[ARC5] CBY-55209 ? MODEL ATA

[Mike Morrow]

Mike / WA4DLF wrote:

> The ATA transmitters and all other ATA system components
> are identical to the Signal Corps SCR-274N series except
> for the data plates...

Close, but...

The nominal AF output impedance for transmitter side-tone
in the ATA system is 300 ohms, while for the SCR-274-N
BC-456-A it is 4000 ohms and for the BC-456-B and -E it
may be internally wired for either 300 or 4000 ohms.

> ...something I have noticed is that the ATA transmitters
> covering 7-9.1 mc don't surface that often compared to the
> 4-5.3 and 5.3-7 versions.

There's no surprise there.  The same may be said for the
SCR-274-N and the AN/ARC-5.  It seems that hams gobbled up
the two transmitters that covered 80/75m and 40m.

> ...may never see an ATA transmitter control box in my
> lifetime!

The ATA control box is not that scarce...diligent search on
ebay will doubtless turn up one every few years.  :-)

> As you probably know, the ARC-5 series replaced the ATA
> beginning in mid-WW2.

I doubt that an AN/ARC-5 installation *ever* replaced an
installed ARA/ATA system.  There was little motivation to
backfit the modestly-improved AN/ARC-5 in aircraft that
already had the ARA/ATA.

The ARA and ATA components were made throughout the war,
long after AN/ARC-5 systems were available for use on newly
constructed aircraft.  That's why it is easy to find late
ATA transmitters with AN/ARC-5 characteristics, such as
an ATA antenna inductor cover panel that is held in place
by four screws instead of the ATA's usual two slide clips.
The production of ARA/ATA components was required for
replacement purposes in the many aircraft installations
that utilized the ARA/ATA command set.

Since the ATA and the AN/ARC-5 co-existed in naval aviation
service, and the transmitting components (except dynamotor
and antenna relay) of the AN/ARC-5 are electrically
incompatible with those of the ATA (and SCR-274-N), the
different equivalent connectors of AN/ARC-5 transmitting
components make inappropriate component interchange within
a military installation unlikely.

Interchange of receiver components is possible with little
or no adverse consequence.  Thus, AN/ARC-5 receiver system
connectors are largely the same for the other two command
sets in this series.  I've seen USN service photos of an
ARA three-receiver rack with an AN/ARC-5 receiver installed,
as well as a photo of a USN aircraft AN/ARC-5 installation
that is using an unpainted BC-442-A antenna relay.

> The result was that many new ATA items went unused.

I don't agree with this.  I've found in the past 45 years
unused SCR-274-N and AN/ARC-5 components far more often
than ARA/ATA components.  The ARA/ATA system was well used
throughout the war in aircraft for which it was the original
command set installation.

I have most of what I consider to be the typical early
Pacific Theater carrier aircraft command set...comprising
the ARA/ATA and ZB-2.  The three-receiver rack contains:

CBY-46105 3.0 to 6.0 MHz
CBY-46145 0.55 to 1.5 MHz, connected to ZB-2 homing adapter.
CBY-46106 6.0 to 9.1 MHz

I strongly suspect that the early PTO was the only time and
place that saw actual service use of the broadcast band
receiver in any of the three command set systems.  The
AN/ARR-2 stand-alone homing receiver was not yet available.
But it was by the time the AN/ARC-5 was out.  What little
use the USAAF made of the YE-YG/ZB homing system appears to
have been a R-1/ARR-1 feeding into the aircraft's ADF
receiver.  That's called out in a couple of the B-29 "-1"
manuals that I have.

Mike / KK5F