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A
I A
Bulletin issued by the lorthern P.0. Box 1010
Branches of the Wireless Institute naunceston
of Australia, Tas. Division. Tase. 7250
September 1974
Vol.4 No
o
k
i
!
Registered at GPO Hobart
for transmission by post Price 20€
Sl s
as a periodical. Category B.
o] ]l b
W TNy
il s iy IO
September_10th North #West Branch, Lakins Hall, Ulverstone,
NOTE the new date. All meetings .+ill be on
the SaCUND TUwsoDaY of the month.
September 13th Northern Branch, AiB rooms, High st.
Lecture by Roger Greenwood VK7UV, PMG
engineer, on TV translator networks.
September 14th Council meeting at the TH of V&7JV, 2pm
September 28th Social film evening at the Postal Institute
Hall, start 8pm sharp.
YRCS
September 27th room 38, Kings ileadows High school.
4 : there is no meeting during the school holidays.
CONTESTS
September 14/15 bsuropean phone contest
September 14/15 SAC CW contest
September 21/22 SaC Phone contest
October 5/6 VK/ZL contest (phone)
October 12/13 VK/4LL contest (Cw)
HAKS 3T HalFusT HAampuoT Haur so® Habifauol
November 14 and 15 Turnevs peach Hall
QeR.M. september 1974, fage 2
Horthernnotes by Reg VA/KK.
Perhaps there's still an interest in obtaining clubrooms?
A committee has been formed to investigate the feasability
of getting somethin. concrete decided in this regard, kd T7HE,
Norm 7HR, Bob 74RF and John 7JV will be advising us,in due
course, of their ideas. If you have any suggestions collar
one of these gents.
It wasn't wd's nighti He also now wears the hat of Social
Convenor. Its good to see ncmbers offering to help share the
work ioad wand no doubt instill further ideas.
attendance was better this month, 38 is rather more respectable
Phil Thompson's (755) talk on PuG radio telephone systeus was
well presented and pitched ut a level suited to all present.
Apparantly we now have a secret weapon against him - present
4 sniff of diesel fuel and he'll run a mile! Obviously the
most valuable object in some of those Cape Barren houses 1is
their Radio-Telephone. Thanks Phil for the trip to iKaatsuyker
and Cape Barren Island.
The R.D. contest is now dead and buried. If you disagreed
with the present rules concerning repeaters , 1 hope that
you'll make note of it on sending in your log. Dont sit back
and let others do your stirring.
Four members are awaiting the postman's knock after the
August AOCP exams, congratulations or better luck next time.
We must be made of moncy! The sranch buys a $20 ex DCa unit
and reaps 5004 profit. I wont put anyone into the doghouse
by mentioning names and prices but thanks for bidding
gencrously to swell our funds. After ed's succes as an
auctioneer he'll be charging a higher commission!
Noticed we have some people willing to assist in consumer
spending, Peter 7pPD and Bill 7Ah with new cars and Danny 74Da
is spending high with new electronics gear.
At the opposite end of the scale . seen Joe 74GJd's garage
recently? Steptoe's got nothing! Washing machines are his
latest exploit, they dont work, he's only flogging the bits!
Suppose there is a story behind the lack of a bumper bar
on Danny's verhicle but havent heard it.
Norm should have known he can trust Ch.48 listeners. Fancy
being worried about someone dobbing him in to Anne. Seems
on a recent North west trip he had a problem diagnosed as a
touch of food poisening. The only food he'd had was some
from home. All he worried about was upsetting Anne, he didn't
want her to find out. What a gentleman:
Incidently there's a big move going on in the 7NR household,
they are moving accross the river to west Riverside.
No doubt in cleaning up he'll find plenty of historical junk
for next years exhibition.
000000000000000000Cc00000
A.TeV. Camera
For those who would like to get on with the job, we have
included some more circuits of the ATV camera which we
started to discribe last month.
