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Bulletin issued by the Northern P.O. Box 1010
Branches of the Wireless Institute Launceston
of Australia, Tas. Division. Tas. 7250
November 1974 )
Vol.4 No 8
Registered at GPO Hobart
for transmission by post
as a periodical. Category B.
_MEETINGS
Nov. Northern Branch, A.E.B. rooms, High St,
Nov. - Council meeting, 2 p.m. at the QTH of Bill VK7AK
10 Reid St. ILaunceston.
Nov. 12 North West Branch, Lakins Hall Ulverstone.
Y.R.C.S.
Nov. Room 38, Kings Meadows High School.
This is the last meeting for the year.
CONTESTS
Nov. 10 Czechoslovakian C.W. and Phone contest
Nov,. 23/24 CO WW DX, C.W. contest
HAMFEST HAMFEST HAMFEST HAMFEST HAMFEST HAMFEST HAMFEST HAMFEST
NOVEMBER 16 and 17th at the Turners Beach Hall
Q.R.M. November 1974, Page 2
Northernnotes by ReqVK7KK.
The display of equipment last meeting kept the standard
up to previous ycars efforts. Its always a surprise to see
projects which pecople have underway, take for example Lindsay
ViK77ZID's series, a $7 chip LED digital clock, an I.C. C.W.
keyer with 4 I.C's and 16 diodes (not 200), an I.C. dice play
toy und his "Barlow Wadley" style receiver. Brian VK7ZBY showed
a recciver digital fredquency display, Peter VK7PF a commercial
VHF set and his teleprinter sct-up, Graemne VK7ZGG's double
side bund finals, Joe VKTZGJ a 432 Mhz transverter and Peter
VK7PG modifications to an AR7 receiver.
I wonder how much of a pile up will appear on 52,525 this
DX season? with the advent of the 60 MR6A's sold recently
there should be a major 1lift in 6 metre FM activity throughout ,
the state. Thanks to, particularly, Joe VK7ZGJ for his efforts
in sorting gear and compiling conversion information.
Ed VK7HE and his helpers are continuing to pour much effort
into investigating possible club house projects. For those who'
didn't make the last meeting, the current suggestion is the use
of a Launceston City Council building currently used by the
Civil Defence Organisation. The building in Upper Bourk St.
contains a room suitable for meetings, has ample room for
aerials and parking, and would be available for our use just
about anytime. It was suggested that we should build a room
onto the place for our use for equipment, this would cost
around $3,000 . Investigations are proceeding.
eO
Any thoughts on the New Years Eve function? One suggestion
is a barbegue at Evandale, or would you prefer to participate
in a cabaret. Social convenor Ed 7HE wants ideas HELP PLEASE.
This months lecture gives electrohics a rest and is
designed to improve your general education, don't miss it.
Remember too that the Christmas meeting is a barbeque.
December 6th at VK7HE's QTH - MARK IT.
Congratulations to:
Brian VK7RR on his recent engagement to Susan.
Malcolm Weldon and Mark Corbould on their pass in the LAOCP
examinations. I believe Malcolm is ready to go on air as
soon as his callsign comes through, with an MR6A low bander
which he converted to high band.
Peter Feltham has received the callsign VK7ZPE and can be
heard on 2m channel 48.
The J.0.T.A. mu8t have been quite a success,if the number
of stations heard are any indication. In the North the
following stations were noted, 7DK in Georgetown, 7BC in
Legana, 7NZ on Mt. Arthur, 7PG in Launceston and 7KK in West
Launceston. Also heard operating from the above stations were,
74H, 7PD and 7TZWW.
Q.R.M, November 1974, Page 3
North West notes by Max VK7MX.
.
What with Bulletins, Broadcasts and QRM it becomes increasingly
difficult to find new things to say. However we may make out
this month as the bulletin is in December.
Our October meeting was a gala affair with the biggest
attendance for years - around 36 present. Our worthy president
has certainly had an impact on branch affairs and it is
encouraging to see the boys backing him up.
