1. SEMIPASSIVE REPEATERS FOR RADIO BRIDGES 2. TRANSISTORIZED CIRCUITS FOR IONIZATION CHAMBERS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A065500300001-1
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 5
• Document Creation Date: December 22, 2016
• Document Release Date: January 19, 2012
• Sequence Number: 1
• Publication Date: November 16, 1962
• Content Type: REPORT

Declassified in Part - Sanitized Copy Approved for Release 2012/01/19: CIA-RDP80T00246AO65500300001-1
ti
CENTRAL INTELLIGENCE
19. U.S.C. Secs. 793 and 794, the transmission or revelation of which in any
C 0 N F I D E N T I
COUNTRY Yugoslavia
SUBJECT 1. Seaipassive Repeaters for Radio
Bridges
2. Transistorized Circuits for
Ionization Chambers
DATE OF
INFO.
PLACE &
DATE AC
REPORT
DATE DISTR.
NO. PAGES
REFERENCES
6 962
1
RD 50X1-HUM
reports,
entitled 1 Seaipessive Repeaters for Radio
Bridges., and ` ans s orized Circuits for Ionization Chambers.
50X1-HUM
C ONF IDENTIAL-
NO FOREIGN DISSEM
STATE X ARMY X NAVY X A{R
X NSA
I N FORMATION RE PORT I N FORMATION REPORT
GROUP I
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dswsyredip s.d
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 rnx1-Hi ink
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1. It is noted that transistor circuits always show an impederce in an input
which is not hi:-h; with special transistors, with a low base current, it is possible,
under determined conditions, to re?-ch the l06 - 107 ohm level.. The transistors do
rot lend themselves, however, to compose the input stn!--,e of amplifiers or electrometers
for iohization chambers. A general application would be verery interesting, on the
other hand, espec'ally insofn.r as it pertains to monitoring apparatus for r^.diological
defense which must be, obviously, very sturdy (anticollision, ctc.)
2. The physicists at Vinca Zt-he Botis Kidric Institute of Nuclear Science
have measured in detail a suitable circuit in this ranee. The input stage (connected
to the chamber) is composed of a "balanced modulator with diodes" (as diodes are used
for the base/collector juntions of silicon transistors), xf which fit, amplified
and detected in phase, emerges as the autobalance. For balancing, the impedence at
the ent.'a-cc of the balance modulator (which is the diagonal of the bridge) is
theoretically infinite; in order for a signal to emerge it is obviously neces ary for
the balance modulator (that is the bridge) tob~alanced, if only slightly; if the
amplific-tion introduced between the bilance modulator and the phase detector is hi;-h,
it is sufficient that the balancing be miniuuntun; the input impedance remains elevated,
ho. , ,, r .
3. With a coil gain of 104, the input impedence is 1012 ohms, amply sufficient,
therefore, for an ionization chamber.
4. The balance modulator is made to function at 500 kcs and, for the best signal/
irtarference r^tio, the aplificntion is selective on this frequency. Because the
capacity in the gap is extremely small (in parallel at the biglance modulator 10 pI)
the velocity of the response of the device is remarkable and by far superior to that
oh ~irnble with electrometrical tubes.
50X1-HUM
The apparatus was tested in
June l9 ?.
50X1-HUM
Dom 'ent : T~ is appears to be an origi al and very interesting discvoery,
above l in view of the o-o-licntion already mentioned, that is for devices for tkH
radiological monitoring in the field. The value of the circuit is, above all, the
*r.te,ral employmmtt of transistors and the exclusion of electrometrical tubes, then
the rapidity of response which i-es not make its use particularly simple and fast.
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Lam... i~.ix
STTRT - S m; nnssi vP T'enepters for Radio Bridges 50X1-HUM
50X1-HUM
1. That which distinguishes passive repeaters (mad up of single directional
dipoles, picirinc? up and emitting, interconnected without the interpositioning of
other amplifying elements) and semipassive repeaters, in which there is a
"ro
11 * eneration" of the signal by the diode tunnel effect,?irith a gain in power,
is as follows: the passive repeater is characterized by a sensitive worsening
of the signal/interference ratio and its practical utilization is therefore
reduced; the semipassive repeater, to the other hand, is charAc~erized above all
by a gain in power that is about 10 db at 200 mcs by which the worsening of the
signal/interference ratio is amply compensated. In general, with the tunnel
diodes used by the Yugoslavs, the noise factor itself
is about 4 - 5 db at 200 mcs, by which the "raal" worsening of the system always
appears treater in the unit. 50X1-HUM
2. ^:;e value of the system is also the -^ct that the tunnel diode ca be
inserted directly into the dipole without the interpositioning of lines or
oscillating circuits requiring the adaptation of impedence and without loss.
By such means the "repeater" may also be composed of a single di,lole (in which is
inserted the tunnel diode), gssuming_ together the fuhction of "pick up" and
"emitter" of the amplified signal.
Comment. The s;ste". is techniaa''ly very interesting and probably
wortL t~Ze extensive research. The name "semipassive" is not completely 50X1-HUM
acciir??te: in re-lity this is an "active" repeater whose amplifying elements
ho,,rever have been reduced to a minimtm and unified on the same dipole.
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