Instruction manual

TM 11 6625-3017-14
SECTION 1
GENERAL INFORMATION
1.1 INTRODUCTION
The TF 2300A Modulation Meter is primarily for
measurement of f.m. deviation but it also measures a.m.
depth. With its wide range of deviation frequency,
modulation bandwidth and carrier frequency, this
instrument is suitable for application to fixed and mobile
point-to-point communications, broadcasting, telemetry
and multi-channel link equipment in the h. f., v. h. f.
and u. h. f. bands. Distortion and channel separation
tests on f.m. stereo receivers and transmitters can also
be made.
Positive and negative f.m. deviation can be
measured in ranges from 1. 5 kHz to 500 kHz full- scale
at modulation frequencies between 30 Hz and 3.4 kHz
on the 1.5 kHz deviation range, and 30 Hz and 200 kHz
on all other deviation ranges. A.M. depth can be
measured up to 95% in a 30 Hz to 15 kHz modulation
bandwidth. Either f.m. or a.m. can be measured in the
presence of the other. Although measurements are
normally made by means of the meter readout, i. f. and
demodulated outputs are available at the front panel for
examination or analysis.
Spurious a.m. and f.m. due to hum and noise are
kept to a level insignificant for most applications but,
where required, crystals can be switched in to control the
local oscillator, or an external local oscillator may be
used. The instrument can be operated without a local
oscillator for measurements in the 1-2 MHz range.
The instrument can be operated from mains power
or a nominal 24 V battery. Voltage regulation eliminates
transformer tap changing except between 115 V and 230
V ranges. On battery, the regulation compensates for
battery voltage variations between 21.5 and 30 V.
Transistorized circuits consuming little current give
reasonable length of operation on battery for mobile
purposes.
Fig. 1-1. FM/AM Modulation Meter ME-505/U
1-1