Distribution Network

Background

The Distribution Network was for the first 37 years of YSTV's history the only way to watch our programmes before the availability of content via our website. It mirrors the Contribution Network used to get video from around campus back to YSTV's studios for broadcasting major events around campus.

The Original Network was installed as the university was being built in the 60's.

Early 90's system ageing

The passing of time had taken its toll on the system. By 1994, various colleges/buildings had been remodelled, leading to removal of the AV racks or cutting of contribution/distribution cables. At the time YSTV moved into G/046, the contribution cable from Goodricke back to the Language Teaching Centre (aka LTC) had suffered a break due to the same building work that had lead to the society's eviction from P/X/002. This lead to the contribution point in P/X/002 being pressed back into service. Cables were trailed over the roof of Goodricke college from the new studio to the physics building. From here it fed back to the AV rack in P/S/016 before being sent on to LTC.

At this time YSTV could be seen in Derwent, Langwith, Alcuin, Vanbrugh and Goodricke (due to the proximity of the Goodricke snack bar and JCR to G/046 these were fed at baseband into a standard SCART television). Wentworth distribution had been lost sometime between 1993-94.

The remaining televisions soldiered on, and when required were repaired by using parts from any spares that could cannibalised from the spares from the garage in Wentworth. Despite best efforts, picture quality was suffering, colour would turn to black and white and then back or various interference patterns could be seen on the screen.

An attempt was made to convince the University to invest in installing a new system of coaxial cable (for unbalanced base-band video) and balanced audio around the campus, but the carrot of allowing them to use it during the conference season was unappealing, and nothing happened.

End of Rediffusion system

During the summer holidays of 1995, Owain Davies visited the station and stumbled across a flyer from Maxim highlighting their MAX435/MAX436 video balanced line drivers and receivers. The example circuit diagram seemed a remarkable simple solution, just one IC for transmitter and one for the receiver. Owain had found in LTC the composite output from the contribution feed from Physics. The picture was in good condition, meaning the interference problems were occurring on the distribution side of the network only.

This lead to a plan to replace all the modulation equipment from the Rediffusion system with base-band video senders and receivers using the Maxim ICs, driving over the old contribution network cables to distribute video to the vent rooms, and then over the unbalanced video cables to the TVs themselves.

This was implemented as a test in Vanbrugh by Owain Davies, feeding the three TVs there, and worked very well. The problem of getting cables run from the vent rooms to the TVs was significant however, as it required cables to be run above ceilings and so on.

Two kilometres of twisted pair

Given that this would be needed for almost all the colleges, Rob Sprowson opted to do the whole job, and run new cable from LTC to the TV locations. The receivers could then be installed near the TVs, and the contribution cables (which anyway did not run to Langwith or Derwent) left alone. This was implemented using 3-pair screened cable, providing for stereo audio and balanced video to all the available or proposed TV positions.

Despite the availability of content online it remains a valuable means of raising the society's profile on campus and generating interest in our output, the Current Status is basically the 1998 layout minus sections lost to new building works, with some new links installed and a few of the TVs relocated.