Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
rb:coventrycable [26/06/2018 00:37]
andrew [Supertrunk]
rb:coventrycable [24/06/2019 17:06] (current)
andrew [Indoor]
Line 1: Line 1:
 ====== Coventry Cable TV ====== ====== Coventry Cable TV ======
  
-Now defunct, the original build was for 450MHz bandwidth carrying about 30 channels. It was built and operated by BT and along with the likes of Milton Keynes was one of the first franchises in the UK.+Now defunct, the original build was for 450MHz bandwidth carrying about 30 TV channels ​as well as the FM radio spectrum. It was built and operated by BT and along with the likes of Milton Keynes was one of the first franchises in the UK.
  
 ===== Headend ===== ===== Headend =====
  
-Located at the end of Whitley Villagethe building ​is now demolished.+Located at the end of Whitley Village ​off the London Road in Coventry (CV3 4HL), Blackburn House is now demolished ​and replaced with houses and flats.
  
 +{{:​rb:​blackburnhouse-aeiralview.png?​200|Aerial view of site}}
 +{{:​rb:​blackburnhouse-vandalised.png?​200|Vandalised rear of building}}
  
 Satellite TV receivers & cable tv modulators and Launch Amplifiers. Satellite TV receivers & cable tv modulators and Launch Amplifiers.
Line 17: Line 19:
 ===== Supertrunk ===== ===== Supertrunk =====
  
-The Supertrunks radiated out from the Head End to distribution sites prior to feeding the local distribution network. These consisted of several amplifiers with one input and one output boosting the signal. The amplifiers were nothing special, just the same as the DLA (Distribution Launch Amplifier) amplifiers but run at lower gain (ie. less noise added to the signal), the supertrunk coax was about 40mm in diameter for minimum signal loss. Due to the inflexibility of the low loss cable, the link to the cabinet was on reduced size cable with the joint in a chamber adjacent to the cabinet (left hand side next to road below)+The Supertrunks radiated out from the Head End to distribution sites located in BT's district telephone exchanges ​prior to feeding the subscriber ​distribution network. These consisted of several amplifiers with one input and one output boosting the signal. The amplifiers were manufactured by Texscan in the USAand were just the same as the DLA (Distribution Launch Amplifier) amplifiers but run at lower gain (ie. less noise added to the signal), the supertrunk coax was about 40mm in diameter for minimum signal loss. Due to the inflexibility of the low loss cable, the link to the cabinet was on reduced size cable with the joint in a chamber adjacent to the cabinet (left hand side next to road below)
 The supertrunk amplifiers were located in smaller green BT fibreglass cabinets and were all line powered from either end of the trunk. The supertrunk amplifiers were located in smaller green BT fibreglass cabinets and were all line powered from either end of the trunk.
  
Line 30: Line 32:
 ===== Distribution ===== ===== Distribution =====
  
-Example ​DLA (Distribution Launch Amplifier) cabinet, this appears completely abandoned, the door is missing, the mains electricity is severed and the input and output coax cables have been cut and removed. These were all housed in grey versions of the BT green fibreglass cabinet used sometimes for the phone distribution PCPs:- \\+The  ​DLA (Distribution Launch Amplifier) ​was made by Texscan in the USA and was locally powered by a Fuba ferro-resonant transformer which also provided phantom power to downstream amplifiers. Mains power was supplied from the utility provider with a consumer unit in the cabinet. 
 +  
 +Example DLA cabinet, this appears completely abandoned, the door is missing, the mains electricity is severed and the input and output coax cables have been cut and removed. These were all housed in grey versions of the BT green fibreglass cabinet used sometimes for the phone distribution PCPs:- \\
 {{:​rb:​20151006_175303.jpg?​200|Distribution Launch Amplifier}} {{:​rb:​20151006_175303.jpg?​200|Distribution Launch Amplifier}}
  
 From left to right:​- ​ From left to right:​- ​
   - Texscan wideband amplifier (White) (450MHz downsteam and approx 5MHz return path back to the headend), one input feed and either one loop through and two amplified outputs or one input and three outputs.   - Texscan wideband amplifier (White) (450MHz downsteam and approx 5MHz return path back to the headend), one input feed and either one loop through and two amplified outputs or one input and three outputs.
-  - Fuba ferro resonant transformer,​ 240v input and  50V ac output. This would feed the amplifier in the cabinet and also line power any downstream line extender amplifiers, these were all located underground.+  - Fuba ferro-resonant transformer,​ 240v input and  50V ac output. This would feed the amplifier in the cabinet and also line power any downstream line extender amplifiers, these were all located underground.
   - 240v power supply feed to Fuba transformer,​ via Wylex consumer unit.   - 240v power supply feed to Fuba transformer,​ via Wylex consumer unit.
 +
 +
 +Each DLA fed several trunks which were split as it radiated out with passive directional couplers. As required when the cable loss exceeded the allowed limits, a Line Extender amplifier was used, this typically had one input, one loop through (at -3.4db) which fed a tap either on a telegraph pole, building or an underground in a footway box, and two amplified outputs. The Line Extenders were made by Pro CATV in Denmark.
 +===== Reverse path and Status Monitoring =====
  
  
Line 53: Line 61:
 ==== Indoor ==== ==== Indoor ====
  
-The coax feed from outside was passed to an amplified splitter in the house which also served to allow a changeover from outdoor grade, UV resistant cable to indoor grade cable which was a low smoke and fume cable in case of fire.+The coax feed from outside was passed to an amplified splitter in the house which also served to allow a changeover from outdoor grade, UV resistant cable to indoor grade cable which was a low smoke and fume cable in case of fire. In addition, it included a galvanic isolator to prevent any egress on utility 240v power to enter the external network in the case of a fault with any internal equipment.
  
 The each output from the splitter would connect to a FM / CATV demux, the F socket going to the Set Top Box and the "​TV"​ style Belling Lee going to an FM radio. These are shown below with the covers on and off. The blue knob is to adjust the gain fed to the STB. On the right hand picture, the connector in the centre is the dropwire input, it feeds in to an AC/DC blocking isolator so any internal faults in the premises could not result in mains electricity being fed back in to the network. The each output from the splitter would connect to a FM / CATV demux, the F socket going to the Set Top Box and the "​TV"​ style Belling Lee going to an FM radio. These are shown below with the covers on and off. The blue knob is to adjust the gain fed to the STB. On the right hand picture, the connector in the centre is the dropwire input, it feeds in to an AC/DC blocking isolator so any internal faults in the premises could not result in mains electricity being fed back in to the network.

rb/coventrycable.1529969834.txt.gz · Last modified: 26/06/2018 00:37 by andrew