1

THE BRITISH
AMATEUR
TELEVISION CLUB
Committee Members and Club Officers

PRESIDENT MAILING LIST Gordon Sharpley G6LEE/T

R .S . Roberts G6NR Lewis Elmer G6AGU/T 52 Ullswater Road,
6 Atterbury Close, Flixton,
CHAIRMAN West Haddon, Urmston,
Malcolm Sparrow G6KQJ/T Rugby, Lancashire .
64 Showell Lane, Warwickshire . Tel . Urmston 8031
Penn, Wolverhampton, Tel, West Haddon 324
Staffordshire . James Cunningham
Tel, Wombourne 3037 EQUIPMENT REGISTRY 3 Ramsden Road,
Alan Watson London,
GENERAL SECRETARY "Somerby View" N11 3JE .
Joe J . Rose G6STO/T Bigby,
Pinchbeck Farmhouse, Barnetby,
Mill Lane, Lincolnshire .
Sturton-by-Stow, Tel . Searby 287
Lincolnshire .
Tel . Stow 356
C Q - T V i s pub-
MEMBERSHIP SECRETARY lished quarterly by the
Nicholas Salmon British Amateur Televi-
11C
Obb Olds" sion Club and is posted
Magdalen Laver, Cyril Chivers free to all members .
Nr . Ongar, Mortimer Street, Single copies are avail-
Essex CM5 OEE Trowbridge,
Tel . Moreton 309 able from the Editor at
Wiltshire . 25p each ; back numbers
Tel . Trowbridge 28148 are also available to
TREASURER
Alan Pratt members at reduced pri-
Dave Lawton G6ABE/T ces .
10 Grammar School Road, 79 Kingsland Road,
Brigg, Boxmoor, Overseas members
Lincolnshire . Hemel Hempstead, may have their copy of
Tel . Brigg 3014 Hertfordshire . C Q - T V sent by air-
Tel . Hemel Hempstead mail, for a surcharge
EDITOR C 0-T V 50516 . depending on their coun-
Andrew Hughes try . Details are avail-
93 Fleetside, John Lawrence G6JGA/T able from the Treasurer .
West Molesey, 40 Aberconway Road,
Surrey KT8 ONQ Prestatyn, Members wishing to
Tel . 01-979 9983 Flintshire . have material published
Tel . Prestatyn 3255 in C Q - T V should send
SALES & LIBRARY the manuscript and draw-
Grant Dixon G6AEC/T ings to the Editor ; art-
"Kyrles Cross" Nigel Walker G6ADK/T icles are invited on all
Peters tow, 1 Eva Road, subjects of interest to
Ross-on-Wye, Gillingham, amateurs and should be
Herefordshire . Kent . of about 1500 words ;
Tel, Ross-on-Wye 2715 larger articles should
be divided into conven-
ient Parts for public-
COVER PHOTO Colin German GM6ADU/T and his 3 cm equipment . ation in consecutive
issues of the journal .
 z

EDITORIAL CONTENTS

As you will see from the report in this Committee Member's Addresses page 1
issue, the 1972 B .A .T .C . Convention was a tre-
mendous success and our thanks must go to all Editorial page 2
who were responsible for organising it, and
especially to the I .B .A . for letting us again Video Line Amplifier page 3
use their Headquarters . A new committee was
elected at the A .G .M . in the afternoon, but as Sine Wave Multiburst Generator page 3
this magazine closed for press before the
committee meeting necessary to arrange new Letter from America page 5
officers, the names printed on page 1 are last
year's officers . C Q - T V No . 81 will contain Postbag page 6
a list of new officers for 1973, until then
the old ones will continue to do the work . Integrated Circuits Part 10 page 8

Gordon Sharpley G6LEE/T who wrote the 'In- Ideas for Amateur Colour Part 4 page 15
troduction to Slow Scan' in C Q - T V No . 79
dropped a big clanger (his own words ;) when 1972 B .A .T .C . Convention page 13
he attributed the first use of FM to WA2BCW .
In fact it was John Plowman G3AST who first 3rd World SSTV Contest page 20
used this system and won the Courtney Price Tro-
phy for original work in this connection . B .A .T .C . Constitution page 22
He later altered his circuits to AM to be com-
patible with Cop McDonald for his transmissions Adverts page 24
on Ten Metres, but after the early transat-
lantic hook-ups, the American Hams started to
look seriously at FM, and hence todays stand-
ards . Our apologies must go to G3AST for our
most serious mistake .

Those of you who use the 70cm band will

find the announcement from the M .P .T . printed
on page 6 very important . There is still
room for a 625 line channel, but please do be hadn't been too busy preparing an "over the
careful about sidebands- they musn't be allowed air" lecture from the top of the Great Orme
to spill over outside the band . Some work is near Llandodno . However, in C Q - T V 81,
being done on filters for amateur use, and we not only will we print "Circuit Notebook
hope to publish details soon . One point No . 12" but also a report on the portable /T
which should be borne in mind is that 435 - expedition .
438MHz are allocated for international sat-
ellite use, and even though in U .K . only fre-
quencies around 435 will initially be used, it
might be a good idea to note when a satellite Ken Wood, K611S, of 17576 Pinedale Avenue,
Fontana, California 92335, U .S .A . has published
is around and not occupy the band for that
short time . a "Bibliography of Amateur Television, Slow
Scan Television and Facsimile" which he intends
If anyone wants a 525 line S .P .G . for to update during December ; he would therefore
$21 .75, the Hughes Aircraft Co . I .C . No . be grateful for any information which may be
of use in this work . Amatuer, Club and Private
HSUB0525 contains all the circuitry necessary publications would be welcomed, and it is in-
except the colour subcarrier generator . The tended to include all available information
only snag is it is sl small it might get lost . from all countries so as to provide a ready
reference to all Amateurs world wide . Copies
Our congratulations must go to John Law- of this bibliography are available from Ken at
rence GW6JGA/T for winning the Practical Wire- the above address on receipt of sufficient
less Designers' Trophy for 1971 . The winning postage . With a weight of 6oz, 76cents or four
design was John's "Digital Frequency Counter" International reply coupons is sufficient for
published by Practical Wireless last year which European subscribers for surface mail .
some of you may have seen . In this magazine
John's series "Circuit Notebook" has now been
running since November 1969 and would have
made it's three years in this issue if John THE EDITOR
 VIDEO LINE AMPLIFIER A SINE WAVE MULTIBURST GENERATOR

by David Wilkinson .

