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THE WIRENES S L_ ^J fNSTITUTE
QF,. ^AU:ST. BAU.A
TASMANIAN DIVISION
BOX 851J, tf. P. O., HOBART
JULY 1963 MONTHLY BULLETIN PRICE 6d
PRESIDENT TREASURER SECB-GTARY
.
Mr. T. Alien Mr, 0. Harrisson Mr. K* Spiegel
VK7AL VK7CH VK7KS
Registered at &*P, 0., Hobar-t, fof transmission by pos-t as a periodical.
:GEI<ERAL MEETING.
The nexfc monthly meeting of the Division •will be held in the Club-Room,
147 Liverpool Street, Hobart, on WEDNESDAY, 3rd July at 2000 hours.
~By courtesy of the Ng-bional Aeronautics and Space. Administratii. on we •wtll
show several colour films, including "Sigraa 7— Walter Schirra's Orbi-bal Flight",
"Aerial - First International Satelli-fce" and "Tiros - Experiman-bal Weather Satellite"
At -the dconclusion-of -bhe film sho1 uing there will be an. auction, of
miscellaneous gear on behalf of a member who has generously donated half. the
proceeds to the I»T*U» Fund* in addi-fcion -fchere are a few odd disposals items to
be disposed of. -•
In all it sl^ould be quite- an in'beres'bing evening so make a point of
coming alon^,
NORTHERN ZONE,
The next meeting •will be- held on FRIDAY, 12-bh July at 102 Charles St,
Launceston at 2000 hours. On -bhis occasion there will be g display of gear
.
built Toy members. If you have any gear •bha'b you have built ,,f.ake. it alo.ng and
let -bhe oth.ers have an o'pportunity-of seeing vhat you have been doing. ^ny
ideas can be picked up by an inspection of the other chaps . 'rop.rk.
NORTH WESTERN ZONE. ••
. "The nexb meeting of -fchis Zone w.11 be held in Lakin's. Hall, -Ul.yers'bone,
on TUESDAY, 2nd. July at 2000 hours. This will be a social e^texiing-arid members
are each asked -bo bring along a few colour slides and also any gear "they would
like auctioned,
GOUN&IL MEETING.
~-fhe:next Council Ifee-bing.uill be held in -the Club Room on MONDAY, 15th.
chi^y at 1930-hours." . -'.••
V. H. F SECTION.
The nescfc meeting of the V. H. F, • Section will be held in the Glub Room
on UEiDNESDAY, 17-fch Ju3y at 2000 hours,
I T V -FUND» • • . :/
I refer you -bo last month's editorial and -bhe Presidentts Appeal for your
support in Helping us to reach our quota of £200 by Eas'ber 1965.
The tvmd has got off -bo quite a good start td-bh donations from VK7AL,
VK7DR, VK7KO, VK7ZZ, VK7JO, VK7GH and Associa-fce Members D. Alien and M. Helper-to
whom we esctend our thanks* \B. Vh •fche proceeds of a special effort at the la st
meeting -which raised £3- 63/~ the -bo-fcal now in hand is £14-6s/- ' ' '
• -These funds are being kept in a special account quite a pa rfc from Club
Funds and the balance on hand viill be forwarded to Federal Exeoutive periodically.
We still have a long •way to go» It is' of the utmost importance •fcha'b wo
have a delegate at •bhe nexrfc I. T.U, Conference, and, if we want to keep our bands
it is up to every one of us to assist in raising -the necessary finance to make
sure we are repreaented,
80 SEND ALONG YOUR DONATION NOW.
The Wireless Insti'bute'. of Australia, TasmaniEin Division,
July 19^3'' ''•"\i '. ' G, ^^fotibhly Bulletin, -, . • ; ', ^ . . Page 2,
.
1 "" •" • . .. •--, . .. i, •I ; .
