I’m almost embarrassed to admit this given my career field (Avionics) but I have been doing some research on early navigation radios on WW II generation aircraft. When I first started getting involved with General Aviation aircraft in 1983 I still came across old Narco MK12 radios that were 90 channel radios. These radios haven been banned by the FCC for years now but even they were considered state of the art compared to what pilots had to navigate with in the 1930’s and 1940’s.
Early navigation, the low frequency radio range (LFR), also known as the four-course radio range, LF/MF four-course radio range, A-N radio range, Adcock radio range, or commonly “the Range”, was the main navigation system used by aircraft for instrument flying in the 1930s and 1940s in the U.S. and other countries, until the advent of the Very High Frequency Omni-directional radio range (VOR), beginning in the late 1940s.
My question is what did the aircraft antennas look like?
ADF, basically an AM radio station, antennae were loops mounted on a post. The Japanese used ADF receivers to home in on Radio Honolulu to attack Pearl.
He’s talking about “radio range” which was a totally different thing. Also technically, ADF wasn’t in use in WWII, it was RDF which was the manual version, not automatic.
The “Adcock” antenna on the ground for Radio range was formed by five towers in a + shape. The aircaraft antenna was the normal “long wire” antenna since the “driectionality” was done by the ground antenna. Radio range was the primary navigational system and remained in service until after WWII when it was repalced by the VOR system.
The antenna for the radio range could be a mast, or it could be a wire in a T configuration, with the vertical portion at the midpoint.
The DF (which as was noted were not a part of the radio range system) antennas were first just external loops, and then the football type antenna replaced that with the loop enclosed in the football for lower drag. At first the radio operator manually rotated the loop, but later refinements made that automatic. A second part of the ADF (automatic direction finder) system added a sense antenna, a wire antenna located fore and aft on the fuselage. The sense antenna determined whether the received station was in front of or behind the receiving unit, which was a difficult part of the DF system, where as I recall the operator could only tell by when the signal got weaker or stronger. Maybe I should go read Ernie Gann some more! The last generation of ADF replaced the football with a low profile synthetic loop antenna, of rectangular shape usually located on the belly of an airplane.
But as usual it’s all good in theory but to get it right you still need the photograph!