This circuit was sent to C Q - T V by R .A . Rowe, Recent correspondence (C Q - T V 78) has

who thought it might be useful to readers . He shown the shortcomings of generators us-
himself has used it and found it to be very ing square waves . This generator, which
good . is very simple to make, uses sine wave
oscillators .
As can be seen from the performance table, the CIRCUIT DESCRIPTION
circuit provides a very satisfactory perform-
ance for a general purpose amplifier with a This multiburst generator produces a
useful gain . Should be quite cheap to build white level burst and sinusoidal burst at
too : 1,2, and 3 MHz, though other or extra fre-
quencies could readily be accomodated .
Faichild uL914 I .Cs are used throughout,
plus two transistors .
The circuit consists of a chain of
monostable multivibrators which produce
successive pulses approximately 12 usecs .
long . These provide the white-level burst,
together with gating pulses for the 3 osc-
illators .
Each oscillator uses half of a uL91L
as a Hartley oscillator followed by the other
half as a buffer amplifier . This is gated
ON by the B pulses . However, it is desir-
able that the bursts be coherent from one
line to the next ; this is achieved by stopp-
ing the oscillator, during the blanking
period, by means of the positive-going pulses
A from Tr1 .
The oscillator outputs are combined in
a resistive network, together with the white
level burst, and amplified by Tr2 .
CONSTRUCTIONAL DETAILS
As it was desired to construct the whole
unit on a 5" x 3" plug-in Veroboard, it was
necessary to select the values of a number
of the components, whereas preset pots . would
have been more convenient .
The oscillator coils were constructed
or wire-ended ferrite cores .
Some adjustment may be needed to achieve
linear operation of the buffer half of the
I .Cs . It will also be noted that the indi-
vidual level setting pots . affect the level
of both the sinewave component and the d .c .
pedestal simultaneously . It might be thought
desirable to separate these functions ; but,
in practice, it is possible to make minor di-
fferential adjustments by shunting one of the
resistors by a few pf . This again takes up
less space .
Whilst the unit makes no pretence of
conforming to professional standards, it will
be found to be extremely useful for rapid
checks of video circuitry .
Further details on multiburst generation
will be found on page 13 of C Q - T V No . 77
in the article by D .J . Long G6ACH/T .
 5

Letter from
America . by Ron Cohen K3ZKO Philadelphia .

Crystal controlled receivers and trans- the same city . Most U .S . amateur tv men use
mitters are the popular topic over here at the J-Slot 8 over 8 or 10 over 10 aerials origin-
moment, in fact, it's the greatest boon ever ally made in Britain but now made by the
for us, getting more people on the air and in- Antennae Specialist Co . They are most rugged
creasing activity fantastically ; we've never and the best performing antennae we know .
had so much before! And it's all so easy . One amateur claims a 20dB gain for his new
4 quad Yagi, and he has written a description
Everyone uses the same frequency, crystal of this aerial in A5 magazine .
controlled in both transmitter and receiver .
The advantage of this is that it eliminates one On the subject of 70cm, we in U .S .A . are
variable, tuning and makes DX contacts up to behind Britain and Europe at the moment - but
100 or even 150 miles quite possible . One only we are fast catching up . In Britain any amateur
needs to orientate one's narrow beam antennae with a high QTH near the centre of the country
to select a station and there's no need to tune . is King ; But here in the States we are working
Video and audio go on the same frequency thus on repeaters to get over the long distance pro-
eliminating one transmitter (or removing the blem of a large country - between Philadelphia
need for a subcarrier) and decreasing bandwidth . and New York and Philadelphia and Washington
This helps us as our 420-450MHz band is very are two that are planned, and one in Chicago
congested with tv, fm, sideband, and CW . Pic- is well established and working well . We bel-
tures are 3MHz bandwidth, and the transmission ieve that using the crystal controlled trans-
system is fully described in the current issue mitter and receiver concept a repeater system
of A5 magazine . will be easily accomplished .
Both signals come from the aerial on the
same frequency, but at I .F . the video signal
is extracted by feeding into a tv receiver
tuned to channel 4 . The audio is taken off
when the signal is amplified in a normal a .f .
stage, via a squelch circuit . Thus one can
watch broadcast television, until one hears
a voice in the speaker calling C Q ; then it is
only necessary to switch the receiver to
channel 4 to receive the amateur tv pictures .
Sensitivity of the receiver is 0.2uv using a
low noise transistor pre-amp taken from the
ARRL Handbook (with AF239s) which is much better
than the 10-12uv performance obtained by a con-
verter .

Even though there is only one frequency,

stations are able to have more than one QSO
at the same time - even several 2-way QSOs in
the same city . By the use of narrow band
aerials, amateurs in one part of a city need
not interfere with others in other parts of
 6

I am the editor of "A5" Magazine, a jour- THE 70cm BAND.

nal which at the moment is supplied with art-
icles by enthusiasts from the Philadelphia area .
We hope to issue with "A5" soon a directory
of amateur tv'ers throughout the USA, possibly
even throughout the world . This is difficult -
for instance, our only list of B .A .T .C . mem-
bers is years out of date' Future issues will
publish circuits of transmitters and receivers The Ministry of Posts and Telecommunica-
(much needed here, although a transmitter need tions have announced that with effect from 1st
only cost 330 if bought) and special effects January 1973, the 70cm Amatuer Frequency Alloc-
units to enable mixing, wiping, inserts, keying, ation will be ammended and become 430 - 440MHz
matting e tc . t o be carried out . subject to certain geographical and power lim-
itations .
Work at the moment here is being carried
out on our next project, which is duplex work- 432 - 440MHz will continue to be avail-
ing, i .e . simultaneous transmission and recept- able to amateurs on the same licence and con-
ion of pictures . ditions as at present whilst as from January
1st 1973 430 - 432MHz will also become avail-
73s to all in B .A .T .C . able to amateurs except in the area bounded
Ron Cohen K3ZKO between latitudes 53' and 55' North and long-
itudes 3' West and 2' East . In practice for
UK amatuers this means the area enclosed by
a line drawn between Tynemouth in Northumber-
land to Longtown in Cumberland to a point
three miles south of Wrexham in Denbighshire
to Boston in Lincolnshire the other boundary
being way out in the North Sea,

In addition to the geographical ban 430 -

432MHz may only be used with the A1, A2, A3,
F1, F2 and F3 modes of transmission and is sub-
ject to a 10 Watt maximum effective radiated
power limit .
PLUMBICON YOKES

A number of plumbicon yokes have found

their way into the hands of B .A .T .C . members
recently, and G6ADK/T has sent details,
printed below for the benefit of those who may
need them . The figures refer to the tags
on the yokes .

1 POST BAG
2 Line coils
3
4 Focus coils
5 Alignment Is
6 Field coils
7 Alignment 2a
-8 Screen
9 Line coils D .B Pitt of 1, Burnwood Drive, Wollaton,
10 Nottingham is interested in reviving the
11 Focus coils idea of low definition mechanical tele-
12 Alignmet1b vision, and would like to contact anyone
13 Field coils who has similar interests or who is think-
14 Alignment 2b ing along the same lines .

