By 1985, the Oberons had their communications mast modernized with the fitting of the AN/BRA-34(V) antenna group. No information is available to show which variant was fitted in Canada's boats.  It is assumed that the Oberons were retired with the BRA-34 antenna group.

The AN/BRA-34(V), AN/BRA-34A(V), AN/BRA-34B(V) are multifunction antenna groups that provide signals for the following radio bands or services: VLF/LF, MF/ HF,  UHF line of sight (LOS), navigation (NAVSAT), UHF satellite communications (SATCOM), IFF (Identification Friend Foe) and GPS (Global Positioning System). There are six configurations for the AN/BRA-34 group. They are as follows: AN/BRA-34(V)1, AN/BRA-34A(V)1, AN/BRA-34B(V)1, AN/BRA-34(V)2, AN/BRA-34A(V)2 and AN/BRA-34B(V)2.

TPUB.com has the best documentation of all so extracts from their documents are posted here.

Click to enlarge
oberon_bra34_general_arrangement_s.jpg This pictorial indicates the major components of the BRA-34 antenna group which 
consists of an antenna control unit located in the radio room , an interconnecting junction box , a hull penetration connector, special purpose electrical cable and an antenna group fitted on a  mast. The control unit houses the power supply, reflectometer  and various control and indicating circuits necessary for remote control operation of the various antennas. 
oberon_bra34_mast_sections_s.jp The antennas in the stack are surrounded by a radome consisting of an epoxy-bonded fiberglass shell which houses and seals all of the antennas from water engress. In turn, this mast was fitted into a separate, external,  teardrop-shaped fairing.  All antenna sections contained within the radome are engineered to operate simultaneously  in any combination of transmit and receive without degrading the others. There was one exception. VLF reception was not required during MF/HF transmissions. See the writeup below for more details.
oberon_bra34_components_s.jpg BRA-34 antenna group component designators. MILSPEC MIL-A-29521( EC) describes the entire antenna group. 

GPS ANTENNA (Unit 1A6E2). The GPS antenna is used for the reception of GPS satellite signals. Frequency range is  1227 +/- 10 MHz  and 1575  +/- 10 MHz.

IFF ANTENNA (Unit 1A6E1). Frequency range 950 MHz to 1150 MHz at a power level of up to 1 kw with a 10% duty cycle. A diplexer separates or combines the IFF and GPS signals.

DEPTH TRANSDUCER (Unit 1A6) - It produces a voltage which is proportional to the depth of the antenna below the surface of the sea. The transducer is capable of withstanding a pressure of 1,000 psi.

VLF ANTENNA (Unit 1A7). The VLF loop antenna system provides radio reception in the frequency range 10 kHz to 170 kHz. It operates in conjunction with coupler CU-1441( )/BRR or CU-2364 /BRR. Another web document quotes the frequency range as 5 to 150 KHz ( it depends on the variant). The antenna uses two antennas whose reception patterns are figure eight's and displaced by 90 degrees.

UHF DIPOLE ANTENNA (Unit 1A2) . This is a vertical dipole antenna intended for UHF LOS transmission and reception, NAVSAT reception, and UHF SATCOM low-angle transmission and reception. Frequency range is 225 to 400 MHz at a power level of 100 watts. Another web documents quotes the frequency range as 240 to 315 MHz. This is probably dependent on the variant of the antenna.

UHF HELIX ANTENNA (Unit 1A3). The UHF helix antenna is a quadrafilar helix  for the reception and transmission of SATCOM signals in an overhead (high-angle) mode. The UHF helix antenna is compatible with a UHF SATCOM transceiver operating in a simplex mode. Its frequency range is is 240 to 320 MHz.

Tim Tyler adds to this . "The 240-315 MHz frequemcy range is the common UHF SATCOM spectrum within the 225-400 MHz military band. US and NATO UHF satellite transponders usually transmit in the 240-270 MHz spectrum, with uplinks to the satellites operating in the 280-320 MHz spectrum. It sounds like this antenna would primarily have been for surface to air and surface to surface, with secondary UHF SATCOM capability, while the 1A3 antenna was the primary UHF SATCOM one".

UHF SWITCH DECK (Unit 1A8). The UHF switch deck separates or combines UHF and IFF signals or amplifies and filters VHF and UHF received signals and provides relay selection of the UHF dipole antenna or UHF helix antenna.

MF/HF ANTENNA (Unit 1A1). The MF/HF section consists of a helical conductor wound within a pregrooved plastic form on which a metallic capacitive top hat is mounted. Inside the helix and top hat, there is a shorting device which consists  of  a metallic shorting tube with shorting brushes at each end to complete the circuit between the helix and the top hat.  Frequency range is 2 to 30 MHz with a power rating of 1 kw. Impedance is 50 ohms

MODE SWITCH  (Unit lA5).  The mode switch provides the capability to disconnect all antennas except the MF and HF antenna for improved MF/HF transmission performance.

DUPLEX FILTER (Unit lA4). The duplex filter combines or separates the MF and HF frequency bands and the UHF and IFF-GPS frequency bands.

Contributors and Credits:

1) TPUB.COM  http://www.tpub.com/content/MIL-SPEC/MIL-A/MIL-A-29521/
2) Tim Tyler <polohat(at)gmail.com>


Mar 21 /10