[1000mp] FT1000MP frequency drift

[Tod - Minnesota]

A few days ago I downloaded the program ARGO (freeware) which allowed me to
use my computer's soundcard to check the frequency accuracy and stability of
my FT1000MP. I found that the MP reference oscillator was 50.6 Hz off after
the MP had been warmed up for about 1 hour. I then used ARGO to make a
snapshot of the drift in frequency from the time I turned on the MP until
after the first half hour or so. My radio has the standard reference
oscillator board and does not have a special TXCO unit. The freq drift was
about 3.5 Hz per minute reducing to about 2.5 Hz per minute 40 minutes after
turning the unit on. The drift seemed to continue almost indefinitely.

I decided that I would see if I could reduce the drift and time needed to
reach 'frequency stability' by incorporating a thermistor on the reference
oscillator board. I fastened a thermistor obtained from Mouser electronics
to the crystal case. The thermistor had a resistance of about 50 ohms when
cold. To limit current drawn from the 9 volt source going to the ref osc I
put a 68 ohm resistor in series with the thermistor. The current drain is
limited to about  75 ma at start up and drops to about 40 ma when the
thermistor warms up.

The result was that that within 90 seconds the ref osc frequency now is
within 2 Hz of the final (desired) value. After five hours the frequency was
still within 2 Hz of the desired value. The ref osc operates at about 10
MHz. A frequency that is within 2 Hz of a desired value of about 10 MHz has
an accuracy of 0.2 ppm. The most expensive of the Yaseu TXCO's has a 0.5 ppm
specification.

It may be that I am the only one who has an interest in this. However, just
in case I am posting my results to the reflector. If anyone is interested I
can put additional 'how I did it' information on my web site.

Tod Olson, K�TO