Richard -
This is function of the aging of the BAND oscillator crystals. The
crystals were originally specified as +/- 0.003% tolerance, which is
about +/- 550 Hz for the 40M crystal, and up to about +/- 1.2 kHz for
the 10M crystal. So when new, the typical variation could be up to +/-
1 kHz, or one skirt division. However, crystals 'age' over time, and
the frequencies change at seemingly random rates and directions. Most
that I am familiar with tend to drift UP in frequency, but this is not
always the case. The aging rate varies, but typically runs 6 - 8 ppm
per year, or 60 - 80 ppm for ten years. This translates to ~1.2 kHz for
the 18.1 MHz 40M crystal. Forty years means ~ 4.8 kHz.....
IF it bothers you too much, you can buy a new set of BAND crystals from
International Crystal Mfrs, specify 0.001% tolerance, and 'fix' it! :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-B, C-Line&
TR-4/C Service Supplement CDs
<www.k4oah.com>
Richard Palmer wrote:
Should I have to calibrate my tuning skirt every time I change bands
or is this indicative of an alignment needed?
(sorry about all the rookie questions but I am a rookie)
Thanks
KB8NXO
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