[MRCA] [Milsurplus] LM-13/CRR-10111

[WA5CAB at cs.com]

Actually, the LM (first model, no suffix number) dates from 1935.  As does 
the BC-221.  The BC-221-T1 (first production prototype) was ordered on 
Signal Corps Order Number 10132-NY-35.

The first several LM models (LM through LM-5) were intended for use in 
aircraft where 12-14V for filaments came from the aircraft and HV came from a 
receiver or transmitter in the aircraft.  LM-6 was the first with rectifier 
supply.  After that, the various models up through LM-21 were a mix of 
external DC (aircraft) and rectifier (ship and ground) except for LM-1, -3, -13 
andf -17, which were all dry battery.  The dry battery models were for flight 
line, hanger deck and flight deck use.

The wooden cased BC-221's are the later models, late 1942 and on.  BC-221-A 
through -R had aluminum cases.  BC-221-AA had both.  And BC-221-AC through 
BC-221-AN were in wooden cases..  All were powered by internal dry 
batteries.

Late in the War, they built CY-182/AR to hold the freq meter removed from 
any model BC-221 case, which then became TS-164/AR.  Several years after the 
War, they finally built two different type rectifier supplies for the 221's, 
RA-133-(*) and PP-79/UR.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 02/26/2017 21:59:07 PM Central Standard Time, 
RAFANTINI at salisbury.edu writes: 
> Yesterday I picked up a LM-13, I always regarded the LM family of 
> frequency meters to be a small version of the BC-221 full size frequency meter 
> that was the standard for set up and calibration for more then a decade from 
> WW2 on. The idea being that the LM was used by the Navy in aircraft for 
> alignment of big transmitters like the TBW and later ART- 13 family of radios 
> where space and weight were a premium.
> 
>  The odd thing about this little LM is that its in a CPR-10111 carrying 
> case that accommodates the LM, Batteries and calibration book that’s about 
> the same size and almost the same outward appearance as the BC-221, not the 
> wooden case but the later aluminum skin version. 
> 
> The questions are first, why did the Navy not just go ahead and use the 
> BC-221 that the signal corps was using? Instead they went ahead and developed 
> a ground or ramp base system to accomplish the same thing? Maybe it had 
> something to do with the operators being familiar with the LM as opposed to 
> the BC-221? Second, what came first the BC-221 or the LM? This LM has a 
> contract date of December 27th 1939, when did the first BC-221 frequency meters 
> start appearing? Is it possible that the LM series where in production and 
> fielded before the BC-221? The wooden case BC-221 always appeared to me to 
> be something that was designed pre war but how far pre war were they?
> 
>  This little LM is in incredibly clean and unmodified condition and would 
> tend to think it was never fielded in a military context. The unit has a 
> Villanova University E.E. Department inventory sticker (#1475) and would tend 
> to think was used by the university as opposed to the military.  It’s hard 
> to imagine today but in the thirties and forties Philadelphia and North 
> Jersey were in a sense the Silicone valley of there day and lots of 
> development occurred around there. This little LM was at the sale over at the NEM 
> yesterday and no one else took it so it followed me home but if anyone is 
> interested in it please contact me off list. It is complete, has the matching 
> book, battery cables and all that sort of stuff.
> 
>   
> 
>  Ray F/KA3EKH 
> 
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/mrca/attachments/20170227/59bdeaf5/attachment.html>