Line coils' resistance is 2 .5 ohms Ted Groves VK2KK in N .S .W ., Australia, writes

Field coils' resistance is 80 ohms to tell us that he is active on all bands
Focus coils' resistance is 4 Kohms and is just itching to turn those warbling
With 675 volts on the wall anode, the sounds on 14 .23OkHz into SSTV pictures . We
focus current required is 14mA . hope your copy of our new booklet "Slow Scan
 7

Television" will help you to get going on lector with no signal processing . The out-
slow scan as soon as possible . Ted sent us put is fed via a short length of 16 wave-
this little rhyme - we thought you'd all guide to a 4" horn antenna . . It is much
like to read it : simpler than a 70 cm transmitter .
A wonderful world it t'would be "The home brew 625 line vidicon
If we could solve politics, with I .C .s : camera also runs from a 12 volt battery and
draws 0 .8 amps . It is crystal controlled
Leo Gary W9VRV of Chicago . U .S .A . has recen- by a pulse generator which draws 0 .4 amps
tly joined B .A .T . C . and sends these details at 6 volts .
of his gear . Video comes from a transistor-
ised camera and the transmitter has a 500w "On the receive side, I have a 2 foot
video input on 440MHz and 250watts input home made adjustable dish on the roof,
audio on 444 .5MHz . This is fed through a with a waveguide feed to a radar receiver
duplexer to an 80 element slot antenna . modified for wideband FM with a 30 MHz IF .
Welcome to B .A .T .C ., Leo ;
"When the equipment was tested over
a six mile path the signal was not suffic-
ient, but there are two ways in which I
intend to increase the range . The first
is to increase the gain of the receiver ;
at present this is insufficient to show
noise on the monitor so obviously could
be improved : Also I intend to make another
2 foot dish for the transmitter, from the
same mould as the receiving dish .

"In case anyone is interested, old

radar sets including Klystrons, wave-
guides etc, can sometimes be obtained
quite cheaply from ship breaking yards ."

This is probably a UK record for

3 cm transmissions, and our congratulat-
ions to GM6ADU/T .

The picture below shows the 19" bay

in the shack, with 3 cm, 70 cm, HF and VHF
Colin German GM6ADU/T in Midlothian, Scot- equipment .
land has sent some details of his 3cm rig .
One Saturday in September Colin took his
portable camera and transmitter a quarter
of a mile from his home QTH and transmitted
pictures over this path for a period of
two hours . Vision frequency was 10,050MHz,
F5, deviation +2 MHz, transmitted power
25mw and quality was very good . The site
had been specially agreed by the M .P .T .
'ADU/T writes "The cameraman had no monitor
but was able to adjust the camera effect-
ively by instructions received over 2metres,
in a similar way to the method used on the
Appollo missions . My helpers on this test
were GM3OWU, GM3ZVB, GM4AOR and GM8BJF ;
I also had this link working over a path
of a few feet at the last Scottish vhf
Convention .

"The transmitter, which measures

6" x 5" x 4", uses a KS29A Klystron (sim-
ilar to the 723A/B) . It operates from a
12 volt battery and draws 1 .5 amps ; a
transistor do convertor supplies the 300v
H .T . and the composite video signal from
the camera is applied direct to the ref-
 8

INTEGRATED PART

CIRCUITS
A.CRITCHLEY Dip El ; C Eng; MIERE .
OP . AMPS . and BRMs .

Unfortunately, the change of gain with potentiometer angle

This tenth part in the series on ICs continues with
Operational Amplifiers and describes the TTL Binary Rate is not linear but if Rf (or Ri) is made a linear variable
Multiplier 7497 together with an application using both resistance then the change will be linear from zero to
Rf/Ri. („r Rf/Ri Fn A)-
types of IC to generate a digital field scanning waveform
for Slow Scan use . A substitute for a retriggerable
monostable is also described .

Virtual-earth voltage adder

The virtual-earth adder can be used to add several
voltages together with differing gains for each input .
Each gain is imply RJR -
Non-linear Amplification

The basic Op Amp circuit has the two resistors R£ and

Ri but there is no reason why either of these should not
be replaced by some other device - active or passive .

For instance, if a voltage dependant resistor (VDR)

is used to replace Rf the amplifier has a high gain for
The inputs may of course be either low-level signals but a low gain for high-level ones .
positive or negative and this is This is because the resistance of the VDR decreases as the
the basis of a vision or sound voltage across it is increased - to the extent of about
mixer . the fifth power of the voltage . This arrangement can be
effective as a null-detector or a volume compressor .
The input voltages can be
fed to the non-inverting terminal as well to effect
subtraction without the need for an invertor but things
begin to get a bit tricky when this sort of thing is done
since the main is now :-

i .e . it increases with every

additional input resistance
on the inverting input .

Whilst the individual input gains remain constant, the

total gain depends on the number of inputs, etc ., so for
more than a few the calculations become rather lengthy .
By putting the VDR in place of Ri instead, the opposite
Variable gain control effect is obtained ; that of a volume expander .

It has already been shown that the gain of an invertor Another non-linear device is a diode . This has a
is proportional to Rf/Ri (i .e . the Op Amp has nothing to do square-law relationship between current and voltage over
with it ) . By making Rf and Ri a potentiometer the gain a small voltage range but is difficult to employ with
can be controlled from unity to A (the open-loop gain) . guaranteed results in a non-linear amplifier .
 A much better non-linear device is an ordinary transistor Gamma can be obtained quite simply with a log/antilog
connected as a diode . This can maintain its logarithmic combination by using the mathematical approach :-
characteristic over as much as a nine-decade range of current
The effect occurs only for one polarity of voltage as might
be expected . When reverse-biassed the resistance is very
high and the gain of the Op Amp is also high . To overcome
this a se condary transistor of
complementary type can be used
in parallel . There still
remains a 'dead-spot' of some
0 .6 volt per transistor before
each transistor turns on .
However, this is contained
within the feedback loop and
the Op Amp effectively reduces
it to 0 .6/A or a negligible
amount . With planar transistors
the reverse-bias across them
So by taking 40 % of the log output and then taking
should be limited to some 5 volts
the antilog the signal is raised to the power 0 .4 . To
This can be done by attenuating
use this system with simple control a secondary path is
the Op Amp output as shown .
provided for the signal without any non-linear effect
such that the peak white-to-black voltage is the same .
A mix from one source to the other allows a smooth intro-
duction to the Gamma effect .

This form of Gamma control can also be used with

negative film, etc ., if the log signal is amplified instead
of being attenuated . In both cases good quality Op . Amps
are essential . (Note, the amplifiers require only one
diode as the correction is unidirectional in a video signal)
One problem with Gamma correcting amplifiers is that the
gain is theoretically infinite at black level - giving
high amounts of noise in the blacks and some form of level
system is required to prevent signals below a certain level
anti-log characteristic . from being affected at all .
It is now possible to perform
mathematical calculations in analogue form by using these
two circuits and a voltage adder Reactive Feedback

If the feedback resistor, Rf, of the basic Op . Amp is

replaced by a capacitor then the amplifier gain depends on
the ratio of the capacitive-reactance to Ri . For high
frequencies the gain will be low - in fact the gain is
inversely-proportional to frequency .

