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Old 23rd Jan 2018, 9:38 pm   #1
John KC0G
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Default Murphy B56A and B56B

I have just been looking at p. 442 of the November 1949 issue of Wireless World. As part of the Radiolympia Review it is mentioned that in order to meet the Post Office specification for merchant ships, Murphy had introduced the B56A and B56B. They are described as slightly modified versions of the B40 and B41.

I can find no mention of these anywhere, including the archives here. Did these receivers actually see the light of day? I could imagine that they were much heavier and more expensive than other offerings elsewhere.

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Old 23rd Jan 2018, 11:35 pm   #2
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Default Re: Murphy B56A and B56B

I wonder if they were aimed at wider supply voltage permutations than the B40/41 series? As far as I know, they were made for AC only, nominal 115/230V input, whereas contemporaneous Marconi receivers such as the CR300 and Mercury/Electra allowed for DC mains and even 24VDC operation- presumably merchant ships had a greater variation of and often less sophisticated power systems than naval vessels.

There's little doubt on examination that the B40/41 would have been very expensive sets, though possibly not much bigger/heavier than similar marine receivers- perhaps just too expensive for the commercial market?
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Old 24th Jan 2018, 3:37 pm   #3
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Default Re: Murphy B56A and B56B

Hi All,
Another contributing factor to the low profile of the 56A/B may be that receivers were becoming available on the market which covered both the LF and MF/HF marine bands in a single receiver, rather than requiring two receivers - one for LF and one for MF/HF as had been the case up until then. Typical of the new breed would be the Redifon R50 which covered from LF to HF and was introduced in 1947/48. Redifon claimed that the R50 was the first receiver available which met the Postmaster General's requirement for a Ship's Main Receiver at both LF and MF/HF in a single set. This is achieved by the use of two IF frequencies - 110kHz and 465kHz - which are switched according to the frequency band selected. This obviously represented a significant saving in cost and space over needing two receivers to do the job.
The R50 uses an external power supply, enabling a variety of different power sources to be accomodated and allowing the power supply - and its associated magnetic fields - to be tucked away so as not to disturb the ship's compass.
Was Murphy active in any part of the marinew elctronics market at this time, or was the introduction of these receivers an attempt to break in to the market? Established players like Marconi and Redifon had large marine service organisations with a prescence in most major UK ports and agents all over the world, to provide spares and support for their equipment. A new player would need to make a major investment in support services to attract shipowners to his product, I would guess.
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Peter G8BBZ
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Old 24th Jan 2018, 3:51 pm   #4
ms660
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Default Re: Murphy B56A and B56B

The Marconi CR300 had two IF frequencies, it covered 15kHz to 25MHz.

Lawrence.
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Old 24th Jan 2018, 4:32 pm   #5
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Default Re: Murphy B56A and B56B

If they were only slightly modified perhaps this was just a factory designation and they just sent them out as B40 and B41.
Don m5aky
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Old 24th Jan 2018, 5:21 pm   #6
John KC0G
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Default Re: Murphy B56A and B56B

I have just looked at the article gain. In the text they were in fact described a models 56A and 56B. Mea Culpa. In the picture on the previous page, which I have only just seen, they were described as model MR56A and MR56B. Searches for all four designations have turned up nothing.

Thank you to you all as to why these receivers were probably not a commercial success.
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Old 24th Jan 2018, 5:36 pm   #7
turretslug
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Default Re: Murphy B56A and B56B

This reminds me that there was a Murphy "62B" receiver, generally similar to the B40, except that 1.5-3.9MHz coverage was dropped for a 150-300kHz range, i.e. the Region 1 LW broadcasting allocation. Murphy enthusiasts will know more of the inside story than me, but I gather that the B40 saga had been problematic for the company- the castings and chassis-work look like expensive investments and the turret mechanism presumably similarly involved quite some design, development and de-bugging effort. Maybe there was pressure to maximise return on significant investment and 56A, 56B and 62B all represented attempts to appeal to wider markets. The 62B would seem to appeal to the "broadcast monitor" market that GEC's BRT400 found a place in, though whether it sold in significant numbers I don't know.
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Old 24th Jan 2018, 6:59 pm   #8
John KC0G
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Default Re: Murphy B56A and B56B

I have just found the two pages from the Nov 1949 issue of Wireless World on this web site. They were posted by Synchrodyne while discussing the Mullard GFR520. See post #87 in this thread:
https://www.vintage-radio.net/forum/...=gfr520&page=5
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Old 3rd Feb 2018, 12:41 pm   #9
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Default Re: Murphy B56A and B56B

http://www.radiomuseum.co.uk/navy.html

Just found this whilst looking for something else as you do.
Higher number but might be a clue.
Don m5aky
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