SKM C450i24093017202
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1.1 T^S DIVISION. DEC. BULLETIN PACT, 5.
MCI550G INTERGR/.TED CIRCUIT (Cont. from p. 4)
Modulation of either audio or 'aven wide-band video can be
applied to pin 10 togother" with about 45. 5 volts bias to give
approximately 10 to 50 mW of amplitude modulsted R. F. output.
The oscillator circuits, 5, 6 and 7, all draw about I0mi\ with a
12 volt supply. A check for oscillation is easy if you monitor the
current, Ths non-osclllating value of about SOm," drops to lOm. f, when. the
circuit is oscillating.
The tap on'the. 'coils in circuits 6 and 7 is about; . one third
of the total turns from the crystal end.
If the MCI5'50'-is used in its differentia]. s. mplifiQr configura-
tion a further s'eries of'oscillators are possible.
Circuit. 8 is a crystal oscillator suitable for low frequonoy
crystals of I Ifflz and below. The oscillator gives se'veral volts of nearly
square-wsve output;, and the variable capacitor will'trim the frequenoy.*
In circuit 9, the feedback of s. Woin-'bridge audio oscillator
is controlled by a resistor from pin 2 to aarth. With 100 ohms in" the
constant current; circuit to control the gain, tho output is 500 mV of
fairly pure sine-wave.
The 0. 05 IVIF capscitors, the S. '6'K. resistor and an internal 5K
resistor determine the frequency of 800 Hz. Small ch..,ngcs of frequQ.ncy can
be made by varying -the 5. 3K resistor. Large changes 'can be madG by varying
both the . 05 MF capacitors to some other value*
This audio oscillator will amplitude modulate circuits 5, 5,6
and 7.
The circuits in this article all gave good results with a
minimum of fiddling.
The MCI550 has a very wide range of applications, yot in spite
of. this, it .. is. ono of the choapest I. C. s on the market, and may be
purchased for SI a 5.0 from the VK7 Division Equipment Store.
See circuits following pages.
GtIRISTM2VS , QUIZ SPECIAL.
I have found in'some litorature supplied by Leo 7RG, a very
interesting 'problem that you might bo interosted in solving over tho
holidays, . ^. s an added incQntlve, the Equipment Store will donate ^2:00
worth of compononts or a 4 c/'O Cradls Relay c. w. socket as a prize for
the cprrsct; or nearest corrsct entry ••submitted. If more than one correct
entry'IS r.S.CQ.ived,. a ballot to decide the outright v^inner will be held.
Pls. a. se sond your"-answer, written neatly, to the "BullQtin Editor", 'A'. I. ^.
Tas. D.iYi-s'io-n, Box 851 J,"". G. P. O. Hobart. 7001. to roach me no later than
the 1st Janu-8;r-.y,, I972. The answer -and winner will be advertised in the
February Bulletin.
Pr,o,blems. I'.. - There ore 12 balls. .which cannot be visually
di.^/felhguished; from each other, but ono ' of them is either heavior or
lighter, ...we don't-. know which. ..'. pair of balanc.G scales are available,
and the .pr'ob'lem is to determine, in three weighings, which is the
different one, and whether hoavler or lighter.'
2. A recent problem in S. '....... A......... which louks easy, but,
There are six, balls, three 61" them are identical in-weight and are
heavier than thre. e 'other balls, identical in weight. They can not be
distinguished from each other visually. Using a pair of balance scales,
determine which three are the heavy ones-and which three are the lighter
ones.
NOVICE LICENCING.
fXe.^la.test figures are:- in favour' 7
against 20
Participatio'n' ln'.. '@urvey 12^111 Don't either way Nil
This is obviously only a small section of the total number of
members capable of giving an '-&nswer. HOW ABOUT IT GENTLE1VIEN. Sursly a
7c stamp is not a fortune! LETS KNO'A' YOUR ANSVuER PLEASE! A DIVISIONAL
POLICY FOR OR AGAINST NOVICE LICENCING CAN ONLY BE FORMED ON THE OPINION
OF THE MEMBERS! PLE/-SE SEND IN IG'UR ANSWER NOW: SEE ZOUR OCTOBER
BULLETIN FOR ALL DETAILS
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