This system can be put to use as a gamma correcting

amplifier . Gamma is the term used to denote the law
relating light and voltage in cathode-ray tubes and camera
pick-up tubes . For a CRT it is of the order of 2 .2 and
the effect is to crush the
whites in the picture . This is therefore an integrator, but it differs from a
For a vidicon it is about simple CR network integrator in that there is considerable
unity and for a photo-cell gain at low frequencies and dc . If a do voltage is applied
it is unity (i .e . it is to the input it causes a change at the output of the Op Amp
linear) . The Image-Orthicon which triesto oppose the input because of the negative feed-
has a variable gamma of about back . At low frequencies, though, the NFB is negligible
the right amount - 0 .5 so the output changes slowly towards A .v . and soon saturates
To give correctly contrasted the Op Amp output . This means that the i amplifier saturates
pictures of unity Gamma the for any voltage greater than a very small amount . This
pick-up tube and camera has steady voltage change is in fact at a linear rate proportional
to have a Gamma of 1/2 .2 or to CR and is known as the characteristic time .
about 0 .4 - it stretches the
blacks . For example, a 1µF and a 1Kohm gives 10-3 secs/volt or
1 volt in 1 me . A typical Op . Amp would saturate at 10 volts integrator one is Ri .Cf . If a frequency is chosen such
in some 10 ms . that Ci .Ri _ Rf .Cf then at this frequency the gain will
be a maximum (of Rf/Ri) . This arrangement provides a
The linear change of voltage with time is very useful differentiator with hf loss which attenuates noise .
if the amplifier is not allowed. t o saturate by ensuring that It is a kind of tuned filter . As an integrator the
the input currents are balanced properly . circuit is stable and free from do drift .

If the input to the integrator is made a squarewave

voltage then the output voltage will be triangular and of
a voltage proportional to the input frequency . A sawtooth
can be obtained if the input voltage is made a pulse shape,
but the best way to obtain a sawtooth is to discharge the
capacitor at regular intervals with some, sort of a switch .
The Binary-Rate-Multiplier7497

This IC device is basically a six-bit serial binary

counter ( :64) with additional circuitry to extract the
input clock pulses according to both the state of the
count and the states of six inputs . The output of the
7497 can be any number of pulses from 1 to 63 from the
input 64 . That is, it reduces the pulse rate to some
fraction between 1/64 and 65/64 .

If the capacitor replaces Ri instead of Rf the circuit

becomes a differentiator which has a rising frequency
response . The problem now is that the gain is a maximum
to pulse edges and the amplifier saturates immediately with
a slow return to zero voltage . The return is linear but
the system tends to be unstable and it is usual to have
another resistor across the capacitor to limit the hf gain
to Rf/Ri .

Inductors can be used in place of the capacitors but

the integrator then becomes a differentiator and vice-versa .
Inductances are 'difficult' components anyway and are best
avoided in IC circuits .

The differentiator and integrator can be combined in

a circuit which wives a differentiator with hf roll-off .

The reduction of pulse rate is achieved by the omission]

of certain pulses from the sequence . If input F is made
low then one pulse is omitted (position 32), input E
causes two pulses to be omitted (positions 16 and 48), e tc .
as in the diagram . The output sequence is therefore
The differentiator time-constant is Ci .Rf and the irregular and not suitable for frequency division .
 rate at which the output can be varied is the oscillator
frequency/64 . It would be tricky to achieve TV lire
rates with a satisfactory waveshape .

Using a Down-counter gives a reversed staircase but

the same result can be more easily obtained by means of
an output inverter .

The title of Multiplier is seen to be rather misleading

as the device is actually a divider .° SLR SCAN-DIGITAL VERTICAL SCAN

For normal use the input-enable and strobe-inputs are This is an extension of the use of a six-Lit Binary
made low as is the clear input . The Z-output then consists Rate Multiplier to handle seven bits for 120 levels in a
of negative-going clock pulses with some missing . The Digital-to- Analogue convertor .
Y-output is the inverse of Z (if the unity-cascade input is
made low)
The IBM is fed with high-frequency clock pulses of
very short duration via a differentiator so that the
If the input clock pulses are positive then the Z-output output consists of narrow positive pulses at the Z output .
is still negative . These may, or may not, be joined by low voltage levels in
the normal manner . The output can be considered as wide
negative pulses with narrow gaps and varying numbers of
these negative pulses are missing . The average do o£
the output depends upon the number actually missing_ and
the clock frequency has no part in the do voltage . The
six gating-inputs are fed with the six Most Significant
Bits of the counter so that the output do voltage would
have 64 discrete voltage levels . However, the count is
reduced to a total of 120 for Slow Scan use and so the
do voltage has only 60 levels . The output for a cont-
The devices may be cascaded to cover 12 bits or more inuous count is a rising staircase .
by connecting the Enable-output to the Enable and Strobe
inputs of the following device . The Z-output is also The Least Significant Bit is handled separately as
connected to the Unity-cascade . follows . The BRM Enable-output, pin 7, has a negative
pulse present '.which occurs once only for the 60-pulse
An output of 64%64 may be obtained from Y when the BRM sequence and this is inverted and gated with the output
is inhibited by the strobe, by connecting the Unity-cascade from the counter LSB and a square-wave from the input to
to the Clock input . the BRM . The resulting output in a negative pulse once
per 60-b-t sequence of one half the normal duration - if
There is a decimal rate multiplier version of the 7497 the LSB is positive . That is, for every other input
with the number 74167 . pulse to the counter the output Is a pulse of a 120th of
the 60-pulse sequence . This is the equivalent of a step
in voltage of one 120th the total output every other pulse
The BUM can be used to make a simple Digital-to- and since the 60 levels each take two pulses to mange,
Analogue convertor (D-A) . Each output pulse from the the result is a 120 level staircase corresponding to 7
bits .
BRM is made almost a whole clock-pulse period by making
the input clock pulses narrow and positive through a
differentiator . The frequency source is of no concern
as long as it is of a high frequency

The output pulses are integrated by a simple CR

network so that the average do of the output varies
between some 4 volts and 0 volts according to how many
pulses are omitted or passed . In practice the voltage
does not descend to zero because of the finite width of
the input clock pulses .

The D-A directly converts a digital state to an

analogue voltage so if a counter is attached to the six
inputs the output voltage will be a 64-step staircase
if the counter is fed with a steady source of clock pulses .

There are two snags to this very simple system .

Firstly, the IC costs some £6 and secondly the maximum
 Various refinements are added to enable the scan to
be stopped or inverted and a pull-up resistor of 1 KU
makes the output voltage almost 5 volts peak-to-peak.
The pull-up resistor does not have this effect directly
on the PPM output pin and this treatment is not recommended
except on ordinary gates .

