BBC Radio now on Astra

INF
The quarterly
for BBC engineering,
technical and operational
SPRING 1993
No 52
staff
BBC Radio now on Astra
Radios 1,4 and 5,.along with BBC World Service in English are now available in
mono on the Astra satellite system. Starting
on page 3, Henry Price describes
how these new services are transmitted
and what is required to receive them.
CONTENTS
ASTRA SATELLITE
- BBC Radio Services now
available
3
FAMILY TREE
- Engineering Division
12
ITU
- Its function and new
structure
16
LOCAL RADIO
- Cumbria refurbished
21
NETWORK RADIO
Radio 2's new transmission
suites
-
NORTH
-
7
REGION
Manchester's
Edit Suite 5
23
RADIO-CAMERAS
-
RD's new switched-horn
system
14
TELECO~CATIONS
-
Part 5: self-provision
OB circuits
TRANSMITTER
of
NEWS
WORLD SERVICE TV
- Impovements to BBCfax
Graphical illustration of Astra satellites lA, lB and 1C in orbit
18
2
11
Radio Romania calls on
BBC expertise
ENGINF
Edited, designed and typeset by
EID, Room 3402 White City.
Tel:" (07) 24316
Editor
Secretary
Typesetter
Graphic Artist
Mike Meyer
Tracy Quinn
Giselle Austin
Paul May
As Eng Infis an internal BBC magazine, it would be appreciated if no
reference was made to it in articles,
magazines etc, published outside
the BBC.
Stories for the Autumn issue should
be forwarded to the editor by Friday
20th August, 1993.
Transmitter
News
The following services have opened or
changed since our last issue:
New TV relays
Kent
Farleigh
Kent
Farningham
West Glamorgan
NeathAbbey
New FM stations
Barnoldswick
N Lancashire
Croeserw
West Glamorgan
Penmaen Rhos
Clwyd
West
Glamorgan
Rheola
F
ollowing a request for assistance from
Radio Romania, JeffBottom of Radio
Projects has made three visits to Bucharest
since last August.
According to Jeff: "The Broadcasting
House in Bucharest was built in the
early 1950s and many of its facilities
are from that original installation by
Siemens. The building is H-shaped
(similar to our BH EXT), with the
transmission studios and CTA in the
lower floors of the centre section. However, the structure of their building suffered severe earthquake damage in
1978, 1986 and again in 1990. As it
cannot be repaired or strengthened
while still occupied, and further earthquakes could cause a total collapse, a
replacement facility is the only way forward."
Assisted by Roy Newrick (previously of
Radio Projects), Jeff has assessed the
situation at first hand and reviewed various alternative strategies for the future.
"The concept of separate project management staff has been introduced and
a project team has begun work on a brief
Radio 1 on FM
Dumfries & Galloway
Radios 1 and 4 on FM
Campbeltown
W Strathclyde
Girvan
S Strathclyde
Llanfyllin
Powys
Llanrhaeadr-ym-Mochnant
Clwyd
Local Radio
As featured on page 21, Radio Carlisle has moved into new stereoequipped premises. The transmitters
now broadcasting
Radio Carlisle in
stereo are Sandale, Kendal, Morecambe Bay and Windermere.
Further information
from EID on
White City (07) 25040.
2
While in Bucharest, Jeff was able to operate his own hand-held Amateur Radio
equipment on 2 Metres FM, using the
call sign YO/G3SDG
under a permit
from the Ministry of Communications.
Many contacts were made in the Bucharest area, mainly using the repeater on
channel RI (input 145.025 MHz; output
145.625 MHz) which resulted in Jeffbeing invited to operate on HF frequencies
using local amateur stations.
Jeff leaves the BBC in July but discussions are in hand to determine the future
of this cooperation with Radio Romania.
Display Screen Equipment
N
ow that the Display Screen Equipment regulations are in force, all
computer workstations in the BBC will
have to be assessed for Health and Safety.
"
Kirkconnel
for consultants to prepare a feasibility
study. An existing partially-completed museum building has been
transferred to Radio Romania, as a way
of speeding up the provision of new
broadcasting facilities that are not subject to earthquake risk. A lot of time has
been spent transferring
knowledge
gained from experiences in the BBC to
the local staff who, although highly
qualified and technically competent,
have not had the opportunity to do any
project work.
There are over 900 screens within the
former Engineering Directorate and a Project Team has been recruited - comprising Les Davis, Tony Dent and Paul
Kinsey - to assess these work-stations
by the end of the year.
Not only are the obvious parts of the
workstation (such as the degree of flicker
on the screen) under scrutiny: incorrect
posture can lead to Upper Limb Disorder,
Repetitive Strain Injury (RSI), backache
etc. Thus, properly chosen and correctlyadjusted chairs are critical to avoid these
risks.
Martin Nutt
Safety Services
Engineering
STOP PRESS...
F
urther to the article inEng InfNo
51 on the LS5/8 and AM8/20, Development
Group now announces
the
AM8/21. This is effectively
a stereo
AM8/20 and comprises: one power supply,
four amplifier channels and two crossovers - all in a 3D 19" case with connec-
tion cooling. The price should be about
IV2 times that of the AM8/20
(ie,
equivalent to two mono AM8/16s).
F
urther details can be obtained from
Graham
Whitehead
at Avenue
House. Tel: (036) 4273
ENG INF Spring 1993
ASTRA SATELLITE
BBC Radio Services now available
In early April, four of the BBC's radio services - Radio 1, Radio 4, Radio 5 and
World Service in English - began transmissions
in mono on the UK Gold channel
of the Astra satellite. Henry Price gives some background
to the Astra system
and describes how to receive these satellite-delivered
BBC radio services.
T
he Astra satellite system is
owned and operated by the
Luxembourg-based
company
SES (Societe Europeenne
des Satellite). Presently,
two satellites Astra lA and 1B - are used to
transmit thirty-two television services and a similar number of radio
channels to most of Western Europe.
A third satellite - Astra 1C - was
launched in mid-May 1993 and is expected to come into operation
in
July/August, increasing the capacity
of the system to forty-eight television
services in total. Additionally, 1C has
two channels intended for cable television distribution which are outside
the frequency range normally covered
by domestic satellite receivers.
The satellites are located at nominally the same position in space: 19.2
degrees east on the geostationary orbit
(about 36,000 km vertically above
Zaire), so that a single dish antenna
will be able to receive all forty-eight
channels. The three satellites, which
each weigh up to 2.7 tonnes and are
about the size of a double-decker bus,
are all located within a 70 km cube.
Their position is closely controlled
from SES headquarters
at Chateau
Betzdorf, Luxembourg,
to ensure
that they do not collide or block one
another's view of the earth.
The three satellites operate within
the fIxed services satellite (FSS) band
as follows:
Satellite
Satellite
Satellite
lA
1B
1C
11.20 to 11.45 GHz
11.45 to 11.70 GHz
10.95 to 11.20 GHz
(The two cable channels operate just
below 10.95 GHz)
The frequency range 10.95 to 11.70
GHz was originally intended for telecommunication
satellites;
not for
Fig l: the footprint of Channel 23 on Astra lB (UK Gold), showing the antenna diameter required
(in centimetres) for direct-ta-home reception
ENG INF No 52
Ariane launching
an Astra satellite
broadcasting,
which ~as been allocated the range 11.7 to 12.5 GHz. As
a result, Astra was not subject to the
original European Community satellite broadcasting
directive, introduced in 1986, which required all
direct broadcast satellites (DBS) to
use the MAC transmission
system.
Hence, broadcasters
using Astra
have been able to operate in PAL or
MACas has suited their purposes.
The satellites are powered from solar
cells which are backed up by batteries. These come into play during the
spring and autumn equinoxes when
the satellite passes into the Earth's
shadow. Over a period of22 days, the
eclipse builds up to a maximum of
around 70 minutes at the equinox
(about 22.10 to 23.20 hours GMT),
then falls away to zero over the next
22 days. During the eclipse, the batteries have to provide the 2 kW of
power the satellite consumes.
3
-
Astra
Satellite
ASTRA
18
ASTRA
1A
11.376
Vertical
-
11.435
11.406
11.479
11.508
11.538
GHz
services, many of which are scrambled. All the services aimed at the
UK use PAL, either in the clear or
scrambled with the VideoCrypt system. Table 1 gives an up-to-date list
of the television services presently
on Astra.
:. 829MHz .:
The VideoCrypt
Horizontal
11.361
11.391
11.420
11.464.
11.493
11.523
11.552 GHz
(UK Gold)
Fig 2: frequency allocation in the region between satellites lA and lB
Transponders
on lA are rated at
47 W, while those on 1B deliver
about 63 W. The signals are transmitted towards Earth via highlydirectional
antennas,
which are
aimed at roughly the French/German border. The erp at the centre
of the beam is about 54 dBW, so
the transmit antennae have a gain
of about 37 dB (which is roughly
equivalent to a standard 60 cm domestic dish).
The satellite coverage area comprises
most of the low countries, Germany,
France,
Switzerland,
northern
Spain, northern Italy and the UK with a total population of some 240
million people. Fig 1 shows the footprint of the UK Gold service on
Astra 1B (which is similar to the footprints of the services on lA and 1C).
