Goodricke-Physics-Hub: Difference between revisions

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Goodricke-Physics-Hub (view source)

Revision as of 16:24, 21 July 2007

964 bytes added ,  21 July 2007
complete description, add colour code labels
(write up the first leg of the journey.)
 
(complete description, add colour code labels)
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=== Structure ===
=== Structure ===
The cable route consists of a series of extensions added on at each major upheaval in YSTV's history to allow us to keep broadcasting via the existing infrastructure. It is therefore less than planned.
The cable route consists of a series of extensions added on at each major upheaval in YSTV's history to allow us to keep broadcasting via the existing infrastructure. It is therefore less than planned.
From the [[G/046|studio]] a 150m unbalanced video cable (originally made for [[Breaker 88]]) and a 3-pair screened audio cable go through the window frame by the monitor rack, along the top of the G/045 windows and up over the room of the college nucleus. From here it wends it's way down along the covered walkway past the (old) Dining Hall and the bar to the "bus stop", then turns left past the cash machine towards the Physics and Electronics building. Just before the doors into this it goes through a hole in the wall of the building to reach the attic room above [[P/X/002]].


=== old stuff to edit ===
Behind the monitor rack in the [[G/046|control room]] is a piece of tag strip screwed to the cable duct, which has three XLR connectors coming off it. These are marked up as Network Audio, Derwent Send and Derwent Return. The last two are basically contribution circuits and re-patched as needed, whilst Network Audio should be fed with the balanced network audio signal. Video is carried on a standard BNC connector plugged in to patch box 6.
The physics link, using entirely rediffusion cabling, was used from the 1970s onwards when YSTV moved from the original rediffusion studio / equipment room in PS016 on the physics spine corridor.


The link from LTC to PS016 is a standard rediffusion contribution setup, used the opposite direction to that originally intended. The single Physics->LTC contribution cable contains two pairs. One is used for broadcast (GoodrickeToPhysicsToLTC) and the other is used to return things to Physics/YSTV that would, originally, only have gotten as far as LTC. The same broadcast/return operation exists for the 6-pair audio contribution cable. Two pairs are used for the return (mono audio and comms) and one for broadcast (mono audio).
From the tag strip a 3-pair sheilded cable of the type used for the 1998 network and the 150m unbalanced video cable (originally made for [[Breaker 88]]) go through the window frame by the monitor rack, along the top of the G/045 windows and up over the room of the college nucleus. From here it wends it's way down along the covered walkway past the (old) Dining Hall and the bar to the "bus stop", then turns left past the cash machine towards the Physics and Electronics building. Just before the doors into this it goes through a hole in the wall of the building to reach the attic room above [[P/X/002]].


The 9-pair Rediffusion distribution cable is not touched by YSTV in PS016, it does however carry URY audio on the white twisted pair (Channel 'E'). See URYBroadcastNetwork.
Above P/X/002 there is a wall box with a white plate on it carrying two BNC connectors and four 1/4" jack sockets (someone in York - please take a photo and add it here). These are the ends of the old Rediffusion local contribution cables to [[P/S/016]]. Originally these would have taken individual camera feeds back to the studio and AV rack in P/S/016, but now they act as a pair of audio and video tie lines. The unbalanced video from Goodricke is plugged into the video lead (possibly via a video DA if we want to send video down to [[Physics Concourse|the concourse]] as well). The audio cable splits to three balanced jack connectors (with a common screen), one of which has the network audio on it. How these are plugged in will obviously change the function of the circuits from here onwards, however both sides are labelled, and this shouldn't need changing.
Routing


The run from LTC to PS016 is (unbroken) Rediffusion cabling, inside the covered walkway across the Central Hall bridge.
The video cable on this section, like most of the other local contribution cables, is a Belden braided foil screened type rather than standard RG59. This gives good shielding and so picture quality, but is very difficult to put a standard crimp connector onto successfully! The braid ends are also sharp, which can make the process painful. The audio cables are unshielded, with two grey and two blue cores in each black outer sheath. The 4 jack connectors wire up all 4 pairs (treating the two blue as a pair and so on) in two cables, without regard to phasing. If anyone ever tries stereo, beware! There is no screen connection to the jacks as the cables are unshielded.


