TELE-TECH & - AmericanRadioHistory.Com

¡use ROHN
communication
and
_ micro -wave
towers
featuring these
special advantages
Imo
Self -Supporting from 50 feet
to 66 feet or up to 200 feet to
300 feet when guyed!
It Hot - Dipped Galvanizing
Throughout - Finest Protective
Coating. Also available in
eather- resistant double -coat
nanui.
Easily and Quickly Erected.
Towers are in 10 -foot sections;
two workmen can erect a 60 -foot
tower in only two to four hours!
Excellent Design and Workmanship
- both proven thoroughly
through the test of time
- thousands of Rohn installadons!
Economically Priced - Saves
you money because you can buy
lust the right Rohn Tower to fill
your requirements.
Variety of Rohn Sizes and
Models: No. 6 with 121/2" triangular
design for guyed heights
up to 120', 50' self supporting;
No. 20 features 14" triangular
design for heights up to 160';
No. 30 has 18" triangular design
for heavy duty use; the
No. 40 for extra heights up to
300 feet or for extraordinary
wind or antenna loading - self -
supporting to 66 feet!
GET COMPLETE INFORMATION,
PRICES AND CATALOG. WRITE,
PHONE OR WIRE FOR
NEAREST SOURCE OF SUPPLY
ROHN Representatives coast -to -coast
ROHN Manufacturing Co.
'116 Limestone, Bellevue
Peoria, Illinois
"Pioneer Manufacturers of TV and Communication
Towers of All Kinds."
TABLE II
The resistance values for switch 2
Switch
Position
r2 (ka)
are:
1 500
2 707 2
3 1000 4
4 1225 6
5 1414 8
6 1580 10
7 1935 15
8 2230 20
9 2500 25
10 3160 40
11 4180 70
12 5000 100
13 6125 150
14 7070 200
Other components are:
r, = 11.3 ohm i/4 w. non -inductive
precision
r r r9, ra = 10 kilohms 1/2 w. carbon
film
r10 = 10k, 1/2 w. carbon
r5, re = 25 k pot.
LI = 30 mh RFC
L2 = 5 henry AFC
C2, Cs, C, = 0.02 of ceramic in
parallel with 2 µf paper 200 v.
S, = DPDT
S, = DPDT center open
F1, F2 = 10 ma fuse
Jt = normally clsed jack to monitor
base current
m m2 = d.c. milliammeter
References
(I) R. L. Pritchard: "Frequency Variation of
Junction Transistor Parameters" pp. 786 -799
Proc. IRE May, 1954.
(2) R. F. Shea et al., Principles of Transistor
Circuits John Wiley and Sons, 1953.
Eddy -Current Bridge
(Continued front page 107)
nearly perfect reflector. Since calibration
has been done, as a rule, by
the substitution of known samples,
the error for any conductor measured
is small.
Circuitry
A circuit based on these principles
is shown in Fig. 3. The electrostatically
shielded driving loop forms
a termination for the driving line.
The 5687 drives the system at its
resonant frequency, adjusted by cable
patching. Loop current is 5 amps.
The ac plate supply produces a half -
sine -wave bursts of r -f. A crystal
diode rectifies the stepped up loss
signal, which then appears on the
scope adjacent to the oscillator
pulse from the 6AL5. Adjustment of
the potentiometer dial to equalize
the heights of loss pulse and oscillator
pulse corresponds to a resistive
(Continued on page 360)
ONLY
GIVES YOU
THE
y;dable D
666
CARDIOID
DYNAMIC
for TV and BC
OUTPERFORMS ALL OTHERS
Combines ruggedness of single
dynamic element with new acoustic
principle. Eliminates pick -up of
ambient noise, unwanted
reverberation and equipment rumble.
Uniformly smooth response 40 to 15,000
cps, laboratory controlled. Highest
front -to -back discrimination.
Virtually no proximity effect. Output
-55 db. E -V Acoustalloy diaphragm.
Blast filter. Detachable clamp -on
swivel stand coupler. Weighs only
11 oz. 7M" x 1 %'. TV
gray. 20' cable. 50 ohms.
Readily changed to
150 or 250 ohms.
Model 666 Microphone. List $255
Model 366 Boom Mount. list $40
Model 300 Stand Coupler. List $10
Model 420 Desk Stand. list $20
Normal Trade Discount Applies
'E -V
Write for Catalog No. 120 -L66
B U C H A N A N ,
M I C H I G A N
Tele -Tech & ELECTRONIC INDUSTRIES June 1956
For product information, use inquiry card on pages 209 -210. 359