Transmission - Testing the Timecode Feed

The timecode has been installed in the TX suite and all thats left to do is a few minor checks and tweaks.

Initially the feed worked perfectly, the clock and VTR's remained on station time (we didn't have time to get into Pharos and check) however after returning a couple of days later we found that none of the equipment was receiving timecode anymore. After tracing the signals back we found that the problem was the SDA, so we switched the back panel over to the redundant unit and removed the original SDA.

The makeshift connectors into the back of the VTR's work really well (BNC to female XLR) which was another surprise as we all reckoned we would need some kind of impedance transformer. Ideally these connections are still only a temporary measure until we can purchase some proper connections for the VTR's. Another minor job is to properly earth the inside the krone connections, although the feeds are working fine at the moment doing this means that the project has been completed properly along with reducing the risk of things going wrong at a later date.

The biggest thing that we discovered during this installation was how a krone block works, essentially each audio feed has its own position on a krone block and jumpers are used to take feeds from one place to another. We thought that each feed was connected on the same krone block, with an input on the top connection and an output on the bottom, essentially minimising the use of jumpers, but also making the wiring a lot messier and more complex (more chance for things to go wrong).

The connection between the line from the krone block (green cable) and the makeshift connection into the back of VT18

The counter on VTR17 showing station timecode

More information on Pres, TX and this project can be found on the Presentation Suite Wiki.

Transmission - Running in Timecode

The Transmission Suite doesn't have a dedicated, manipulable feed of timecode, the aim of this installation was to provide this. During Rave on Air timecode is used in TX during tape ingest, in Pharos and also on We know that there is a feed of timecode running to Pharos control unit from the clock in CAR. To check that this was working we connected it to the unused clock and let it run for a couple of days to check that it held its time.

The original feed of timecode running into Pharos from CAR.

Once we had verified that the feed worked we began planning how to get timecode into the presentation suite. Along with running the initial signal we also wanted to achieve a few other things:

• Have timecode appear on the audio jackfield (J/F)
• Run timecode to four initial pieces of equipment; Pharos, the VTR’s 17 & 18 and the clock

The most efficient way to run the feed would be to take the original working line of timecode into Pharos and instead run it through an Analogue Distribution Amplifier (SDA) and then onto the other pieces of equipment, as with all audio, the feeds would have to run through the krone block.

The equipment needed to achieve this task would be:

• Audio multicore
• Krone Block
• SDA (in rack mount)
• Audio twisted pair cables with male XLR ends

Due to the lack of any Probell SDA cards we started looking at other spare SDA’s (Avitel and Drake). We choose to go with the Drake DA’s (# PD 7051), primarily in use for the Talkback system, but also used in CAR to deal with a lot of the analogue audio feeds. The limited space in the racks meant that we used a 1U DA Crate that can hold three cards but positions them on their sides to save space.

The installed 1U crate, below the Axis router in rack 5.

Using the back panel connector (# PD 7051) the multicore was attached to SDA while the other end was connected to a krone block.

Back panel connector (# PD 7051) with multicore attached.

Once the multicore was wired up the rest of the feeds were plotted on a basic cable diagram.

Cable diagrams showing the lines from CAR through until the SDA's outputs and the feeds running from the SDA's outputs through to the separate pieces of equipment.

The original timecode feed was passed along an audio twisted pair (#46904). The cable was relaid to appear at the krone block and its end was removed to enable it to be punched into a krone block. Both the clock and Pharos took XLR as their timecode input, so two cables were made up and run from these devices and back to the krone block (#C264, #C265). The VTR's took BNC connections as their timecode input, so as a temporary measure two BNC-Female XLR cables were used for the male XLR cables to connect onto from the krone block (#C266, #C267), these cable runs will be tested and if the BNC-XLR connections work, they will be permanently installed.