[ARC5] ARR-1

[Mike Hanz]

On 9/16/2014 7:15 AM, Brian Clarke wrote:
> The Japanese were well aware of VHF during WWII. 

Indeed!  I posted some photos of the WWII Japanese FB-T airborne VHF 
surveillance receiver in the NASM collection at 
http://aafradio.org/sidebar/FT-B _Surveillance_Receiver.html - it had a 
tuning range of 81-660MHz.  It was the rough equivalent of our early 
AN/APR-1 and its antecedents, without the plug-in tuning units.

Their problem with figuring out the ZB/ARR-1 signals was the 
supermodulation frequency.  Normal detection schemes at the end of the 
VHF receiver chain, like the diode detection in the FB-T, fell off in 
response to signals less than perhaps 100kHz, and that simply wasn't 
wide enough to see the modulation with a scope, even if you could 
receive it in the first place because of the line of sight requirement.

> Professor Yagi and his English translator assistant Dr Uda 
> collaborated to develop the parasitic antenna before WWII.

Which, in a twist of irony, was then used on the Hiroshima and Nagasaki 
atomic weapons for the radio altimeter fuses.

73,
Mike