Two notables in attendance were old-timers Frank VK7FH
and Bob VK7zAA, after so long it was good to see them again.
However there was a long list of visitors, newcomers and old-
timers. Visitors included Frank VK7ZFR from the North.
There was considerable business to get through and this
was followed by an offering of some very useful goodies, most
people availing themselves of a range of cheap components.
Once again some Morse practice was given by Harold VK7MZ,
Finally we were treated to a practical demonstration of colour
T.V. by Athol VK7IR., We were quite intrigued by the colours
up front and the multitude of circuitry at the back. Don't
know how many he placed that night.
One outcome of our meeting was the re-establishment of
the equipment store. However, henceforth it will be restricted
to cheap disposals and firm orders.
The Jamboree of the air has passed once again and a
number of stations participated in our area. As far as we
-
know those taking part were; VK7's AI, AX, EM, LH, MZ, MX, TT.
From reports some good contacts were made. This year we
confined the number per troop and at the same time tried to
select suitable voices and those with the wherewithal to
conduct conversation. This appeared to be an improvement.
We have two new licensees in our area. Congratulations
to Brian Lord and Adrian Sherriff. Don't know of any call signs
yet but they will be heard soon.
A visitor through our area recently was VK3YHU Peter.
Recently had the pleasure of a mornings fishing with Harvey
VK7ZYZ. The pleasure was confined to Harvey's company as it
poured with rain and results were nothing to boast about.
Better luck next time.
And finally don't forget the HAMFEST. It promises to be
a good show, and if the work going on indicates the shape of
things to come, it will be good.
Took note the other day that the turn off to Turners
Beach is just under one mile from the Forth River Bridge on
the Devonport-Ulverstone Highway.
So see you all at Turners Beach
MAX VK7MX
vk %kok ke k& deode ke kedeok ko keok ke ke ke
_ADIES/» PAGE
CHOCOLATE
QUEEN PUDDING .
2 cups soft white breadcrumbs % cup of sugar
2 eggs essence
% teaspoon salt raspberry jam
2 cups of hot milk 2 tablespoons of castor sugar
3 level teaspoons of cocoa
Plate breadcrumbs into a greased pie dish, cover with the
hot milk and leave to stand for % hour. Beat egg yolks, sugar
and 3 level teaspoons cocoa blended with a little water, add
to bread mixture with salt and essence. Bake in oven 400°
reset to 3509, until set (40-45 minutes. remove from oven and
spread with raspberry jam. Beat the two egg whites stiffly,
fold in the castor sugar and pile on top of pudding. Return to
oven to brown and set meringue (15 minutes).
Ann XYL 7NR
o ke dede g dkde de vk e d vk ok de e vok %k vk Rde e keok
VHF notes by Joe VK7ZGJ.
6 metre openings are Just around the corner so if your gear
isn't operating, now is the time to get it going.
According to the number of xtals ordered from Kevin we
should have around 30 units on 52.525 within the next month.
I am pleased to report that all the MR6A's have now been sold
and more than half of them should be operating for the coming
DX season.
Danny VK7ZDA appears to be enjoying the few openings we
have had on 2 metres recently. On the 2nd October he worked VK3's
ZUR, ZBB, AKC, BMD, ALZ,and AFW. Danny has been having regular
skeds with VK3AKC and VK3ZSJ, (Brian) who runs a Yeasu FT220
barefoot with excellent results. Brian also runs a FT620 on
6 metres into a 6 ell yagi.
On the 14th October Steve 3ZAZ, running 400W P.E.P. into
a 7 ell yagi 70ft high, worked Danny on forward scatter, signals
were around S3 bursting to S8 at times.
The 23rd was a very fine day and I noticed Danny once
again working VK3AKC, at around 21.50 local time Gregor VK3ZCG
was working through our repeater.
Hope to have more news next month, till then
73 Joe
Ge-R.M. November 1974 Page 5
H.F. DX Notes by DenVK7DK.