Due to lack of time we were unable to prepare the discription
and hook-up diagrams, these will be published next montn
The design of this camera is by Va2ipPi/T and has been
compiled by VK74FR.
circuits on 2uage 6 and 7
ERET R
Q.R.M. Seotember 1974, Pagze
I have just seen a revolution and I wasn't watching TV either.
OQur branch has been getting pretty lethargic, metaphorically
speaking. The sign of the times no doubt. Anyhow something had
to be done and who better to launch a renaissance, to coin a
phrase, then Tony 7AX. He reasoned, and rightly so, that a good
stir was called for and promptly got on with it. He pointed out
to all and sundry that our hranch is & co-operative affair run
by the members for the members, and the result was that we had
a pretty good roll up at the annual general meeting.
Before the election of officsrs the same gentleman addressed
the meeting with a fes suggestions and enthusiassm mounted.
S0 much so that it wasn't long before Tony was elected president
for the coming year. A very wise move as we all feel that with
RR
Tony's enthusiasm behind us we can look forward to a good year.
The election of other officers resulted in the following-
Vice President Terry VK7TT
secretary David VK7MS
Treasurer Graham ViL7ZAQ
QSL Officer Harold V£7i
Branch Correspondent Max VK7.X
Activities Committees Qrsham VEKT7ZAL
Sid VK73
Adrian sherriff
I was agreeably surprised vhen the meeting, after scue discussion,
decided that we would orgeanise th: Hamfest for the Division this
year. There was a definite vote in favour, and those who
supported it were formed into an orgacnising committee.
- --
This is good news and they are certainly getting on with it as
I heard something going on 2 metres a week later which indicotad
that a meeting was already under way to do the initial planning.
S0 keep that date free at the end of November and we will keep
you informsd on developments. It will be somewhat different
we think.
‘e have now got into the swing of the sunday Broadcast from
our branch. Perhaps someone else would like to tage part.
sid 7SF turned up at the meetins ©ith some real goodies from
overseas (lielbourne I think) and these were guickly taxen up
by the boys including some of the Northera visitors.
Which reminds me, we were pleased to welcome T7AK, 74BY, 7£F and
7JV, to the annual meeting. I am sure that they returned with
some new armtwisting ideas so look out Northeners.
A little bird whispered that a certain Ham has been stucik into
the tzll building at Sandy Bay. You Izuember the gee-gee
computer thingo, well ne is working on one to break the pang
down South. Hope its O.x. ON.
Peter 7PF has been hesrd in our =arza quite freguently, almost
a North wester agsain.
In concluding these notes there is ons very important notice
sB
to members, after many years our meceting nizht has been chanrzed.
It used to be the first Tuesday in the month, forget that.
It is now on the second Tuesday at the sasmz place, so that the
next meeting will be Szptember 10th. scee you all thers.
Max VRE7.X
i e
e Rolls September 1974
Page 4
H.F. notes by Den VK7DK.
With conditions as they sre it is difficult to know what
to write =sbout, but I Zuerss if the conditions were really
wide open it would be difficvlt to chose what to leave out.
Actually the Z0 metre band hae had a Tew good momente and
some very rare ones hafe popped up, such as P.ANS, on the
Pernando de Noronhas Isl. sl via PY7NS. He was heard oue
morning with a s5 signal. There was Crozet isl., FBRWR,
He was on one afternoon for a short time, but was frightened
off by the =normous dogpile that developed in minutes., Col,
VK7L%Z mansged a contact. Gonod work Cnl. The 20 metre band
opened to 4sia on the 20th of August, but wee back to its
normal guiet state next oight. You will notice that there
are no listings for 0800/1000z. Not because there are no
sige to be heard, but it happens to co-incide with my prime
T.V viewing time.
15 has h2d a little dx activity, mainly JA, KA etc. Only
two stations were heard on 410, snd bnth vere within 8 miles,
so hardly dx. Hi. Well , here are the ones I have heard ir
the 1lsst month.