IffiGEIfTS. ' • • --•••--. - •..•. '....•. . -. •'. --.... :........... '.. :.......:•,,,,,..•.,. ,.;
"Receip-fcs are ;on .hand fox- ; 793. VK7SJ^ 794 :H. Hu-bchinson. 796 H. IIarjono
797 R. de Balfour. 798 VK7DR. 799 VK7GF.. $QQ VK7XY'.. 814 R. Sho^thouse. 816 H.
Hu-fcohinson, 817 G. Gannock. 818-D. Alien. . 83.9,'VK7BT. 820 TK7№. 821 VK7BP. 823
VK7JB. 828 VK7DA. 829 R. Belbin. 830 VK7AK. 831 YK7RL;'83'5 VK7LR. 836 VK7FM.
837 C. Russell-Green. 96 YK72AZ. 97 VK7FM. 3* D. Allen.
WANTED. ' '....:„.... .. : '., ' •- '"—/ '. - •
Athol Idanning VK7LR, 6. Fraiikiin St., D©vonpor:b 'wants "Ama-be-ur Radio" for
i^arch and April 1958. ' "••. '..' .. ;. .. :' '• ., ':'.. :..^
R. S. Q. 3. mi^BOOKS. '•''•: "• •;:;:;^. -;::•"•'. '. -.. :•
Once y£,ain we have sold. all the last shipment of this very popiilar
;"&aaabo'ok, bat have sent off another .io3i>aer<, ..We have already sold about half a ;' /
;. "a^aen, ^o! if you wan-fc one send yQur;'35s/-;'bo -bhe Secre-fcaiy immedia-be]y (plus''3,^«-. -... ^;
po'a't'Et. ge if applicable) and we w.11 reserve"one' for you. Delivery is expected, : -''.' . -.':
about, tihe.-. ejxi .of July, ,-
•NEW-MEMBERS. •••-•-•-•• --. . . ^'.. '. -;.. ;. ;.:•
This month we welcome as new members Messrs* W. J. Henry VK7ZAP. ' . H. D. Spehce
VK7DS. B, W, Proudlock VK7BP, and R. F. Jordan VIC7IL and as associafe wembers Messrs.
.
G. J.:'Wilson, ^B..M.№tir, D, R. Brundle and P. W. Chalk. ./:^ /;^" """" ' "" • '
:HISTORIGA£ CALL SIGNS. . . - . : ^- . •
. •': •
: .. '., . Eederal'. Executive are,'desirous of. obtai.m. ng.'axy. information regarding the
;' holders, -of , the • fQll6uingf:. cgll .. signs whi.ch. appeared -in- ^ 'booklet, published- in,. 19U:
XZA. A.. G»Dixon». • %mgrard, . -.XZH. U'P. Hallam, '. ' .. Hobarb^ . !-^
XZB E^Kirby,, . .. .^vlfobarb:;,, ; XZJ. V. Ba-bchIer'"" • ': ' " ;"
<• XZG'^Harvey,:,. ,:•.. .., ^' '::.'. SZO..^.O. Duffy. :':.. "'-: •• "'1 -'" "• "--:-
XZD F. W. Medhurst " ' XZP R. S. Dawso^l • < *'".••. •.,-
XZE ,.R«;James.. ';: .. . " -... •.. ... ••,, : - XZQ H. D. ifeiisfleldt.,. '., Bunu. e* • •'.
Aiy information or any'other matter of "his-fcopi6al-interest'-bo. the 'Ins-fcitute
- war service is of particular interest - would be welcomed ty -bhe Federal'-':i':'
His-fcorical Officer, ML-. G. Glover VK3AG, Box 2147T G. P, 0., Melbourne,
Of course we all know -bha-t XZD, the late "Pop" Medhurst VK7AH ua a for
iaa^ y@ars;:Pre. siderA-i8Rd Pa'fcron'of. -bhis Di'yision, r • . , : . ; ; ^"...-—. ;:.:^... :.,.
REMEMBRANCE ,DAT CONTEST,. '^ , ., •.... .. ':.. •- '. ;" '; •' • ':-: • . ^..