Listening time has been rather limited ffor me during
the mooth being engaged in home decorating and work,
but we did Jjot down a few calls heard. At the risk of
being repetative, I can only say once more that the
bands nhave been very chaungeable. On the 8th of October
There was a great deal of activity from all over the
world, aund that day was one of the few when 1t was
possible to work all continents in the period of half
an hour.
Jim S5WAAL is now at Zi7 and will be on for 7 weeks
using the call ot ZM7AI. I believe Jim will be on this
island with only the birds(feathered variety) to keep
him company. Tom Swi1AR will be operating from ZuM7 , on
3 different islands for 2 days on each.
The Chatham island expedition should be on and
possibly completed by the time you read this. I hope
those that require this country managed a SO with this
all YL DXpeditione.
15 has shown & little of its old self with & few
openings to Europe around 9pm local time. 10 metres has
been reported as being open to USA some mornings, but
I have not heard sny signals as yet.
20 metres has been heard to be reasonable, with times
and calls as listed below,
0000/0200z VU, JA, XU1DX.
02/0400z 5z4, OA, HK, LU7, CE, A35, VE, W, UA3.
04/0600z 0z7, YN, HI8, KS6, 8R1, 0OAL4, TI2, Sil.
06/08002 Gu6, ¥, G, I, W, OA, Di25K, FK8, DL,
JA, EA3, UO5, OK1, TI2, Y.J8, SM, PAd,
7X2, HB9, 3A2, CX3, KHO6.
08/1000z GR8AC, 9V1, DU1, JA,
10/14L00z Du2, VU, UK9 OH2, Uk2G, KG6, DU, U2,
s, JT, JA, LS7, KS6, Xw8, LA, FB8ZD,
(qsl to ¥8US), 9M8, HI, G3, VS6, DJ,
OH2, HKZBKX (San Andres isl, gsl WAGAHF).
14/1800z JA, F, UK5, Hz1, I,, DL.
18/2200z 0A, LU, 9YL, A35, kA6, YV, W, TI2, F, OK1.
22/2400z W, JA, HL, VU.
llost of these were heard in the early part of the
month, and the conditions deteriated, paticularly the
night time DX, as the month progressecd.
Ran into an old DX buddy of mine, ex VR2DK, . Owen
is now operating with the call of VK80Q0M, so those who
knew him keep a lookout for his new call.
That winds up the months activity, so lets look
forward to lots of DX this month,
73& DX
Q.R.M, November 1974, Page 6
LETS TALK ABOUT SPORADIC E
Sporadic E occurrence has, in recent years, undergone intensive study
and some of the findings with special reference to VHF communication are
presented here. There appear to be three main areas where Sporadic E
occurs - (i) along the magnetic equator, (ii) in temperate regions, and
(iii) in polar regions. (i) is well knowa and leads to trans—equatorial
propogation, while (iii) is unexplored and could well be worth investigating.
The 'normal' sporadic E experienced by the Australian amateur is the
temperate region variety and this is the one that will be dealt with. .
The E layer generally is about 100 km high and 2 = 3 km thick and is
found nearly always both at night and in the day. It is only when
irregularities of an intense nature occur in this E layer that DX
communications can take place. There are two main mechanisms involved in
DX communication namely (i) scattering and (ii) reflection.
The scattering mode is characterized by high attenuation (>45 dB) of
the signal, gradual variation in level (about 10 seconds) and fine and rapid
fading (about 0.5 sec.). The reflecting mode is characterized by low
attenuation (X 45 dB) and abrupt variations in a wide range of levels. The
course of events during a sporadic E event is for the scatter type to
appear first, then the reflection type (probably in combination) and, finally,
a reversion to the scatter type. The comments by some hams ghat 'the band
has not settled down yet" indicates the presence of scatter type prior to the
establishment of reflection type. In general the scatter type is due to
small irregularities involving high densities of electrons. The reflection
type is due to large (1 - 10 km), nearly horizontal clouds of high electron
density.
