[ARDF] Piccon mods

[freyra at aol.com]

Ken:  We did an ARDF practice session this past weekend using the older PIC controllers, prior to the green cased ceramic filter units, and had no problems.  They were set for an initial three hour delay, came on exactly as programmed, than ran at least another 2.5 to 3 hours with no drift at all. I have three of the newer units and plan to program and test them this week.  I will let you know if I see the same type of problems. 
 
Later  Bob
 
-----Original Message-----
From: Kenneth E. Harker <kenharker at kenharker.com>
To: ardf at kkn.net
Sent: Mon, 14 Nov 2005 10:35:30 -0800
Subject: [ARDF] Piccon mods


     I've modified one of my piccons by desoldering the ceramic resonator 
and replacing it with a 3.579545 MHz crystal and two small 22pF caps.
See my photos:

http://www.wm5r.org/piccon/

     Unfortunately, the controller is still running slow - at the 
rate of about 2.3 seconds per hour.  This is an order of magntiude 
improvement compared to the worst I experienced with the ceramic 
resonator, but it's still not good enough.  The IARU rules specify 
that the maximum deviation of the transmitting periods is only five 
seconds for the entire competition (which could be eight or nine 
hours.)

     Any ideas?  Should I try changing the caps to a different value?
Would I increase the value? (27 pF? higher?)   Decrease the value? (18pF?
lower?)  Do I need to add resistance anywhere?


     I am mildly annoyed that I have to do any of this just to get a 
timing controller that can keep proper time.

-- 
Kenneth E. Harker WM5R
kenharker at kenharker.com
http://www.kenharker.com/

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