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

[JAMES FALLS]

I could never get that old code to work right, so I made a chart by scratch years ago.  I discovered my BC-221-AK wasn’t fully linear from max to min on the VC. It had an ever so slight belly to the line as frequency increased. 

Having OCD over such things, I spun the dial, and plotted the curves, split them into 1/4’s, then wrote an algebra equation for each section. I plugged everything into Excel and cranked it out for the intervening values. Tedious, but it worked. 

Ended up close enough, I could set my BC-312-L to SSB net frequencies with only a bit of Donald Duck, and that cleaned up using the fine tuning vernier. 

The -AK and it’s book moved on to another owner, and (inevitably) the spreadsheet was lost to a computer crash. It’s tempting to recreate the spreadsheet now that retirement approaches. If my “Round Tuit” arrives, I’ll share it “around”. 

73 ALL ES GUD DX DE
Jim Falls K6FWT 

> On Mar 25, 2022, at 13:31, DaveJ <cjack93907 at charter.net> wrote:
> 
> All:
> 
> I have a pdf a photocopy of the BC211 calibrator article in Electronics Magazine, May 1944 issue if someone wants it.  
> 
> It is also downloadable from World Radio History.  Search for "Electronics"
> 
> https://worldradiohistory.com/Electronics%20_Master_Page.htm
> 
> Electronics Magazine, May 1944 issue
> 
> 
> sincerely,
> 
> 
> Dave WA4OBJ
> 
> -----Original Message-----
> From: arc5-bounces at mailman.qth.net On Behalf Of Bob kb8tq
> Sent: Friday, March 25, 2022 11:08 AM
> To: Kenneth G. Gordon <kgordon2006 at frontier.com>
> Cc: Jack Antonio <scr287 at att.net>; Roy Morgan <k1lky68 at gmail.com>; ARC-5 <ARC5 at mailman.qth.net>; Milsurplus <milsurplus at mailman.qth.net>
> Subject: Re: [ARC5] [Milsurplus] WTB Original LM-10 manual
> 
> 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. I have memory of a photo of the 
>>> calibration setup, as well as the printer that made the calibration 
>>> books.
>> 
>> Yes. That is correct. The calibration books are unique to each 
>> "freqency meter". And I too remember seeing a photo of the calibration 
>> equipment at the time. It was quite large. The technology of the time was quite impressive too.
>> 
>>> 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.
>> 
>> If you no longer have a DOS based computer to run it on, you can 
>> install one of the DOS emulators on your computer and run it by that means.
>> 
>> Ken W7EKB
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