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ITN's Westminster Eye
The use of
remotely controlled cameras is now commonplace in broadcast
applications; often a live chromakey background is required behind a
presenter or a well placed camera in a key position can be used for
weather or general views in breaking news stories.
One of ITNs longest standing and most used fixed-site locations is
their camera atop No. 1 Millbank, giving stunning panoramic views
over London, the Thames and, more specifically, Big Ben and the
Houses of Parliament.
Technology and audience expectations have moved on considerably
since it's original installation so a recent challenge for ITN was
to bring the camera and remote telemetry into the modern age but
without being able to renew the well-buried existing cable run
linking the head end to the ITN control position at No. 4 Millbank.
Rotronics Systems were brought in at an early stage
to look at the problems and come up with solutions that could be
carried out during the Parliamentary recess. “Our initial task was
to find out exactly what the two rather elderly existing coax cables
were capable of” comments Rotronics M.D. Bob Head.
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The returned pulse method used by Bob and his team calculates
distance by precise timing of a signal sent and received down the
cable. This established a cable length of 260 meters. “Our brief
from Martin Swain, Project Engineer at ITN, was to try to get SDI
down the old PSF 1/2 primary coax; sending 270 MB test signals
immediately produced not unexpected evidence of failed bits, the
sparklies on the screen clearly showing the poor condition of the
cable, so we had to come up with a more sophisticated solution. I
realised that it should be possible to frequency multiplex the
analogue component output and get a stable digital signal out at the
other end, even through the ageing coax.” |
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Tests were carried out using a triax adaptor from Cytech that had
originally been developed as an on-camera back. “The Cytech
freestanding prototype had composite, component and digital
component outputs which was more than enough to meet the ITN
requirement. As well as driving triax, the signals could also be
sent down up to 500 meters of coax. What was useful, indeed
essential, was that the return path capability meant both D.C.
powering and a reference signal could be sent back down the same
coax to the camera”.
Having successfully tested and installed the internal electronics it
was then necessary to put up the external camera equipment. A rugged
Panasonic AW-E600 camera head was chosen for its compact size, 850
line resolution and low light sensitivity. A Canon H15a x 6 lens
capable of zoom, iris and focus remoting made both wide angle and
long lens shots possible.
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The weatherproof housing complete with sunshade, heater and
wash/wipe facility was now ready to be put in place high on the
London skyline. “Technically the cable problem was the biggest
headache” recalls Bob “ but the exterior installation was certainly
the most dangerous! Luckily, safety harness fixings were available
but the location was such that the rigger's ladder had to be removed
while he was actually fitting the camera housing ”.
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The Rotronics team had developed control and telemetry cards for the
pan/tilt and remote control of the 3 lens functions, wash/wipe and
remote fault diagnosis for the camera head. “Because of the exposed
location of the camera we had to use high torque motors, capable of
moving 15 Kg loads, to enable subtle on-air camera movement, even in
the highest winds; that meant designing a special PWM card”.
Problems solved and all the remotes and triax head end are now up
and running at 4 Millbank, with a single operator controlling lens
functions and using a single pressure sensitive joystick for
pan/tilt.
In use day and night by a number of broadcasters and available in
any weather this key remote camera has finally been brought into the
digital age. “There's rarely a simple job in our business”, comments
Bob on completion. “There are often constrictions in any brief;
sometimes it's financial, sometimes logistical, this time it was
using existing cable runs. We enjoyed the challenges of this job
although I'm still glad it wasn't me actually installing the camera
high above London.”
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