FM stereo

[KeithsTV]

I remember the quadrophonic broadcast which I think was in 1974. I took my tuner, amp and speakers round to a friends house for the test. I can't remember much about the content of the programme but I think at one point the sound "moved" diagonally.

I wonder if a copy of the broadcast still exists?

Keith

[red16v]

Originally Posted by Dai Corner

I may be imagining this, but didn't they try experimental quadrophonic broadcasts using two of the stereo networks some time in the 1970s?

I thought I remembered that, I had it in mind that the BBC broadcast The Who's 'Quadraphenia' but Googling reveals nothing to back that memory up.

I built a Heathkit tuner amp in the early days of stereo, and noted that the de-emphasis components supplied were for the American specification (50us instead of 75uS? - I can't remember after all this time). I wrote to Heathkit UK about it and they not only thanked me for pointing out the error they also sent me the correct R&C components in a small plastic bag to correct my own model.

[Nuvistor]

Quadraphonic sound, we got a couple of units but had to virtually give them away, not a lot of interest from the customers we had. I don’t remember the makes but they were Japanese units, the equipment was decent quality.
Others may have sold lots but not in the shop I worked at.

[John10b]

I remember having to study the Foster-Sealy discriminator in my C&G exams way back in time ( 1960 - 1970 ish or was it later? ).
Cheers
John

[ms660]

Me too, in the late 1960's at Stockport College.

Lawrence.

[Alvin]

I remember it well - the upstairs flat brought their stereo down to us and 4 or 5 of us sat huddled tightly together as close as possible to the centre of the 4 speakers - I don't recall the programme content and I can't say we were overly enthralled at the novelty.

According to Genome it was on July 6th 1974

https://genome.ch.bbc.co.uk/5c91d7ea...a8f9f158bb044d

Alvin

[Ted Kendall]

Interesting that the producer was Raymond Raikes, who had produced the first stereo dramas for the two-transmitter tests some fifteen years before.

[Restoration73]

After the twin transmitter quadraphonic broadcasts were abandoned, encoded quad based on ambisonics was tried, not using proprietary SQ or QS formats but their own standard known as Matrix-H, although I don't remember when these ended. There may be a decoder design somewhere.

[Ted Kendall]

Matrix H!

This had little to do with Ambisonics, which was a comprehensive system capable of encoding height information, and led to developments such as the Soundfield microphone.

Matrix H was an attempt to combine the least worst features of SQ, QS and Regular Matrix. Chief tweak was the application of a phase shift on centre-front signals, which was played about with over time, but ended up somewhere around 30 degrees. I have some tapes of Matrix H transmissions, which to be frank I haven't listened to closely, but the consensus at the time was that the clarity of the stereo picture was affected, and when I asked Tony Askew, who balanced Proms with it, his reaction was basically " awful thing - waste of time!"

If I remember right, Matrix H staggered on through a couple of Prom seasons and was then quietly interred, along with the rest of Matrix quadrophony.

[kirstyd]

i have this hacker RG200 bought by my parents back in 1968 that has a decoder fitted [as an optional extra]and the stereo beacon although i have never known it to work .There is some mention of stereo broadcasting in the user manual

[Ted Kendall]

That's interesting - is it connected to a roof aerial? It may just be a matter of signal strength.

[Synchrodyne]

It’s interesting to compare the UK and US situations, as the US also had a period of twin-transmitter stereo broadcasts before the Zenith-GE system was adopted in 1961. In that case, the norm was to use an FM transmitter for one channel and an AM (MF) transmitter for the other, as indicated in this Wireless World 1958 December item:



The US hi-fi equipment makers developed and offered appropriate equipment, as well. Typical was an AM-FM tuner that had completely separate, and separately tunable AM and FM sections so that they could be used in parallel for stereo broadcasts. Usually the AM section was of the wideband, hi-fi type, and a multiplex signal output allowed the FM side to work with future FM multiplex decoders. Also, some makers also offered multiplex decoders for use with the early experimental multiplex broadcasts. These I think were mostly using the Crosby FM-FM system, which predated most of the other contenders. Such units would have become redundant once the Zenith-GE system was adopted, whereas the AM-FM tuners had ongoing utility even if their combined stereo function was no longer required.

I also recall seeing somewhere that one of setmakers offered a matching pair of table radio receivers, one AM only and the other FM only, for use with stereo broadcasts. But I can’t now trace it, so it is unconfirmed. (It might have been in a magazine like Popular Mechanics).

In the UK the more limited scope of the experimental twin-transmitter stereo broadcasts would have made it harder to justify the development of specific receiving equipment. Still, for hi-fi applications, the Jason JTV FM & TV Sound tuner, which dated from mid-1958, provided a means of accessing the TV sound channel in a high quality way, that being its primary mission. (I don’t think that Jason mentioned the two-transmitter stereo application in any of its literature. The following JTV2 of late 1959 did have a multiplex output, though.) Lowther catalogued a couple of FM & TV Sound tuners circa 1960, but evidently these did not make it into production. One was said to have “double drive”, although whether this meant that it could simultaneously receive an FM and a TV sound broadcast is unknown. Two valved VHF receiving chains operating in parallel inside a small box would seem to create great opportunity for mutual interference.

