[ARC5] Navy LM Use

Thu May 23 09:16:05 EDT 2013

I consider the P2V-7 statement I made to be 100% accurate as the person who 
photographed the P2V while a crewmember was the same person in the P2V-7 as 
an ATN2 which stands for Avionics Technician Navigation/Communications petty 
officer for you landlubbers.

Carl

----- Original Message ----- 
From: "Scott Johnson" <scottjohnson1 at cox.net>
To: "'Geoff'" <geoffrey at jeremy.mv.com>; "'Mike Morrow'" <kk5f at arrl.net>; 
<arc5 at mailman.qth.net>
Sent: Wednesday, May 22, 2013 10:45 PM
Subject: RE: [ARC5] Navy LM Use

>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
>
>
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