Table of Contents
Advertisement
A L I G N I N G A M
R E C E I V E R S
A typical adjustment of A M receivers is that of the I F
transformers.
Connections are made from
generator to the receiver at the rotor and stator of the
receiver variable capacitor. T h e leads from CO-1506 are
connected across the volume control variable resistor of
the detector circuit observe the detector output.
Sweep generator connected at the 4 5 5 kHz
IF input or R F output
Tuning circuit
Volume control variable resistor
in the detector circuit
T o CO-1506 E X T S Y N C / H . I N P U T
Fig. 11 Adjusting AM receiver
MODULATION MEASUREMENT
T h e CO-1506 works if the measured modulated carrier is
below
1.5MHz.
Connect the modulated
I N P U T (1) and adjust with V E R T A T T (4) and V . G A I N
(11) to produce an envelope as shown in Fig. 12.
This modulation envelope is a result of constant modulating
frequency which will be displayed with stability on the
scope when synchronized with controls (6) and ( 1 0 ) .
T o find the degree of modulation, measure maximum and
minimum values A and B .
A ^ x
1 0 0 . . . Modulation in %
A + B
Another method of modulation measurement is the use of a
trapezoidal pattern.
In this method, the modulated radio
signal to be measured is fed to A C terminal (1) with S W E E P
R A N G E
(6) set to E X T position.
modulating signal applied to H. I N P U T (8) will produce a
trapezoid or rectangular pattern on the scope. Assume the
longer side as A and the short side B, then the above same
equation applies to find the degree of modulation.
10
the sweep
T o CO-1506
V E R T I C A L
I N P U T
Common
carrier to V .
Connect this lead to
appropriate terminal
In this set-up, the
A - B
Fig. 12 How to measure modulation degree
terminal
Fig. 13 Method of selecting power supply voltage
.
Advertisement
Table of Contents
