G1SLE MK2 Repeater Controller Alignment.
Alignment of the Mk2 controller is relatively simple, it is advised that before aligning
the controller you fit it to your repeater according to the instructions in the ‘G1SLE
Mk2 Repeater Controller Connections’ document, you will also need to program your
controller according to the instructions in ‘G1SLE Mk2 Repeater Controller
Programming’
To align your controller you will require:-
Repeater with controller connected.
Oscilloscope suitable for audio frequency use.
Frequency counter for audio frequency use.
Signal generator inc. 2 x modulation sources able to generate CTCSS tones and 1kHz
tone.
Deviation meter able to operate at the repeaters TX frequency.
RF power meter able to measure the repeaters TX power.
Once your controller is fitted to the repeater and programmed with your callsign etc.
switch on the repeater with the ‘progmode’ jumper open.
Using the oscilloscope find a square wave on pin 5 of the NE567.
Adjust the ‘Set 1750Hz’ preset to achieve 1750Hz on the counter.
If the waveform is unstable temporarily disconnect the unmuted discriminator input
from the controller.
The next step is RSSI adjustment, this assumes your receiver has a signal strength
output that ranges somewhere between 0 and 5 volts with higher voltage
corresponding to stronger signal.
Apply signal to the receiver at the level below which you require a ‘weak’ signal
report. Use your oscilloscope to look for a low level on pin 27 of the 89s5252, adjust
the ‘Set Lo’ preset to the point where the level abruptly falls to near zero.
Next increase the signal level to the level above which you require a ‘strong’ signal
report. Move your oscilloscope to pin 26 of the 89s5252 and adjust the ‘Set Hi’ preset
to the point where the level abruptly falls to near zero.
Now apply 1khz. modulation to the signal generator at full deviation (5 or 2.5khz.).
Check the waveform at pin 10 of the FX805, it should be free from any distortion,
particularly check for clipping and if clipping is present reduce the audio level from
the receiver so that the waveform remains undistorted even at full deviation.
Once distortion free audio is being fed to the FX805 check the waveform on pin 11 of
the FX805, this is the filtered audio out to the transmitter, again it should be free from
distortion and clipping.
Now move on to the waveform on pin 11 of the 25 way D connector, this is the
buffered output to the transmitter, adjust the TX AF Gain preset to achieve a level
similar to that on Pin 12 of the 25 way D, again checking for distortion and clipping.
This procedure will ensure that the through audio path is free from distortion and of
roughly unit gain.