Astra
has standardised
on a
transponder bandwidth of 27 MHz,
compared
to the 36 or 72 MHz
transponders
used on many other
telecommunications
satellites. Each
Astra satellite has eight transponders operating on horizontal polarisation and eight on vertical. Fig 2
shows how the frequency is allocated
in the region between satellites lA
and lE. As can be seen, the spectrum
from adjacent transponders overlaps
very significantly - interference-free
reception is thus very dependent on
the receiving antenna being able to
discriminate between the two polarisations. In practice, this seems to
4
cause little problem -
provided the
receiving dish has been correctly
aligned during installation.
Five ofthe 32 transponders presently
in operation carry D2-MACtransmissions; the rest carry PAL television
System
When Sky first started broadcasting
scrambled services on Astra in 1989,
it standardised
on the VideoCrypt
system. This is an active-line-rotation scrambling system which only
scrambles the picture; it does not
scramble the sound. Although the
picture is scrambled, the line and
field syncs remain intact as does
any teletext signal. So a television
receiver fed with a VideoCryptscrambled signal continues to operate normally - there is just no
sensible picture!
The system uses a combination
smart card and over-air addressing
Service
Ch
RF Carrier Sound Carrier
(MHz)
(GHz) + P
RTL2
RTL Plus
TV3 (Sweden)
Eurosport/Quantum
VOX
Sat 1
TV1000
Sky One
TV Asia
Teleclub
3 Sat
FilmNet
Sky News
RTL4
Pro 7
MTV Europe
Sky Movies Plus
Premiere
Movie Channel
ARD Eins Plus
Sky Sports
DSF
MTV Europe
UK Gold
Children's Channel
Japan Sat TV
N3
Adult Channel
Movies Gold
TV3 (Denmark)
CNN
N-TV
Cinemania
TV3 (Norway)
Documania
1
2
3
4
5
6
7
8
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
24
25
26
26
27
28
29
30
31
32
11.214 H
11.229 V
11.243 H
11.258 V
11.273 H
11.288 V
11.302 H
11.317 V
11.317 V
11.332 H
11.347 V
11.361 H
11.376 V
11.391 H
11.406 V
11.420 H
11.435 V
11.464 H
11.479 V
11.493 H
11.508 V
11.523 H
11.538 V
11.552 H
11.567 V
11.567 V
11.582 H
11.597 V
11.597 V
11.611 H
11.626 V
11.641 H
11.656 V
11.670 H
11.685 V
Television
7.02f1.20
7.02
Digital
7.02
7.02f1.20
7.02f1.2
Digital
7.02f1.20
7.02f1.20
7.02
7.02f1.20
Digital
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
7.02f1.20
Digital
7.02
7.02f1.20
7.02f1.20
Digital
7.02f1.20
Coding
Pal
Pal
D2Mac
Pal
Pal
Pal
D2Mac
Pal
Pal
Pal
Pal
D2Mac
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
Pal
D2Mac
Pal
Pal
Pal
D2Mac
Pal
of
to
. Encryptlon
Clear
Clear
EuroCrypt
Clear
Clear
Clear
EuroCrypt
Clear
Clear
Nagravision
Clear
EuroCrypt
Clear
IRDETO
Clear
Clear
VideoCrypt
Nagravision
VideoCrypt
Clear
VideoCrypt
Clear
Clear
VideoCrypt
Clear
VideoCrypt
Clear
VideoCrypt
VideoCrypt
EuroCrypt
Clear
Clear
Nagravision
EuroCrypt
Nagravision
Table1: the televisionservicescurrentlyavailableonAstra
ENG INF Spring 1993
Astra Satellite
-
-
control access to the service. A subscriber's smart card can be updated
over the air, either to remove the ability to receive services or to extend
entitlement.
!
SOUND CHANNELS
VISION
I
,
OdB
"
Mono
Mode
VideoCrypt
can also operate in a so
called "soft-scrambled"
mode. This
means that the signal is scrambled,
but that a VideoCrypt
decoder can
descramble
the signal without
a
smart card. The UK Gold service is
operating in this mode at present.
In the early days of the BSkyB Astra
service
(it was just Sky at that
time), a separate satellite receiver
and VideoCrypt
decoder were required to receive the scrambled pictures.
Today,
most
satellite
receivers sold in the UK have the
VideoCrypt
decoder built
in and
are known as IRDs (Integrated
Receiver Decoders).
In continental
Europe, however, most PAL receivers will not incorporate
a Video-
People often remark that it is quite
astonishing that a transmitter with
the power of a standard domestic
light bulb is capable of being received 36,000 km away on Earth.
The physics of the situation is no
less astonishing. In effect, the 50
Watts or so of power from the satellite is spread fairly uniformly
over the whole of the western half
of Europe, an area of some 5 million square km. The resulting average power flux density from the
satellite ~s, therefore, about -110
dB(W/m ). This is about 7 dB
lower than the DBS power density
specified at WARC-n.
The standard 60 cm receiving antenna now intercepts about 0.3
square metres worth of this signal
(-115 dBW) and delivers some 60%
of it (-117 dBW) to the receiver. A
"standard" low-noise block (LNB) on
the dish, with a 1.8 dB noise figure,
will result in a carrier-to-noise ratio of
some 13 dB at the receiver's input
which gives a reasonably noise-free
picture and sound.
Incidentally, the WARC-77 DBS plan
assumed a 90 cm dish, an LNB noise
figure of 8 dB and a carrier-to-noise
figure of 14 dB.
ENG INF
No 52
-18<1B
Stereo Stereo Stereo Stereo
Mode A Mode B Mode C Mode D
j
j
-22dB
Freq uency (MHz)
...
8.6
6.6
Fig 3: Panda
1 arrangement
of FM sub.carriers
Crypt decoder, as BSkyB channels
are only intended for UK residents.
7.02
7.38
7.74
8.10
7.20
7.68
7.92
8.28
above the vision signal
nal-to-noiseratio.
The peak deviation of these subcarriers is 50 kHz.
Not all receivers use the proprietary
Wegener Panda decoding system,
The transponders
which carry PAL and in some cases this can result in
the sound quality being less than
services can also carry several radio
ideal. Receivers which use licensed
channels, in addition to the normal
Panda decoders can be identified by
television sound. In fact, each televithe "Panda" symbol (see Fig 4) which
sion signal could in theory be accomis usually displayed on the front of
panied by up to nine or ten sound
signals although,
in practice, no the equipment.
channel carries more than seven at
present.
WEGENER
COMMUNICATIONS,
INC.
Radio Services
on Astra
The sound signals are modulated
onto high frequency FM subcarriers
which are added at baseband to the
video signal. On Astra, the lowest
frequency subcarrier
-
N 0 I S ERE
D U C TI 0 N
located at
6.5 MHz -.always
carries the television programme
sound in mono
with a deviation of 85 kHz and a
pre-emphasis
of 50 118. As this is a
relatively high-level subcarrier, the
sound is not compressed.
For the rest of the sound signals,
nearly all the channels on Astra use
a particular
sound multiplex and
compression system called Panda 1,
developed
by the Wegener Company. Referring to Fig 3, this system
can carry multiple FM subcarriers
spaced 180 kHz apart, starting from
7.02 MHz. Because these subcarriers are injected at a relatively low
level, the sound is compressed at the
up link and expanded in the receiver
in order to provide an adequate sig-
Fig 4: the "Panda" symbol
The subcarriers
can be used separately to carry mono sound signals or
grouped in stereo pairs as follows:7.02/7.20, 7.38/7.56, 7.74/7.92 and
8.10/8.28 MHz. With a mono television service, the 7.02 MHz subcarrier
is usually used for the programme
sound. If the programme sound is
stereo then the 7.02 and 7.20 MHz
subcarriers are used.
Table 2 lists the radio services that
are presently available on the Astra
satellites.
BBC Radio Services
The BBC's radio services are carried
on UK Gold using the Wegener Panda 1
5
- Astra Satellite system, on the following subcarriers
above the normal video signal:
6.50
7.02
7.20
7.38
7.56
7.74
7.92
MHz
MHz
MHz
MHz
MHz
MHz
MHz
TV Sound mono
TV Sound Stereo (left)
TV Sound Stereo (right)
World Service in English
Radio 4 (as on FM)
Radio 1
Radio 5
Modern satellite receivers are usually able to receive all these sound
channels. However, some early receivers (in particular
the Amstrad
SRX100 and SRX200 models) could
only receive the 7.02, 7.20, 7.38 and
7.56 MHz subcarriers. These receivers will not be able to receive the
Radio 1 and Radio 5 services. However, upgrade kits are available to
enable them to operate over the full
range of subcarrier frequencies, but
their installation is very much a job
for a trained technician.
