[Milsurplus] LM freq meter calibration book accuracy
Bill Cromwell
wrcromwell at gmail.com
Mon Jul 29 07:27:23 EDT 2013
On 07/28/2013 10:36 PM, John Hutchins wrote:
> My two cents-
> Turn the meter on wait 30 minutes.
> Slap a frequency counter near by and you will note that it rises and
> falls either side of the mark, setting <= ~100hz on the primary band,
> by observing the digital frequency counter; Yes is does drift up and
> down but the drift is slow, over a ~20 minute period. This may be
> due to outside air getting into the unit through the phone jack, among
> other places. That being said the settings are right on if the
> reference crystal is adjusted correctly. I have two LM-13's and two
> BC221-AK's
>
> I compare this to my HP 8601A the drifts all over the place no mater
> how long I let it warm up. Setting on the desired frequency in the
> lower bands is a real challenge to say the least.
>
> Forgot, was it Clete, who described wrapping the LM or BC221 unit in
> a heavy towel; that makes a lot of sense. This would cut down on the
> air flow exchange with the outside air and limit any drift... I'm
> going to try this trick on my HP8601A see if a heavy towel will quiet
> the drift. Kind-a like a BBQ smoker.... an even temperature....
>
> Hutch
Hi Hutch,
I should do an evaluation like that with mine. I do know it's well more
stable and accurate than is required for ham operations. With any
receive setup I have, if I can get within 100 cps (actually within a
couple of kc) of your listed net frequency I will most certainly find
you. Even If I have the bandpass knothole smaller than 100 cycles. Ain't
panadapter displays wunnerful.
73,
Bill KU8H
More information about the Milsurplus
mailing list