A reminder tba.-b -fch©-R. D,.Gon1bes't is on asatu noscfc month. : Best 'overhaul.
your gear now and'.get, all ready .-for the fray, ... It'is esgpected that the rules wLll
appear in this'mon-fch^s "Amateur Radio"'. •" ' i:'i;'
. ;JAMBOSi3EOFTH]I:. AIR... .:,. . :, !.. '- , :• . . . -. .,..L •. '-.....^•. '..;: ...., "'... ..:~"'
., , This-j. ©ay's Jamboree-of jfhe'^.r w. ll, bo held from OOOl hours t9t'h Oc-bober
•b.o. 2359 hours .20-bh October, next* .№re of -fchis la-fcer.. . :' • • •
SUBSGHIPTIONS.
There are still a number outstanding and although -those unfinancial on
: 5th-»Tune Uave. beqn reiiioved from.•bhe"Ania-beur.. Radio" circula-fciori..list,,,we. Mill
continue -bo send them a Bulle-fcin for s'month'or •buo tn the hopes^t.ha'b, they m. ll
see the ligh-b and pay up, .. We, cannot afford to-lose members, 'like'dse 'we "Gamiot
afford to keep sending "A.. R. " -bo unfinancial bods. -'... A' '
DISPOSALS. """' ' ' * '. ..;. 1"", ; ^.•;'-'' -i: • . •"
All those who ordered,, gear from Igs'fc month's list may coll-ect same a'b 'fche
nexb mee-bing or by contacting 'VK7QH, Parcels for Nor-fchem Zone andl. N, W, Zone
/ •m. ll. t)e.-!deliV9:a?e^, ;Gareof VK7GA- (^Lawxces-bon) gnd VK7JP (BuKnie) a>6-:'^qon;.. :.as^ipo.-ssible»
The ,ov@i^ll , respon,se -to'our disposal s'.offer s has besn ^di'sappoin-fcing and
corisQquen-fcly it i. s; np-fc .intended ..16 ciak.e .any fiirt.Iier'purchases-uirtil. gear on. hand
.
'. isdispQsed of. and/pr more'-iaterest is shown, . . " .^. .,. . :'.:. •• -
3-.-. ^•. ;; ; :..... ;;. -. • : . - - -;•-;. - - - - . -. i- : ' • . -..•. ' ' •• •'' . \ '. :' • -
BULLETIN. .:•.. ',. ;'- •"••':. :., -•;'-" . 1\'.'•.. . " : . ":;•• '• •• •..•-•..•
',<:_•„:, ' ,. ... zon& secreta^es. a^ a^.Pthers .who/have ;anytMng for the
• r^le^. a re .reminded -fchg-fc no-fces niust be in -the-hand s of. •the S.ecre-fcary or VK7CH
, 1^the-bhJ-rd, Mo^ay'iathQmonth», ' . •^.•^'"~~'' '^{:~"
The Ifchthly BiLLle-fcin'of -the l&reless Insti-fcuto of Aus-fcrglia,
Jy3y 1963 iasnanl3n Division* Page 3
TECHNICAL.
The__Tn-Vee Antenna ty Associo-be Greg Johnston" •••"•'
-Soon after Bud Pounset-b's article "The Inverted Veo An-fcenna" appeared in
October "A. R. " for 1962, impressed by bo-fch -the mon^y and space saving gspec-fcs of
the antenna described, irork 'ua s commenced erecting a carbon copy.
After much trial and error the arrangement described below was settled
upon as -bhe best coapromise of tiiae and effor-fc for bet-ber than average performance,
Not being in a'po'sitlon to'obtain comparative signal report-s "on -the air" fai-bh
was, of necessity, placed on compara-bive strength of signals recoiVGd. The
yardstick an-fcenna'tiia a "G5RV11 co-linear ^-fch the 80 metre element of -bhe^Tn-Vee
and some 5 fee-fc higher at each end» Despite the fac-b/bhat the G51W i©s fed^via^an
antenna tuner into -bhe receiver the Tri-Voe (untiined) performed, about tw S .. units
be-b-fcer on 80, 40 and 20. metr6s - the G5RV has now. been discarded.
On gazing a-C the strdc-biu'e, the folloviing points shoiild impress :
(q) Only"one pole is required, '(b) The an-fcenna"elements serve as guys. .