Most receivers have a number of
audio modes. In order to select the
appropriate mode, the user usually
has to press a button marked 'mode'
or 'audio' on the remote control which
steps the receiver from one mode to
the next. For instance, a typical receiver might organise its audio modes
as follows:
Stereo
Stereo
Stereo
Stereo
Mono
Mono
A
B
C
D
1
2
7.02/7.20 MHz
7.38/7.56 MHz
7.74/7.92 MHz
8.10/8.28 MHz
6.50 MHz (Tunable)
7.02 MHz
Radio Service
RF Carrier (GHz)
+ Polarisation
AsdaFM
BBC Radio 1
BBC Radio 4
BBC Radio 5
BBC World Service
CNN Radio
Deutscheland Funk
Deutscheland Funk
Deutschewelle
Eviva
Holland FM
lOB
Maxat FM
NDR2
NDR4
QCMR
Quality Europe FM
Radio 538
Radio Asia
Radio RMF
Radio Ropa
Radio Sweden
RTL4
RTL Radio
Sky Radio
StarSat
Sunrise Radio
Supergold
Spare
Sputnik
Switzerland
SWF3
11.435 V
11.552 H
11.552 H
11.552 H
11.552 H
11.266 V
11.288 V
11.288 V
11.229 V
11.332 H
11.479 V
11.538 V
11.435 V
11.582 H
11.582 H
11.376 V
11.435 V
11.317 V
11.597 V
11.420 H
11.406 V
11.597 V
11.391 H
11.391 H
11.317 V
11.406 V
11.479 V
11.376 V
11.508 V
11.464 H
11.332 H
11.493 H
Sound Carrier
(MHz)
7.74
7.74
7.56
7.92
7.38
7.92
7.74/7.92
7.38/7.56
7.56/7.38
7.74/7.92
7.56
7.74/7.56
7.92
7.38/7.56
7.74/7.92
7.38
7.38/7.56
7.74/7.92
7.38
7.74/7.92
7.74/7.92
7.74
7.74/7.92
7.38/7 .56
7.38/7.56
7.38/7.56
7.38
7.92
7.38
7.38/7.56
7.20
7.38/7.56
Mono!
Stereo
M
M
M
M
M
M
M
S
M
S
M
M!S
M
S
S
M
S
S
M
S
S
M
S
S
S
S
M
M
M
S
M
S
Table 2: the radio services currently available on Astra
Mono
Mono
Mono
Mono
Mono
Mono
Mono
3
4
5
6
7
8
9
7.20
7.38
7.56
7.74
7.92
8.10
8.28
MHz
MHz
MHz
MHz
MHz
MHz
MHz
(WS)
(Radio 4)
(Radio 1)
(Radio 5)
UK Gold's programme sound is stereo, so the receiver should initially be
set to Stereo Mode A. If this is the
case, then the audio button will have
to be pressed seven times to get World
Service (7.38 MHz), eight times to get
Radio 4, etc. Alternatively,
the receiver could be set to receive UK Gold
sound in Mono Modes 1, 2 or 3, in
which case the number of button
presses will be less!
Some modern receivers use on-screen
graphics menus, both to display and
select the required subcarrier
frequencies, and to store the appropriate
settings. Since such procedures vary
considerably
from receiver to receiver, the user will need to consult
the receiver
handbook
or their
dealer.
Finally, Fig 5 shows a typical installation where the satellite receiver is
linked to both a television set and a
hi-fi system. Such an arrangement
is ideal if the receiver is going to
be used frequently for radio listening.
Fig 5: a typical satellite receiver installation
6
Henry Price
HEID
ENG INF Spring 1993
NETWORK RADIO
Radio 2's new transDlission suites
John Tidy describes
Radio
just
2's new transmission
B
ankruptcies, lockouts, steam
baths and General Elections:
not the kind of things you
would associate with building three
on-air transmission suites for Radio 2
perhaps. But all these had a hand in
shaping the story of how Continuities
G, Hand J - the rather shabby and
tired-looking places where Radio 2
originated half of its DJ programme
output - were turned gradually into
Transmission Suites IG, IH and IJ:
a comfortable
comprehensivelyequipped production centre for all Radio 2's presenter-led
programmes.
But first I must set the scene.
In the beginning...
... there were continuity suites and
there were studios. The continuity
suites were only used by DJs; the
studios were used by, well, non-DJs.
Thus you could never be sure where
Radio 2's live programme was coming
from
-
especially
if, say,
non-DJ
N eil Kinnock was standing in for a
professional self-operator like John
Dunn. Things could quite well arrive
late or go missing.
a few problems
suites.
which
Then some clever beggar had a bright
idea: why not combine the two functions in one area? And so the concept,
then a little later the project, was
born. All.that remained was to come
up with a control desk that would
handle a full set of replay equipment
in both the studio (for the DJ) and the
cubicle (for an operator to use with a
non-DJ). The whole lot would have to
be crammed into a space that already
seemed quite full with only half that
amount of gear. It should be quite
straightforward
really!
It was soon realised that the only
control desk capable of supporting
the required
facilities
was Solid
State Logic's SL5000 series, and
gradually
a satisfactory
proposal
was worked out between SSL and
the technical design team. The job
of getting all the equipment to fit
exercised many minds but eventually a plan evolved which in general
worked, apart from Suite IG's cubicle where a few millimetres
error
in a drawing meant having to move
a tape machine at the last minute to
the other side of the door!
preceded
the opening
of
In the middle...
The whole exercise was taking place
in the middle of a complete refurbishment of BH, following the Governors' decision to keep Radio there
rather than moving out to West London. So once it became known that
BH had a long-term future, it was
clear that something had to be done
about the general working environment - especially the acoustics, the
air-conditioning
plant which was
slowly rusting away on the roof outside, and the chill wind which steadfastly blew down the back of the
DJs' necks.
Working to a brief from Radio Projects, a team from ACED (now
BDMS) set about redesigning
the
whole area and its services
-
taking
account of the requirements imposed
by the new equipment and the desire
to improve the appearance and acoustic environment, but without making
major structural alterations.
Within the boundaries of the existing
Camden partitions, a complete transformation was to take place. A complex
SUlllIJ
Plan
ENG
view
of Radio 2's new transmission
INF
No
52
suites
7
- Radio 2 ridor, could not be worked on separately - noise, dust, too many people
wanting to come and go, and deliveries of building materials would see to
that. However Con G (to be given the
treatment last) would be all right,
being separated from all the disruption by a room we used to call the
Network Supervisory Area which the
builders would later transform into a
reception area and phone-in room.
This left us with two remaining sets
of temporary facilities to find. Suite
1C would be eminently suitable as it
was equipped with the same Type D
desks so familiar to Radio 2 from the
original Cons Hand J. And to complete the temporary
facilities, we
needed somewhere to act as a temporary home for another Type D package (recovered
from the original
continuities which were demolished
to make way for Radio 5's production
suites).
j
c"
:r:
"
d
arrangement
of duct-work around
the windows to the outside was designed to enable the removal of the
old supply and extract system, while
still allowing in natural daylight.
minimise the possibility of creating
distracting
reflections.
High-frequency fluorescent fittings have been
supplemented by dimmable low-voltage spots on tracks.
The acoustic treatment
was re-designed by Tony Woolf of RDER to
allow a slightly longer and more even
reverberation time than before, particularly in the cubicle. Diffusers
were specified to make up some ofthe
wall treatment. In addition the floor
around the producer's and operator's
positions was required to provide a
long-lasting surface for the chairs to
run on and to cut down the area of
sound-absorbing
carpet, the join between the two having been designed
to allow a chair to run smoothly
across it.
Although a control desk specification had been agreed with Solid
State Logic, and the finance approved for the purchase of three of
these desks, this was by no means
the end of the technical installation
story. We agreed with SSL at the
start that their desk would contain
only standard equipment: anything
they could not supply using catalogue options would be for others to
provide. In any case, as SSL do not
offer an installation
service, we
would need the services of an installation contractor
to fall back on.
Thus with input from Studio Operations and Radio 2, a specification
was written for the special facilities
that would be needed to make a liveon-air studio operate effectively.
The new observation window is made
up from three parallel panes of lowreflectivity glass, which seemed to be
ideal for what we needed. The only
problem is that you can't see it and
it's possible to bang your nose against
it leaving a smudge on the glass not to mention your pride - if you're
not carefuL
All lighting has been recessed within
the ceiling acoustic treatment,
to
8
More taxing was the problem of how to
keep Radio 2 on the air while the early
part of the refurbishment was carried
out. The network requires three transmission facilities to keep the programmes going out. Cons H and J,
being separated by only a narrow cor-
Studio SI was available but, as it was
the location of the original Baird-system experimental TV transmissions,
it was of special interest to English
Heritage. So, when we came to apply
for planning consent, we had to be
most careful over what we did to it.
A Clever idea....
All good projects have an event
which, on reflection, can be seen as
the point at which success or failure
was determined. Such was the case
with the clever idea which someone
-I'm not quite sure who - had next.
It ran as follows: why spend good
money reinstalling a 20-year old control desk, however cheaply, if you can
temporarily install a new one and get
some use out of it? It made good
sense. Installing the first of the new
SSL desks in SI would overcome the
limitations imposed by the old Type
Ds, test the new design and give us
the chance to iron out those little
snags that always haunt new installations. Then, when the time came,
the equipment would be moved to 1G.
Brilliant! Now all I had to do was
amend the specification to include
the temporary installation work (as
it was to be a cheap job) and persuade
ENG INF Spring 1993
-Radio 2the Architects and Building Services
Engineers to quickly throw together
the plans for alterations to SI. To be
suitable, the cubicle and studio had to
be reversed, an apparatus room had
to be formed, a lower ceiling had to be
constructed in the new cubicle using
steel beams and woodwork slabs, and
a new entrance door had to be cut
though the wall of the structural
tower going up the centre of old BH.
The latter caused a few worries when
major cracks running up the tower
wall were discovered and had to be
repaired.