The angle of arrival differs and is narrower for the scatter type and
usually arrives at about 4 vertical elevation with a sharp fall-off above
and below this figure. The reflection type arrives between 2 and 6 '
vertically and over a wide angle horizontally, in fact for reception of
this type a narrow beam is a distinct disadvantage both in transmission and
reception. The reports of $9+ on "only a dipole old man" are to be
expected, not marvelled at. The area of reflection includes points
ceveral tens of km from the great circle path joining transmitter and
receiver, This wide angle effect diminishes as the stations are separated
but is still of the order of + 10 for maximum range, single hop than-
smission.
The variation in sporadic E occurrence follows the 11 year sumspot
cycle but in addition there are other regular variations. In the northern
hemisphere May to August is the normal "season" with a small subsidiary
maximum during December and January. The southern hemisphere shows a
reversal of this cycle so that the maximum occurs during local summer. The
diurnal variation shows a maximum in the late morning hours, usually around
10.00 a.m. and a secondary maximum in the evening which is more distinct
for latitudes further from the equator.
The reason for the generation of sponadicfhas not been fully
established but the commonest popular theory ds that it is caused by wind
shear and turbulence effects in the upper atmosphere although this is
insufficient on its own to explain all observed phenomena.
VK 700
Q.R.M. November 1974, Page 7
Putting the MR6A on 52,525. by Joe VK7ZGJ
Components required:
3 - 4.7 pF Disc ceramics 2 - 10 pF Disc ceramics
1 - 33 pF Disc ceramic 1 - 12 Pf Disc ceramic
1 - 10.905 Mhz Xtal, RX 1 - 2.188500 Mhz Xtal, TX
Originally the MR6A used a high IF, around 12 Mhz. This
put the local oscillator frequency on 65 Mhz giving you an
operating frequency of 77 Mhz. By leaving the oscillator on
the same frequency and setting the RF and Mixer stage to
"
52.525, only a very simple modification is required. This
entails placing a 4.7 pF disc ceramic capacitor across Ll
L2 and L3. Now switch the set on, place a 0-1 mA meter in
TJB receiver oscillator test point and tune the top slug of
TR2 for maximum, L6 for maximum and the bottom slug of TR2 .
for minimum. Because your 10.905 Mhz xtal is close to the
original xtal frequency, the stage should have oscillated
as soon as it was switched on and tuning should require no
more than one or two turns of any one slug to obtain the
correct reading.
To align the RF stage.
Tune the signal generétor to 52.525 and adjust for
centre zero on a meter 50-0-50 uA plugged into Disc. jack
TJF. Connect a 0-1 mA meter into the 2nd limiter jack and
peak L1 to L5, and the top and bottom slugs of TR1l, reducing
your signal as you peak each slug so that the meter does not
exceed 200 uA. Repeat the alignment of all slugs, to ensure
accuracy of tuning adjustments.
After alignment a 1 microvolt signal input to the
antenna terminal should give not less than 250 uA in TJD.
All this takes about ten minutes if you have the correct
equipment.,
The Transmitter.
Originally the transmitter used a 2 Mhz xtal and
multiplied 36 times to 72 Mhz. Because we wish to maintain
the original frequency, we reduce the multiplication to 24
by making the second tripler a doubler, and from this stage
we have to lower the frequency of the coils from 72 to 52 Mhz.
To do this place a 33 pF capacitor in parallel with the
existing 33 pF capacitor of TR10. This reduces the frequency
from 36 to 26 Mhz. Next place a 10 pF capacitor across L9 and
L1l and a 12 pF capacitor from pin 6 to pin 8 of V21 (QQE03/12).
Transmitter Alignment.
1) Disconnect screen resistor at pin7 of V21.
2) Plug a 0-1 mA meter into jack TJ6 (lst tripler grid).
press PTT and tune top and bottom slugs of TR8 for max.
