[Hammarlund] ATD matching receiver?

[Meir WF2U]

Mike,  

The ATD transmitter (manufactured by Bendix)is one of two competing designs
which were procured in 1940 for the US Navy for Navy aircraft, which were
supposed to replace the ATB transmitter. The ATB had relatively low power
and only 2 remotely selectable preset frequencies. The receiver used with
the ATB was the ARB receiver. 
The ARB receiver is also remotely controllable and has accessories to use it
as a direction finder for navigation. Unfortunately, not too many ARB's left
intact, as most in ham hands were modified in various ways - some cosmetic,
some survived with significant circuit modifications. The usual mod was to
remove the remote control bandswitch motor, removing the gear for the remote
frequency control dial, and removing the power connector and dynamotor to
use it with an AC supply.
The ATD was short lived and most of the procured units were never installed,
because the competing project by Collins Radio, the ATC was a much more
versatile transmitter, with higher power, autotune, remote control capable,
with 11 presettable frequencies having the same footprint as the ATD. The US
Army Signal Corps also adapted the ATC design, and procured it under the
ART-13 nomenclature for Army aircraft (the Air Force in WW2 was not a
separate service branch but was part of the Army). The ARB receiver was used
with the ATD also, and carried over to Navy aircraft equipped with the ATC
(Navy aircraft in WW2 didn't use the BC-348 receiver which was used with the
ART-13 and the older BC-375 on Army aircraft). There is a nice video of an
operating ARB receiver/ATB transmitter pair on Youtube:
http://www.youtube.com/watch?v=2Z_4Mva-YsQ  .

I have a working ATD/ARB setup, all in original, unmodified condition,
running from 28VDC with the original dynamotor. I operate it periodically to
check in to the East coast "OMRN" (Old Military Radio Net) on AM on 3885 KHz
Saturday mornings starting at 5:30 AM Eastern, and on CW on 8570 KHz, at
9:00 PM Eastern on Saturdays. 

By the way, the best you'll get from the ATD is 40W output. Matching it to
50 ohms is a pain in the neck. If you have a 1:9 unbalanced-to-unbalanced
toroidal or other configuration RF transformer covering the frequency range
of your interest, it's is helpful. The output impedance of the ATD is very
low, under 10 ohms. A series variable capacitor is useful to match it to 50
ohms.

Good luck and enjoy it! Maybe I'll hear your ATD sometime and have a 2 way
ATD QSO.

73, Meir WF2U
Landrum, SC

-----Original Message-----
From: hammarlund-bounces at mailman.qth.net
[mailto:hammarlund-bounces at mailman.qth.net] On Behalf Of Mike Durff
Sent: Sunday, October 14, 2012 12:50 PM
To: Hammarlund at mailman.qth.net
Subject: [Hammarlund] ATD matching receiver?

Hello to all: 

I am assembling a vintage station including my WW2 surplus  ATD transmitter.
As most of these were not put into service... any best guess as to a
matching receiver? I have a Hammarlund super-pro ( 779 / 1004) and or a
BC-348 I could use. 
I have never seen a "system" nomenclature showing a matching rcvr.
I have DC and AC power available. 

Thanks Mike
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