While all this was going on, we had
tendered
the installation
package
and subsequently
engaged Elliott
Bros Ltd. They immediately got busy
building the add-on goodies that did
not come as part of the SSL equipment. Thereafter, the process of putting Sl into service in May 1991 was
surprisingly uneventful.
Not so for Judith Chalmers, however,
who let out a shriek of surprise one
day when a soil pipe from the littleused Gents above the studio gave
away its secret hiding place in the
structural
column, which we had
packed full of sound-deadening material to prevent just such an incident.
Some you win, some you lose!
A catalogue
of problems...
Soon it was August and the contractors moved into 1H and 1J. Work
started well but, after a couple of
months, progress was slipping and
we began to detect that the builders
were having financial problems; they
were not making payments to subcontractors, who were threatening to
leave the site. Finally, in January
1992 following a lot of frank exchanges, the main contractor admitted to being
on the point
of
insolvency. There followed a furious
week of meetings, faxes and phone
calls at the end of which we had extricated ourselves from the original
contract and agreed a new contract
with another builder.
The project team heaved a huge sigh
of relief, until just a few days later:
the mechanical subcontractors
(who
ENG
INF No 52
were doing the air conditioning) told
us they couldn't provide the bank
guarantee we required to ensure they
would complete the contract, and so
would also be calling in a Receiver.
The benefits of cheap prices from contractors were now turning into a liability with a vengeance.
Despite all the difficulties, progress
on Suite 1J was only just behind timetable. Elliott Bros had moved onto
part of the site and the second SSL
desk had arrived. Before we knew it,
they were ready for us to begin testing
the first of the three new permanent
suites. Amazingly, everything went
smoothly and preparations were being made for the first live broadcast on
Monday 16th March. Only later did I
discover that someone had locked the
temporary door to the site which the
builders had still not taken away,
leaving
minutes
get the
prepare
the production
team only
before the first broadcast to
key, set up the studio and
to go live at 6.00 am.
While the installers
continued to
work on Suite 1H, Radio 2 broadcast
from 1J, though they nearly stopped
one day during the Jimmy Young
programme when suddenly the studio began to fill with steam! It was
so fog-like that Jimmy and his
guest, only four feet apart, could not
see each other and condensation ran
down the windows. The explanation
was in the new air-conditioning
system, which includes humidity control by injecting steam from the high
pressure main into the ducts; somehow a sensor had been installed in
the wrong place and so did not throttle back the control valve. Fortunately no damage was done.
CUBICLE
SSL SL5428 frame comprising the following:
16
4
8
6
6
1
2
Stereo line-level input channels controlled by cubicle or studio faders
Audio sub-groups with compressor-limiter
VCA groups
Mono mic/line inputs
Stereo outside source channels
Instant reset computer
End-table sections and rack mountings
Tapes
3 x Studer A80
1 x Studer A810
Gram
2 x EMT950
CD
3 x EMT981 or 2 x Technics SLP1200
Carts
3 x ITC99
Cassettes
2 x Studer A710
1 x Neal 6278 logging machine
LS Monitoring
BBC LS5/8
NTP OS selector panel
Drake network switcher panel
Jackfield: 23U double-density 24 jacks per row
STUDIO
Grams
3 x EMT950
CD
3 x Tascam 701
Carts
3 x Soniflex HS200
LS Monitoring
BBC LS3/5A
Custom Frame: sixteen channel faders and four VCA groups. This contains no audio but provides control of the cubicle channel VCAs
The technical equipment
installed in Radio 2's new transmission
suites
9
- Radio 2
The run-up to the General Election
saw Jimmy Young playing host to the
party leaders. Sadly no-one had made
it clear that when the PM's turn
came, as well as checking the building site, his security staff would want
the area completely cleared, stopping
all progress for half a day.
With the third installation in 1H complete and undergoing final checks, Ed
Stewart decided that the Sl Studio
desk needed refreshing with a cup of
coffee. The SSL of course doesn't like
coffee and so it packed up. The programme makers took a chance, moved
into 1H and got on with the broadcasting. We kept our fingers crossed, but
need not have as all went smoothly.
With Sl, 1J and 1H in service, together with 1C, it was now time to
start on 1G. This work went very well
as the contractors, having done the job
twice already,
knew what was
wanted. However, there were some
snags with getting the speciallow-reflectivity observation window glass
installed properly. A new glazing contractor had to be found, as the first
was still owed money by the original
main contractor and was trying to
recover the losses by charging extortionate prices. The new glazier took
three goes and two sets of glass to get
it right!
Another
idea....
There was a lot of noisy and disruptive work going on in BH at the time
(and still is). We became conscious
that somewhere
like Sl, tucked
away in a corner, would be useful to
have while all the crashing
and
bashing went on. Also the flexibility
of the equipment meant it was well
liked, so much so that when it was
Suite 1G Cubicle with view of studio through the low-reflectivity
10
clever
suggested we should buy another
(fourth) set of equipment
for 1G,
the idea was readily accepted.
SSL was happy to make another desk,
and Elliott Bros were happy to accept
the variation to the existing contract to
install it. All went well; they were old
hands at it now, after all. And in
the end, the technical commissioning engineers were very pleased with
the result - praise indeed!
So Radio 2 now has three bang-upto-date transmission
suites to take
them through to Charter Renewal
and beyond. It was a long journey,
with quite a few bumps along the
way, but in the end we got there safe
and sound - most importantly,
ahead of time and within budget!
John Tidy
Radio Projects
window glass
ENG INF Spring 1993
WSTV Europe
IDlproveDlents
Viewers
of World
Service
TV
Europe
-
to BBCfax
from the Nordic
countries
to Spain,
and
well into Eastern Europe - have a teletext service called BBCfax, which is
similar to Ceefax on BBC2. Peter Weitzel describes
how new equipment
has
greatly speeded up and improved this service.
W
ith the dash for new technology at Ceefax (as described
in the previous
issue), there was also pressure to provide a better service for BBCfax. In
particular, with the use of only three
line-pairs in the vertical blanking interval (VB!), BBCfax was very, very
slow. One solution was to buy a new
transmission
system
for WSTV
Europe -like the two that have now
been provided for BBC1 and BBC2but this would have involved a substantial refit of the Ceefax computer
room. The cost and time required to
do this, prior to the relaunch of Ceefax, ruled out this option.
WSTV viewers were also interested
in the depth of authoritative information that Ceefax provides on BBC2,but
with programme listings information
about World Service (rather than
BBC2) in Magazine 6, ie the 600 series of pages. So the requirements
were rapidly worked out:
o The service had to be branded
BBCfax
o The time in row zero should be
Central European Time (CET)
o
The service should be "BBC2 Ceefax" in content, but with a WSTV
listings magazine
o Page 100 and a few other pages
should be unique to WSTV.
o BBCfax should be comparable to
Ceefax but should not overload or
limit the Ceefax operation, either
editorially or technically.
Conceptually,
the easiest solution
seemed to be a box - a databridge which took in BBC2 Ceefax and put
out BBCfax. The databridge could be
told what modifications
should be
done to the page header - CET is not
always one hour in front of UK time
and when does a day start?! The list-
ENG INF No 52
ings pages for WSTV could be "dripfed" as part of the normal BBC2 output datastreams
and stored in the
databridge;
other pages unique to
WSTV could be dealt with similarly.
MRG Systems had a suitable 1000page databridge inserter, and experience of controlling remote teletext
equipment via teletext! In conjunction with Protext Services, who were
doing software modifications for the
relaunch of Ceefax, we all managed
to work out a suitable method of sending the WSTV listings pages and a
command page.
The Ceefax computer has to take the
listings pages from a library and
work out what "today" is, so that it
can determine
tomorrow's listings
and so on. Having assembled the
pages and added the Fastext links, it
creates
the command
page
-
The whole of magazine 6 on WSTV is
transmitted once a day - around 0430
hrs - and if a page is changed during
the day, the updated page is automatically transmitted.
If anything goes
wrong, the whole of the WSTv listings
can be re-transmitted;
each page is
sent about twice in 15 seconds.
With the exception of a few pages, the
WSTV viewer now gets the whole of
BBC2's Ceefax magazines 1, 2, 3, 4, 5
and 7
-
packaged
as BBCfax
-
with
the improved speed of access now enjoyed by Ceefax viewers.
The programme
listings are also
transmitted
on two other line-pairs,
to give an access time of under four
seconds. This means that BBCfax
with 11 line-pairs has more VBl space
than any other broadcast teletext
service.
which
tells the bridge what pages it has to
store and what today's row zero is.
