Radio Testing:
Testing a chassis
for fidelity with a Type 600-A Standard-Signal Generator. In
this
photograph
we see from left
to right the Type 513-B Beat-Frequency Oscillator, the Type 600-A
Standard-Signal
Generator, the chassis under test, the Type 483
Output Meter and
the General Radio Cathode-Ray Oscillograph.
This is a typical test setup used by radio
manufacturers in 1931. A Beat-Frequency oscillator was used to
modulate a Standard
Signal Generator to provide the antenna input to the receiver
under test. An Output Power Meter and an Oscillograph were
used to evaluate the output of the receiver. Later a Distortion
Meter
was added.
Frequency Monitoring:
Simple LC Tuned circuit wavemeters were
used to measure and monitor frequency up to about 1932 when stricter
requirements on the stability of commercial radio stations were
established. General Radio pioneered in the development of quartz-crystal
frequency standards, which were combined with multi vibrator
dividers, heterodyne multipliers, and various modulation meters,
etc. as
complete monitoring assemblies for the nation's 200 or so radio
broadcasters.
Frequency measurement was simplified in
the 50's and 60's with the advent of frequency counters and synthesizers.
Accuracy was improved with the new crystal standards, and ultimately,
atomic standards based on rubidium oscillators. General Radio
was a major supplier.
Station Frequency
Meter Type 532
|
1142-A Frequency Meter and Discriminator
1151-A Digital Time and Frequency
Meter
1162-A Coherent Decade Frequency
|
Synthesizer 
The Type C21H Primary Frequency
Standard, introduced in 1928, was the most accurate
instrument commercially available for the measurement
of frequency and thus soon became the reference standard
in laboratories throughout the world. |
|