3) Plug a 0-1.mA meter in TJ4 (2nd tripler) and tune top and
bottom slugs of TR9 for max..
4) With a 0-10 mA meter in TJJ (2nd doubler) tune TR10 for max.
5) With 0-10 mA meter in TJK (PA grid) tune L9 and L1l for max.
6) Re-connect screen resistor and connect wattmeter to aerial
connector.
7) Tune the PA anode capacitor C96 for maximum power out, then
re-adjust L9 and L1l for max. drive in (PA grid).
8) Gradually couple Ll14 aerial coupling link into L13 PA coil
keeping C96 tuned to resonance untill a power output of 10
watts is indicated with a PA anode current of 75Ma or less.
Q.R.M. November 1974, Page 8
Typical meter readings.
1st Tripler, -5 to -8 2nd Doubler, 1 to 1.4
2nd Tripler, .8 to 1.2 Drive 2 to 4mA
Adjust diviation and frequency with the appropriate
equipment. You are now ready to work a lot of DX mobile on
52.525 this summer.
Next month I will produce an A.C. power supply circuit,
suggested modifications and things to check to ensure years
of trouble free operation.
Total time for the above modifications is around 30 minutes.
khkhkkhkkkkhkkhkkhkhkhkkkhbikk
Whadayeknow, next month already.
Check the following resistors they may tend to go high
in value R7, 8, 14, 18, 19, 23, 30, 34, 38.
Cathode bypass capacitors on V9a, 10, 14, 16, all dry
out in time so replace them with 25 Mfd 25VW,
Here is a circuit for an A.C. power supply for the MR6A
6.3v b Amp Filansnrs
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300V 7o
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240V Ac. 7o Pr7 RelAy
And BiAs =
SoMF
v Kk kRdeokok KKk ek Kkokok kK -
FOR SALE FOR SALE FOR SALE FOR SALE
German PE2020 automatic turntable, original cost $245.00.,
automatic mechanism not operating, with handbook $70.00
AWA ST25 amplifier with quadraphonic adapter $80.00
AWA MRT25A with chrystals for ch.40 and 48, solid state with
valve final $120.00
AWA MR20B low-band, not converted $10.00,
All the above from Joe VK7ZGJ,
40 Lavender Gr. phone 443882
kK kv Kk ok K ks gk g vk kR
Q.R.M. November 1974, Page 9
SSTV _TEST PATTERN GENERATOR.,
by Kevin Henricks VK7ZAH
The need for this unit arose when I was experimenting,
some time ago, with SSTV sync seperator circuits. I required
a source of correctly timed synchronizing signals. At the
time I couldn't find a circuit for such a unit in any of the
usual magazines, so it meant designing my own or go without.
I designed my own and here it is.
It was decided early in the piece to use 7400 series
integrated circuits as they were readily available and
relatively cheap.
The block diagram of the unit is shown below and I will
endeavour to describe its operation.
§ms
'
7400 V+H Syme
74121 boms
S04
7400 7476
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7400
7492 74121
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This unit was designed for the 50Hz SSTV standards but at
a later date it is planned to run the unit from a xtal oscillator
so 50 or 60Hz may be selected.
The 50Hz input is taken from the secondary of the power
supply transformer, fed through a squaring circuit then to a
divide by three counter (7476 and 7400). The output of the
7476 is at a frequency of 16 2/3Hz which is the frequency of
the line synchronizing pulses. As the line sync pulse is
required to be of 5mS duration a monostable multivibrator
(74121) is triggered from the 16 2/3Hz with its duration set
to 5mS. So we end up with pulses of 5mS duration at a frequency
of 16 2/3Hz.
The standard number of horizontal lines for SSTV is 120,
therefore the line frequency has to be divided by 120 to obtain
field frequency. The 120 times division is performed by a
7490 (:10) and a 7492 (:12) to obtain a frequency of 1/7.2Hz
or 1Hz in 7.2 seconds, this is passed onto another monostable
multivibrator with its duration set to 30 milli seconds. So
from the monostable we have a 30mS pulse every 7.2 seconds or
a 30mS pulse every 120 lines.