At PS016 the incomming balenced video signal on the twisted pair is received, amplified and unbalanced by an original Rediffusion No 6A amplifier, to drive a standard 75ohm coax output. The audio is just jointed (chocolate block!) without any active electronics.
These cables join the mass of other Rediffusion cables running down the wall, through the hole in the floor and into the cable duct in the room below. From here a 6" pipe is laid under the floor of the physics concourse (so I was told), which has a T off to the right near the porter's desk to reach the start of the physics spine corridor. Somewhere here the cables make it up and into the ceiling void above the corridor, where they run until they reach [[P/S/016]].


Between PS016 and PX003, the video is on a 75R coaxial cable, and the audio on two twisted pairs, originally part of the contribution links from camera points in PX001 to the control room in PS016, now used in reverse. Note that this is Belden foil-braid cable not standard RG59, so fitting connectors is not easy.
In P/S/016 the audio cables are joined straight on to the 6-pair Rediffusion audio contribution cable which runs to the [[Broadcast Hub|Hub]] (originally to LTC). The unbalanced video is fed into a line driver in order to drive one half of the shielded twisted pair Rediffusion video contribution cable to the Hub.


This cable goes up through the cupboard in PS016 with all the incoming cables in it, into the ceiling void, and on down the spine corridor to the concourse. Somehow it gets into a 6" cable duct under the concourse floor, which splits to reach the covered way towards Central Hall, and emerge into PX003 somehow. How the latter gets there is uncertain, but may well involve the physics first floor calorifier room, accessed via a door from the PX003 attic. For more on the layout of these locations see the PhysicsDept page.
These contribution cables go back up into the ceiling void, and then back along the corridor to the concourse, and into the pipe under it, now taking the right turn by the porter's lodge to head through the building and out into the covered walkway towards Central Hall. This duct goes across the bridge (exactly how is unknown), then into the underground duct past the front of Central Hall, before coming back up to reach the Hub. This run consists of unbroken Rediffusion cabling.


At PX003, the audio and video got straight through (passive) to the cables laid on top of the covered walkway between Physics and Goodrike. Return audio uses two of the three pairs in the grey cable (same cable type as used elsewhere in the 1998 broadcast network), and video is on 150m of standard RG59.
=== Core Colours ===
This reflects the wiring in place as of 2006. As all the joints are soldered or terminal blocked, it's unlikely to change, although the patching of the connectors may well do so.


The return feed video cable is the one that comes down from above with the audio in PX003, not the one that comes up through the floor (which is net video). This has changed, so old documentation may list them the other way round. Both go to the control room anyway.
{| border="1"
!Circuit
!Colour PX002<->Goodricke
|-
|Derwent Ret
|White / Black pair
|-
|Derwent Send
|Red / Black pair
|-
|Network Send
|Green / Black pair
|+ Colour Code in Goodricke to P/X/002 cable
|}


In the Goodricke control room both cables come in to the left of the monitor rack near the window. The audio cable goes to a piece of tag strip behing the rack, which splits it into three XLR connectors. The video comes out to trailing BNC, which should be marked, and coiled up on the window-ledge.
{| border="1"
!Usage (nominal)!!Label in PX003!!Colour PX003<->PS016!!Colour PS016<->Hub
|-
|Derwent Ret||Derwent Return||Grey in 1st Cable||Yellow pair in 6-pair
|-
|Derwent Send||Derwent Comms||Blue in 1st Cable||Grey pair in 6-pair
|-
|Network Send||Net A1||Grey in 2nd Cable||Blue pair in 6-pair
|-
|Unused||Net A2||Blue in 2nd Cable||no circuit
|+ Colour Code in P/X/002 to P/S/016 to Hub cables
|}


Until the direct Goodricke to LTC link is repaired (see GoodrickeToLTC) URY use the YSTV comms channel of this return as a bodged method of getting audio from Goodricke to URY. The wire is split in LTC to wherever YSTV want audio (usually Derwent) and to one channel of the Vanbrugh to LTC audio contribution, used in reverse (see VanbrughToLTC, VanbrughToURY?).
The return feed video cable is the one that comes down from above with the audio in PX003, not the one that comes up through the floor (which is net video). This has changed, so old documentation may list them the other way round. Both go to the control room anyway.
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