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Amateur
Television
Handbook
By John L. Wood, G3YQC and Trevor Brown, G8CJS
Acknowledgements
The British Amateur Television Club expresses its gratitude to the following companies, societies
and individuals who have provided material and assistance for this publication.
Blean Video Systems, Canterbury, Kent
Plessey Semiconductors Ltd., Swindon, Wiltshire
Radio Ref. Paris
Radio Society of Great Britain, Doughty Street, London
Wasco Electronics, Queens Street, Leicester
C. Browabridge
M.Chamley
M. Crampton
C. G. Dixon
A.Emmerson
J. Goode
A.F.Wood
F3YX
G8DLX
G8CGK
G8PTH
G3RDC
D.E.Jones
J.Lawrence
T. Mitchell
R. S. Roberts
R.T.Russell
N. Walker
GW8PBX
GW3JGA
G3LMX
G6NR
G4BAU
G8AYC
© British Amateur Television Club, 1981
This special A4 sized edition edited by Ian Pawson, August 1998
Editors note:
This book was originally printed A5 size. This version has the same content, but has
been rearranged to A4 size. The quality of some of the diagrams and pictures is not up to our usual
standard as they have been scanned in from an original paper copy.
Amateur Television Handbook
Page 1
Contents
Contents
Acknowledgements............................................................................................................................................................................... 1
Contents ................................................................................................................................................................................................. 2
Preface.................................................................................................................................................................................................... 3
Principles ............................................................................................................................................................................................... 3
Scanning ..................................................................................................................................................................3
Television Standards................................................................................................................................................4
The Modulating Waveform......................................................................................................................................4
Bandwidth and Channel Space ................................................................................................................................5
The Station...............................................................................................................................................................6
Aerials .................................................................................................................................................................................................... 7
Feeder Systems ........................................................................................................................................................7
Receivers................................................................................................................................................................................................ 9
The ELC1043 Series Tuners....................................................................................................................................9
A High Performance Wideband Tuner ..................................................................................................................10
An Amateur Television Receiver...........................................................................................................................12
Transmission........................................................................................................................................................................................ 16
Video Modulators ..................................................................................................................................................16
A Modular Linear Amplifier..................................................................................................................................16
Vision Sources..................................................................................................................................................................................... 20
An Electronic Character Generator........................................................................................................................20
Page 2
Amateur Television Handbook
Preface
Preface
Amateur television is a large and complicated subject
and to do justice to its many facets a book of several
volumes would be required.
Amateur television handbooks in the past have tried to
cover as many subjects as possible and consequently,
due to size limitations, each subject has been treated in
rather less detail that one could have wished. The
original conception of this handbook was to deal in
greater depth with the more complex and in some cases
less-well publicised techniques used in the modern
amateur television station. You will therefore find less
information on basic principles, aerials, operating
techniques,
licensing
requirements
and
even
transmitters, all of which are adequately covered in
books and frequently found in magazines. Instead,
emphasis has been placed on subjects such as modern
receiving systems, electronic video sources, vision-
processing techniques and of course colour television.
These subjects are particularly susceptible to changes in
modern techniques and innovations and therefore the
designs need to be periodically up-dated.
The newcomer to ATV has not been forgotten however
and a chapter explaining such things as the composition
of the modern TV signal and the organisation of an
amateur station has been included. There is also
guidance on aerials, feeders, simple receiving
equipment and colour television principles and it is
hoped that this information will adequately augment the
large amount of already published data in other books
and periodicals.
Almost all of the projects in this volume have never
before been published and indeed some were designed
especially for this book. Printed circuit boards will be
made available to the constructor in order that the more
complex circuitry may be successfully built by less
experienced constructors. The video projects are all
compatible with each other and the PC boards have
been made to a standard size and use standard edge
connectors that enable them to be installed in a
card4rame cabinet system if required. This ensures
complete flexibility and permits the use of only those
units that are required.
The British Amateur Television club is pleased to
present this book in the hope that it will encourage and
stimulate television amateurs throughout the world to
strive for technical improvement and will help
newcomers to enjoy this fascinating hobby.
Principles
There are several methods of picture transmission; high
and low definition television, slow scan television and
facsimile (FAX) for still pictures, pictures built up using
radio teletype, and so on. This book is mainly concerned
with high definition television and sets out to describe
the equipment necessary to build a modern amateur
television station.
The broad principles involved in television transmission
are well known, and this brief review is intended to
highlight many of the important features of a modern
system which are dealt with in full detail in the
following chapters.
All forms of picture transmission
and reception differ from normal
‘seeing’ with a human eye in one
important respect, the human eye
uses
about
150
million
simultaneous channels of visual
communication, but an electronic
system uses only one channel at
any instant in time, consequently a
process termed ‘scanning’ has to
be used whereby the visual
information to be transmitted and
received is explored bit by bit and
translated into electrical terms for
modulation of a transmitter. The
received signal is demodulated and
used to build up a reconstituted
picture on the screen of a cathode-
Amateur Television Handbook
Page 3
ray tube.
Scanning
To simplify the explanation we will consider a picture
made up of only eight lines and displaying a black
square in the centre of the screen.
Scanning requires, firstly, that the picture to be
transmitted is framed in a field of view having an
‘aspect ratio’. The standard aspect ratio for television is
4 x 3 units, as shown in Fig 1(a). It is seen that the
actual picture size is of no importance so long as the
aspect ratio is correct.
