Cushman Electronics Inc. CE-5 Communications Service Monitor
1.01 The Cushman
CE-5 Communications monitor accurately
measures the frequency of the output of FM or AM
transmitters. The range of measurement is from 20 MHz to
519.999 MHz.
It also measures the frequency deviation of the modulated
output of these transmitters, and using the Model 313
plug-in the percentage of AM may be measured.
1. 02 The
CE-5 functions as a signal generator covering the
same range of 20 MHz to 519.999 MHz with the same accuracy
as in the Monitor mode- The output level Is calibrated from
0.1 to 100 microvolts. The output may be either FM,
AM or CW and the modulation and level are both adjustable.
Modulation, both FM and AM, is from an internal 1 kHz
source. Modulation from an external source, 60 Hz to 20 kHz,
may also be used for both AM and FM. In addition both
Internal and external modulation may be applied simultaneously.
1.03 In the IF Frequencies mode signals from 1 kHz to 40 MHz
are available at a separate output, with the same accuracy
as the generator. Level is adjustable but not calibrated.
These IF Frequencies may be used for alignment and
troubleshooting of
Receiver IF and audio circuits.
1.04 In the generator mode the
CE-5 may be used to align and
check the sensitivity of receivers. Since both internal and
external modulation may be used simultaneously or several
external modulating frequencies may be summed and used to
modulate the output, the instrument may be used for testing
and aligning of tone operated receivers.
1.05 When a measurement of the received frequency with
greater resolution is required a counter may be connected Co
the 100 kHz IF OUTPUT connector. This output is 100 kHz *
the error of the signal with reference to the dialled In
frequency. The accuracy now will be the accuracy of the CE-5
Master
Oscillator crystal frequency = the accuracy of the
counter.
GENERAL DESCRIPTION
1.06 The
CE-5 is a specialized VHF/UHF superheterodyne
receiver. With it a
Transmitter can be monitored for correct
carrier frequency and amount of modulation deviation. The
assigned
Transmitter carrier frequency is "dialled in" and
the actual carrier frequency of the received signal Is
compared with an internally generated standard. This
standard is the local-oscillator (LO) frequency.
1.07 When the incoming signal is of sufficient amplitude, a
frequency error detector is activated and a meter shows the
difference between the assigned carrier frequency and the
actual carrier frequency. Discriminator circuits are also
turned on which provide an indication (on a Deviation Meter
or Oscilloscope) of frequency deviation.
1.03 The
CE-5 must be operated with either a
Cushman model
301 Oscilloscope or a Model 302 Deviation
Meter inserted into the left-hand plugin compartment, and
the broadband mixer, one of the RF Preselectors or one of
the other available plug-ins in the right hand compartment.
1.09 The incoming signal is received at the
Antenna
connector of whatever RF plug-in is used and a first
intermediate frequency (IF) signal is produced with a
frequency that is 10 MHz ± carrier frequency error. LO
frequency = dialed in frequency ±10 MHz. Dialed in frequency
= assigned carrier frequency, therefore the difference
between the LO frequency and the actual carrier frequency is
10 MHz ± the carrier frequency error. The LO frequency may
be either 10 MHz above or below the dialed In frequency.
1.10 The first IF signal is mixed with a stable 9.9 MHz
signal from the Master
Oscillator (MO) to produce a second
IF signal with a frequency of 100 kHz ± carrier frequency
error. The error is detected and displayed on the FREQUENCY
meter.
1.11 The second IF signal is also demodulated and the
resultant audio frequency signal is
amplified in the Deviation Meter or in the Oscilloscope to
give an indication of the amount of FM deviation present due
to the modulation on the received carrier.
1.12 In the Signal Generator mode the LO is used for the
output signal, but is shifted ±10 MHz
so that the output frequency will be the same as the dialed
In frequency.' This 10 MHz shift is automatically taken care
of by mixing an internally generated 10 MHz signal with the
LO. This 10 MHz signal can be modulated, either FM or AM, or
left unmodulated for CW output. Modulation is by an
internally generated 1 kHz signal or may be from an external
source, or both may be used together.
1.13 The level of FM, AM or CW signals generated by the CE-5
is controlled by attenuators
which are calibrated to give an output of between 0.1 and
100 microvolts through a 20dB fixed attenuator which is
supplied with the Instrument. This fixed attenuator should
be used for protection, but approximately 10 times more
signal is available.
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