Peter Weitzel,. Senior Engineer,
Developments, TE&PS
11
FAMILY TREE: En
Chief EngineE
Bert (;
I
Personnel
Engineering
and Admin, Tx
Finance
Divisional Accountant, Eng
Andy Jameson
Head of Pers and Admin, Tx
Terry Wing
I
Transmission
General Manager, Transmission
Oavid Sandbrook
I
I
I
I
Head of Engineering
Transmission Projects
A/an Rees
Head of Engineering
Transmission Site Development
Peler Mensforth
Site Acquisition
Site Sharing
I
Head of Engineering
Transmission Operations (UK)
Graham Smith
Head of Engineering
Transmission Technical Operations
Martin El/en
Antennas
Communications & Control
Power Systems
Support Structures
Transmitters
TOC (Project)
Special Projects
Project Business & Services
(Finance &Drawing)
I
Head of Engineering
Transmission Operations (OS)
David Wilson
EIC Inverness
CM Antigua
EIC Black Hill
RE Ascension Island
EIC Skelton
RE Cyprus
EIC Holme Moss
RE Masirah
EIC Lisnagarvey
RE Seychelles
EIC Woofferton
FERE Singapore
(Inc CM Hong Kong)
EIC Wenvoe
EIC Crystal Palace
Senior Operations Engineer (OS)
EIC Wrotham
EIC Rampisham
Senior Operations Engineer (UK)
Daventry Services
Transmission Operations Centre
Senior Operations Engineers
(TV, Radio, Antennas & Safety)
Operations Business Services
\
I
;-
Commercial
Services
Commercial
Manager
Nige/ Turner
Telecommunications
Head of Telecommunicatio'
A/an English
I
Assistant
I:
CommericalManager
Linda HancoJr
I
I
I
Structure
12
of Engineering
I
Admin Assistant
Manager Business
Development
David BeNs
Division (part of the new Resources, Engineering
I
~
I
Telecommunicatio
BusinessManage
Ra/ph Miller
Jim Sleigh/
Manager,Engineering
InformationTechnology
ManagerTelecommunications
Projects
Manager, Consultancy
and Contracts
Paul Milchel/
I
Project Engineers
Communications Systems
Broadcast Systems
j
to
Nick Davies
I
I
Manager Telecom Network
Local Area Networks
Business
EMIAS
Engineering Project Support
and Services directorate):
I
Network Bookings & /'
Tariff Negotiation,
Licensing
Regulation
15 June 1993
ENG INF Spring 1993
gineering Division
~r, Resources
,aI/on
Project
Finance
Personnel
Head of Corporate Capital Accounting
Dave Renwick
and Admin,
Eng Services
Head of Pers and Admin, Eng Services
Effric Smith
Research
Department
Head of Research Department
lan Childs
I
I
I
Head of TransmissionGroup
Paul Ralli"
I
I
Head 01 Service
Planning Section
Nigel Laflin
Head of RF
Systems Section
Peler Shelswell
I
Research Executive
Colin Smilh
I
I
Head of Digital
Systems Section
Bob Ely
,
Head of Studio Group
Howard Jones
I
I
Head of Sound
Section
David Meares
Head of Systems
& Recording Section
Mike Croll
Head of Image
Scannin~ Section
Bob lorey
-I
Development
Head of Development
John Astle
I
I
I
Control Systems
Section
David King
Studio
Section
David Bradshaw
I
TransmlSSlon
I"
1
Business &
Quality Manager
Peler Gregory
Section
John Sykes
1
Services
Co-Ordinator
Chris Smilh
Cost Recovery
Assistant
Kim Shannan
J
Building Design and Management Services
;
General Manager, BDMS
Richard Fowler
I
I
ManagerCorporate
ManagerBroadcast
Telephony
Network
David Russell
Dave McGhee
'
I
I
Energy
Management
John Ross
I
Building Design Group
Andrew Fuller/on
and Alan James
I
nin.
Architecture
Structures
Interiors
Acoustics
ENG
INF
No 52
I
Environmental Services
Group
Derek Adams
I
Business
Management
John Winfield
I
Mechanical Services
Electrical Services
Public Health
Lift Engineering
13
RADIO-CAMERAS
RD's switched-horn
Richard
Evans describes
flexibility
of radio-cameras.
how
new
technology
system.
is improving
the operational
adio-cameras are a familiar
sight at major sports events,
where their mobility allows
the cameraman to get in close to the
action (see Eng Inf Nos 34 and 46).
However they can suffer from picture
break-up or colour distortion caused
by multipath propagation, in which
the reflected (and therefore delayed)
signal interferes with the direct signal. Reflections can be caused by the
structural steel work, the seating, or
even the ground itself.
R
Current
radio-cameras
The existing single-operator
radiocameras use antennas with an omni. directional pattern which allows the
cameraman
to turn and yet still
transmit towards the receiving dish.
To reduce the effect of multi path
propagation, the antennas generate
circular polarisation (CP), allowing
much of the reflections to be rejected
at the receiver. These antennas were
developed at Research Department
and, although they have been successfully used for several years, the
use of circular polarisation does not
overcome all the problems and, in
some situations, the omnidirectional
pattern can still cause severe multipath problems.
One way around the problem is to use
a two-man radio-camera team, with
the second person carrying the transmitter and a directional
antenna.
This arrangement allows the cameraman to concentrate on the artistic
quality of the picture, while the second operator' points the antenna towards the receiving dish, but it does
limit the cameraman's
mobility.
Some manufacturers
have tried to
emulate the action of the second operator by using a motorised antenna
which constantly tries to point at the
receiving dish. However, these systems suffer from noise, vibration and
speed of operation and, as they can
14
The switch-horn
radio-camera
on test at Wembley
only hunt for the strongest signal,
they can easily lock up on a reflection.
is automatically selected to carry the
pictures but, if the camera is turned,
then an adjacent horn will be selected.
The
In order to choose the best horn, the
quality of the transmission
path
through each horn is first assessed.
During the field blanking interval a
video test line is transmitted through
each horn in turn, and these lines are
then analysed at the receiving site by
a processing base station. A decision
is made as to which horn produced
the best test line and a data signal is
then sent back to the camera, via a
vhf radio link, telling it which horn to
use for the following frame of video.
Thus, by constantly updating this decision every frame, the switched horn
Switched
Horn
system
To counteract
these problems, RD
engineers have designed a steerable
12 GHz radio-camera
system which
is entirely electronic and completely
free from mechanical problems. The
Switched
Horn System
as it is
known uses a cluster of six directional
transmitting
antennas,
aligned on bearings which are 60°
apart. Each of the six horns has a
horizontal beamwidth of 60° so the
system covers all points of the compass. In use, the antenna which is
pointing towards the receiving dish
ENG INF Spring 1993
quite successful with the pictures
from the switched horn system being
used approximately twice as often as
those from the 2.5 GHz CP camera.
Q
po:
:;;
~
~
.0
N"
..c:
o"
....
The switched-horn
this year
radio-camera
(f'arleft) and the 2.5 GHz omni-CP radio-camera
system can adapt to the cameraman's
changing position and orientation_
In its simplest mode of operation, the
base station
merely chooses the
strongest signal; at the Research Department demonstration
days in November 1992, this basic system was
shown to work very effectively. Since
then, the switched horn concept has
been taken a stage further with the
introduction
of additional software
running inside the base station which
measures the amount of multipath
distortion on the transmission
from
each horn. This means that a weaker
but cleaner signal may be selected in
preference to a stronger signal with
colour saturation errors.
The Technology
Although the switched horn concept
is quite simple, the implementation
has required considerable resources,
particularly
in the camera pack
which must be very compact. The use
ofXilinx Programmable Gate Arrays
(see Eng InfNo 43) has allowed us to
squeeze what would normally be
about seventy integrated circuits into
one square inch of board space. Although the camera pack has many
complex functions, including test line
insertion and decision-data error detection, we have managed to produce a
unit which is almost pocket sized, as
can be seen from the photo on page 14.
ENG
INF No 52
at lo.furrayfield
The Murrayfield
Match
At the Scotland v Wales Rugby International at Murrayfield this year, two
radio-cameras were required to cover
the touch-line action. We thus had
the opportunity to demonstrate the
full system live on-air, alongside a
conventional
2.5 GHz omni-directional CP system. The event proved
Commercial
developments
The existing switched horn system is
still rather modular and so some further development is really required
to integrate the components into a
single unit containing the transmitter, data receiver and horn cluster
control circuitry. A licence agreement
has recently been signed with Multipoint Communications to manufacture such a system. The company
already manufactures a radio-camera
system with an electro-mechanically
positioned
antenna,
and so the
switched horn system with multipath
software is an obvious progression.
Multipoint also hopes to provide a
reverse vision facility as well as remote control of camera functions (carried on the same radio-link as the
horn selection data). This will make
the system operationally identical to
a cabled camera.
Richard Evans
RF Systems Section
Research Department
A new Fast Response Vehicle
for Northern Ireland entered
service earlier this year. It has
been designed to send live or
recorded news material back
to base with the absolute minimum of rigging time.
The main link is a 7.5 GHz
microwave system, mounted
on a 12m mast. A wide range
of radio talkback facilities are
available, as well as compact
sound, vision and communications
systems.
Bi-media
working is fully supported,
with dedicated radio facilities
in the cab.
~
1I
The project was managed by
Thlevision Engineering
and
Project Services (TE & PS) to
meet the customers' requirements, and IP Kinlock was the
main contractor.
Further information can be
obtained from 7revor Parkins
{project Engineer, TE & PS}
on TC 67063.
15
The ITU
Its function and new structure
lan Davey guides us through
the new structure
communications
Union (ITU).
T
he ITU has its origin in the
early days of telegraph communications (late 1830s), before telephony
or radio
were
invented. There was no need for international cooperation or agreement
in those days, as long as telegrams sent by wire - were limited to points
within a country.
As the service was extended and telegrams were exchanged between countries, international agreement became
necessary - not only in regard to the
type of equipment which should be
employed, the type of coding which
should be used, or the rates that
- should be charged for telegrams, but
also in regard to juridical questions
as a consequence of telegraph wires
crossing national borders.
The popularity of this "ingenious"
means of communication led to significant traffic and in the number of
countries using it, resulting in ad hoc
agreements becoming too complex to
negotiate and cumbersome to implement.