(c) The xAiole issue fits in-bo quite a small space (d) It sports (i) 4^Y®lengfchs
on20~(ii)~2'wvGlGngbh8 on 40 ^snd (iii) 1 wavelength on 80. (e) Omni- direcfctonal
coverage is ob-baiited and (f) No szd.l.ching is necessaiy.
The mea suremen-bs given below xd. il produce an antenna resonant at the
follo'wing a pproxj.ma te frequencies : 3»6 mc/s, 7«1 mc/s, 14. 2 rac/s.
The'antenna is fed a-b the apex of the lover or 20 me-bre eleiftents uith a
line of 50 ohms impedance,
.,+/
.
PLAN VIEW
(Not to scale)
All eleiaents connected
-bogether -ui-fch 50.^bffl coax,
SIDE V-IEW preferably and fed -a-b "A"
with same,
\^0 ^x
Y
•<-. \ ':• rr, t »'r s
\/- j
A Brid ed -T Phase t'fodulator , by D. Thome VK7ZAI
ThLs, phase modula-fcor circuit. is inuch more conipgc-b. thein ^the tubQ type., and
may be used in the 7 and 8 megacycle region. A few volts of; audio from a 500.
ohm output speech amp* id.il •vary the resistance of •fche two type OA95 diodes and
producea "phase'shift'through the netxrork. The phase shift in the 7 -GO 8 megs.
region may be increased to-a wider frequency svd. ng by frequency multipliers,
such as wulcl be used in any VHF transmi-fc-fcer. In -the construction of this^i.mi-b
two requirements must be net; first, enough drive level must be available to
drive the neyb stage through the ns-fcwork loss, and second, the link circxii-b should
look like 50 ohms in and ou-b wi-bhin reasmnable limits*
(Circuit on next . page))
-; The Wireless Institu-fc.e of Australia* Tasmani.an Di^asion,
July 1963 • ' • MQnthly Bulletin., . :; ; Page 4
TECHNICAL.
A Brid ©d - T Phase Modulator (G.on-binued)
50 •ohn
' •'i'Inpyb'
7-or 8 ) .50 olim output 'Phase Mod,
mc/s 7 or 8 rac/s
A. 'F» Input,
from
LI. 7 mcs. 9 tums. 22 enamelled i-11 x
8 me s, 8 . turns*22 enamblled ^" x
Speech .'
Amp, . "'
$00 ohm ''a-."
i'.;i".line " -
The. DipolG, " ' ':
One of'the first questions that often arises is .how eff.oc-fcive a dipole is
on one frequency as compared to a dipols on another frequency. Free space
considerations give some insight into -bhe pro'blera,
Picture a -bransraiAting antenna which is out in space and radia-bing equally/'
in all directions, as being the centre of a huge sphere. Due to the uniform
radiation, the sgme amoim-fc of'-power raus-b be transni-b-bed •bo each unit of surface
area of tjae sphere. If broadcas'b. half yove elements are used on the surface of
the sphere-fco intercep-b or receive the powar, they should be spaced side' by side
with half -wavelengfch spacing. ..Each half VQ-VQ eXement in a sense, -bhereforo,
covers an area one half vavelQngth on a side and each eleiaent intercepts the same
amount of eleinen-fc,
'
power as every other A two elemen-fc anteima vLti h the t'uo
elements widely separated on the surfaco of -fche sphere, but properly phased and
matched to the load would therefore intercept t'wice as much power as a dipols and
provide_a^gain of 3 decibels. Similarly L, half wave elements so used give 6 db
gain and 8 elements give 9 db and 16 elements give 12 db gain over a dipole.
Incidentally, power is the importan-fc consideration here becsuse even though
we want raicj'ovolts on the grid of the receiving tube, the microvol'bs are greatest
when the power put into the receiver input; impedance is grea-bes-b.
