Message-ID: <00a701c0769f$dac20580$0748073e@default>
From: "Alan Melia" <Alan.Melia@btinternet.com>
To: rsgb_lf_group@blacksheep.org
Subject: LF: Freq Stability....TV line sync
Date: Thu, 4 Jan 2001 22:24:33 -0000
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Hi, there also have been some articles in the past in Elektor Electronics on
using TV line sync as a standard. (I have copies but will have to dig with
the aid of an incomplete written index) 15.625 kHz is 1MHz/64 so an easy PLL
circuit will lock a 1MHz VXO.  I recollect a system which coupled to the
scan coils by means of a pick-up coil on the outside of the TV cabinet. The
TV needed to be on AND receiving a programme, of course.

A technique I saw somewhere (maybe a Tek or HP App note) for freq
comparisons suggested triggering a 'scope from the standard 1MHz (or 10MHz)
signal and then timing the drift of a cycle the 'unknown' 1MHz (RACAL 9420
/5 in my case)  across the screen with a stop watch. I have certainly
calibrated counter timebases to parts in 10^10 (possibly optimistic as
Droitwich is probably not that stable over 1000secs.....or is it?) by this
technique. I have a Halcyon Off-air standard source, which offers the option
of the French station at Allois.

Cheers de Alan G3NYK
Alan.Melia@btinternet.com