VHF Corner

Moving to the right of the SCR-522 in the flight deck is a corner devoted primarily to other VHF sets of the period. Emulating the Navy's and British success with VHF but wanting their "own" design (naturally), the Signal Corps finally brought out the VHF AN/ARC-5 in 1943, in direct competition with the SCR-522 that they were forced to repackage from a British design (see The British Connection for the rest of that story. The VHF ARC-5 is located with the rest of the ARC-5 set elsewhere on the Flight Deck.)

Both the SCR-522 and VHF ARC-5 were deficient in the number of pilot selectable channels available - only four were possible, reflecting the technology up to 1941-42. Perhaps motivated by the Navy sponsorship of the ten channel AN/ARC-1 development effort, the Signal Corps embarked on a program to create a similar set for the AAF - resulting in the AN/ARC-3 at the top of this bay. Far from an integrated set, it followed the configuration concept of the SCR-274N, with separate receiver (top right), transmitter (top left), and dynamotor supply (just a slice visible at far left.) Even the shock mounts and connectors were largely interchangable with the SCR-274N (except for the U-15 plug on the transmitter.) Production delays and logistics prevented its widespread deployment until the spring of 1945, and then only in the Pacific theater.

Below the AN/ARC-3 are three Navy-inspired sets and a VHF frequency meter. At upper left is an airborne version of the TS-323, a VHF parallel to the venerable BC-221. To its right is an AN/ARC-1, a ten channel crystal controlled transceiver that was actually delivered later than the AN/ARC-4 directly below the TS-323 - testimony to the haphazard nomenclature issuing process during the war. The ARC-4 was another commercial set (the WE-233) that was pressed into service with little more than a JAN nomenclature plate addition. It was effective at close distances to the other party in a communications link but suffers from poor sensitivity in the receiver. The control boxes beneath the ARC-4 provide channel control (C-51/ARC-4) and power (J-23/ARC-4) for it. Note the use of the AN/ARC-5 "command set" style boxes and connectors.

To the right of the ARC-4 is a relatively uncommon set - the AN/ARC-12. This is the first of the aircraft UHF sets developed during the war (all the rest were pressurized and so had cases with seals and a Shraeder valve in the front.) It was driven by the discovery of "ducting" over water of VHF signals for long distances, and the interception of them by the Japanese. The nomenclature for this set is frequently confused with the Aircraft Radio Corporation's Type 12 commercial set for small aircraft, which was packaged in command set format, but as you can see it is entirely different. Both the ARC-1 and ARC-12 used the same shock mount and control box - the C-45 control boxes are beneath the ARC-12 here - which made swapping over to the UHF set very simple. It is not clear when these arrived in the fleet. The contract numbers and manual appear to be from the 1947 time frame, though the original nomenclature was probably issued sometime in late 1944. It is crystal controlled, using small barrel shaped crystals with axial leads, mounted on a rotating drum for channel selection. It is the last VHF/UHF set made without pressurization for high altitudes, as the writing was on the wall for the need to operate at full power above 45,000 feet. Like the AN/ARC-1, no operator adjustments were possible while in flight, so a simple cover for the front of the set is all that is visible during normal operation.

Although the particular bay was intended to focus on VHF sets, at the bottom simply because there was no other place to put it is a belated 100W HF tranceiver design that was "type"-issued before the end of 1945. It was not actually produced until the early 1950s because of inter-Service wrangling on "joint" requirements. Following the trend that began in late 1944 for pressurized enclosures at 1 psi to help reduce size without causing high altitude arcing, this set had quickly replaceable modules that made servicing on the flight line faster (once you got into the interior.) This particular unit (an upgrade to the original ARC-21, called the ARC-65) was designed as a replacement for the ART-13. It admittedly bends the 1939-1945 rule for the flight deck to its extreme, but because of the original type issuance date, it enjoys a honored if precarious position, just as the AN/ARC-27 does.

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