80. W's vJ8, VR4, YBd.
Lo. Ja, OT2RL, G3A00, LZIBF.
20.
0000/0200z. TI2, HE9, VU2.
0£20/0400z. 4's VKZ, KGL, 541, HIS8, ,
0L00/0620z. I's, 3A2G6X(.Sivia I1SGL), 0X3, VRY, XE,
HR6, (Swan Iel), VE3/5/6/7, 7Q7, VKERKL(L.H.)
0600/0800z, EA6, LX¥1, DL, 3, 3G1, .i8s, Vi's, Sk, CR8AC,
\ FB8WB(;SL via ¥3US;.
1000/12002. VEHE, gL9, KA, JA, P29, SM, KL7, 0X3, DJY,
. and W' s,
1200/1400z. X&', LU, JA, VU, ¥YB4, VS5, #'s, VS6, OH6,SkES
! 0Y3X, CYZ(Ceneda), NJ9, AC3PT, XV5, 9X2,
w2, UKL, LA.
1400/1600z. OH, KA6,, DL, HS1, YO, SH5, UR2, HLS.
2200z PY@NS. LU7, G, (.
AW1AL 1s rumoured to be heading for ZL7. VEIYP on CCcos
igs active on 20 metres.9oratler Islend wes to he sctivated
but when within sight of the 1island, great sctivity was
noticed, end due to the recent contraversy over the islsand,
the operator decided thet degeretinn wns the hetter part
of valour. SV1GA/A, t. Athos, was Lo be on from aug 16,
but nothing has been hesrd Af this =tation from this 57,
%ith the coming of the gpring, the conditions should
improve somewhet, but thst remain-s to be seen,
The VK/ZL/Ociana conteet is on Getaber 5(phone), and Ci
on the 12th, (see A,R., Auguet). This contest cs&n bring
some of the rare countriceg, €2 make s note of these dates.
That about winds it up for this month, =92 good DX to
you all,.
Qe ReM. September 1974, lage 5
__SQCIAL _NIGHTOUT_
The film "2001 - a Space Odessy" will be screened on
Saturday, 28th September, at the Australian Postal
Institute Hall, 84 Cimitiere street, at the rear of the
I
District Telephone Office.
This is the filim version of Arthur C. Clarke's novel
"2001 ~ a Space Odessey" a futuristic science fiction
r-I
masterpiece by the man who predicted the use of
communications satellites in 1948 ana currently is a
scientific adviser to N.A.DJ.4.
r-I
The film runs for 2 hours and starts at 8.00 pe.u. sharp.
Bring the whole family for a night out. Good chit chat
after the film. Supper provided by the men, laaiss nexi
r-I
time.
(§1.00 donation for adults, a maximum of 32.00 for family)
r-z
0000000000000000000G00
r-I
VHE notes by Joe VK74Gd.
The 6UP state of the art contest provided plenty orf activity
on ém, it is surprising the numoer of people who will get up
r-I
at 5.45 to try and have a contact.
As luck had it, only one morning in tuenty I .as unuble to
exchange a report with another station.
r-I
VK2ZQJ was the most consistent stution, being worked 13 times,
24KY 5 times, 24YP once and we heard VK34.id once, I asswoe on
back scatter from a meteor shower.
r—;
On the morning of the R.D. contest wevin Vi74al workad roar
states, which is not bad considering the time of the year,
they were, VK24GJ and VK5 on 6m meteor scatter, VK3AKC on
144 hz forward scatter and of course VK7 on 6 and 2 metres.
[_1
Stations heard on 52,050 in the past month include VK7's
00, %AH, JV, ZGJ, 4GG, 4ZDA, 4BY, ZWX, ZIF.
73 Joe
[—1
[MI;[—X
0000000VIJUICI0000VLO0
Northern Sranch weeting sctivities.
