When Did Radio Stations Start Recording In Stereo?

[Gordon]

The first experimental stereo broadcast was in December 1925 from Daventry (5XX). Hamilton Harry conducted.

"The 5XX longwave transmitter beamed the right hand channel and all the local BBC medium wave transmitters including 2ZY broadcast the left hand channel."

This is intriguing - there is relatively little information on the web about this but still searching - and follows the same pattern as was deployed around 1960 when some experimentation took place [see Ferret's post above] using the mono FM service together with the TV sound channel. In either case the prospects of anyone taking the trouble to arrange reception getting anything approaching modern decent stereo would be quite remote. Nevertheless those were the days when amateurs would build kits to engage in the latest whizzo technical innovation. Anyone remember Heathkits or even Stern-Clyne?!?

In this 1925 case the concert was in Manchester and clearly two microphones were placed at the venue. The output of the "Right" one was carried, presumably by GPO mono landline, to Daventry some 100 miles to the S and E whilst the Left channel was taken directly to the local Manchester MW transmitter [call sign 2ZY]. Other MW stations around the country would be given a copy feed of this channel too including 2LO in London and 2NO in Newcastle.

So to get stereo one would need 2 receivers [possibly crystal sets without valves or loudspeakers] one tuned to the Long Wave transmission from Daventry and the other tuned to the local MW station. At this time not that many receivers were in existence, mostly concentrated in and around London.

So, for reception in Manchester the Right signal would travel all the way to Daventry by cable then back to Manchester over the air. Apart from the obvious differences in propagation characteristics of the LW and MW channels as well as the 2 receivers, the prospects for good stereo were a bit dubious with a relative delay in arrival between the L and R signals. The relative delay would depend on actual location within the MW reception area and which region of the country reception took place. I suspect however that the achievement of high quality stereo was not the point at the time - it was more that it could be done at all. It may also have had other purposes - the see the end of the post.

I'd estimate that the relative delay in Manchester between the two paths would be more than 1 milli-second which was in fact well outside the tolerance of 200 micro-seconds that the BBC set in the early 1960s for adequate stereo effect [reference some BBC Research reports of the time]. The radio wave itself from Daventry to Manchester [or actually to London too] would take about 500 microseconds [say 93 miles at 186,000 miles per second] not counting the landline delay from Manchester to Daventry - probably a bit more circuitous a route at a slower rate so say about another 750 micro-seconds. With a relative delay between the channels of this much, together with the propagation issues and a small bandwidth, the stereo effect would have been less than perfect!! In London the location would make the relative delays different again but possibly less than in Manchester because the differential would be between a cable path carrying the R channel from Daventry to London and over air from Daventry possibly in the region of 250 micro-seconds so possibly giving a better stereo effect.

Fascinating stuff!! Incidentally it was the potential growth of radio and its possibility for stereo that forced the record companies to turn to electrical recording starting in earnest in the UK in 1925. After some years of experiment formal contracts were in place between the major companies like HMV and UK Columbia and Western Electric - commercial arm of the Bell system in the US - to use the WE technology. It wasn't the music industry that developed this technology, it was a telephone company!! However stereo on disc never happened commercially until 1958, closely followed by radio in the early 1960s.

The following comes from Wireless World, June 1958, author Captain H J Round,

"Hi-Fi and Stereophony
There seems to be a revival of interest in stereophonic sound and this brings back the memory of our first experiments in the subject in the 1920s.
Working in conjunction with the late Capt. A G D West of the BBC we fitted up one transmission from the Opera House, Covent Garden, for stereophonic work in 1925. The two radiators were 2LO and Daventry. How many heard the result, aside from ourselves, I have no record, but to our own receiving arrangements it was fairly satisfactory.
Two microphones spaced a foot or so apart were fixed on the edge of the stage by the footlights at the Opera House and their output ran via two amplifying systems to the two transmitters.
It had previously been noted in earlier non-radiating tests with spaced microphones that, when receiving with two telephone earpieces, movement to the right or left was clearly defined but that in the main the sounds came from the back or the top of ones head.
I believe it was Mr W I Picken who remarked to me on hearing someone walking across the microphone room that it sounded as though someone was walking over his grave.
When using two loudspeakers the effect vanished as the sounds were, of course, being put artificially in front of one.
However, a new effect was noted during the opera transmission. The microphones were, as I stated, placed by the footlights and they were between the stage and the orchestra. With a soprano singing on the stage and the orchestra accompanying her I noted at once that with telephone reception she seemed to be in front of me, but the orchestra sounded behind. Male voices, however, joined the orchestra, so that the effect was in some way due to frequency. West and I had many discussions as to the reasons for these curious effects. Many obstacles of course are in the way-of hi-fi and stereophonic sound for normal house use, particularly from radio transmissions. Rooms are not large enough and many wives and neighbours object to the volume of sound necessary for correct effects.
The question of sound strength and correct quality was pretty thoroughly thrashed out many years ago - after Harvey Fletcher had published his monumental work on Speech and Hearing (Macmillan, 1929), and correcting devices for all strengths were worked out. But then, as now, quality and naturalness were the worry of only a very small percentage of the population. Nearly everybody in those days, and very probably now, was content with the sound of his own loudspeaker."