UK Bandspread Receivers

[Synchrodyne]

Some time back there was a thread on the Bush EBS.44, at: https://www.vintage-radio.net/forum/...431#post276431.

It seems that during the early 1950s at least, maybe predating that, some of the UK setmakers produced export market multiband models with electrical bandspread facilities for the major shortwave broadcast bands (typically 6 or more). The Ambassador Viscount seems to have been one of the most advertised bandspread models of the period, at least judging by its occurrence in “Wireless World” magazine. But it is evident that with the EBS.44, Bush joined the electrical bandspread club, and I understand that Murphy also had some export models. I would guess that given their tuning sophistication, most of these bandspread receivers would have had better-than-average circuits, inclusive of RF amplifiers.

The use of electrical bandspread also moved into the tuner (and tuner control unit combination) market, with models such as the Chapman S6BS, Armstrong EXP119 and BS125 and Dynatron T139. I think that the Chapman and Armstrong models dated from around 1953. At least judging by the Hi-Fi Yearbook entries, most of these had disappeared by about 1960-61, although the Chapman S6BS survived until 1969.

But for how long did the major setmakers like Ambassador, Bush and Murphy offer their electrical bandspread models. For the UK domestic market, the advent of FM brought major change, with simpler (perhaps oversimplified) AM sections in FM-AM receivers, often deleting any shortwave coverage at all. However, I would think that the more sophisticated AM-only receivers (and radiogram counterparts) would have been required for the export market for a few years longer. Perhaps some stayed in production until the time that transistors started replacing valves in mains-operated receivers?

Cheers,

[JoshWard]

I have a Murphy B818 transistor set from the late 60s here with Band Spread, this allows better reception (well would have done, I guess, I wasn't around at the time!) for stations such as Luxembourg and Caroline etc.

[Paul_RK]

Models with bandspread at the low end of MW were popular here throughout the 1960s. As regards SW bandspread sets, Pye were probably their most prominent exponent of all here, from the pre-war International through a multitude of eight- and nine-band '40s and '50s models to some that came very late in the valve era. As Synchrodyne suggests, later table models with bandspread tuning would chiefly have been for export markets, and I can only think of Pye and (same company) Ekco models that went down the 8 or more band route as late as the 1960s. For the domestic market here, Vega/Astrad portables invariably marketed as Russian sold well at highly competitive prices in the 1960s, and would largely have satisfied such demand as remained among the public for casual SW broadcast listening.

Paul

[PJL]

I had a 1939 Murphy A92 (UK model) which used bandspread on SW. It bacame quite a popular feature in late 30's sets. It is possible to arrange the local oscillator to cover a reduced range by choosing the correct fixed/variable capacitor and inductor. Bandspread as far as I can see is a marketing term which means a narrower than normal band coverage whatever normal means. Ferguson and others were making multi-band short-wave receivers in 1937.

[Station X]

There are several forms of bandspread. Mechanical bandspread just uses a reduction gearbox so that many turns of the tuning knob are required to move the pointer a very short distance. (RCA AR88) This may be associated with a slow motion drive having coarse and fine tuning knobs (R1155). Electrical bandspread uses a low value tuning capaciitor in parallel with the main one often with its own tuning scale (Trio 9R59DS). Narrow wavebands may also be provided by reducing the capacity and thus tuning range of the TF and LO sections of the tuning capacitor without restricting its mechanical movement.

[dave walsh]

There's quite a few Pye sets. I've got the [rather large] A39J/BS. One site illustrates it's export version the PYE 41 [1951] sent to Kenya originally.
A search under Teleflic on here brings up the EBS44 thread plus more info on Bush export sets inc the EBS4/EU4 model I once had [1948]. It took maybe 15 years for FM to get established in the UK but I'm not sure that would have a direct relationship on the export market. It does seem likely that sets for export would have continued to be needed for quite a while longer though. Dave W


PS I believe those Murphy A92's were used at the beginning of WWII as the RF stage and BS was the nearest thing to a comm rx available at first.

[RGD Dennis]

In 1955 my family purchased a Murphy TA194L model radio which our dealer told us was an export model a few of which had become available for the domestic market.

I have recently added two of this model to my collection one of which has has a complete cabinet/chassis restoration and both work very well.

[Maestro Maker]

If my ancient brain is working properly I am sure Pilot Radio sold bandspread shortwave radios in the late 1930s. They were made in the UK from parts purchased from Pilot Corp. USA until WW2 put a stop to such imports. The main item was the so called tuning heart - the three section ganged tuning capaitor and associated multiple SW band tuning coils and waveband switch all built as a sub -chassis. Are there none lurking about now? It's not quite 70 years ago!

[Synchrodyne]

Thanks very much for the comments. It is evident that some of the UK setmakers did maintain decent export AM models in their ranges after the advent of FM-AM domestic models in which the AM sections often declined in performance as compared with previous AM-only models.

In this context I was thinking more of the electrical bandspread models that had a multiplicity of shortwave broadcast bands, each covering just one of designated “metre bands” from 11 through 49 metres. (Bandspread coverage of the 60, 75, 90 and 120 metre bands seems to have been less common.)

I am familiar with the Bush EU.24, which had the “Teleflic” mechanical/optical bandspread system. In fact that was the first radio receiver I ever encountered, and as an aside, something I learned from it, when comparing it with later but simpler valved receivers, was that RF amplifiers were highly desirable not just for SW and distant MW reception, but also for dealing with very strong local MW signals. Perhaps Bush moved to electrical bandspread, as in the EBS.44, to remain competitive.

I suspect that many of the UK export bandspread models went into what Eddystone referred to as the colonial “tea planter” market, where SW reception of the BBC World Service was a must and where local FM broadcasting probably did not arrive until the 1970s or later. Interestingly though, as far as I know Eddystone never offered a model with electrical bandspread coverage of the shortwave broadcast bands. So Mimco, which seemed mostly to rebadge Eddystone receivers, sourced from Dynatron for its bandspread marine receiver.

Cheers,

[Synchrodyne]

I have since found the Murphy radio site, at:

http://www.murphy-radio.co.uk/index.html

This shows several bandspread models in the export section.

It would appear that these remained available through the late 1950s and possibly into the early 1960s. Most, but not all models have an RF stage.

A curiosity in the 1956 to 1961 period was the TB233, a 4-valve battery-vibrator superhet with 6 bandspread SW ranges, 11 through 31 metres.

Also very interesting (although not involving bandspread models) is the New Zealand Murphy section

Of note are designs apparently new in the late 1950 and still using B8A valves, and some MF-only receivers with RF stages, something that would surely have been rare in UK practice by that time. New Zealand AM reception conditions at the time were generally relatively benign, but many areas would have been well outside of the 2 mV/m dB contours of the main transmitters – many of which had antifading radiators - hence the desirability of the extra sensitivity and lower noise that an RF stage conferred.

Cheers,