Al ahalysis of Lorthern pranch meeting activitics ia
the period way 1971 to april 1974, indicates indicates
an average meeting attendance of 33 meiwers, Lhere wus
[h
also an average attendance oi >> members on Lecture aights.
Maximum attendsnce was 50 in June 1373, and mindipum
attendance was 24 on several occasions. as percentages
-
of the nwnber of meetings in the period, the following
activities occurred:
'
Lectures 43.0 %
e
Films 13.8 %
auctions 1160 G
ILA,
wguipment display 3.0 %
Nothing 19.0 %
Rte wally Va74wx
L
100.0 Lecture ofrficer
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Orviyners IV
Q.R.M. September 1974, Page8
Reprinted from "THE RADIO BULLETIN" Nov.-Dec. 1371
TRANSISTOR REGULATED POWER SUPPLY DESIGN
by John Reynolds, VK3ZMU.
1. Power Supply Specifications.
Voltage: Variable from 6 to 15 volts.
Current: Up to 5 amps DC, continuous.
Regulation: Approximately 1% snywhere within the voltage
range from no load to full load currcnt.
2. Initial Design Procedure. (see fig. 1.)
Working backwards from the load current, the series pass
transistor must be connected in the Darlington configuration
in this case, so that the gain of the series pass string enables
the output current to be controlled by a current many times
smaller.
For an output current of 5 amps, the base current of the output
transistor is 5/B amps. Since in the Darlington configuration
the output transistor base current is the same as the driver
transistor emitter current, the driver base current is 5/B1/B2
or 5/B1B2 amps, i.e. the gains are multiplicative. (This is why
this configuration is often called a Beta multiplier.)
For 4 transistors in the string, the driving current reguired
is 5/B1B2B3BY4.
To select Q1, consideration needs to be given to the current
handling capability, the gain at the maximun carrent, and the
dissipation capability under the worst operatisg conditions.
SupPPLy oureur
(5A)
fi = CuRREMT GRAIN
Comirollirg
CURRENT
(2;—2;—;‘—.>nnrs Fig.1. Basic Darlington
A B34 regulator circuit.
With the particular transformer used, the DC input to the
regulator was measured as being 24 volts at 5 amps load curreat.
The worst case in terms of dissipation occurs when the full
o
load current is flowing and the Vce of Q1 is a maximum: the Vce
maximum of Q1 occurs when the output voltage is 6 volts.
The maximum dissipation of @1, with 24 volts at the input is:
Pi= (24-6)45
e
18X5
90 watts
ETTYYaah
Q.R.M. ' September 1974, Page 9
Transistor type 2N3055 is rated at 115 watts dissipation at 25°C
With the transistor mounted on a LARGE heatsink (with a plentifull
amount of thick silicon grease around the washer), which should
be bolted onto the metal case, the dissipation should be held at
a safe level, especially if the maximum rating is not continuous.
At a current of 5 amps, the current gain of the 2N3055 is
approximately 20 (say 15 to be on the safe side).
Thus we require the driver (Q2) to deliver 3230 mA maximum.
The maximum dissipation of Q2 is:
P2 = (24 - 6 - Vbet1)X 0.33
o
17.4 X 0.33
5.8 watts upproximately
Since a 2N3054 costs around the 31.80 mark, it was selected; it
will handle 6 watts when mounted on a heatsink.
At a current of 330 mA, the current gain of the 2N3054 is about
25. Thus Q2 requires a base current of 13 mA at full load.
As the transistor driving Q2 will deliver 43 mA of emitter
current, it will have a dissipation of:
P3 = (24-6-(Vbei+Vbe2))X 0.013
158 X-0.013
220 mW approximately
Although most general purpose epoxy cased transistors are ratead
T A add T ad@2
for 300 mW in free air, it was thought best to use a metsl-cased
device with a greater safety margin. The 2N3053 transistor is
rated at 1 watt in free air, and 1is atle to handle the 13 mA
eagsily. It is therefore used as 23.
