Difference between revisions of "BBC Circuit Order Form"

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The reason for the visit was to test lines for the John Dunn Show which was to be broadcast on  Radio 2 on 4th April. [[File:StMarys_COF_3.jpg|frame|right|200px|St Mary's COF]]Live programmes of any description from the Islands in those days was a bit of an ask. Connecting with the mainland was via an undersea cable - not fibre then - and/or making special provision to use BT's microwave link to St. Just.
 
The reason for the visit was to test lines for the John Dunn Show which was to be broadcast on  Radio 2 on 4th April. [[File:StMarys_COF_3.jpg|frame|right|200px|St Mary's COF]]Live programmes of any description from the Islands in those days was a bit of an ask. Connecting with the mainland was via an undersea cable - not fibre then - and/or making special provision to use BT's microwave link to St. Just.
 +
This was Easter weekend with the transmission scheduled for Easter Monday. The lines test would normally be a day or so before the programme, but there were no seats available by air, given that it was necessary to fly in and back on the same day.
 +
 +
I arrived with some time to spare and had a look around. It was fascinating to be able to walk from the north coast of the island in Hugh Town, St Mary's to the south coast in 2 minutes! There was a superb view out from the battlements over the bays and islands, and down beneath me The Scillonian ferry was loading its cargo for the trip to Penzance.
  
 
== Technical requirements ==
 
== Technical requirements ==
 +
 +
The usual circuit requirement for a Radio Outside Broadcast such as this was one Music from OB to destination, and one Control line. The latter was usually a 2-wire equipped with voice-frequency ringers. Sending 17Hz down this line would activate the ringer which generated 520Hz at the exchange. Another ringer at the other end would convert the tone back to 17Hz to contact the destination. No ringers were available on St Mary’s  however.
 +
But this was not a typical radio O. B. It was the era when technical standards seemed to matter, and Radio 2 was a stereo network.  With no chance of providing stereo circuits from the island, the solution was for John Dunn to be mono with discs played in at the London end. Therefore two way talk back was needed for cueing purposes.
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The order form specifies where the lines should be provided – here on the battlements of the Star Castle.
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https://en.wikibooks.org/wiki/Communication_Systems/Frequency-Division_Multiplexing#Analog_Carrier_Systems
 
https://en.wikibooks.org/wiki/Communication_Systems/Frequency-Division_Multiplexing#Analog_Carrier_Systems
  
 
  [[File:LE_main_cof.jpg|frame|left|200px|Circuits]]
 
  [[File:LE_main_cof.jpg|frame|left|200px|Circuits]]

Revision as of 13:58, 13 April 2017

Introduction

On a warm and sunny March day in 1988 I took a morning flight from Penzance to St Mary's, the main island of the Isles of Scilly. The islands lie some 30 miles Northwest of Penzance and experience weather and plant life which are claimed to be subtropical.

The reason for the visit was to test lines for the John Dunn Show which was to be broadcast on Radio 2 on 4th April.
St Mary's COF
Live programmes of any description from the Islands in those days was a bit of an ask. Connecting with the mainland was via an undersea cable - not fibre then - and/or making special provision to use BT's microwave link to St. Just.

This was Easter weekend with the transmission scheduled for Easter Monday. The lines test would normally be a day or so before the programme, but there were no seats available by air, given that it was necessary to fly in and back on the same day.

I arrived with some time to spare and had a look around. It was fascinating to be able to walk from the north coast of the island in Hugh Town, St Mary's to the south coast in 2 minutes! There was a superb view out from the battlements over the bays and islands, and down beneath me The Scillonian ferry was loading its cargo for the trip to Penzance.

Technical requirements

The usual circuit requirement for a Radio Outside Broadcast such as this was one Music from OB to destination, and one Control line. The latter was usually a 2-wire equipped with voice-frequency ringers. Sending 17Hz down this line would activate the ringer which generated 520Hz at the exchange. Another ringer at the other end would convert the tone back to 17Hz to contact the destination. No ringers were available on St Mary’s however. But this was not a typical radio O. B. It was the era when technical standards seemed to matter, and Radio 2 was a stereo network. With no chance of providing stereo circuits from the island, the solution was for John Dunn to be mono with discs played in at the London end. Therefore two way talk back was needed for cueing purposes. The order form specifies where the lines should be provided – here on the battlements of the Star Castle. 

https://en.wikibooks.org/wiki/Communication_Systems/Frequency-Division_Multiplexing#Analog_Carrier_Systems

Circuits