The need for an international convention was recognised and, in 1865,
twenty states founded the International Telegraph Union and met to
draw up and write the first set of
telegraph regulations - the first International Telegraph Convention.
The eight organs
In 1932, the organization's title was
changed to the present International
Telecommunications
Union (ITU).
The purposes of the Union, as defined
in the International Telecommunications Convention, are:
*
*
to maintain and extend international cooperation
between all
Members ofthe Union for the improvement
and rational use of
telecommunications
of all kinds,
as well as to promote and offer
technical assistance to developing
countries in the field of telecommunications
to promote the development
of
technical facilities and their most
efficient operation, with a view to
improving the efficiency of telecommunications services, increasing their usefulness and making
them, so far as possible, generally
available to the public.
Pre-March
1993, the Union comprised eight organs as shown in the
table below.
The Plenipotentiary
Conference
The Plenipotentiary Conference (or
Plenipot for short) is the supreme body
of the Union. It normally met every
five years and laid down the general
policy ofthe Union and the methods of
of the ITU (pre March 1993)
General Secretariat
permanent
International Frequency Registration Board (IFRB)
permanent
International Radio Consultative Committee (CCIR)
permanent
Intemational Telegraph and Telephone Consultative Committee (CCITT)
permanent
Telec0l!lmunications Development Bureau (BOT)
permanent
Plenipotentiary Conference
.
~"
Administrative Conferences (eg. WARCs)
periodic
Administrative Council
annual
16
of the International
periodic
Tele-
giving effect to this policy, which it
embodies in the Convention. It established the budget, the limit of expenditure ofthe Union, and the basis on
which annual
contributions
-
to pro-
vide for the cost ofthe Union - should
be made by the Members (current membership stands at 177).
The last full Plenipot was held in Nice
in 1989. At that conference a debate
was held which started as an examination of the future of the CCIR, CCITT
and the IFRB. The debate however
developed into a proposal for a special
committee to undertake a comprehensive study on the structure, working
methods, financial aspects etc, not only
ofthe CCl's as originally intended but
of the Union as a whole, including all
its permanent organs.
A High Level Committee (HLC) comprising some twenty-one
Member
States was set up and, in April 1991,
their far-reaching report Tomorrow's
ITU : The Challenges of Change was
issued with ninety-six Recommendations. To maintain the impetus, a
Drafting Group was set up to prepare
a draft revision of the ITU Constitution and Convention which reflected
these Recommendations.
To review the
dations of the
work of the
Plenipotentiary
was convened
riod 7th-22nd
report and recommenHLC, within the frameITU, an Additional
Conference (APP-92)
in Geneva over the peDecember 1992.
APP-92
With approximately
800 delegates
participating,
representing
137
Member States, APP-92 finished on
time - with considerable credit going
to the efficient Swiss Chairman of
the Conference. However, this was
not achieved without some lengthy
evening sessions over the final four
ENG INF Spring 1993
days, where the firmness
of the
Chairman
assisted
the forward
momentum
of the Conference
when matters
appeared
to get
bogged down. His resistance
to be
sidetracked
and not let debates
meander was in stark contrast to
WARC-92 (see EnglnfNo
49).
!Jg ~
World Set.,..
I
Ptenlpolenftary
Conference
L
Main conclusions
The main conclusions enshrined
the Final Acts of APP-92 are:
in
o A revised Constitution and Convention
o A new structure of the ITV (see
Fig 1)
o The Plenipotentiary
Confer-
ence remains the supreme organ
with a 4-year cycle of meetings
and with a maximum duration of Fig 1: the new structureof the ITU
four weeks
o The Administrative Council is retained with an unchanged membership selection procedure but in
future will be referred to as "the
Council"
.
o There are three principal Sectors
of the ITV, namely Radiocommunications, Standardisation
and
Developments:
o Radiocommunications
consists of the current
IFRB
(Board and Secretariat)
with
the predominant
part of the
CCIR (see below for an expansion of this topic).
o Standardisation
consists of the
CCITT with elements of the
ccm not included in Radiocommunications.
o Developments incorporates the
activities
currently
in the
hands of the existing Telecommunications Development Bureau (BDT) set up at the 1989
Plenipotentiary
Conference in
Nice.
o Within the Radiocommunications
Sector there will now be a new Radio
Regulations Board. This was probably
the most contentious issue atAPP-92
and concerned the future of the
existing five full-time members of
the IFRB (the Board). The HLC pro-
ENG INF No 52
posed a part-time Board of nine
members.
sembly where Technical matters will
be dealt with, essentially taking
over the ccm Plenary activities
but placing the existing ccm output on a more definitive footing
within Conferences. Attempts by
a few countries to renegotiate the
recently adopted "fast approval"
procedures for Recommendations
within the CCITT (Resolution 2)
and the CCIR (Resolution
97)
were defeated.
During nearly ten hours of debate
on this topic within committee, there
was a clear majority in support of the
HLC recommendation. Those in favour of the status quo just did not
want change, or were mainly concerned over the impartiality of parttime members - particularly when
participating at Conferences.
This issue was resolved, in committee, by a secret vote in favour
of a 9-member part-time Board.
Attempts during the final stages
of the Conference to provide a trial
period for the part-time Board, with
the 1994 Kyoto Plenipotentiary
Conference reviewing the matter,
failed. (The Japanese were most
concerned that the topic should not
be left open ended!)
o The timetable for World Radio
Conferences
(WRCs) are now
more structured; every two years
for Radiocommunications,
which
will deal with "treaty work" and
will involve work allied to the Radio Regulations, and every four
years for Standardisation.
o Associated with World Radiocommunications Conferences, there
will be a Radiocommunications As-
o Within the Radiocommunications
and Standardisation
Sector, Advisory Groups should be established
to review and provide guidance on
the activities of the two Sectors.
Timetable
for Change
A timetable for change was agreed at
APP-92 as follows:
.
The new Structure and working methods would provisionally enter into
force on 1 March 1993. The 9-member
part-time board will be elected at
Kyoto (1994) but, in the meantime,
the existing 5-member full-time
board will oversee the transition.
.
The new Constitution and Convention of the !TU will come into force
on 1 July 1994 with all Member
States encouraged to "sign up" as
quickly as possible, even to the point
17
-ITUof noting that it is
sary for Members
respective national
dures of the Nice
.
no longer necesto take up their
approval proce(1989) Articles.
The first World Telecommunication Standardisation Conference
will be held in Helsinki in March
1993, replacing the scheduled
CCITT Plenary.
gramme and the study groups for
the new Radiocommunication
Sector, including any future work on
HF Broadcasting, taking account
of any IFRB report on the application of Resolution 523 ofWARC-92
..." (Res 523 instructed the IFRB
"... to propose a flexible, simplified
planning method ...")
Until a date which is to be specified by
Conference
(Kyoto 1994), the duties of the Directors of the new Radiocommunication
and Telecommunication
Standardisation Bureaux will be undertaken
by Mr R Kirby (current Director CCIR)
and Mr Th Irmer (current Director
CCITT) respectively.
. There willbe a short WorldRadio- the next Plenipotentiary
communication Conference in November 1993 to:
make recommendations
on
the Agenda for the 1995 WRC
including also the report ofthe
VGE* and to facilitate the use
offrequency bands allocated to
the Mobile Satellite Service.
make recommendations
for the
preliminary
agenda for the
1997 WRC.
.
.
.
Associated with the 1993 WRC
will be the first Radiocommunication Assembly, in place of the
scheduled CCIR Plenary. This
Assembly was requested inter alia
"... to establish the work pro-
the activities of the 1993 Assembly,
any work involving HF Broadcasting
should be dealt with at Study Group
level - with possibly 1999 being a
date for a WRC to deal with the longrunning saga of HF Broadcast Planning.
Although Member States could still
press for the 1997 WRC to include HF
Broadcasting, in our view there are
other more important items - already identified in the minds of many
- for consideration in 1997; for example, a WRC for the planning of
Broadcast Satellite Services (Sound)
in the 1-3 GHz band, as called for by
WARC-92, or a Regional Radio Conference to deal with the development
of DAB in the vhf bands
From BBC World Service's perspective, although HF Broadcasting appears on the "agenda" of the 1993
Radiocommunications
Assembly,
this is only in the context of the
Sector planning its future work. HF
Broadcasting,
under a Resolution
passed at the APP-92, should not
appear on the agenda of the 1993
WRC. By placing the subject within
_
only relate to Broadcast
-
and these
issues!
Ian Davey
Broadcast Coverage Department
World Service
*
The task of the Voluntary Group of Experts
(VGE) is to "Study allocation and Improved
Use of the Radio-Frequency Spectrum, and
Simplification of the Radio Regulations.
TELECOMMUNICATIONS
Part 5: self-provision
of OB circuits
Concluding our short series on Telecommunications
in the BBC, Roger Palmer describes the self-provision of OB production and engineering co-ordination circuits.
T
he majority
of production
and engineering
co-ordination circuits between OBs
are hired from British Telecom for
the duration of each' programme,
the greatest demand being in the
southeast of England. For financial
and operational
reasons, both the
Radio and Television services have
been examining alternative ways in
which these type of circuits can be
established.
This short article describes one solution.