At 43 mA collector current, the 23053 has a gaian of about & 120,
Thus Q3 requires a base current of sbout 120 uA at full losd.
Characteristically of the lowest goin devices in the chain, the
actual current drawn may vary by up to <2:1 from this figure.
Now that the control current requirzasats ars known, the sensing
and controlling stage can be designed.
3, Sensing and Controlling Stage.
The driver chain (Q1-Q3) requires a base current of up to 200 ua
or so, at full load. Referring to Fig. 2, the controlling
transistor Q6, should draw at least twice, preferably ten times
the driver current, to ensure the best stabllity of control.
r - e = w e -
!
+$ufP[y . ' Ql’al.GB | + REqulared
© ourTpPur
(RAW)
Fia.2.
Q.R. M. oeptember 1374, rage 10
The sampling network in Fig. 2 can be a DC resistive voltaze
divider as in Fig. 3a. The disadvantage of this is that auy
variation of output is similarly divided before it reaches Q6.
If the circuit of Fig.3b is used, the zener diode exhibits a
very small resistance to voltaze variations, while still
performing the voltage dropping function. The voltage divider
ratio with the zener in the top allows a much larger percentage
of change to be coupled into the base of (6.
.f
oy : ZD
@ @”{ R32 ® %
Qb
Qb S
Fig.3. Types
ofvoltage dividers.
The exact voltage divider ratio is dependent on the swing of
voltage required and the zener voltages availsble.
Since the output will have a rangs of 6 to 24 volts, the worst
case is 6 volts. The differzntiasl sensing and control stage to
be used is shown in Fig.l.
VS J V our
Fig.4. Differential Seneing smplifier.
Consider the circuit shown in Fig. L. Also assume that Vg is a
fixed fraction of V out. Vout is controlled by the collector
voltage of @6, which is an inverse measure of the current drawn
through Q6 (i.e. as Ic Q6 goes up, Ve Q56 goes down).
Rc5 and Rcb are not large enough to limit the current srawn
through Q5 or Q6. Transistors Q5 snd Q6 will both drive emitter
currents into RE untill VE reaches a voltage which is:
VE = VREF -~ VBE (Q5).
Since VREF and VBE are constants, VE is also a constant. The
current from Q5 is constant azlso, so any variations in the base
voltage of Q6 (VB) will change the current in Q6 by changing
VB (Q6).
oStil etitiee st e e
B
i Q-R.M. ' September 1974, Page 11
m The changing current into the collector changes the collector
voltage of Q6, and causes a change in available base-emitter
voltage driving Q1, Q2 and Q3.
B
If the Vout rises in a positive direction, the VB (Q6) rises;
VE is constant, so VC (Q6) drops. The drop of VC (Q6) reduces
the total voltage across the base-emitter junctions of Q1-3,
and forces legs current through their collectors. As Q1 passes
B less current, thecollector-emitter voltage increases (it is
tending to turn of), and Vout decreases (provided the collector
voltage of Q1 is constant). In practice, Q1's collector voltage
B will drop with increased load current drawn, and the current
around the loop will stabilise at a value slightly higher than
expected.
Conversely, should Vout drop, VB drops, Q6 takes less current,
H enabling Q3 to take more current from Rcé and thus turn @ion
a bit more, thus reducing VCi and increasing the output up to
the original value, whereupon it will again be stable.
B The feedback amplifier Q1, Q2, Q3 and Q6 thus acts as a null-
seeking device, which will be nulled when VB is equal to VREF.
This 1s the principal of operation of differential amplifiers.
B « Designins the Differential Sensing
Since Q3 will draw 200 uA at full losad,
Stsxe.
let the current through
the transistor Q6 be say, five times that, l.e. 4 ma.
B The cifferential transistors should draw about ecuzl
(1 mA eacl,.
