[ARC5] WWII-Era VHF Command Set Frequencies and Crystal Information (plus survival radios)

[D C *Mac* Macdonald]

I don't remember the exact nomenclature of the emergency 
bailout beacons we had when I was EWO on B-52Fs during
the Arc Light campaign of B-52s in Vietnam war, but I seem 
to recall that they were AN/URC-4. They ran on 121.5 with
simultaneous doubling to 243.0.
 
* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* Oklahoma City, OK * 
* USAF, Ret (61-81) * 
* * * * * * * * * * * 
 
 
 
 
 

> Date: Thu, 17 Nov 2011 19:10:34 -0500
> From: kk5f at earthlink.net
> To: ARC5 at mailman.qth.net
> Subject: Re: [ARC5] WWII-Era VHF Command Set Frequencies and Crystal Information (plus survival radios)
> 
> Ken wrote:
> 
> > However, I thought the GC (Guard Channel) frequency was always set 
> > to 121.5 MHz, the emergency frequency.
> >
> > At least the ARC-1 I got from AFMARS back in the 1960s had that 
> > installed there...
> 
> The first VHF frequency that became a guard and/or emergency channel
> was 140.58 MHz. That's what you'll find on all the WWII-vintage VHF
> sets (even USAAF). It's channel 1 (P-P) on the AN/ARC-4 (likely
> the first VHF set that had a guard channel), and channel C on the
> AN/ARC-5. The AN/ARC-5, and the USAAF SCR-522-A and AN/ARC-3 did
> not have a guard channel that could be monitored while another
> channel was active. The R-67A/ARC-3 was modified to have an input
> to its IF string for a proposed external guard receiver, but I've
> never seen any indication that such an addition was ever made. The
> new UHF-AM command sets (like the AN/ARC-27) most likely eliminated
> any concern about monitoring a VHF guard channel by the military.
> 
> Sometime after WWII, 121.5 MHz was established as a standard
> emergency channel, primarily for civil air use, while 243.0 MHz
> became standard for military use. Both of these frequencies
> are multiples of 40.5 MHz, which became the military's tactical
> low-band VHF FM emergency/guard frequency.
> 
> All these older sets still in service would later have been altered
> from 140.58 to 121.5 MHz. I have another RT-18/ARC-1 with the guard
> channel on 121.5 MHz.
> 
> 
> Diversion of topic follows:
> 
> The earliest military survival radios were the SCR-578-A and
> AN/CRT-3 "Gibson Girl" sets. These were transmitters only on
> 500 kHz A2 (and 8280 kHz A1 for the AN/CRT-3). The USAAF added
> the Setchel-Carlson Model 591 dry-battery beacon-band receiver as
> the AN/CRR-1 to the SCR-578-A to enable two-way communications
> with the distressed party, allegedly for arctic use. I suppose
> that suggests one use for aircraft transmission capability in the
> beacon-band.
> 
> The early pocket-able survival radio, the AN/CRC-7, operated on
> 140.58 MHz. Sometime after WWII, but before the Korean War, the
> well-known 121.5 and 243.0 MHz standards were established. The
> next pilot survival radio, the AN/PRC-17, -17A, was made during
> the Korean War and could operate on 121.5 or 243.0 MHz, determined
> by a control switch on the side. A little later, the RT-159*/URC-4
> became standard everywhere and could operate on 121.5 or 243.0 MHz.
> That was replaced by the RT-285*/URC-11 for 243.0 MHz only, plus there
> was the nearly identical RT-350*/URC-14 for 121.5 MHz. I've never
> seen any indication the the military ever used the 121.5 MHz version.
> The ones I've seen have no federal contract or order numbers on them.
> But I know some airlines like PanAm carried the AN/URC-14 in the
> civilian airliner's emergency equipment!
> 
> Mike / KK5F