MT-MR PLATINUM. POINT TO POINT AURAL RADIO RELAY SYSTEM
33
3.- Before turning equipments on, check transmission & reception frequencies within allowed sub-band, by verfying
Transmitter Oscillator and Receiver Local Oscillator settings at Display screens.
4.- Adjust variable RF attenuator to obtain a nominal -40 dBm signal at receiver's input. [+30-( -40)
→
70 dB att.]
5.- Rotate power control potentiometer at transmitter fully counter clockwise, decreasing power output to a
minimum.
6.- Turn on both transmitter & receiver equipments.
7.- Once transmitter & receiver PLLs are locked in phase, slowly turn clockwise power control potentiometer at
transmitter, until it reaches its nominal power output of 10 watts (+30 dBm). Check that reflected power at
transmitter is well below the allowed security margin. Transmitter is set for Stereo transmission (pre-emphasis &
filter OFF).
8.- Verify receiver Display reading in <
SIGNAL>
> line. This reading must coincide with the received signal level
of -40 dBm. Log reading.
9.- Connect the mute circuit at receiver (<
MUTE
> switch ON) and progressively decrease received signal by
increasing attenuation with the variable attenuator, until mute circuit just triggers on. Assure that no noise or "hiss"
can be heard in the monitor speaker of receiver during this procedure. Check the attenuator scale reading. Its
reading must be equal or more than 100 dB attenuation. Log receiver's Display reading for this RF signal level.
10.- Restore input signal level at receiver of -40 dBm by reducing attenuation. Turn on baseband tone generator.
Calibrate it to produce a 1 KHz/ 0 dBm tone. Adjust transmitter baseband input level to deviate ±75 KHz.
Remember that Baseband Tone Generator must be connected to Stereo Baseband Input BNC Connector at
transmitter.
11.- Check receiver Display at <
DEV>
> bar indicator.. It must indicate 75 KHz deviation or 100% modulation.
12.- Perform a frequency response check, from 30 Hz to 100 KHz, keeping output amplitude of Baseband Tone
Generator constant, and reading receiver's Check that frequency response keeps within the receiver's Technical
Specifications. Log any frequency drop values at SCA sub-carrier frequencies between 67 & 92 KHz. Log stereo
baseband frequency response curve.
13.- Set Baseband Tone Generator to 1 KHz / 0 dBm. Connect its balanced output to XLR input connector at
transmitter. Set pre-emphasis & filter ON. Verify that transmitter's deviation keeps in ±75 KHz.
14.- Connect an Audio Test Set or Psophometer having a calibrated VU Meter (in dB) in Hi-Z to XLR balanced
audio connector output at receiver. Verify that VU Meter reading is 0 dB.
15.- Set receiver for monaural reception. Read VU Meter. The reading should be the same as before (0 dB).
16.- Perform a frequency response check for monaural mode. Always keep output amplitude of Baseband Tone
Generator constant, and reading external VU Meter. Frequency response will run between 30 Hz and 15 KHz.
Check that obtained frequency response curve is within the allowable receiver's Technical Specifications. Log this
curve.
