[HCRA] W1MBT/R Status

[Marc]

               W1MBT/R Repeater
(446.775 MHz, - offset, PL77, repeater IDs as W1MBT/R
PL77)


After extensive scientific study, well long hours
anyway, I found that the excessive transmitter
frequency drift problem was directly related to
ambient temperature changes.  The frequency would
drift down about 2 to 3 KHz with a 10 deg F change in
ambient temperature.  This was repeatable.

After looking at the appropriate documentation, it
became clear to me that the crystal modules were not
temperature compensated, either properly or at all. 
So, off the crystals went to ICM to be changed/temp
cpmpensated/and set on freq.  I will get them back
somewhere at the end of January.

The crystals were drifting about 5ppm over that
limited temperature swing.  At 440 MHz, this is 2.2
Khz which is just what I saw.  If the repeater was
operating at 6 meters, the drift would have been
unnoticable at 270 hz.  At 146 Mhz, the drift would
have been about 730 Hz.  Since I did not do any
temperature testing over a bigger range, I'm not sure
what the overall effect would have been.

So for all you 440 MHz crystal operated repeater
owners, watch your temp compensation circuits!

Marc
K1MZ



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