a
preamp will be required for satellite work.  If anyone is interested I keep
posting my findings.

I expect it will be a few weeks to get a crystal.

73,
Joe
ka0yos@amsat.org

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