[ARC5] Tower Comm and VHF Homing

[Robert Eleazer]

Late in the war some USAAF fighter aircraft, especially the P-51's on Iwo Jima, were equipped with the ARA-8 homing system, which apparently worked in conjunction with the ARC-3 comm sets.  It consisted of a couple of what I suppose were AN-104 antennas on the rear fuselage, side by side and an adapter that seemed to be some sort of a switch.  

I would guess that the adapter switched the receiver input between the two antennas to detect direction.  Not sure how well this could have worked, given that the distance between the antennas looked to be no more that a couple of feet at most.  Modern homing adapters for aircraft VHF radios want you to mount the two antennas pretty far out on the wings.  I have never heard any description of how this system worked but you can see the antennas on pictures of the Mustangs that escorted the B-29's to Japan.  And I have no idea how the directional info was displayed to the pilot.   I had a chance to buy an ARA-8 adapter a few years ago but instead choose to put my mad money at that point into an APG-30, the gunsight radar used in the F-86.

By the way, in addition to the standard tower freq of 278 KHZ that pilots with LF receivers like the Detrola listened in on to receive traffic instructions, the aircraft transmitted to the tower on 3105 KHZ in the daytime and 6210 KHZ at night.  I would guess this was because they did not want towers at night picking up the 3105 KHZ transmissions from all over the country.  Given that to me 80M seems to be open as often as 40M at night I wonder if this approach did any good.

Back in 1989 I looked at an Ercoupe tha was for sale that still that that LF receive/HF transmit equipment installed.   

Gordon White once mentioned that after WWII an LF Omni system was developed but due to "night effect" it was abandoned.  I presume they had problems with the LF signals going too far and that people in Newark would be trying to navigate using Omni signals from Chicago.

Wayne
WB5WSV