Westinghouse Type KR Installation & Operating Instructions Manual page 53

T YP E KR CAR R I E R S ET
A P P L I C A T I O N
1. Receiver Sel ectivity (Fig. 14)
This shows a typical curve of th e overal l sel ec­
tivity of t h e r eceiver under
tions.
2. Transmitter Output Sel ectivity (Fig.
Typical curves ar e shown
bandwiths for k eying purpo s e s can be determi ned for
any carri er frequency between 30.. k c and 200.. k c.
3 . Minimum Channel Spacing (Fig. 1 6 )
This i s a g raph fro m which minimum channel
spacing can be obtained provided the signal strength
of the interfering transmitter and th e sensitivity set­
ting of the receiver are known. Thes e can be obtained
from c alculations or by m easurements.
For example , if the interfering transmitter volt­
age is measured ( at the r e c eiver) and found to be 2. 5
TYPICAL R F SI GNAL M EASU R EM ENTS FOR T R ANSMI T T E R
C H E C K P OI N T
T S- 1 t o Gnd.
T5-3 to Gnd.
J 13 to Gnd.
Q 1 0-C to Gnd.
T6- 2 to Gnd.
Q 1 2-B to Gnd.
Q 1 5-B to Gnd.
Q 1 2-C to Gnd.
Q 15-C to Gnd.
T7-5 to Gnd.
Output to Gnd.
steady state condi ­
so
1 0 )
that approximate
TAB L E 5
VOL TS
5 . 5
1 . 0
0 . 0 8 5
6 . 0
6.0
0 . 8
0 . 8
38 . 0
38 . 0
9 . 8
8 . 0
volts , this w ould b e 10-db down from 8 volt s. This
point can be located on the right hand column of the
graph. Then , if the receiver sensitivity were set to
op erate on 0. volts or 20-db , this point would be
8
located on the left hand column. A line could then be
drawn through the two points as shown by the dotted
line. The intersection of this line with the center
line indicates the minimum channel spacing. In this
case if the interfering signal is being keyed on-off, at
1 5 p p s , the minimum spacing would b e 2. 5-kc.
4 . Tran smitter Output and Receiver Sensitivi ty
Vari at ions with Voltage (Fig. 1 2)
The se curves s how the variation of transmitter
output and receiver sensitivity with changes in supply
voltag e , at 1 20-kc and 25°C. The increase and de­
crease in
transmitter
may be obtained in db from the transmitter curve.
watts is about 8.0 volts with a 60-ohm load.
1 . 0
The increase and decrease in receiver sensi­
tivity above or b elow 40 millivolts c an similarly be
output above or below 1. 0 watts
1 3