[Milsurplus] HF SigInt, airborne platform

[Hue Miller]

I am wondering why the need for airborne SigInt receiving capability in the upper
HF range, say above around 11 Mc/s up. The 96-2 Japanese trans-receiver has the
about the highest frequency range of the Japanese HF AC radios i have seen, and
that one tunes up to 11 Mc/s.  So, what kind of fighter control network were we
supposedly listening to? Japanese VHF equipment began at about 30 Mc/s. So use
a BC-348 or RAX for what, please? "Many" Japanese small aircraft used the 99-3
radio, which had a single 807 final, for a few watts output only, in the range up
to about (i think...) 7 Mc/s, so where is the need for the upper HF range?
Clearly, the photo Mike Hanz referenced shows the RAX in liaison role. ( I suggest
an extra HF receiver in form of ARC-5 or ARA, could have been preset to a 
common air-ground freq, such as 4495...). The cover of the March (is it? ) 1945
CQ magazine shows radioman seated in front of 3-RAX set in PBM. This also
is liaison. I regard the talk about RAX as a sigint receiver, or designed for that 
purpose, as fantasy. -Hue