As in the US, from the late 1950s multiplex outputs were incorporated in British FM tuners. Probably with the export market in mind, Quad arranged the switching in its 22 stereo control unit of 1959 to allow separate FM and AM tuners to be used independently or as a stereo pair. Or a third tuner could be used to form a stereo pair with the first, or a multiplex unit could be used with the FM tuner.

Another interesting case was Japan, where two transmitter AM-AM stereo was used for a few years before FM multiplex was adopted. The industry produced hi-fi units incorporating two AM tuners, which evidently had different IFs to avoid mutual interference. Also mirror-image pairs of AM table receivers were available. See: http://www.japanradiomuseum.jp/FMstereo-e.html. A close look at the National SA-32 tuner-amplifier illustrated therein shows that it had two AM tuners. The left-hand one also had an SW band, whereas the right-hand one looks to have been MW only. I’d hazard a guess that the left-hand unit had the standard 455 kHz IF, whilst the right-hand unit had a lower number, perhaps 260 or 110 kHz. I think some care would have been needed to obtain similar overall bandpasses.


Cheers,

[Ted Kendall]

In a Sounds Good programme around 1975, Angus McKenzie spoke about being so impressed with the stereo experiments that he bought himself a TV sound tuner on the strength of it. I imagine this would have been a Jason.

[Synchrodyne]

Originally Posted by Restoration73

After the twin transmitter quadraphonic broadcasts were abandoned, encoded quad based on ambisonics was tried, not using proprietary SQ or QS formats but their own standard known as Matrix-H, although I don't remember when these ended. There may be a decoder design somewhere.

Yes, a Matrix H decoder was described in Wireless World 1977 June, p.34ff.

This was effectively - although probably not formally - part of a series in WW through the 1970s. The attached spreadsheet provides a partial list of these articles and related items.


Cheers,

[Synchrodyne]

Originally Posted by Ted Kendall

In a Sounds Good programme around 1975, Angus McKenzie spoke about being so impressed with the stereo experiments that he bought himself a TV sound tuner on the strength of it. I imagine this would have been a Jason.

Probably, as Jason was the only UK maker of TV sound tuners from 1958 until it folded around 1966-67. From 1971 both Lowther and Motion Electronics offered TV sound tuners, both solid state. The Lowther model was UHF/FM only, whilst the Motion Electronics model was UHF and/or VHF and AM/FM.

Cheers,

[fetteler]

Originally Posted by rambo1152

I think it must have been, there was a subconscious urge to use that particular word.
Can anyone else recall "stereo beacon"?

https://www.vintage-radio.net/forum/...ad.php?t=74092

Yeah, I remember the idea of a stereo "beacon", in fact I remember using a (then quite exotic) red led for just thet purpose in a stereo tuner I built in 1973. One of the first things I listened to was John Peel's show and I recall him playing the whole of Dark side of the Moon. Superb.

Steve.

[kirstyd]

Originally Posted by Ted Kendall

That's interesting - is it connected to a roof aerial? It may just be a matter of signal strength.

It was connected to a roof Ariel when it was at my parents house but i dont ever remember hearing stereo radio on it .Sometimes when tuning along the scale the red light flickers but its very faint.As you say it may just need a good Ariel [it wont be helped by the fact that my house has a steel frame]

[Restoration73]

Non-PLL decoder beacons could light up on a mono broadcast if a 23kHz tone was present.
I assume this was transmitted for an engineering purpose.

[Ted Kendall]

A note on one of the BBC's encoders describes the provision for inserting external 23khz in the absence of pilot tone "for transmitter signalling". Most stereo lights fire on interstation noise, too.

[Nymrod121]

Originally Posted by Restoration73

Non-PLL decoder beacons could light up on a mono broadcast if a 23kHz tone was present.
I assume this was transmitted for an engineering purpose.

Yes - my post (#34) refers.

Originally Posted by Ted Kendall

A note on one of the BBC's encoders describes the provision for inserting external 23khz in the absence of pilot tone "for transmitter signalling". Most stereo lights fire on interstation noise, too.

For what it's worth ... according to my copy of "BBC Designs Department Handbook No. 6.173 (79): CD2/11 Stereo Coder and PA20/17 Interface Unit", if the unit was manually selected to mono, the 23kHz pilot level (when internally generated) was 60mV into 75 ohms, compared to 90mV into 75 ohms when in 19kHz (stereo) mode. I'll see if I have/can dig out the corresponding DDHB* for the CD2L/4 which was the earlier ("book-case"-style) unit.

* found it - DDHB No. 6.179 (80) - yes, the CD2L/4 did the same i.e. 19kHz @ 90mV, 23kHz @ 60mV

Guy