9.2
RF BOARD OPTIONS
9.2.1
DISCRIMINATOR POLARITY
The polarity of the discriminator output at pin 14 of J102 is configured at the factory such that an
i
ncrease in RF frequency causes an increase in DC voltage. This is considered “normal” mode.
An inverted mode is available where an increase in frequency causes a decrease in voltage. This
is effected by removing R130 and placing it in the open pad pair denoted as R125.
10 ALIGNMENT
Warning: Alignment must only be performed by qualified and trained service personnel.
The DTX module is aligned at the factory before shipment and should need no further
adjustment. It is possible that the gain settings for the audio input and output signal paths may
need optimized. The frequency trim, deviation, and balance should not need adjustment. The
procedure for performing all of the alignment steps is detailed below. The unit should not be
opened for alignment; all adjustments are electronic and effected through the programmer
software.
10.1 REQUIRED TEST EQUIPMENT
Depending upon which alignment steps are to be performed, some or all of the following pieces of
test equipment may be required:
DC Power Supply - capable of operating at the correct voltage for the module and capable of 7
Ampere minimum current.
RF Signal Generator- capable of operating at the carrier frequency of the module with an output
level adjustment and able to be frequency modulated.
FM Demodulator/Deviation Meter- capable of operating at the carrier frequency of the module.
RF Frequency Counter- must operate at the RF frequency of the unit with a resolution of 10 Hz or
better and an accuracy of +/-1 ppm (+/-150 Hz at VHF, +/-450 Hz at UHF) or better.
Audio Oscillator- must have sinewave output allow for output frequency and amplitude
adjustment.
Oscilloscope
RF Power Attenuator or Dummy Load with coupled output- must be 50 ohms impedance at the
operating frequency and rated for the output power of the module and have an output which can
drive the FM demodulator at the correct level and the frequency counter.
RF Power Meter- capable of accurately indicating the RF output power of the module.
Note: Except for the power supply, a two-way radio test set may include most, if not all, of the
required equipment.
10.2 ALIGNMENT PROCEDURE
It is not absolutely necessary to perform all of the alignment steps detailed below. However,
some adjustments interact somewhat with others e.g. balance affects deviation, deviation affects
AUX IN gain, and the output power AUX IN gain has a slight affect on TX frequency trim. It may
be prudent to spot check all of the adjustments which interact. These will be indicated in the
particular alignment step.
