[ARC5] Navy LM Use

Wed May 22 22:45:45 EDT 2013

I don't think the P2V-7 carried a 618T in 1962.  Most definitely the
ARC-38A.  I haven't
Come across a P2V-7 or SP2H that had a 618T installed, I'm sure some of the
SP2Hs that were held on to into the seventies may have had them installed,
but 
I would think the 618T  would have come later, perhaps in the P3.  Even the
early E model Hercs had 618S sets installed, later to be retrofitted with
618Ts.
I gutted the APS-20B and all the comms from a P2V-7 down in Tucson about
eight years ago, and the HF setup was an ARC-38A, ARR-41, Mite.

Scott W7SVJ

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Geoff
Sent: Wednesday, May 22, 2013 6:11 PM
To: Mike Morrow; arc5 at mailman.qth.net
Subject: Re: [ARC5] Navy LM Use

>> ...bring up the question again of why the USN included an LM 
>> frequency meter with essentially every large aircraft radio 
>> installation.
>
> I don't believe this is a valid observation.  No WWII-vintage USN 
> transmitter or receiver system had the capability to be set on 
> frequency accurately with the indications on the radio set itself 
> until the ATC.  Most liaison transmitting systems of the era have a 
> CFI input terminal that goes to the LM-*, the LM was integral to 
> frequency adjustment.
>
> An accurate assessment of USN installations would simply be that *ALL* 
> aircraft with a radio operator (and liaison system) always carried the 
> LM-*.  Aircraft without a radio operator did not.  The only exception 
> might be the large single-engine aircraft like the SBD, TBD, and the 
> like, which had radio operator/gunners.  I don't know if an LM was 
> always standard in such aircraft.
>
>> This continued postwar, with the Navy version of the C-119 having an 
>> LM installed.
>
> That's an obscure citation...there were only about 90 total R4Q-1 and
> R4Q-2 aircraft built.  But nonetheless, an LM-* would indeed be on 
> board, just like a SCR-211-* would be on board the C-119* that didn't 
> have something like an AN/ARC-21 or later liaison set.
>
>> Of course the USAAF had the BC-221 and theoretically, at least, the 
>> unit of issue was one with every B-17 and B-24 and perhaps other 
>> aircraft as well...
>
> The statement I made above for the USN use of the LM-* applies to the 
> USAAF and use of the SCR-211-*.  All aircraft with liaison sets and 
> radio operators had the SCR-211-* on board.  USAAF radio sets were no 
> more or less accurately set and maintained than their USN equivalents.
>
>> - but it is rarely seen in photographs.
>
> Which doesn't mean it wasn't there.  It most definitely was.
>
>> So why did the USN place such emphasis on having an LM freq meter on 
>> board?  Were their radios more prone to getting off frequency or was 
>> there some operational need...
>
> There is *no* difference between the USN use of the LM-* and the USAAF 
> use of the SCR-221-* that exists to be explained.
>
> The real question about frequency meter use applies to both USN and 
> USAAF installations.  The very first liaison transmitter that had a 
> built-in accurate calibration frequency indicator (CFI) was the ATC.  
> Without
> *any* external frequency standard, the ATC (and T-47/ART-13) could be 
> operator set at 5 or 10 kHz intervals, depending on frequency.  The 
> USAAF's
> T-47A/ART-13 was even better...it could be set to 1 kHz accuracy for 
> the full 2 to 18.1 MHz range without use of any external frequency
standard.
> Once the liaison transmitter is set, the liaison receiver is easily 
> netted to the transmitter. (The USAAF did a better job of this with 
> the NORMAL-MONITOR netting switch that was part of the AN/ARC-8.)
>
> There was little need for a frequency meter for liaison sets with the 
> T-47 or T-47A.  There was none needed for the crystal-controlled 
> commend sets like the USN AN/ARC-1 and -12 or the USAAF AN/ARC-3.
> Yet often a LM-* or SCR-221-* was still carried.
>
> The LM-* was even less important for the USN AN/ARC-25, which is the 
> combo of the AN/ART-13 and the AN/ARR-15.  In this system, the 
> AN/ARR-15 receiver can easily be set to 1 kHz accuracy without external
calibration.
> Yet, the LM-* often appeared even where the AN/ARC-25 was installed.
>
> In USAAF aircraft, the SCR-211-* disappeared as AN/ARC-21 HF sets 
> replaced the AN/ARC-8.  In USN aircraft, the LM-* disappeared as the 
> AN/ARC-25 was replaced by the AN/ARC-38.
>
> Mike / KK5F

Here is a P2V radio install in 1962, the LM is quite prominent.
http://www.hypertools.com/neptune.jpg

In the same year during the Bay of Pigs fiasco the P2V-7 carried the
ARC-38A, ARC-94(Collins 618-S, 618-T respectively), ARR-41, plus crypto and
a Mite TTY.

Carl

______________________________________________________________
ARC5 mailing list
Home: http://mailman.qth.net/mailman/listinfo/arc5
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:ARC5 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html