[ARC5] [Milsurplus] WTB Original LM-10 manual

[Roy Morgan]

Bob,

Your memory of the calibration books being made specifically for each LM (and for the BC-221) is correct. 

However, a re-created calibration book can be made and would be useful, as I understand it. Bob Keys wrote a computer program that accepts a file with many data points for settings at Crystal check points. It does interpolations and multiplications to create at least the semblance of the missing  original calibration book and formats it into useful form. Once the book result is printed, the LM now becomes useful again. 

Notes:
1) I have not created such a replacement cal book, though I hope to in the near future. 
2) I do not know how closely the result functions compared to an original cal book. 
3) It is an untested assumption that the decades-old program operates on current DOS/Windows computers. Presumably the available source code could be compiled again on current Windows and/or Mac (or Linux?) computers. Some update of the code might be needed. 
4) I have not seen Bob Keys on the radio mail lists for quite some time. 
5) We can assume the printout would be in normal paper-size format and would not fit below the LM in the space provided for the original cal book. 
6) I have a digital copy of an article describing the system originally used to create the cal books. I am unaware that any such system exists today. 
7) I have an LM born just before I was: 1944. It and it's power supply work very well indeed. 

Long live the LM Frequency Meters!!

Roy

Roy Morgan
K1LKY Western Mass
K1LKY68 at gmail.com

> On Mar 25, 2022, at 2:08 PM, Bob kb8tq <kb8tq at n1k.org> wrote:
> 
> Hi
> 
> However impressive the cal setup is in the pictures, it was even more
> impressive in real life. I came across a good portion of one in a surplus
> outfit *many* years ago …..
> 
> Bob
> 
>> On Mar 25, 2022, at 1:57 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
>> 
>>> On 25 Mar 2022 at 13:38, Robert P. Meadows wrote:
>>> 
>>> Folks, To the best of my memory and knowledge, the LM series of
>>> "frequency meters" were individually calibrated, and the book for same
>>> serialized to the instrument.


>>> Making a calibration book by any means absent the actual measurements
>>> for the specific LM is useless if the instrument is to be used with
>>> any degree of accuracy. R 
>> 
>> Well, Bob Keyes' program does a good job of recreating a calibration book, although the 
>> result can then be tweaked for better accuracy after that is done by using a good, accurate, 
>> frequency counter at selected frequencies. Making an accurate calibration book is a 
>> time-consuming process, but others have done it.