A 741 Op . Amp . is included to convert the 0 to 5-volts

staircase to a -l0-volt one with which to drive the scan
coils .

FURTHER NOTES ON THE CQ-TV SPG GENLOCK SYSTEM .

There is no reason why this system should not be used
for Slow Scan line scan too except perhaps that 120 steps The performance of the Genlock system with helical
may not be enough in the horizontal direction . The raster scan Video-tape recorders is generally satisfactory but
would in fact be a dot matrix of 120 x 120 dots rather than
when a poor quality machine and tape are used the Genlock
120 lines . The amount of integration shown is not critic] is not sufficiently rigid, indeed, it sometimes will not
except that it should not greatly affect the scan flyback
lock at all
. The effect shows as ragged lines and the
time . To keep this small the clock frequency must be of field twitches or may not lock .
the order of several MHz and a two-stage integrator may be
of use here . In fact, the 741 can have a capacitor put The basic causes are tape drop-out and noise spikes .
across Rf to do the same job .
The spikes do not upset the field superlocking but because
they occur between line pulses they do upset the genlocking
bistable in its generation of squarewaves and this causes
the master oscillator to receive sudden error voltages
which make it change frequency . Whilst this is usually
Retriggerable Monostable Substitute only enough to cause a line twitch,it may upset the SPG
generation of field pulses .
The 74123 retriggerable monostable is a very useful
device but unfortunately is rather expensive and difficult Many VTRs have a head changeover period during the
to obtain . An effective substitute can be made by using field blanking interval and the resultant noise and spikes
a shift register and oscillator system . get through the genlock system via the equalising pulse
detector because this depends for its operation on narrow
The oscillator is used only as a clocking source for pulses .
the shift register . The serial input of the shift register
is connected to +5 volts via a 1 KU resistor to enter a 1 The bistable can also be upset by missing pulses and
into the first stage . This would normally appear sequent the nett result is that the odd line or two is missed out
ially at all the other outputs ; however, the clear input i of some fields by the SPG counter system . This in turn
also used to prevent this happening unless the time between means that the field pulses, which turn on the superlocking
clear pulses is longer than the time taken for the 1 to system, arrive rather early . The SPG then is open to
progress down the register to the output stage . being falsely reset by noise - causing a vertical jump of
the picture because the SP0 makes two fields in rapid
So if the input clear is fed with closely-spaced pull succession .
the shift register output remains low . If the pulses are
widely spaced then after'n'pulses the output goes high and What can be done about it? The speed of response
stays high until the next pulse arrives . This is exactly of the correction voltage can be reduced by increasing the
what a retriggerable monostable does to the input pulses . 2 .2 µF capacitor to some 47 µF, or the 470 Q resistor in
series with the 220 pF capacitor reduced . However, this
The actual period of delay depends on the number of ruins both the pull-in speed and range and is not very
shift stages and the frequency of the oscillator . This effective anyway .
is a random frequency but the delay period can be more
accurately defined if the oscillator is stopped during the An alternative is to reduce the loop gain of the
time that the input pulses are low - if the pulses are of correction feedback by increasing the 2 .2 KU output resistor
a guaranteed width . thus giving less effect at the oscillator.
 There are two easier and better ways, however . The The only way to overcome the problem is to redesign
bistable can be largely prevented from toggling in both the mainslocking system using a sample-and-hold type of
directions by feeding the internal reference line syncs correction voltage generator .
to the clear-input instead of to the NAND-gate to mix it
with the external pulses . This means that the bistable For those amateurs wanting a slow roll-in of the field
now acts as an R-S bistable requiring alternate input rather than a superlock it is hoped that a practical circuit
pulses to give square-waves . Repeated clear pulses will may be given in the next issue of CQ-TV .
now give no more than a single half-line pulse of error .
In the latest version described in CQ-TV 77 this means
using the line sync + a line after the two-input HAND-gate .
This connection may be merely added to the clear-input in
Crystal Oscillator system for the SPG
fact as it will over-ride itself at the clock-pulse input .
It may be necessary to swop over the Q and Q outputs of
the 7473 . Several people have enquired about a suitable crystal
There is also the problem that the clear-input
must be unused during mains or field-pulse locking . oscillator and divider system for the 15Q-TV SPG so here is
The
solution is to add another pole to the control switch . one . The counter shown is a typical one but the actual
Afurther slight improvement may be obtained by earthing division ratio depends upon the crystal frequency .
the K-input to stop the bistable toggling more than once
per line .

The second method, which may be done as well as the

first, in to remove the output feed from the equalising
pulse detector to the superlooking system so that only
broad pulses are used . These are wide pulses which are
less sensitive to disturbances than the equalising pulses
and their detection system ignores both spikes and missing
pulses . The snag is that the SPG will lock up 22 lines
late - down the picture . (the lines will still be phased
correctly so that the fields are in fact in error) .
Whether or not this matters greatly is up to the user -
at least the fields will be stationary .

These modifications will. take care of all but the

worst signals from VTRs . Further improvement can be
effected by reducing the bandwidth in the sync separator
by increasing the 100 pF capacitor .
The system of gates at the end of the counter should
be retained whatever the counter ratio as a direct feed
For those who have yet to try the mains locking system
is required for the Genlock board but a switched feed for
here is a simpler squarer to replace the two transistors . the SPG .
It cannot be put on the Genlock board though .
The oscillator circuit will work with most crystals
of between 1 and 10 MHz but will not work with the glass-
enveloped types of twice-line frequency . Do not forget
to decouple the 5-volt rail close to the oscillator and
counter stages . Two .1
0 µF disc capacitors should be
sufficient .

Protection of output stages of SPG

When the SPG is used to drive other equipment there

is always the possibility that the coupling capacitors
may, at switch-on or switch-off, charge or discharge into
the ICs voltages in excess of the IC's ratings with dire
The mainslocking system used in this SPG relies upon consequences .
the filtering of a 50 Hz square wave for the correction
voltage fed to the master oscillator . As a result there The problem can be prevented by the use of Zener diodes
is always some portion of this fundamental frequency across the pulse outputs as shown . The Zener diode does
present in the correction voltage no matter how good the not normally conduct as the IC output voltage maximum is
capacitors . This manifests itself as a 50 Hs phase-mod- less than the Zener voltage but any sudden increase in
ulation of the lines resulting in wavy verticals . voltage is limited to this Zener voltage - the diode
Unfortunately, there is no simple cure for this other than passing the charging current of the capacitor . If the
using picture monitors without flywheel line sync . The voltage goes negative then the excursion is limited to
normal type of line scan easily follows the phase modulation -0 .6 volt since the diode then acts as a normal silicon
and the verticals are vertical . diode .
 the coil with the decoupling capacitors at any frequency
within the normal passband of the ICs otherwise the effects
will be magnified instead of reduced . This is one reason
why IC circuits have only a small value of Lf decoupling
capacitor - usually some 10 µF or so . Another reason is
to allow the regulator to regulate at a high speed .

