[ARC5] [Milsurplus] LM/BC-221 cal books
William Cromwell
wrcromwell at gmail.com
Sat Mar 26 08:19:04 EDT 2022
Hi,
It is easy enough to make a "cal book". Ken Gordon has a DOS program for
making one but even easier is using a spreadsheet program. Measure the
frequency at several points across it's range and enter them with the
dial reading/frequency in the spreadsheet. Then use the spreadsheet to
plot a graph with a smooth curve. I have the original books with my two
LMs but I used this method with my RAK-7. We get very close using the
graphs and of course, they are reliably resettable to a logged
frequency. Using the graphs I have been able to initially preset a
desired frequency and have the RAK right on frequency when the desired
station came on the air :)
73,
Bill KU8H
bark less - wag more
On 3/25/22 6:59 PM, howard holden wrote:
>
> I have an LM with no book. Actually I had one with a book but traded
> it for one on the USS Ling so they would have a complete one. It was
> pretty easy to make a cal chart using a calibrated frequency counter
> whose clock I set to exact zero with WWV. I calibrated every 1 Khz
> from 3500 Khz, for the first 100 Khz. CW is all I’m interested in so
> that was fine. I did this in 2015. Used it many times since, and with
> the built-in calibrator it’s simple to adjust to the beat frequencies,
> and it’s quite accurate between beat points. Requires very little
> adjustment to get it on beat from marker to marker. Calibration has
> remained as I originally set it. I also have a BC-221 with a book, and
> the shift in one Khz steps takes 2.1 on the dial at 3500Khz, and 2.0
> on the dial at 3600Khz on both units. Accurate enough for me, and I
> used it in an FMT when I first calibrated it, and read the freq off
> the interpolation scale to within 47 Hz while W1AW’s freq was nowhere
> near a marker. Plenty accurate and repeatable enough for my old BA gear.
>
> Howie WB2AWQ
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows
>
> *From: *Kenneth G. Gordon <mailto:kgordon2006 at frontier.com>
> *Sent: *Friday, March 25, 2022 1:11 PM
> *To: *Milsurplus at mailman.qth.net <mailto:Milsurplus at mailman.qth.net>;
> ARC5 at mailman.qth.net <mailto:ARC5 at mailman.qth.net>
> *Subject: *[Milsurplus] LM/BC-221 cal books
>
> Well, I own two BC-221-AKs and two LMs. Both 221s have original cal
> books, but both LMs
> were bought years ago as "parts", although both are complete.
>
> Neither has a cal book.
>
> I'll go to work here to re-create their cal books, then will report
> back here as to method and
> results.
>
> Standby.....
>
> Ken W7EKB
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