Principles
Fig 1(a) shows a scanning spot that traverses the field
line by line, (similar to the manner in which we read a
book page), translating the variations of light and shade
(and possibly colour) into voltage variations which are
used to amplitude-modulate the transmitter. The camera,
with its optics and electronics carries out this operation.
At the receiver, a CRT beam is swept across the face of
the tube in synchronism with the camera scan, and the
demodulated signal is used to modulate the beam
current, thus writing a reproduction of the picture
scanned at the transmitter.
the field. There are many reasons why amateur
television should follow existing broadcast standards,
not least of which is the availability of receivers. There
are two UK broadcast standards, the original 405 line
‘black and white’ system A, and the later 625 line
system I which includes colour. Both use an aspect ratio
of 4 x 3, and both transmit 25 pictures per second. The
highest modulation frequency generated during
scanning in system A is about 3MHz, whilst 5 to
5.5MHz can be generated in system I.
Any TV system can include a sub-carrier with colour
information, the normal 625 line system uses a colour
sub-carrier frequency of 4.43MHz. A black and white
system does not of course require a colour sub-carrier.
The Modulating Waveform
The scanning system output will be used to amplitude-
modulate the transmitter, and it is necessary for the
receiver tube beam to be in the same two-dimensional
position as the scanning beam in the transmitter camera.
As stated earlier, a single communication channel can
only handle one bit of information at any instant of time
but, in addition to the video information, it is necessary
for the transmitter to send synchronising information to
the receiver indicating the precise position of the
scanning spot in both horizontal and vertical planes.
Fig 1(b) shows the voltage obtained by scanning (say)
line four of the picture. Because electronic circuitry
cannot respond instantly the changes from white to
black and from black to white at the edges are not
sharply defined. To improve
resolution the spot is made
smaller and the number of
lines increased.
Television, in dealing with
moving pictures, requires a
complete scan of the field to
be so fast that, compared with
any movement taking place in
the scene, each complete scan
is of a virtually still picture.
Standard broadcast television
in the UK scans 25 pictures
per second.
All
broadcast
television
systems use a technique
called ‘interlaced scanning’,
this means that the screen is
scanned and every other line
is displayed onto the screen,
during the next scan the in-
between lines are displayed
thus completing the picture.
Referring to the eight line
picture in Fig 1(a), interlaced
scanning would require that
the complete field would be
scanned by lines 1, 3, 5 and 7
and then the gaps would be
filled by re-scanning the field
with lines 2,4, 6 and 8.
Television Standards
Picture quality is determined by the scanning spot size
and, therefore, the number of lines required to fully scan
Page 4
Fig 2(a) shows the modulating waveform during a one-
line scan. The video signal varies the transmitter output
according to its amplitude. Time is taken from the
complete video line scan by ‘blanking’ the video signal
Amateur Television Handbook
Principles
for a fraction of the total line period. During the
blanking period a line-synchronising pulse is inserted
which takes the transmitter output from 30% to near
zero. This pulse is processed in the receiver to ‘tell’ the
sweep circuits when to start the line scan across the
CRT face. When the line scan reaches the bottom of the
field, a field blanking pulse blanks several lines and a
train of broad pulses are inserted during the blanking
interval (Fig 2(b)). The receiver processes this train of
pulses to return the CRT beam to the top of the display
tube to retrace its vertical sweep.
Fig 2(a) shows what is termed ‘positive’ modulation as
used in system A, in which peak white corresponds to
maximum transmitter output. The 625-line system I uses
the same principle but an inverted waveform (‘negative’
modulation) is used in which sync tips drive the
transmitter to maximum output, and peak white is near
zero.
cycles) is inserted on the back porch, together with the
timing associated with the line blanking pulse.
Bandwidth and Channel Space
Television is characterised by the need to handle very
high video frequencies throughout the system from the
camera to the receiver, and this includes the aerial
system Amplitude modulation of the transmitter would
produce the normal double sidebands which, for system
A, would require a channel space of about 6MHz, and
up to 11MHz for system I. Including a sound channel to
either system would increase the channel width by about
another 1MHz.
It was realised very early in the history of broadcast
television that the heavy demands for channel space
would limit the number of available channels, and a new
system for saving channel space was evolved and called
‘vestigial sideband’ (VSB), or ‘asymmetric sideband’
For a black and white system, a complete picture
requires two cycles of video and synchronising
information, as shown in Fig 2(b). Colour requires, in
addition, further information in the form of a ‘burst’ of
about ten cycles of sub-carrier on the back porch. This
burst experiences a phase change on every line and,
although interlacing is completed in two scans, the
complete cycle of blanking, pulses and colour-burst
phase requires four fields, as shown in Fig 2(c). Fig 2(d)
shows how the burst of colour sub-carrier (about ten
Amateur Television Handbook
(ASB). Fig 3 shows the channel spectrum for one
system I channel. VSB involves filtering off a large part
of the lower sideband, leaving only about 1 MHz or so,
and an overall channel width (with guard bands) of 8
MHz. With suitable tuning of the receiver IF circuits
distortion of the vision signal by the loss of part of a
sideband can be reduced to negligible proportions.
The bandwidth required for a single system I channel is
8 MHz. The 2-meter band is thus quite unsuitable for
television transmissions. The 430 MHz band can only
Page 5

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