Defiant MSH901 Receiver

 This old superhet receiver from 1933 or 1934 is very interesting. That is apart from the fact that someone has decided to restore it by totally removing its patina! It's maker and it's name are unusual. It was made by Plessey in their Ilford factory, a place I knew well as I used to visit there regularly when running a government communications project called HDRS. If you click on the link you'll see a picture of the Ilford factory and what happened to it. Back in the 1930s radio sets were very expensive and a war was in progress in the UK over the business of selling sets. Prices were fixed by manufacturers and their products were only sold to businesses that toed the line and didn't offer discounts. To maintain this practice all manufacturers were signed up to an organisation that policed the policy. In a way the policy wasn't that bad because it meant that small one-man businesses in villages could make a living. Competition wasn't a problem because buyers, unlike today, couldn't find a particular model of radio being sold for anything less than the manufacturer's published price. True, the large retailers might be able to buy in bulk and make higher profits, but they couldn't undercut the small shops.

One of the ways for a large retailer to get round the problem was to sell only a single make of radio and for this radio to be made by a company that did not belong to the price fixing ring. Hence the Co-op engaged Plessey to make receivers for them. This was partly, if not solely triggered by the fact that the Co-op had a scheme whereby customers could accrue credit in the form of a dividend. Every time a Co-op customer who was signed up the the "Divi" scheme purchased anything they'd amass credit and this credit could be used to buy, say a Marconi radio. In other words the Co-op would gain an advantage by effectively undercutting the manufacturer's fixed price. Of course the manufacturers had no option but to refuse to sell their sets to the Co-op. The Co-op therefore decided to make the own sets...


 Here's a view of the chassis. It's definitely good quality. Not many sets had a painted chassis. It has a vaguely military look about it because Plessey made radio equipment for the military. It's a superhet and in 1933 was at the cutting edge of radio design. Many manufacturers were still making TRF sets but the superhet with it's single knob tuning and no need for a reaction control was vastly superior.

The valves were all made by Mazda. The RF amplifier/local oscillator is an AC/TP with a relatively uncommon B9 base, the IF amplifier an AC/VP1 variable mu pentode with a B7 base, and the output valve an AC2/PEN/DD with a B7 base which includes the detector and AVC diodes. The HT rectifier is a UU5 with a B4 base.


 The loudspeaker was made by Plessey although the name "Jensen" is interesting. Maybe Plessey licensed manufacture from the Jensen loudspeaker Componany of Chicago? The transformer is detached from its mounting perhaps dislodged when the set was in transit to me? I suspect the speaker has at some time been removed and refitted upside down so the picture is rotated by 180 degrees so you can read the label.

A nice touch is the wiring. Most sets used rubber covered wire. The rubber perishes, goes brittle and drops off leaving bare wiring but here the wiring insulation has a woven covering and in good condition.



 The name "Defiant" means exactly that. The Co-op made their own radio sets in defiance of the organisation set up to fix prices.

The blue label is there because many radio sets familiar to purchasers of this radio would have used a high impedance loudspeaker. This may have been a type with a high impedance coil or later a type with a low impedance coil but fitted with a transformer to match it to the audio output valve.

The practice of fitting extension speaker sockets was just about universal during the 1930s and an early set like this had the label to remind users to use a speaker with a low impedance coil.





The dial looks fairly plain and has an uncluttered appearance because, when this set was designed radio broadcasters hadn't yet agreed on their transmission wavelengths. This agreement was to come a year or so later and dials were marked with dozens of stations.

Note the double-triangle logo also used in the label above.

Thinking about the model name "MSH901". New Defiant radios were still available in the late 1960s. Some sets after WW2 were called RGSH and TRGSH as well as other MSH models. "RG" stands for Radiogram, "TRG" Table Radiogram and "MSH" must surely stand for Mains SuperHet. The MSH356 was a 1955-56 radio so maybe "56" is the year but what is "901"? There is also a CR100 which is a car radio and a battery transistor portable A503. Going back to the 1930s there's a 770 AC/DC

Below, I've shown a slightly earlier Defiant set, the Model 770 AC/DC. It appears from the view of the chassis that this model is related to the MSH901. From the comment on the drawing it seems that the Co-op serviced their own sets and grudgingly supplied the details of this long obsolete model nearly 20 years after its introduction.


Return to Reception