Comments on the CQ-TV SPG

The author would be pleased to hear of any comments or

criticisms about the SPG and Genlock systems .
Mains interference

Thermostatically-controlled soldering irons and other

mains equipment can cause high-frequency interference spikes
on the mains which get through the regulator onto the #5 V
rail and upset the SPG counters . One method of reducing Acknowledgement
the problem is to fit a Zen- diode across the 5-volt rail
as shown here . This limits the spikes to the Zener voltage The author wishes to thank the Directors of EMT Sound
in the positive direction . It is important to ensure that and Vision Equipment Division Ltd . for permission to
the diode passes no current in normal operation by picking publish these articles .
its voltage high enough above the rail voltage to allow for
component tolerances otherwise the supply will disappear Next issue
down the zener .
The next issue will contain more about Op . Amps, and
Another interference suppression technique is the use how to use them. Some other kinds of Linear Ice will be
of a small RF choke in the 5-volt rail where it enters mentioned also . OIL seven-segment decoders and indicators
the board . The value must be small to avoid resonating will be described .

BOOK REVIEW by Arthur W . Critchley . the binary system and compares RTL,TTL and ECL Integrated
Circuits . It then describes the 54/74 series TTL in
"Designing with TTL Integrated Circuits" detail, including Schottky-clamped TTL . A thorough
analysis of TTL follows which explains all about current
by the IC Applications Staff of Texas Instruments Inc . sinking, threshold, types of output stages, loading rules
Edited by Robert L . Morris and John R . Miller . and Schmitt gates . Next is a section on Boolean Algebra
Published by the McGraw-Hill Book Company in the Texas and Karnaugh maps and how to combine logic for various
Electronic Series, Size l 0j x ?-1 x 1 inches . Price functions including code convertors . There is a chapter
about £8 .90 on bistables (flip-flops as the Americans call them -
bistable is much more definitive)
. Decoders are mentioned
At last - a good book about TTL ICs . It gives just as are arithmetic devices and counters of many types and
the kind of information that is required and gives ,_t in shift registers, The book finishes with a chapter about
a very practical manner with plenty of diagrams, circuits various applications .
and explanations .
Altogether this is quite the best book I have seen
The book starts off by introducing digital logic and about TTL ICs and I highly recommend it .
 Ideas for Amateur
Part 4 G6 Colour ADK/T T r

For those of you who may be interested in over before the end of field blanking . There
greater detail in the mixer described in the should, of course, be a sufficient number of
last issue of this magazine, this article con- clock pulses to , clock the shift registers to
cerns itself with the switching logic used by the last output . The switcher relies for its
the unit . operation on the fact that a button remains de-
pressed for a period of at least 20ms, but in
Figure 1 shows the master switcher which practice it is found that this is easily achie-
selects one of the ten channels when the app- ved ; in fact, however hard you try to catch it
ropriate button is depressed ; Figure 2 shows out, it always seems to switch correctly .
the waveforms that are used to drive the swit-
cher . The timings are quite non-critical, The master switcher can be used on its
providing they are such that the switching is own if it is situated close enough to the cut
amplifiers . However, if a remote control pan- Here are some notes on the Video Combin-
el is required, a slave switcher can be made ing Unit of the mixer, as printed in C Q - T V
which switches in step with the master . This No . 79 . The base of the output emitter follow-
is shown in Figure 3 . er should connect to the collector of one of
the bottom TIS50's ; connection to the other
collector would result in an inverted output .
There should be two 1K resistors connecting
pin 6 to the positive supply, and also pin 9
to the positive supply . The rail should be
+24v, not 12v . A "741" can be used in place
of the LM310 shown in the circuit in C Q - T V
79 ; the connections are shown below .

H E L P F U L H I N T

Copper wire can be used as fuse wire if you

know the correct size to use . Here are a
few useful ones :-
1 amp 47swg 5 amp 38swg
2 amp 43swg 10 amp 33swg
3 amp 41swg 15 amp 30swg
4 amp 39swg 20 amp 20swg

Have you any helpful hints you feel other mem-

bers would find useful? Send them to the Edi-
tor for publication .
 18

1972 BATC
Convention,

The 1972 B .A .T .C . Convention was once

again held at the I .B .A . Headquarters in Lon-
don, after a four year absence, and with
about 200 members present proved a tremendous
success . A programme organised by our Con-
vention sub-committee of Don Reid and Ian
Lever went smoothly (as was to be expected of
such a team :) and the Club benefitted from a
very friendly meeting .

In the foyer of the Conference Suite

stands were run by the R .S .G .B ., B .A .T .C . Club
Sales and C Q - T V, as well as a Reception
Desk and a corner for members' sales and this
proved a very busy area all day . All down
one side of the main hall, and along one end,
a line of tables held individual members dis-
plays of equipment and these were so many
and so comprehensive that it is impossible to
describe them here . Some of the photos show Robert Skegg's 625-SSTV Convertor
what was there, and a very splendid display it
was .

During the afternoon three well known mem-

bers delivered short lectures on topics of part-
icular interest to amateur tv . Arthur Crichley
started the series with a very instructive talk
on Integrated Circuits . By now Arthur has be-
come our oracle on I .C .s and on this occasion
he proved that he still has more information
up his sleeve to give to us . His series of
articles in C Q - T V on digital circuits us-
ing I .C .s is soon to be published as a booklet
now that he has gone on to tell us about linear
I .C .S .

Nigel Walker G6ADK/T next gave a lecture

on colour television for the amateur, particu-
larly on his own colour equipment which was
very impressive . He gave details on circuitry
for coders, monitors, mixers, special effects
generators and mentioned his use of shift
registers for switching logic in vision mixers .
He apologised that he hadn't been able to
bring his colour camera along, but it wasn't Nigel Walker and his colour display
quite finished :
 19

G3RHI, Mr . B .J . Arnold gave the third lec-

ture, which was all about slow scan television .
His booklet on the subject was published on the
same day as the Convention, and as can be imag-
ined, it sold like hot cakes : Mr . Arnold's
lecture was an informal affair, with his aud-
ience clustered around him and his equipment
stand . Judging by the size of the crowd, the
talk was very popular indeed- your editor just
couldn't get near enough to hear!

The Annual General Meeting of the Club

also took place during the afternoon, the
agenda having been published in C Q - T V No .
79 . Chairman Malocolm Sparrow G6KQJ/T intro-
duced the meeting, thanking Don Reid for organ-
ising the Convention so well, and Bob Roberts
G6NR introduced himself to the Meeting, as our
new President .

