How to do RS422 properly on the big Blackmagic Universal Videohub?

A job we're working on at the moment needs a big 288x288 HD/SDi and RS422 router. Budget means that the Black Magic is the only one that can be considered and it's hard to argue with sub £100k - Probel, Quartz-Everts etc would all cost four times that amount and so we're trying to figure out how to cable this one nicely.

The issue is going to be with the RS422; video will dress nicely on the cable tray down each side of the cabinet but the remotes are presented on a proprietry connector in the centre of each card. The only way of connecting to this is via a pre-made breakout cable that in only a metre long. So, after a lot of thinking and measuring we've come up with a solution.

 So far I've not been able to locate this connector - anyone have any thoughts?!

 Chopped breakout cable to see what the colour code of the cores is.

Nice 1/2u high cat7 jackfield which we'll use (need a dozen of them) to run down the intermediate rackstrip at the rear of the matrix to allow proper RS422 breakout.

The colour code we've settled on for this router when it's being cabled on cat6.

Estimating the time a job takes

For the last eight years I have spent a lot of my time quoting for broadcast installation builds. From small single edit suites to £1.5m broadcast editing centers I think I have a good feel for how long most jobs take. I recently did a search of my arrogated purchase orders folder and discovered I've bought more than 500 equipment cabinets, nearly 1000 video jackfields, and just over 100 kilometers of bulk fibre optic cable - all in the last eight years!
Anyhow - I often get quotes thrown back at me by chief engineers who assume I'm trying to fiddle them and they will typically say;

You've quoted ten days for a wiremen to wire those audio patch panels back to krone blocks; I'm sure my guy could do it in seven.

Even as a chief engineer he's probably only built one or two big machine rooms in his time. He might think he has experience of wiring technical facilities, but I've hired and paid wiremen to do many hundreds of audio panels in recent years. Possibly more than all the panels every chief engineer in Soho will oversee this decade! I know how long things take.

Anyway - for the last five years I've done an audit at the end of each year to compare the number of wiremen and engineer days each job used against what I thought when I quoted. It turns out that I naturally underestimate the time required by around 25% - If I quote 100 wireman days it'll be nearer to 130 when all is said and done. This isn't down to me not knowing how long each part of the job takes - it's a function of wasted time;

• Client won't provide passes to everyone and so guys have to wait idle in rooms or go looking for the pass.
• Deliveries are late, guys are idle
• Customers change their mind, but not enough (or it isn't politic) to warrant a change order
• Faulty parts - we always have to replace those for free!
• Various other things you didn't expect.

So - I've made it my habit to still estimate the number of days as I think it should be and then add on the 25% extra. Consequently my quotes have been getting a lot more accurate over the last few of years. I also discovered the same effect with parts but in the other direction; I always over-estimate the amount of cable/connectors required by around 10%.

So far I haven't done anything about that!

Balanced to unbalanced audio - wiring?

Simon, one of our wiremen asked me the following question;

...why do we always cut-back the black core when wiring FST into RCA (phono) connectors?

Back when all broadcast gear drove balanced lines with a proper rep-coil (a 1:1 audio transformer) you could safely bodge-unbalance a balanced line by shorting the cold to the screen and you get full signal across half of the sending rep-coil and everything worked. Nowadays not all equipment drives a balanced line this way - may bits of gear use op-amps to derived the +ve and -ve going halves of the balanced pair (via the inverting and non-inverting inputs - think 741 Op-amp). If you pull one of the signal cores to ground you effectively short one bit of silicon and it sits there warming up. That may not be a problem, but in the case of Avitel distribution amplifiers (well, after 1995) they driver stage burns out after a few months (long after the SI engineers have left!). This exact problem bit my backside when I worked at Oasis TV and all the monitoring switchers in the machine room had unbalanced inputs.
The only downside of using my method is that you loose 6dBs of level, but probably into a piece of equipment that wasn't calibrated (like a DVD recorder or TV). I think that's a worthwhile compromise to avoid the possibility of frying the backplane on audio distribution amps (or suchlike).

A trip down misery lane

Here are a few pictures from the original install of Oasis Television's building on Great Pulteney Street. Remember when edit suites cost £500k and had many pieces of equipment that all had to talk to each other! I'm the fresh-faced chap on the right of the sofa and the other chap is my old mucker Chris Clegg. The other reprebates were my wiring team - Amos and Jim are still in the industry and Tony (on the right) is sitting behind me in the workshop today! Both of us have more grey hair now.

HD over standard def coax

People often ask me about this and I normally repeat the received wisdom - you get away with it over short runs etc. etc. BUT, I didn't realise how close to the hairy edge sending 270Mbit SDi over Image 360 was. Look at the chart - I assumed that (as per most bandwidth calculations) that a cable designated Image 360 would have better than 6dB of loss at 360Mhz over 100m (the spec) - but no - worse than 16dBs down at 100m (almost down to an eighth of the signal level). I suppose it is testament to how good drivers/receivers and error recovery schemas are.
Now - imagine that you're sending 1.48Gbits per sec. That's two and a half octaves extra bandwidth above SDi - so probably another 12dBs of loss - so over Vision 360 you're looking at 30dBs of loss over 100m! Even over short distances it is a miracle that HD-SDi goes over normal coax.

Blogging on the train on the way to Leeds - free WiFi!

From the sublime to the ridiculous

We've been doing an install at a Soho facility and as ever Tony and the wiremen do a superb job - neat and accurate. The right-hand image shows our cabling on the top cable tray and the previous systems integrators efforts below; Un-numbered cables that have been just thrown in. They've attempted to run HD-SDi over skinny coax and fibre channel over long pre-made tight-buffered optical cable. By contrast we do all video on Vision 1000 and all fibre on kevlar-armoured loose-tube cable. I'm amazed that previous company had the cheek to submit an invoice!