REH Receiver

The REH is an amenities receiver used by the United States Navy. It was made by the Belmont Radio Corporation, Chicago 39, Illinois, USA, in 1945 and has the designation of CDL-46271.

An "amenities" receiver is intended to provide radio news and music to off duty serviceman. In the USA it was known as an "Entertainment" receiver, or called a "troop morale" receiver. In the UK it was known as a "NAFFI" receiver because it was placed in the canteen, and also known as an "Invasion" receiver because that is where you would hear of the invasion landings. This type of receiver is normally a ruggedised version of a domestic receiver, with the additional ability to operate from several voltages, and in hostile climatic environments.

The REH is a 7 valve superheterodyne receiver with a 455 khz IF, and has 5 frequency bands covering the ranges:
Broadcast    540 - 1600 kcs
49 Meters    5.96 - 6.19 mHz
31 Meters    9.1 - 10.0 mHz
25 Meters    11.45 - 12.16 mHz
19 Meters    14.14 - 15.46 mHz
This is the normal broadcast band and the short wave broadcast bands. It also has a phonograph input. It can operate on 110 or 240 volts AC and 50 or 60 cycles. The receiver is in a strong steel case, and slides out the front when 5 captive screws are released. It has built in feet, a carry handle, a telescopic antenna, and is painted with grey wrinkle paint. The nameplates on the front panel, carry a warning that it is not to be used on ships, as it does not have radiation protection, and so may betray the ships position to the enemy.

The controls are very simple. There are only 3 knobs.  The left hand knob is the volume control, the centre knob is the band change switch, and the right hand knob is the station tuning knob. There is a row of push buttons to select pre-set stations.  By pushing these buttons, the tuning knob spins and the station is selected. The RIGHT most button is the ON/OFF control. The LEFT most button is the TONE control. Next to the TONE push button is the PHONO button, (but this has to be pulled, not pushed). The manual has a sheet of American station call signs, that can be cut out and affixed to the push buttons. Each button has a clear removable cap, that can be popped out,  and then replaced with the station call sign visible behind it. To set a station, you first push a button to set the old station, then pull the button out, then you tune in the new station, and press the button in. The new station is now set. Above the buttons is the square dial, showing the frequency. Above the dial is a magic eye tube to show the signal strength. On the RIGHT hand side is the speaker. The power cord comes out the back. Also on the back are the PHONO terminals, the ANTENNA terminals, and a telescopic antenna. The manual recommends operation on the telescopic antenna for nearby stations, and a 50 foot wire and earth for other stations. There is an internal chassis mounted toggle switch, to select 110 or 240 volt operation.

The radio has a conventional steel chassis, with the octal valves mounted in the normal fashion. The RF tuning section is a separate module that can be removed. It contains the mixer, tuning coils, RF amplifier, dial, and push buttons. On top of the tuning module, is a rack containing a spare set of valves.
Most of the valves are the metal type. It has a mains transformer, with a switch to select 110 or 240 volts AC. It has no provision for DC or battery operation.
There is a 5Y3 rectifier, with a capacitor choke HT filter. The audio output valve is a 6V6 pentode which drives a large oval speaker. The audio pre-amplifier, detector, and AGC rectifier is a 6SQ7 triode double diode. There is a TONE control circuit on the triode plate, that switches in a fixed capacitor, or a fixed resistor with the capacitor. This is activated by the left hand push button, that cycles through 3 positions, one for each push button press. The triode grid is switched to the rear PHONO terminals for external input, or the IF transformer for normal radio reception. This is activated by the second most left hand push button, but instead of pushing, you pull it for PHONO and push for radio. The single IF amplifier is a 6SK7 pentode, and the 455 kHz IF transformers are slug tuned with fixed capacitors. The mixer/oscillator is a 6SA7 heptode. The RF amplifier is a 6SK7. The receiver has AGC and this is applied to the mixer and RF amplifier only, not the IF amplifier. The tuning method for station selection is not the normal variable tuning capacitor, but variable slug tuning. There are 3 slug tuned coils for the broadcast band (RF, mixer and oscillator). The short wave bands are combined, and all are tuned by just 3 slug tuned coils (RF, mixer and oscillator). To change the short wave coverage, there are additional fixed coils switched in circuit, and the oscillator coil is tapped. There are 6 slugs in total. A note on the circuit diagram, explains that there was a loop antenna, but the telescopic antenna has replaced it.

When I acquired the radio, it was described to me as not performing very well. Upon examination, it showed that several people has worked on it, as there was evidence of many different repairs. I had no circuit, so I put the radio aside until I managed to locate a manual.  A friend scanned the manual and emailed to me, complete with the station list for the push buttons, and the original purchase receipt. Thank you very much, it has been a great help.