The Chairman in his speech told of what

the Club had been doing since the last A .G .M .
two years ago . How the subscription had had
to be raised to meet inflation, how a member-
ship drive had been conducted to raise new
members, how an A .T .V . International Contest
had been organised, and how a series of nego-
tiations on licence conditions had been con-
ducted with the Ministry of Posts and Tele-
communications by Ian Waters G6KKD/T and
Jeremy Royle G6NOX/T . On this last subject,
the changes of licence conditions had already
been printed in C Q - T V, and the changes of
frequency allocation were expected to be annou-
nced soon as 432-44OMHz with 430-432MHz at
reduced power .

The Treasurer gave a resume of the Club's

financial situation, pointing out that although
we were still solvent, we were operating very
near the line and it was going to be touch and
go towards the end of the year . The main ex-
penditure was C Q - T V, costing about £600 or
more in a year ; Club Sales was non-profit mak-
ing, and thus if the new Value Added Tax raised
our costs significantly it might be necessary
to raise subscriptions . It was very much
hoped that this would not be necessary .

The changes in the Club Constitution pub-

lished in recent issues of C Q - T V were una-
nimously agreed by the Meeting, and on the fol-
lowing page you will find in full the current
Constitution . This it is hoped now covers all
conditions and will suit B .A .T .C . for some time
to come .

Alan Watson, the committee member respon-

sible for the Equipment Registry reported that
the system was working well and was fulfilling
a much needed place in the Club's operations .
Once more he begged members to enclose a
 20

stamped addressed envelope with their queries,

mentioning that several stamps would be use-
ful as often much correspondence was necess-
ary to meet a members demand . Still 90% of
forms received have only the "Requirements"
section filled in, not for the sale section,
and of course this limits the number of demands
that can be met . Alan made a special plea
for all B .A .T .C . members to look out their
surplus gear and send him details of the pieces
they don't want . Monitors and Plumbicons are
the most wanted items at present .

The entire committee stood down prior to

a new election, when Ian Lever, Ian Watson and
Cyril Hayward declined invitations to stand for
re-election . The rest if the Committee were
re-elected, together with James Cunningham,
Dave Lawton G6ABE/T and Nigel Walker G6ADK/T .
Fuller details of this committee are printed Arthur Critchley talking about I,C .s
on page 1 .

3rd World SSTV

Contest
Sponsored by cq elettronica Magazine

cq elettronica Magazine proposes the 3rd Worldwide Slow Scan Television Contest .
The purpose of this Contest is to promote increased interest in the SSTV mode of operation as
used by Radio Amateurs .

RULES
1) PERIOD OF CONTEST
1st 15 .00 - 22 .00 GMT February 10th 1973
2nd 07 .00 - 14 .00 GMT February 18th 1973

2) BANDS

All authorised frequencies on : 3,5 - 7 - 14 - 21 - 28MHz

3) MESSAGES

Exchangeof pictures and number of the message

 21

4) EXCHANGE POINTS

a) A two way contact with a station -receives one point (total points will be the
number of individual stations contacted) .

b) No extra points for the same station contacted on different bands .

c) A multiplier of 10 points for each Contintent and of 5 points for each country . The
ARRL Countries list will be used except that the W Call areas WO to W9 and the VE
Call areas from VO to VE7 will be considered as separate Countries .

5) SCORING

Total exchange points times the total of the multipliers .

6) PRIZES

1st A free 12 month's subscription to cq elettronica Magazine

2nd A free 6 month's subscription to cq elettronica Magazine
3rd A free 6 month's subscription to cq elettronica Magazine
Special SWL prize

7) SWL
This Contest is also for the SWL's

8) All logs must be received by March 20th 1973

Send them to : Prof . Franco Fanti
via A . Dallolio 19
40139 BOLOGNA Italy .

9) LOGS

Logs to contain : Data, Time(GMT), Frequency, Call sign, Number sent and received, Multi-
pliers Country, Points and Final score .

10) RULES OF BEHAVIOUR AND PENALISATION

The Logs must be compiled in accordance with the Rules listed in (9) . The contacts must
be made by means of the SSTV mode and it is not permitted to use other modes of trans-
mission either before, during or after the exchange of message by Slow Scan TeleVision .
Contacts will only be valid if the contacts are confirmed by the Contest Logs received
from entrants with whom contact has been made . During the Contest it is expected that
Amateurs will observe the fundamental rules of courtesy and good operation during con-
tacts . Failure to observe any of the above Rules will result in the exclusion of the
entry from the final results, and any such Logs received will be considered as check Logs .
All Logs received become the property of the Edition CD, and will not be returned .
The decision of the organising Committee in any dispute will be final, and any subsequent
controversy cannot be referred to the Civil Court .
 22

1972 BATC CONSTITUTION .

INCLUDING CHANGES AGREED AT THE 1972 B .A .T .C . CONVENTION .

1 . The Club shall be known as the B .A .T .C .

2 . Membership of the Club shall be open to anyone interested in amateur tv in the British
Isles or abroad .

3 . The Club shall be affiliated to the R .S .G .B .

4. A group may affiliate to the Club by paying a subscription as one member ; the affiliated
group then shall have one vote and be entitled to all benefits as if it were one member .

5 . A membership fee of ten shillings per annum, or other such sum determined by the Committee
and approved by a General Meeting of the Club shall be charged,, and this shall become
due on 1st January each year . If a member does not pay the subscription, then after
six months his membership shall cease .

6 . The Committee of the Club shall consist of the Officers of the Club, namely the Chairman, the
Secretary, the Treasurer, and the Editor of C Q - T V, together with any others the Committee
shall deem necessary (all of which are honarary appointments), together with not more than
fifteen elected members . All Officers and Committee Members having been in office for two
sessions (i .e . approximately four years) must retire, but shall be eligible for re-election .
The Committee shall have power to co-opt members of the Club to serve as Officers of the
Club or as Committee Members, but all such co-opted members shall be required to retire at
the next General Meeting . A minimum of half of the Officers and half of the elected members
shall retire at each General Meeting .

7 . Committee business may be transacted by post, and the Secretary is empowered to act in
any matter which has received the approval of three Officers of the Club, unless an ob-
jection is put forward by three or more members of the Committee . The use of the name
of the Club shall be solely at the discretion of the Committee .

8 . A President shall be appointed by the Committee ; such President to hold Office for not
more than four years ; retiring Presidents are to be listed as past Presidents of the Club .

9, General Meetings of the Club shall be held bi-annually at one of the Conventions which shall
be organised from time to time by the Committee, at intervals of not more than three years .
 10 . An extraordinary General Meeting may be called by twelve members provided they give three
months notice in writing to the Secretary . Such extraordinary General Meetings shall be
held in London and the cost of such a meeting shall be borne by the members demanding it
and not by the Committee .

11 . All Resolutions at the General Meeting shall be carried by a two-thirds majority of those
present . A Quorum shall comprise of thiry ordinary members apart from the Committee .
Only members whose subscriptions are paid may vote at a General Meeting .

