B40, B41 and 62B

Murphy  Radio in the UK built this classic family of receivers.  Consisting of the B40, B41 and 62B this family was used  by the RAN from the forties right up to the eighties. The  B40 is the HF version, and was known as outfit CDW or CAQ. B41 is the MF version and the 62B  is the MF/HF version for SRE (Sound Reproduction  Equipment) use. The 62B also had an upgraded audio stage  for higher quality reproduction. Photograph at left is an early B40. Photograph  at  right shows my main operating desk, with the B40 at  right, and a 62B at left. At far left is an Admiralty  remote control unit common on RAN ships. See my Diamantina page for more information on this receiver.

COMMENTARY

Many regard the B40 as the king of boatanchors, and I agree. It weighs 114lbs. I drove from Sydney to Brisbane with one of these in the boot and I certainly felt the difference.

The set is beautifully built, consisting of four sections. The chassis houses the massive perspex drum which shows the current frequency and the chain gearing system with connects the frequency control knob to the tuning capacitor.

The power supply and audio sections are mounted in a tray in the base of the receiver.

The RF section is mounted on the top right of the receiver .It contains the main tuning capacitor and the massive coil turret. The turret contains all the necessary coils for the bands used by the receiver. When changing bands the entire turret rotates to select the correct set of coils. Switches mounted on the rear of the turret switch in pilot lights which light up the correct section of the perspex drum with the frequency scale on it.

The IF section is mounted on the left hand upper section of the receiver.

The sections are connected together via multi-pole connectors. The three main sections may be removed from the chassis by removing the knobs on the front panel, disengaging the multipole connectors and removing the securing screws for each module. The RF section must also have the gearing disengaged although I have done this several times and is not particularly difficult. This design allows each section to be serviced relatively easily.

Most of the tubes are of metal envelope loctal type. Later variants used glass miniature tubes.

Controls are quite easy to use and very functional. There is a loudspeaker ON-OFF switch which allows selection of the internal monitor speaker, or an external speaker may be selected. There us a noise blanker and level control. Later models had an AGC manual or Auto control. The bandwidth control allows selection of  8Kcs (AM only), 3 Kcs or a 200Hz note filter. Later models replaced the note filter with a 1kHz  crystal filter which is a nightmare to align. Also the BFO is operational in the 8Kcs position. There is a standard AF gain control. The System switch is multi-function in nature. The CAL position switches in the calibration oscillator for correct setting of the dial scale. The R/T position switches off the BFO. The TUNE position is used to zero-beat on a desired station. The CW HIGH or LOW position injects the BFO signal in on the high or low side of the carrier. This facility can be used to receive SSB in ham use. The MANUAL switch (B40/A only) switches of the AGC (replaced by toggle switch in later versions). The B40D has a FSK position for when the receiver is interfaced to appropriate TTY equipment. The GAIN control affects the gain of the IF stage. The ANTI-CROSS-MOD. control is adjusted to minimize cross-modulation interference. The CRYSTAL switch allows the selection of a crystal for single channel operation.

The receiver has low and high impedance aerial inputs. There are various other outputs to support other equipment. Large numbers of B40s were used on many ships. Often common aerial working (CAW) would be
used to minimize the number of physical aerials required on the ship.

The B40 is a single conversion superheterodyne type, with three IF amplification stages and two RF amplification stages.

This is one of the nicest receivers I have ever used. I can't explain it in technical terms, but for CW work it will take the most ordinary signal and produce the nicest not to listen to. Despite its tinny monitor speaker, the note that the B40 produces is just beautiful. The B40D is better suited to SSB work than it older brothers but I have had no difficulty in receiving SSB on my example.

TECHNICAL SPECIFICATIONS (B40)

Frequency Range:                    650kC-30Mc
Mode:                                     AM, CW, FSK on B40D
Sensitivity                                AM 4uV, CW 2uV
Weight:                                    114lbs

CONSTRUCTION

The B40 is a typical Admiralty design, big and heavy. Just the way I like it!

Below: Top view of the B40. The metal envelope valves are in plain view. The tuning capacitor is underneath the cover at the centre of the unit.
 

Below: Right hand side of the B40. The massive tuning turret with the contacts for each coil box can be seen. Just to its left are the massive gears which rotate it.
 

Below:  Left hand side of the receiver. The power supply and audio tray can be seen through the cutout in the receiver's side panel.
 

OVERALL RATINGS

    Engineering rating (taking into time of design).

             As solid as they come. Beautiful performance for a non synthesized receiver. 10/10

    Fitness for purpose rating

             Saw service for more than thirty years. 10/10

    Usefulness as ham equipment rating

             Excellent for CW work. A good general coverage receiver. 9.5/10

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