When two dipoles are placed close -bogether as in a double Zepp the gain
is found in pirac-bice -to be nearer 2 db instead of 3 db, vhich fact can'be
at-bributed to the prb3dLmity of the two elaaents. The exfcended double Zepp can
be •bhou. gh-fc^of as sepQi-Qting the dipoles, yet laaintaining -bho proper phasing and
matching -the load, in this case the gain'aore nearly approaches the theoretical
3 db, -Ln all ac-fcual arrays this proxiMty effec-fc changes the 3 db figure so -bhot,
each time the number of elements is doubled the theoretical gains are changed
soaevhat.
The same concept of antenna area can bo used to predict the effoc-bivoness
of an-benngs on^tw different frequencies. For example, if the -bw froquencies
are 100 and 200 Me, the 100 Me antenna ui.il be -bvice as long and correspond. to an
area 4 times as large a a 200 Me antenna. The 200 Me dipole id. il bo 6 db poorer
than -the 100 Me dipole. Here we see a dipoXe is no'fc equlvQlent -bo a dipole 06 a
differont. A 4 element 200 Me antenna having the sane area as a 100 Me dipole wUl
be needed for equivalent received power over shor-fc distances. It is of interest
•bo note that if a 4 elonen-fc 6 dti gain gu® beam is.. us.ed:a-fc:the 20Q Mc..Jiransciit.ter
and also:-at the receiver, the 200-Mc systent vLU then be" 6'db betlter -bhan the
100 Me sys-fcem using dipoles a-t each end for'short distanc'e work,
73
Ghas* Harrisson" 'VK7GH
for Bulletin Gbmrait-bee
The-Wireless Institu-be of Australia, Tasmanian Division,
July 1963 Monthly Bulletin, Page 5
DISPOSALS.
Items listed last month are st still available wL-bh the exception of Nos»
G,5, G7 and 08.
The following additional items are also available to financial members on
the usual conditions. Applications on a-fc-fcached form to reach Disposals Gommi. 'fctee
toge-bher •with remittance, ly. July 15-fch,
Item No, Descri tion PrLce
Dl Fixed condensorg -lots of 10 mixed mica and ceramic (at least
7 different values^- together vi.th 5 electrolytic (a-fc least 4 different
values-) All new , . . . 10s/-
Values on hand include 25, 150, , 003 ceramic, . 005, 100, 200 mica
etc. and 100 infd. l50v, 500 mfd 65v, 50 mfd 200v, 4 mfd 350v etc,
^
As they come - we camiot supply special valuQS*
D2 4700 obm 5 wtt resistors. New •*... ••• . I/- each or 4. for 3s/-.
D3 Concentric trimmers, enclosed type, New • . • , I/- each or 4 for 3s/-
D4. Knobs It' Gold insert, New/r/. ............... Is/-
D5 Wafer switches, 3 miscellaneous, including one 3 bank long sh^ft 7s/6d
D6 Minature 6 volt gramo mo'fcors .....•.. « 5s/-
D7 1, 5 mfd 4000 volt oil fUled condensers <••.... •• 4s/-.
D8 Electrolytic condensers, 24 plus 24 mfd 300 v. New •.... • 3s/»
S P E CIAL
D9 One onl,y, Gossor 3" Oscilloscope Uni-b. 29 ininature tubes. 3" CRO tube».
HoriLzon-fcgl - 5 time speeds, 15m/s -1. 5 m/s - 100 u/s - 50 u/s ~ 15 u/s
Calibrated horiaon'fcal shif-fc control for frequency measuremont,.
Verbical - 3 Attenuator positions, 15 ra/v -150 n/v -1, 5 vol-bs
RMS plus other attenuator levels»
Trigger Selec-t.or SvL-fcch. External Y amp, P. P., L stSG, Trigger Level
control, Focusy Brightness control^
Power supply 115 vol-bs 1296 cps»
The C. R. O, is complete, requiring only a power supply modification to
operate. Also includes a pulse generator unit on a separate chassis,
Overall size 8 x 10 xl4 deep, BRAND NEW.
Best offer gets this. There is a reserve of £17. Send your offer
to the Disposals Committee by July 15"bh» in a se ara-fce envelo e marked " "
- these va.il then be opened at the next Council Meeting and the successful
tenderer advised - don't send monqy for this item,
^\.