[ARC5] AN73 Antenna Coax Connector

[Mike Morrow]

Mike wrote:

>...the drawing says, "The antenna mast is used with the SCR-522 radio set 
>and for that reason is insulated completely from the fuselage.  Care 
>should be taken to prevent accumulation of conductive debris around its 
>base."  Only a closeup photo of the inner conductor interface will 
>confirm the theory, but all the clues point to it.

That description and caution as far as it goes would of course apply also
to the AN-74 and the later AN-104.  The pictures I've seen of the *external*
mast on the A-36-A looks like an AN-74.  It almost sounds like that NAA
special VHF antenna mast is like an AN-74 with an oddball SCR-522-ish coax
connector rather than the AN-74 SO-239 connector.  Maybe this NAA antenna
is the antecedent to the AN-74.

So...in the midst of all this discussion, what happened to the "AN73" term?
Is that mystery NAA antenna the "AN-73"?  If so, it's not seven feet long as
suggested on the Chesson pages (which possibly was actually intended to apply
to the AN-75 instead).

Not related to any of this, apparently at one point there was to be an antenna
for the SCR-522-A that was variable length, positioned to preset lengths
by control signals from the BC-602-A control box.  That was the purpose of
the smaller connector on the back of the BC-602-A...the one that was deleted
from the BC-602-B.  The motorized variable length antenna never was needed
because the broad, flat, passive AN-74 and AN-104 VHF mast antennas are
amazingly broadbanded.  They provide surprisingly low VSWR across the 100
to 156 MHz operating range.  That would have been radio tech hell, having
to retune that variable length antenna along with the SCR-522 itself every
time an operating frequency change was ordered for a flight of aircraft.
I've spoken with a fellow who was an ETO SCR-522 tech, and he hated altering
the channel frequencies in the SCR-522.

The USN had a VHF rod antenna called the AT-8/AR just like a lengthened
AT-5/ARR-1 or AS-32/APX-1 that seems quite rare.  It's just as well, for
it could not possibly have the broadband characteristics of the AN-74/104.
Maybe that's why so few are seen, and why the Signal Corps AN-74/104 was 
used in most USN aircraft VHF installations.

Mike / KK5F