Both the vertical and horizontal are now mixed in the
sync mixer (7400) which produces a series of pulses of correct
timing to synchronize the SSTV monitor.|
Q.R.M. November 1974, Page 10
The sync could be applied to a voltage controlled
oscillator, then filtered to remove frequencies above 3Khz.
The produced FM signal may then be applied to an SSTV monitor
but would only provide a raster at black or white, depending
on the type of modulator. To make the unit more usefull, a
test pattern generator was also constructed to produce the
following test signals:
1) vertical bars
2) horizontal bars
3) vertical and horizontal bars
4) dots
5) black
6) white
The block diagram is shown below. .
from squarer
50Hz
V+H Sync Vertical bars
Horizontal bars
from
7490
pfig 12 V+H bars
Vertical and horizontal sync are passed through a sync inverter.
It is necessary to invert the sync to negate video information
during the sync period. If this- wasn't done the spot on the CRT
would appear bright on retrace and interfere with the already
scanned picture. So this signal can be called blanking.
To produce vertical bars the blanking signal is mixed with
the squared 50Hz signal which will appear on the monitor as
3 cycles of black and white or putting another way 6 alternate
black and white vertical bars. To increase the number of
vertical bars the 50Hz signal must be increased in frequency.
This could be done when the xtal oscillator is used to drive
the S.P.G..
Horizontal bars are generated by applying blanking and
the output from the 7490 (:10). These two signals produce
alternate blackand white horizontal bars of 10 line duration
on the monitor.
The next pattern is a combination of the two previous
signals,
The fourth test signal produces white when the vertical
and horizontal bars coincide, thus producing 12 rows of
3 white dots. .
©
Q.R.M. November 1974, Page 11
For a black picture ecarth is applied to the video select
switch and for a white picture +5V is connected to the switch.
From the video output of the video select switch, video without
sync appears. The sync must be added to the video before the
signal is applied to the FSK modulator.
The sync video mixer modulator unit discribed works, but
there¢ is a lot of room for improvement. The principle of the
sync video mixer is to produce a signal which has different
D.C. levels for sync, black and white, to drive the voltage
controlled oscillator. Without the mixer, sync has an extremety
somawhere around -5 volt and video is ¢ volt for black and
about +5 volt for white, so the FSK modulator can not
differentiate between the black level of sync and the white
level of video because they are at the same D.C. level. The
sync video mixer, mixes sync aad video, sync appears as g volt-
and white at a level of some arbitrary positive voltage. At
intermediate levels of voltage various shades of grey appear.
The video varied voltage is used to drive the voltage
controlled oscillator, which consists of an astable multivibrator
with R.C. time constants varied by the applied voltage, which
of course varies the output frequency of the oscillator.
The output of the oscillator is of square wave form and is
therefore rich in harmonics. To reduce the output bandwidth
of the oscillator a low pass filter should be used, followed
by a transformer to make the output signal something like
a sine wave.
As stated previously there are sections of this unit which
could be improved, namely the method of deriving 50Hz input
signal and design of the modulator.
It has been decided to design the input circuitry so that
50 or 60Hz standards may be selected and derive the input
frequencies from a xtal oscillator. To do this a xtal on
probably 3Mhz will be used and divided to the required
standard.
For the modulator, a phase locked loop V.C.O. will be
used and operate at 4 times the normal frequency. The video
information will be fed to a 741 I.C. which will connect to
the voltage control input of the oscillator. This will produce
various tones for various video shades. When sync is required
the phase locked loop will be locked to the 4800Hz oscillator
in the input circuitry and produce sync frequency of very high
accuracy. The output of the oscillator is then devided by 4
and fed through an active filter to limit the bandwidth.
Kevin VK7ZAH
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November 1974, Page 13
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