[MRCA] SRC-274-N VHF set in use today

[Ray Fantini]

I would avoid attempting to use any radio that's no longer type accepted on a aviation frequency, type accepted radios have to be not only 25 kHz minimum they also have to be 30 ppm stable and all of that old stuff won't come close. The receivers are so wide they will hear three channels at once and all sorts of other issues may occur.  Think the best thing today is if you want to use an old obsolete radio in any aircraft is to have it channeled up on a Ham frequency like 144.25 but attempting to use it on any aviation frequency would be a mistake.
This is from the FCC web site:

As of January 1, 1997, each VHF aircraft radio used on board a U.S. aircraft must be type accepted by the FCC as meeting a 30 parts-per-million (ppm) frequency tolerance (47 C.F.R. § 87.133). The vast majority of aircraft radios that have been type accepted under the 30 ppm frequency tolerance utilize 25 kHz spacing and have 720 or 760 channels. Each aircraft radio has a label with an FCC ID number on the unit.
This rule applies to all U.S. aircraft radio stations, including those no longer required to be licensed individually. The effect of this rule is to require a 30 ppm type accepted radio to be placed on board if the pilot intends to use a VHF aircraft radio for communications. There is no requirement, however, for an older radio to be removed from an aircraft in cases where the pilot does not intend to use it to transmit radio signals (e.g., receive-only operation, an integral part of a navigation/communications unit, or decoration in a vintage aircraft).

The FCC has a web site that explains all this along with a list on the last page of obsolete or no longer type accepted radios, interesting to see things like the King 170 have been dropped from type acceptance  category. I always liked that radio.

https://www.fcc.gov/aircraft-stations


So all that vintage radio and radar equipment can be used on Ham frequencies only, or just to receive. All that old WW2 stuff wont come close to being legal to transmit.

Ray F/KA3EKH





-----Original Message-----
From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> On Behalf Of MARK DORNEY via MRCA
Sent: Saturday, September 7, 2024 4:15 PM
To: Mrca Mailing List <mrca at mailman.qth.net>
Subject: [MRCA] SRC-274-N VHF set



Exploring putting together a USAAF SCR-274 set for a USAAF C-47 based here in NY ( yes, the C-47 was equipped with the SCR-274-N ). Here's the rub. We need at least 1 VHF set pair ( transmitter & receiver) for the aircraft to talk to ATC if they want to use the 80 year old comms to do anything useful in the aircraft. Now I know that the USN ARC-5 had such a set up available, but the C-47 won't be set up for the USN ARC-5 system, and the the transmitters for the two systems are not compatible with one another. Did the SCR-274 have a VHF transmitter/receiver set. If so, what is the nomenclature of the transmitter and receiver? Gives me something to start looking for.

73

Mark D.
WW2RDO