12 . A Resolution for the disolution of the Club shall require a three-quarters majority of
those present . Any assets of the Club on disolution shall be distributed among the
members who have currently paid their subscription .

The sawtooth voltage present on pin 11 of a Both base and emitter can be decoupled and the
SN74121N monostable I .C . can be made extremely linear resistor R situated at a distance . The value of R can
by making the timing resistor into a constant current be 0 to 1M ohm . With the capacitor value shown and
source-that is, one where the changing voltage does not this range of R the monostable delay has a range of
change the current . Such a source is to be found in a 10uS to 10mS continuously variable . The sawtooth on
transistor where the collector current is constant with pin 11 has a linearity of less than 0 .1% . Voltage and
changing supply voltage if the bias is kept constant temperature stability are excellent .
(like the pentode valve) .
A very high input-impedance Darlington Pair is
The diagram shows how a transistor can be used used to extract the sawtooth in order to prevent the
for this purpose . A diode is used in parallel with the loading from worsening the linearity by shunting the
Vbe drop in order to minimize temperature effects by constant current source .
changing the base voltage to match the emitter voltage
drop . It is not essential though .
 24

MEMBERS ADVERTS

EQUIPMENT REGISTRY a very good cheap starting point for amateurs

can help out with your problems . If you wishing to build their own cameras .
have surplus gear, or if you want a particular
piece of equipment, send details (including a WANTED
S .A .E .) to Alan Watson whose address is on page
1 of this magazine . Spares for Phillips EL3400A/Peto Scott ET2610
video recorder, including service manual and
ADVERTISING RATES heads .
Back page £12 Teltronix 'scope, working or not, or Thorn
Full page £10 equivalent .
Half page £6
Members small ads free ; a charge of 10p per 1" video tape (Chromium dioxide preferably)
line is made to non-members .
For the above "For Sale" and "Wanted" adverts
phone 01 - 397 - 1230 after 8pm, or reply to :
D . Pattinson
31 Kelvin Grove,
FOR SALE Chessington,
Surrey .
A number of two inch video tape spools,
some empty, some containing reject tape .
These are free to members able to collect FOR SALE
from the address below . Hammarlund HQ-17OA/vhf amateur band only
communications, receiver . 160m - 10m with
A . M . Hughes 6m and 2m amateur bands . Recently over-
93, Fleetside hauled . £85 . o .n .o .
West Molesey Marconi Mk . III 4'' inch Image Orthicon
Surrey . camera channel, complete with 3 lenses and
handbooks . Offers are invited .
M . J . Sparrow
FOR SALE 64, Showell Lane
Penn, Wolverhampton
A quantity of TK204 Ikegami cameras with tube Staffs .
less lens, working £16 + postage

A quantity of Pye Lynx cameras with tube less

lens, working £25 + postage

2 8'-z " Beulah monitors, working £10 + postage

1 82" Beulah monitor less line output transi-

stor £8 .50 +postage

3 82" Beulah monitors less line output trans- 21 YEARS AGO IN C Q - T V

former and line output transistor
£5 + postage "Here is a late flash from Doug Wheele . As
he was walking down Lisle Street, he saw a
4 9" Ikegami monitors, working £25 + postage familiar tube in the window of a certain
shop . Sure enough, 'twas a 5527 Iconoscope .
6 16" monitors, working £15 .50 + postage And the price? 35/- : However, Doug felt
it was his good day, and offered the bloke
3 19" monitors, working £15 + postage thirty bob, and was accepted . He reports
that the tube appears to be brand new, works
2 23" monitors, working £13 + postage well and that they have NO more . . . . Happy
Christmas Doug :"
2 24" BRC monitors £13 .50 + postage (C Q - T V December 1951)
(New readers ; there's one in the Science
A number of Beulah cameras at prces from £8, Museum, go and see! ED .)
all with tube, less lens . This camera makes
 25

slow scan television

JUST PUBLISHED'

A new 12 page booklet on slow scan television

by B .J . Arnold M .A . G3RHI

Chapters on Principles, Background, Monitors,

F .S .S . and Cameras .

Circuit diagrams and constructional details .

ONLY 25p (plus 3p postage)

from
B .A .T .C . Club Sales .
"Kyrles Cross"
Peterstow
Ross-on-Wye, This booklet is the first of a series to be published by C Q - T V
Herefordshire . further issues will be announced in this journal and will include
a reprint of Arthur Critchley's articles on Integrated Circuits .

i N THE NEXT CQ - TV

Circuit Notebook No . 12

More on amateur colour

All the regular articles again .

A Reproduction of the B .A .T .C . Reporting Chart

on sale from Club Sales . The full-size Chart
measures 81 /2ins x 101/2ins and is printed on white
card .
 26
Club Sales Price List
Camera Tubes English Electric P849 Amateur grade €10 . 50
E .M .I . 9677 Amateur grade €10 . 00
9728 Amateur grade €10 . 00
(integral mesh) 1066.7 Amateur grade € 8 . 00
44 inch Image Orthicon 9564 or 9565
(older "sticky" type) €10 . 00
ex-studio vidicons as available € 5 . 50
Vidicon Deflection and Focus Coil Assembly `£10 . 50
Vidicon sockets (paxolin) 17P
Vidicon sockets (moulded) 25p
"C" Mount in Aluminium for use with cine lenses 50p
Lapel badges 20p
Lapel badges (with call-sign - to order only) 30P
Adhesive emblems (for decorating gear with Club badge)
Windscreen stickers 06p
B .A .T .C . Reporting Chart (A visual scale of video noise) 06p
B .A .T .C . Notepaper and envelopes (100 sheets) €1 . 50
Filmstrips of C Q - T V . 10 copies on each film .
(Please state which decade you require i .e . 31-40, 41-50 etc .) €1 00
Back Nos . of C Q - T V as available 25P (15p to members of B .A .T .C . for issues up to No . 69, and 20p
for issues thereafter)
Please send cash with order to :

B .A .T .C . Club Sales
"Kyrles Cross",
Peterstow,
Ross-on-Wye,
Herefordshire .

Printed Circuit Boards for the C Q - T V SPG

SPG Board €1 . 50
Genlock Board €1 . 50
Please send cash with order to :
A .W . Critchley Esq .,
70, Sussex Road,
Ickenham,
Uxbridge, Middx .
N 0 T E T H I S L I S T C A N C E L S A L L 0 T H E R S
P L E ASE

B. A . T . C . AND R E A D C Q - T V R E G U L A R L Y
J 0 I N

The Membership Secretary will send you an application form on request - ask for some for your

friends too .

For an annual subscription of only €1 .00 you receive this journal quarterly, can buy cost-price
amateur tv gear from Club Sales, and at the same time belong to an internationally known
British association dedicated to the cause of amateur tv .

So why not join now?