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Old 7th Mar 2019, 7:53 pm   #1
Sparks
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Default Radio 1 Roadshow, 1970s and 1980s

Does anyone know the means by which the BBC conveyed broadcast sound from the Roadshow site to Broadcasting House in London ? I assume the GPO/British Telecom were involved somewhere, somehow. Would it have been wire or microwave links to a telephone exchange or relay tower ?

Thankyou.
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Old 7th Mar 2019, 10:40 pm   #2
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Default Re: Radio 1 Roadshow, 1970s and 1980s

At school in the 70's we had the road show, went by telephone lines (two pairs to get the bandwidth) I was much more interested in the OB van than the show. I vividly remember thin twisted pairs being attached to large screw terminals. I was in East Anglia at the time where Radio 1 (MW only) reception was awful.
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Old 7th Mar 2019, 11:19 pm   #3
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Default Re: Radio 1 Roadshow, 1970s and 1980s

PO lines before stereo. but at first had satelite link from BT when needed stereo.
I don't think there were 2 pairs used on the one circuit, It would have been 1 pair for programme line and one pair for control line (talkback)
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Old 7th Mar 2019, 11:34 pm   #4
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Default Re: Radio 1 Roadshow, 1970s and 1980s

https://drive.google.com/file/d/1Tx3...M5vV2beX9/view

Interesting article here.
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Old 7th Mar 2019, 11:38 pm   #5
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Default Re: Radio 1 Roadshow, 1970s and 1980s

Thankyou Merlin and Peter. How would use of telephone lines work in practice ? For a regular subscriber to access the telephone network means plugging an approved instrument into a wall socket which is in turn connected to a telegraph pole or something similar. How would a broadcast mixer interface with a telephone line ?
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Old 8th Mar 2019, 7:29 am   #6
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Default Re: Radio 1 Roadshow, 1970s and 1980s

The broadcasters used "Music lines" when avaliable which were equalized for frequency at the receiving end.
They were connected at both ends with balancing transtormers and fed from an impedance of 75 ohms in the case of an OB or 600 ohms in the case of a shorter fixed line.
Terminated with 600 ohms at the receiving end.
The lines for the OB's were set up by BT so would be just the cable ends coiled up out of sight somewhere near or a terminating box if used frequently.
The mixer would be connected to a dedicated box which had the line sending and receiving amplifiers all in one unit for the programme line out and the control line (talkback) in.
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Old 8th Mar 2019, 8:28 am   #7
Electronpusher0
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Default Re: Radio 1 Roadshow, 1970s and 1980s

I remember attending a Radio 1 roadshow at Portsmouth when I was at the Polytechnic (now a "University", don't get me started).
The only thing I remember is how boring it all was despite the presenter trying to whip up enthusiasm.
Peter
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Old 8th Mar 2019, 10:08 am   #8
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Default Re: Radio 1 Roadshow, 1970s and 1980s

That was a nice read, loved the bit where the engineer said they had sometimes used the output of a PA amplifier to drive the BT lines in remote places so the audio arrived in London intact!
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Old 8th Mar 2019, 10:27 am   #9
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Default Re: Radio 1 Roadshow, 1970s and 1980s

I was a TA on BBC OB Comms in the early 80's. I used to have to go out on sound lines testing, and test equalization and frequency response on the pairs before the big day. I'd leave a little card with the the equalizer settings, so that the box could then be attached and quickly set with the correct settings.

With the Radio 1 Roadshows, we used a mobile satellite uplink on a trailer IIRC, and off air programme monitoring from the nearest VHF broadcast station.

For TV OB's, we set up microwave (7GHz approx) links back to the nearest main TV transmitter, such as Crystal Palace in London, Wenvoe, Sutton Coldfield et. al. The main site would have have steerable antennae, so we would be on the end of a "left a bit, right a bit" type situation getting it set up right. Some of these links would be multiple hop as well.

happy days
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Old 8th Mar 2019, 10:41 am   #10
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Default Re: Radio 1 Roadshow, 1970s and 1980s

Thankyou for such detailed replies everyone. I knew there had to be more than plugging a mixer into a telephone but I didn't appreciate the level of consideration.
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Old 10th Mar 2019, 9:41 pm   #11
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Default Re: Radio 1 Roadshow, 1970s and 1980s

Hi,

This is a tad off topic, but I remember in the early 70ís the Radio One Roadshow using the Orange (as in the amplifier manufacturer) 200-Watt slave amplifiers. This was a great piece of valve engineering by the great Mat Mathias using 4x KT88ís with the GEC/Williamson/88-50 type driver circuit.

According to the Orange web site and folklore Emperor Rosko (Now - thatís a real DJ name!) used them in his Roadshow/Disco system and on his recommendation, they were adopted by the Radio One Roadshow.

Regards
Terry
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