The underneath showed that the 110/240 volt switch was disconnected and a new mains transformer had been fitted. There was indication of pitch leakage, so the original transformer may have failed and been replaced. I began by connecting it up to a VARIAC and bringing the voltage up slowly to 240 volts AC, while monitoring the HT voltage. It came up to full voltage without and smoke or any other problems. I let it stay that way for a some time, while checking the filter capacitors for heating. I found that the audio coupling capacitor was passing positive voltage to the power output valve grid. This is a common fault. I removed the capacitor, pulled out the insides, and concealed a modern capacitor within the cardboard tube, then filled it with wax. The scratchy volume control proved that the audio stages were now working properly. The control was lubricated to remove the noise. The manual said the IF was 455 khz so I connected a signal generator into the mixer grid and attempted to tune the two IF transformers. The slugs came all the way out to their stop,  without peaking, very strange. I aligned one of the RF bands, but could only get a 160 mv sensitivity, which indicated something was wrong. The RF amplifier seemed to be very low on gain, and when I checked the grid it had a positive voltage on it, indicating a gassy valve. I replaced the valve, the voltage was now zero, and the gain improved.

Nothing else seemed to increase the gain, so I removed the IF transformers. I took the can off, and there was the normal pile wound windings with  a capacitor across each one. I unsoldered one end of each capacitor, and checked it with the capacity meter. They should be 75 pf, but the reading was 1200 pf and changing as I watched it!  It was not steady, so there was something wrong with the capacitors. I checked the resonance and it was 350 khz. I fitted new capacitors, and used a signal generator and oscilloscope to set each winding individually to 455 khz. The level was much higher, and the peak very sharp. The method I used, was to remove one capacitor, and use this as the primary untuned winding, driven from the low impedance signal generator, set at 455 khz. The IF secondary was connected to the high impedance oscilloscope. I tuned the secondary slug, for maximum level  which was resonance. In this way there was only one tuned circuit, so there were no interactions. I then reversed the procedure, and set the other winding to resonance using the other slug. I reassembled the IF transformers, put them back in the radio, and realigned the IF. There was much more gain this time, the slugs peaked properly, and the radio came alive, with a sensitivity of 50 micro volts at the mixer grid.

I aligned the broadcast band mixer and RF coils, and then the shortwave bands. One band was dead, which proved to be an open circuit oscillator coil. I repaired the broken wire and then this coil aligned properly. There was a disconnected capacitor, with a new one tacked on to the band change switch. This was C8 which coupled the signal from the RF amplifier to the mixer. I checked and this was passing DC from the RF plate circuit. Here was another capacitor of the same manufacture which had failed. I snipped out the faulty one, and the unsightly replacement, and concealed a new one within the switch wafers where it should be mounted. The magic eye did not open or close when a station was tuned in. I removed the rear cover from the magic eye base, where it is mounted above the dial, and examined the 1 meg ohm resistor there. It was open circuit. I replaced it with an identical style good resistor, and the eye now worked properly. The green fluoresent screen, was a light green, and on the section where it closed, it was a darker and brighter green. This is probably due to the radio being operated for a long time in the faulty condition, and the screen wearing out. The part that was never used is as good as new.

The radio was distorted on some of the stronger broadcast stations. I checked the AGC and it was only reaching negative 6 volts, whereas I would expect about negative 30 volts. I checked at the AGC diode, and its voltage was in this order, but it was low by the time it reached the grids. I found that the AGC bypass capacitor was measuring 2 meg ohms, so this was loading the AGC line. I replaced this capacitor, the AGC voltage was now much larger, and the distortion went away. The oscillator grid resistor had been replaced with a modern style resistor, and it was sitting up on long leads. I found a suitable resistor in the junk box, that matched the style of the other resistors and fitted it to the radio.

The radio now has sensitivities of:
Broadcast band 3 uv
49 Meters band 2 uv
31 Meters band 2 uv
25 Meters band 2 uv
19 Meters band 3 uv

The case and front had been painted with light grey paint. I checked under the removable panel, and discovered that it should be dark grey wrinkle paint, so I repainted the front and the case, with grey wrinkle paint, and baked it in a n oven. It came up nicely.

The radio reforms well for a domestic receiver, considering it only has one IF stage and one RF stage. It is easy to use, with the push button controls and the external whip aerial. The large speaker gives a good sound. Having spare valves inside is very convenient for remote repair. The radio could be improved, by using all the push buttons for station TUNING, and adding a separate ON/OFF TONE control switch. There could also be a RADIO/PHONO (and even MICROPHONE) switch. Having one switch as a "pull out" for PHONO is strange. The manual has a comment in the "Fault Finding" section, which says that "if the radio does not work, check the setting of the internal 110/240 switch, and if it is set wrongly, replace all the valves".


Ray Robinson VK2NO

Back to the INDEX