[MRCA] Crystals ID

[Mike Morrow]

This is a easy problem for very precise ID.

Those are crystal units for channels 6 and 7 of the AN/ARC-9 or -9X, which is the USAAF version of the Bendix RTA-1B HF Aircraft Receiver-Transmitter:

  http://jptronics.org/Military/JANAP161/an.ac/an.arc-9.pdf
  http://www.radiomilitari.com/arc9.html

The RTA-1B operates on ten crystal-controlled channels, 2500 to 13000 kHz, 50 watts, A3 only.  It has a 6-tube transmitter using two 807 PA tubes and two 807 modulator tubes.  It uses an 8-tube receiver with no BFO.  Two dynamotors are built into the main chassis.

In addition to the special two-crystal unit for each channel, there are five circuits for each channel specifically tuned for the operating frequency.  All ten channel circuits are mounted on a turret that rotates to change the channel.  The RTA-1B appears in civil aircraft radio literature in 1942.  The USAAF's AN/ARC-9 components bear no JAN ID on them, but the AN/ARC-9 was supplied from Bendix equiped for A3 operation on the following ten standard frequencies:

CH #   kHz
 1     3105
 2     4220
 3     4495
 4     4575
 5     4465
 6     5588
 7     5662
 8     6210
 9     6440
10     6500

It's a very interesting set, but it would have been very labor intensive to alter channel operating frequencies.  It would have had very limited ham appeal.  I have two AN/ARC-9 RTA-1B units, but not the mount or control box.

Mike / KK5F

-----Original Message-----
>From: Thomas Chirhart <k4ncgva at gmail.com>
>Sent: Jan 18, 2020 2:53 PM
>To: Military Collectors Association <mrca at mailman.qth.net>
>Subject: [MRCA] Crystals ID
>
>I found these two in my crystal box while looking for a 4075 for another member. 
>Bendix Aviation SC7549A
>5133/5588 and 5202/5662
>455 IF
>Same size and configuration as crystals for the TCS rigs.
>Any ideas what radio they go to? Did Bendix make crystals for the TCS? A 5 Melgar could have been a TG/TF common channel or Harbor Control...or?
>73 Tom K4NCG