The voltage VE = 2 mA X RE is Zetermined by VaEr and
currents
74
H If VZ = VREF = 3.3v nominal, the two bases
equal voltszes for Vout = 6V, Yor nisher output volt.g:zs to
result, thz base is simply tupped down to ihe bottow. of the
will be at -sororxinat-l
_
voltage divider, so that the output must rise in order to
produce the same potentiul at the base of "gb.
Assumingz that Vikar = VB (@6) = 3.3V, then
-
VE = VRs - VBE («5)
= 2‘13 —Ooé
; 2e7V.e (=2 ma & Rs)
-
Therefore, R = 1.35K ohms (say 1.24) ‘
If the output range is 6 - 16 volts, then the voltage VC (Q6) is:
VC (g6) = Vout + VBE1 + VB2 + VBu3
nnu
6 to 16 + (3X0.6)
7.8 to 17.8 volts
The supply voltage for the differential amplifier is approximately
49 volts regulated, so the maximum voltage to be dropped across
RC (Q6) is:
VRC (Q6) VS-VGC
nunn
19 - 8 volts
11 volts
¥ith Ic (Q6) = 4 mA, then RC (g6) = ¥§C Q“j = %1 ma =11K.
Say RC (Q6) = 12K. also for best rejection of ripple on the
supply rail, RC (Q6) = RC (Q5) = 12k.
Q.R.M. September 1974, Page 12
#+ /9V (AP7ROX)
’ Fig.5. Design of
Regulator stage.
l 5 mA
Rref = R
_ 15.7K
—> uA = 5
/u = 303K
/N 33V
To keep VC REF constant, about 3-5 ma should be passed through
it. Since the regulating zeners produce noise, they should be
bypassed, 1 uF tantalum electrolytics are fine.
To complete the sensing cicuitry, the bias divider resistors
must be calculated.
The output varies from 6 to 16 volts. The junction between the
zener and the control pot varies from approx. 3 to 13 volts
about a 4:1 variation. With the pot slider at the top, the
output voltage will stabilize when the potential is 3 volts,
i.e. when Vout = 3v + 3,3v = 6.3v. This is close enough for
the moment to satisfy the lower extreme of voltage.
With the slider at the bottom end of the pot, the output
voltage will stabilize when the potential on the slider is 3v.
When this is so, the voltage at the output is reguired to be
maximum, i.e. 16 volts.
Referring to Fig.6, when Vout = 16 volts, VX = 13 volts approx.
V our %
SOVY=3V=R-K—;_§R—B— X 13 volt
Or, 3RA + 3RB = 13 X RB.
=MIN, x
ouUTPUT RA = 10RB = 3 33 RBe
“» = 3 = °
A= 5 = 20’_2.& & n_
&
RA If RA 2+5K, then RB 5. 35 750
o
SuUTPUT = MAx.
RB
Pig.6. Bias Resistors.
I . -
e - '
Q.R.M. September 1974, Page 13
L At this stage the circuit of the complete regulator is as in Fig.7
" Q1 = 2N3055 (on heatsink, NOTE: sampling leads are taken
I ) Q2 = 2N3054 (on heatsink5 direct to the output terminals
Q3 = 2N3053 via sepersate wires which do not
G4 = 24010, 283565 etc. carry the load current. This is
= Q5 = 8elj010 to prevent the regulation from
Wb = SsL010 being affected by voltage drop
Zener diodes are 400 mW in the wires.
3 +22-28 V
C 5'"? oUuTPUT
II 0 +
g J Q!
IIE:!E
II =
K Ha
\J]/
, N33V
= \"' #3 : et 1ceoprF
o
4ol
METER
Bb
i Qé
Y &
1
1 0SL
=
Next Month: Overload pProtection Circuitry.
000000000000000000000000000000
LADIES PAGE
AB you can see, wa aiaa't Jorget the ludies page, but gou Gid!
If you like to xeep the Ladies ruge poing you'll just have
to supply us with matericl, how about next moath?
Medne WMULVOL.
Yolil[
&T GUNNP-4
50 Brisbane Street,Launceston.
Telephone 2 2251
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