[ARDF] Piccon mods

[David Ward]

I had a very similar experience with the same results. Using the ceramic 
resonator the controller ran slow by about 20 seconds per hour (~ 5500 PPM). 
I then replaced the resonator with a 3.579 MHz crystal with 15 pf 
capacitors. It now runs slow by about 2 seconds per hour (~500 ppm). I 
haven't got around to replacing the caps with smaller values yet but from 
what I read I'm not sure any value will be enough to overcome the 500 ppm.

One thing I wondered about was whether the crystal should be a series or 
parallel mode. Anyone have any opinions?

Dave
VE3BIP


----- Original Message ----- 
From: "Kenneth E. Harker" <kenharker at kenharker.com>
To: <ardf at kkn.net>
Sent: Monday, November 14, 2005 1:35 PM
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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