[ARC5] ZB-* Homing Adapter Notes And Its Installation With ARB

[Mike Morrow]

Exactly as Jack Antonio has stated, an ARB with ZB should not use the nt-23214 ZB Control Box, the nt-29173 ZB Antenna Switch, nor associated cables and mounts.

The elimination of these components is explained in the ARB section from this excerpt of Navy Radio & Sound Bulletin No. 8, 1 October 1942 as found at Mike Hanz's Treasure Trove:

  https://aafradio.org/docs/atb-arb.html

Here are the cable configurations required to operate the ZB-* without control box and antenna relay when the ARB is the host receiver.  (This also applies to use with the ARA CBY-46145, R-24/ARC-5, and BC-946-B.)

(Connector designations all come from the AN/ARR-1 (ZB-3) manual schematic except one for the ARB accessory connector J103.  Refer to links below.)

ZB-* filament voltage switch S102 must be locked in 24 volts position and the associated plate on outside should indicates that configuration.

A.  ZB-* J101 connects to VHF Rod Antenna AT-5/ARR-1 with 50-ohm coaxial cable.

ZB-* J101 is a coaxial connector that mates to cable plug P501 (nt-49195, equivalent to Army type PL-259).
AT-5/ARR-1 requires coaxial cable plug nt-49195, equivalent to Army type PL-259.

B.  ZB-* J102 connects to ARB L1 and L2 posts with 50-ohm coaxial cable.

ZB-* J102 is a coaxial connector that mates to cable plug P502 (nt-49195, equivalent to Army type PL-259).
ARB L1 is a push-post connector for the center conductor of the coaxial cable.
ARB L2 is a push-post connector for the shield conductor of the coaxial cable.

C.  ZB-* J103 is a 4-pin connector that is not used in this configuration.

D.  ZB-* J104 is a 3-pin connector that is not used in this configuration.

E.  ZB-* J105 connects to ARB J103 with 3-conductor cable.

ZB-* J105 is an 8-pin connector that mates to cable plug P508 (nt-49062, equivalent to Army type PL-63).
ARB J103 is a 5-pin connector that mates to cable plug P509 (nt-49234, equivalent to Army type PL-56)

P508 Pin 40 connects to P508 pin 52 to set DISTANT sens.
P508 Pin 41 connects to P509 pin 25 for HV B+
P508 Pin 48 connects to P509 pin 35 for LV A+
P508 Pin 52 connects to P509 pin 27 for A-, B- (ground)

OPERATION
The aircraft LF/MF/HF communications wire antenna connects to ARB post At (trailing wire) or Af (fixed wire).  This antenna is used when the band selected is under COMM service.

To activate ZB homing:
1.  Select CW.  This also selects MVC.
2.  Select HOMING BAND A or B associated with the ZB homing modulating frequency (540 to 830 kHz).  This also connects the ARB to the signal applied between its L1 and L2 posts and disconnects the signal at ARB post At or Af
3.  Tune ARB to the MF (540 to 830 kHz) signal demodulated by the ZB-* from the VHF (234 to 258 MHz) homing signal being sent from a YE or YG homing transmitter.
4.  Copy the AF Morse letter demodulated by the ARB from the MF signal received from the ZB-*.
5.  Determine true bearing to the transmitter using the ZB decoding card.

REMARKS
The absence of ZB control box results in
1.  ZB-* adapter is energized whenever the ARB is not OFF.  Eliminates need for ON/OFF switch.
2.  ZB-* adapter MF output is received through ARB L1 and L2 posts whenever ARB HOMING BAND A or B is selected.  Eliminates need for HOMING/COMM switch.
3.  ZB-* is set on P508 to maximum RF gain as the ZB-* manual normally requires.  Eliminates DISTANT/LOCAL switch.
 
No official diagrams appear to survive of the ARB/ZB configuration eliminating the ZB control box and antenna relay, but there are also no official diagrams showing USE of those components with the ARB.  This loss of documentation is common for systems and configurations that became obsolete before extensive usage.  I have seen no in-service photos of an ARB with a ZB-* Homing ADAPTER.  It is likely that the improved stand-alone AN/ARR-2 "ZB Homing" RECEIVER made ARB use with ZB-* obsolete just as it did the R-24/ARC-5 with AN/ARR-1.

Even if a ZB homing adapter was used with the CBY/CCT-46145, R-24/ARC-5, or BC-946-B, the adapter's control box and antenna relay would be wasted complexity.  The cables exactly as described above would work without any change except for the coax's connection to the MF host receiver's antenna and ground posts.

The full ZB-* installation with adapter, antenna relay, and control box is necessary only for RU-* receivers CBY/CW-46051* or CBY-46064 in the later RU/GF command sets. Such systems have several dual-band coil sets with one band for the desired communications frequencies such as 3000 to 4525 kHz, and the other band 540 to 830 kHz for reception of precisely the range of modulation frequencies used by ZB homing system YE or YG transmitters.

>From Mike Hanz (Thanks Mike!):
1.  Explaination of ARB use with ZB-* Adapter:
  https://aafradio.org/docs/atb-arb.html
2.  ZB-3 (AN/ARR-1) manual:
  https://aafradio.org/docs/ARR-1.html
3.  Simplified (omits band-switching) ARB schematic:
  https://aafradio.org/docs/ARB_schematic.png

Mike / KK5F