[ARDF] My PicCon "script"

[Jay Hennigan]

On Tue, 25 Oct 2005, Kenneth E. Harker wrote:

> I'll check into this.  I have the current model of PicCons, in the
> translucent green cases.  The ceramic resonator Y1 has three connections
> to the PC board (let's call them left, middle, and right.)

Ugh.  They've cheapened them by going to a ceramic resonator instead
of a crystal.  That's why they drift.  Makes little sense as colorburst
quartz crystals are 36 cents in quantity one from Mouser, dropping to
24 cents each for 100.

Mouser 815-AB-3.579545-B2 is a HC-49 can, 36 cents each.

A smaller cylindrical one is a whopping 58 cents, 520-ECS-357-18-10 .

> Do I put a cap in line between left and its pad on the PC board, and
> then do the same with right?  Or do I leave the resonator in place and
> put the cap between left and ground and between right and ground?

Yank the resonator, replace with a crystal between the two outer pins.
Don't connect anything to ground.  You may need to put a 1 meg or
thereabouts resistor in parallel with it.  Easiest is a chip resistor
right across pins 7 and 8 of the 8870 chip.

> Does temperature have anything to do with it?  Between the time I set out the
> transmitters and when we picked them up, the air temperature had gone
> up like 20 degrees Fahrenheit.

The crystals will drift very slightly with temperature, but not nearly
as much as the ceramic resonators.  Should track within a few seconds
over a day even if you have one T painted black in the desert and another
buried in a snowbank on the same hunt. The crystals are specified at
+/-20 ppm tolerance, which is an absolute worst case error of 0.144
seconds per hour or under four seconds per day assuming two units at
opposite ends of the tolerance range.  Early Piccons used real quartz
crystals!

> Some of the PicCons had drifted well over 60 seconds off their cycle over
> a period of 7 hours.

Lose the resonators, replace with quartz crystals.  I wonder how many
cents they saved by going to the resonators.

--
Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
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