Currently
Television
18
it is possible
for the
service to provide some of
its own circuits,
tion of:
using a combina-
(a) one of the two available FM subcarriers above vision on an shfvision
link incoming from the OB venue,
and
(b) a vhf or uhf audio link bearer in
the reverse direction, carrying a fivechannel Frequency Division Multiplex (FDM) signal.
High quality audio circuits (15 kHz
bandwidth)
are used to relay the
FDMsignal
in both directions be-
tween the OBmasthead terminal and
the nearest studio-based
Central
Technical Area(CTA) and, for network
television OBs, between the studio
CTAand Television Centre. Whenever
reverse vision circuits are required,
the outgoing second sub-carrier to
the OB venue is available for the reverse FDM bearer, instead of the
audio link.
The Radio service is able to establish
similar audio bearers using vhf or
uhf audio links in both directions.
Development -Group has been responsible for the design and manu-
ENG INF Spring 1993
(a)
Ch32
vision carrier
Ch33
villon carrier
sound tarrie"
FM
colour
sub-carrier
-10
-8
-6
-4
-2
o
MHz
(b)
4
6
8
10
vestiga tion to establish
whether two 2048 kbitls reverse carriers could be accommodated in each lower
adjacent uhf broadcast channel. Each 2048 kbitls carrier
offered the potential for six
high-quality
audio circuits,
thirty toll-quality
circuits
(using the Nicam circuits as
bearers for the FDM equipment) or a combination ofthe
two. By suitably allocating
the channels, one digital carrier could support more than
one OB on those occasions
when the requirement
for
circuits was limited for individual OBs. The incoming
bearer was planned to be a
2048 kbitls above-vision digital sub-carrier. These abovevision digital modems are
readily available commercially. Initially the Television
Service requirement was for
three 2048 kbitls carriers.
Fig 2: (a) spectrum of transmitted signals (2 Mbit/s and
BBC2); (b) relative position of carriers in Channels 32 & 33
facture of the audio links and the
FDM equipment,
known as Audio
Multiplex Equipment.
Unfortunately the capacity available
using these techniques, particularly
as far as Television OBs is concerned,
is limited. For state occasions in the
Capital, and in the summer during the
Wimbledon 'Thnnis tournament, alternative methods are needed if the BBC
is to be largely self-sufficient in the
provision of these type of circuits.
Initial
Research Department identified that, in each adjacent
channel, the two digital carriers
could be located 5.6 MHz and 3.6 MHz
below the wanted vision carrier, respectively.
Fig 1 shows this in diagrammatic
form. The spectral plot shows the one
carrier at 5.6 MHz below the wanted
carrier. It will be noted that the colour
sub-carrier image is present to the
right of the digital sub-carrier and this
requires removal if the second subcarrier is to work satisfactorily. Interference calculations established that
the maximum radiated power of the
digital carrier, to avoid interference to
domestic reception, would need to be
25 W for each sub-carrier.
Based on this, assuming the use of a
simple digital modulation scheme such
as Quadrature Phase Shift Keying
(QPSK)and typical system parameters,
it was possible to produce a prediction
of service area coverage (Fig 2) from
Crystal Palace. The coverage is extensive, offering the possibility of establishing the digital reverse bearer
directly to those OB venues where
the shf link carrying the programme
back to Television centre would require two or more hops.
These initial predictions were supported by an extensive field trial.
An experimental
QPSK transmitter
was established
at Crystal Palace,
using the reserve uhf antenna to
enable interference
and coverage
measurements
to be carried out.
Haslemere
was established
as the
most likely area to suffer interference to domestic reception and tests
confirmed
that, if the radiated
power was kept below 25W for each
Proposals
Some years ago, to meet a requirement
to provide a NICAMdistribution circuit
(2048 kbitls) to the Channel Isles, Research Department established that it
would be possible to transmit a lowlevel digital carrier in the lower adjacent channel to either BBC 1 or 2
from Stockland Hill without causing
interference
to domestic reception.
Transmission Engineering Department
subsequently managed the installation
of this system which is now in service.
It was agreed that Research Department should carry out a similar in-
ENG
INF
No
52
5
9
Fig2:predictedcoverageof reversebearertransmissionsfrom CrystalPalace
19
digital
carrier,
the
chances of interference
were negligible.
Part of the coverage tests
included going to those OB
venues on bearings where
the reserve antenna pattern exhibited large nulls.
This was done in case
the reserve antenna was
chosen to transmit
the
digital reverse bearers,
rather
than the main
broadcast
antenna.
No
significant problems were
found.
Telecommunications
,
,
,
CENTRAL
APPARAJUS
ROOM
,
CRYSTAL
':(,'
PALACE
~
A/7
'iI
"...."....
'
,I
I
i
i
1- -8-ROA;CAS~;- ~OUS~--I
i
i
i~A/7'
I'
.
L
"~"I.J.J-lItll
L
ooCll"l
~~~::_~
Fig 3: layout of the system used by the Television service
Evaluation of practical systems by RD
showed that the performance offered
by QPSK was superior to TFM. In fact
the TFM system did not perform as
expected and further development
work would have been needed to
make the necessary improvements.
Commercially, the most readily available systems are based on QPSKwhich
has the added advantage of being
fitted with Forward Error Correction
as a standard feature, offering an improved threshold performance for a
slight increase in radiated bandwidth.
The down side is that some development work would be needed to enable
them to operate in Band IV and to
provide sufficient receiver filtering to
reduce the adjacent vision carrier to
acceptable levels (the ratio between vision carrier and digital carrier is 46
dB and is only 5.6 MHz away).
Transmission
also investigated
an
alternative
approach based on several 728 kbitls digital carriers to replace individual 2048 kbitls digital
carriers. The advantage of this approach was that use could be made of
Development Group's new uhf audio
link. This equipment has been designed to replace existing worn-out
analogue equipment and can accommodate a 728 kbitls digital modem
and Nicam codec cards. Since the basic uhf link design used non-linear
power amplification techniques, the
modulation
scheme had to be one
offering a constant RF amplitude,
which precluded the use of QPSK.
Development Group is currently developing a Generalised TFM system
TFM
QPSK
Constant RF amplitude so non-linear
amplifiers can be used
Simple circuit design, many commercial
implementations
available
in the presence
Linear amplifiers must be used, as RF
amplitude can vary
20
'j
AT~
I
System
Considerations
It has already been noted that, if two
digital carriers are required in an adjacent channel, the colour sub-carrier
image and other out-of-band inter. modulation products will have to be
removed. The most effective way of
doi:Q.gthis is to fit filters to the main
transmitter
combiner which allows
access to the main antenna for the
digital carriers, thus avoiding use of
the reserve antenna with its inferior
radiation
pattern.
The choice of
modulation scheme lay between QPSK
and Tamed Frequency Modulation
(TFM). The relative merits of the two
systems are summarised in Table 1.
Superior error performance
noise compared to TFM
-
of
Less bandwidth
More complex
power
required than for QPSK
implementation
than QPSK
that includes a small amount of error
correction to improve the robustness of
the system at low signal levels. Receiver
selectivity
considerations
limited
the number of 728 kbit/s carriers to
two, in the spectrum occupied by
one 2048 kbit/s carrier. This offered
four Nicam circuits (twenty tollquality circuits or a mixture of the
two) rather than the six available at
2048 kbit/s.
The radiated powers of the 728 kbitls
carriers were reduced on a pro rata
basis to avoid interference to domestic reception.
Although
coverage
would be slightly less than that offered by the original system, the loss
was considered to be small. An experimantal system was produced by
Development
Group and operated
from Crystal Palace. This confirmed
that the system was viable and would
produce useful coverage.
Final System
Configuration
Television decided that the provision
of three 728 kbit/s carriers would.
be sufficient for their purposes, with
a fourth being allocated to Radio: two
carriers will be located around a centre frequency of 5.6 MHz below the
BBC 1 vision carrier and the other
two at the same point below the BBC
2 vision carrier. By using only these
two carriers on each service, filtering
and combining on to the main broadcast antenna system is not necessary. Also, the reserve antenna can
be utilised, resulting in a much more
economic arrangement. Astandby an-
ENG INF Spring 1993
- Telecommunicationstenna system with reduced coverage
will be provided to cover those occasions when the reserve antenna is
required for broadcasting.
the Nicam coders are fully duplicated.
The incoming
leg from
the OB venue
is provided
by
above-vision
2048 kbit/s modem
and Nicam decoders, and the shf
Three sub carriers
will offer six links and coders are fully dupliNicam channels, thirty toll-quality
cated. High quality audio circuits,
circuits or a combination of the two. permanently
hired from BT, are
Extra capacity will be provided by used for connection
to Television
reverse vision link systems, with
Centre, where the FDM equipments
over-vision 2048 kbitJs modems in encode and decode the 5-channel
both directions.
FDM signals to provide the toll. quality circuits.
Fig 3 shows the system layout for
the Television
requirement.
The
Radio will be given access to the
three working
transmitters
are
combiner for their one unduplicated
supported
by one standby, while
728 kbitJs reverse bearer. A 1.5 GHz
728 kbitJs 1ink will also be installed
between London BH and Crystal
Palace, instead of hiring permanent
circuits. Radio intends to use a new
non- Nicam 728 kbit/s codec system
that offers two high-quality
circuits and one toll-quality circuit, or
six toll-quality circuits.
