Dymar Electronics Limited 1785 Other
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AM FM Modulation Meter
The Dymar AM/FM Modulation Meter Type 1785
is an all
solid state instrument for the measurement of depth
of modulation or frequency deviation of transmitters.
It is operated either from A. C. Mains or from its own
rechargeable battery and as much is equally suitable as
a laboratory instrument or as a portable field servicing
The frequency range covered is the whole of the V.H.F.
band and extends into the U.H.F. band to include
the mobile band of 470 MHz.
The sensitivity over the whole of this range is better
than 2.5 mV in 50 ohm (-40 dm) which permits loose
coupling to the transmitter under test.
The instrument is specifically designed for measurement
of narrow deviation transmitters in todays mobile
and portable radiotelephones, the most sensitive
deviation being 3 kHz. The local Oscillator
residual F. M. noise of typically 44 db below 3 kHz.
Auxiliary outputs are provided both at the Intermediate
Frequency (500 kHz) for viewing the modulation envelope
and at Audio Frequency for measurement of distortion.
Service and User Manual
1.37 Mbytes (1439991 Bytes)
Scanned document, all readable.
21 January 2013
1. General Description, 1
2. Specification. 2
3. Operation, 5
4. Technical description. 9
5. Alignment procedure. 13
6. Component List. 16
7. Circuit Diagrams, 29