It is expected that both systems will
be operational during the last quarter
of 1993
R Palmer
Comms & Control Section
TED
LOCAL RADIO
CUDlbria refurbished
Radio Cumbria has moved into brand new accommodation
Carlisle, as described
here by Graham Innes.
E
ight months before the lease
expired on their previous inadequate
accommodation,
and ahead of the establishment
of
a rival commercial station in the
city, Radio Cumbria has moved into
new purpose-built
premises in the
centre of Carlisle.
The station
serves the largest
graphical area in
now broadcasting
first time, as well
RDS
travel
local radio geoEngland and is
in stereo for the
as transmitting
information
-
making
itself known to an additional audience of passing motorists on the M6
motorway.
in the centre
of
The layout of the new two-storey
building includes two adjacent cubicles facing through a common studio
to a phone-in area on the ground
floor, together with an NCA studio,
a Production and Preparation
Area
(PPA) and a small television contribution studio. The first floor accommodation includes a News Preparation
Area (NPA) and a newsroom equipped
with thirty desks designed for Electronic News Service (ENS) operation.
Cubicle A
Apparatus
Room
TVArea
Studio
PPA
NCA
Ground floor plan of Radio Cumbria
ENG INF No 52
Cubicle 8
Phone
in
The specification for the supply and
installation
of the technical equipment was compiled by Radio Projects
in close liaison with the station EiC,
Alan Ross, and is based on the Local
Radio Mk IV operational specification.
ME! Broadcast Systems was awarded
the resulting contract, following competitive tendering procedures.
MB! equipped
each of the two
main cubicles with a presenter-operated 26-channel
desk, based on
their Series 24B console. Their ergonomic design included wings to
21
- Radio Cumbria
main cubicle desks, two os channels on
the NPAdesk, an os channel at each of
the four outstations, and an interrogate/override controller in the apparatus room. Sources include the four
outstations'
radio-cars,
for which
automatic
switching connects the
relevant base station, via the dedicated
lines, to Carlisle's Nova control unit.
The small television
contribution
studio has been equipped by regional
television
staff using equipment
transferred
from the old premises.
The camera and lighting can be controlled remotely from Newcastle, using the internal data network.
Radio Cumbria's cubicle A
house the turntables,
CD and CD
jingle players, cartridge,
cassette
-and DAT machines, as well as the
.
effects unit, the visual talkback
monitor and a jackfield "normalled"
to give a standard
configuration
with no cords inserted.
Each console provides comprehensive aural and visual monitoring,
and has Telecaster answering and
routeing units integrated
into its
centre section between the script
area and the PPMs. A panel is provided to give control and indication
ofthe status of an MBI transmission
switcher, that can route any of eight
sources to as many as four transmitter networks. Each of the console's
six outside source channels is interfaced to a dedicated port on the station's telephone exchange, enabling
the PSTN to be used for control-line
working without the use of one of
the station's six broadcast telephone
balance units.
for twenty-eight
outside sources at
Carlisle, but could also remotely select up to twelve outside sources at
each of four outstations (at Barrow,
Kendal, Whitehaven
and Penrith).
The system utilises the dedicated
incoming and reverse music lines to
each ofthe outstations, and sequential tone signalling.
A key-pad selector has been provided
for each of the nineteen destinations;
six os channels on each of the two
Radio Cumbria is now well endowed
to commence the battle for listeners
with the forthcoming ILR competition. However, it has not forgotten
its old BBC-built Mk III equipment;
one of the redundant
control desks
is to be displayed in a forthcoming
exhibition
of broadcasting
equipment, in the city council's adjacent
Tullie House Museum. This will be
a fitting mark of respect for over
twenty years of continuous stalwart
service.
Graham Innes,
Project Engineer
Radio Projects
The small NPA and PPA cubicles
have been equipped with self-op
10-channel desks, based on MBI's
compact Series 20 consoles but with
a wing added to each, to house the
ancillary machines and equipment.
As part of the contract, MBI designed and built an outside source
(OS) matrix that could not only cater
22
Radio Cumbria'sstudio
ENG INF Spring 1993
NORTH REGION
Manchester's Edit Suite 5
Tony Anstis
describes
the new on-line
F
ollowing
the recent
restructuring
of Television
Operations
into Centres of
Excellence, Manchester is to specialise in Youth and Religious
programmes. In order to handle this
increased workload - under the new
environment
of Producer
Choice
-
the post production resources in Manchester are being redeveloped to offer
a more comprehensive range offacilities.
Phase I of the development was a
seven VT machine, on-line, composite
edit suite. Outline project planning
started last September and the first
programme booking was scheduled
for transmission
during the first
week of January this year.
VT editing is the major post production element of all documentaries,
light entertainment,
features and
drama programmes. The VT editing
suite is where the final programme
tape is compiled - typically from as
many as thirty source tapes. The skill
and expertise of the editor are combined with the facilities available to
efficiently produce an amalgam of
video, audio, graphics and effects under the direction of the production
staff. The style of the editing technique chosen for a particular
programme will reflect and enhance the
programme material.
VT edit suite at Manchester.
Sony BVE 9100 edit controller. The
right-hand
section of the edit desk
can readily be moved some 700mm
towards
the editor's position,
to
allow one-man
operation
of the
suite. This section
houses
the
GVG 200P vision mixer control
panel and Abekas A51 DVE controller. An assistant
editor's position
is formed when this section
is
pushed back, providing access to
operate the Aston Motif character
generator,
vision mixer and DVE.
In front of the control desk is an
array of colour and monochrome
picture monitors, along with a pair
of LS5/8 loudspeakers
driven from
the new AM8/20 Chord power amplifier (as described
in the previous issue).
"The new arrangement achieves
an
ergonomic
layout
of the two control
desks,
and provides good access
within the existing
room shape."
Operation
and
Equipment
The on-line suite houses the facilities
for processing
broadcast-quality
vision and stereo sound, using timecode control to synchronise sequences
for previewing and recording edits. A
previously-prepared
floppy disc ofthe
Edit Decision List (EDL), made in an
off-line edit suite, can be loaded into
the Sony BVE 9100 edit controller to
provide the basis for the final edit
session.
The BVE 9100 forms the hub of the
suite by providing
the following
features:
o Control of all seven VTRsincluding
playback/record,
slow motion,
video and audio pre-read on D3
machines.
o Control of vision mixer and provision for audio mixer.
o Control of DAT and SSAR (Solid
State
Audio Recorder).
o Control of Abekas A51 twin channel DVEand combiner.
o GPI control of the Motif, Wallet,
VT clock, DAT, CD, GVG 200 and
DVE.
o Advance EDL management
logging and data entry software.
Layout
The suite control room was designed
to offer a comfortable environment
for staff working long hours. The
new arrangement
achieves an ergonomic layout of the two control desks,
and provides good access within
the
.
existing room shape.
The rear of the control room floor is
raised 350mm and supports the production control desk with a seated
viewing area for production
staff
and clients. The desk houses a production monitoring position and 40U
of bay space facing the edit desk. Two
Beta SP VT machines - for use when
the programme
requires frequent
rapid
The editor sits in a central position
at the Edit control desk, having
access
to the Amek 3B audio
mixer, system control panels and
ENG INF No 52
changes
of tape
cassettes
-
are rack mounted on sliding trays in
the production desk, alongside the
Sony 7030 DAT recorder and Sony
CDP 2700 CD player.
An adjacent apparatus
room contains the seven equipment
bays
which house all the mainframe electronics,
telephone
intercom
and
talkback
modules, DAs and jackfields. The suite has on-line connections to the Central Technical Area
and to the Graphics
Production
Area, providing feeds of Paintbox,
Wallet, Aston 4 and Caption. The
VTRs in the machine bays can be
selected to replay into the CTA and
provide network contributions.
23
- Manchester ... continued from previous page
The other major pieces of equipment
in the suite are:
*
GVG 200/2P vision mixer with
twenty channels and two mix!
effects banks.
*
Amek 3B audio mixer with fourteen stereo channels, four mixing
banks and two output groups.
*
Aston MOTIF character generator
with video grab stills store option.
*
Abekas A51 dual channel DVE
system with recently-developed
composite combiner.
*
VTRare designated
machines.
BEL 6000S SSAR
The suite is configured
seven VT machines:
to control
o Two Sony Betacam SP BVW-75Ps
in the control room production
desk
DOne Sony Betacam SP BVW-75P
in the machine room
o Three Panasonic D3 AJ-D350s in
the machine room
o One additional VTRbay, pluggable
*
*
Sony PCM 7030 DATrecorder.
Sony CDP 2700 CD player.
in the machine room
The VTmachines are all bay-mounted
on sliding rack trays, with sufficient
space for housing the deeper Pan asonic D3 machines in all positions.
The machine room Beta and one D3
as the edit record
Monitoring of the VTRs, locally in the
machine room, is aided by a FOR-A
quad split multiviewer, giving a confidence check of cassette tape position.
The suite went into service just before
Christmas 1992 and, after a short
training period, was used to edit and
transmit the current series of Reportage. The technical installation
was
managed by TE & PS and TSL was
selected to carry out the installation
work. It would not have been possible
to achieve the final service date without good co-operation from everyone
contributing to the project.
Tony Anstis, Project Manager
Post Production Systems
TE & PS
General uiew of Manchester's Edit Suite 5
24
ENG INF Spring 1993
Print'" by Illlfl -..000 NOKTON