EA4TX – ARS-USB Manual – June. 2024 Page 11
Unfortunately as previously discussed, not all rotors have a standard voltage value
for V. The A/D converter accepts 5V as maximum voltage. To obtain the maximum
digital output level, the signal from the rotor will have to either be attenuated or
amplified. Again this will depend on the individual rotor.
In the previous example we found that a HAM-IV or T2X rotator gives 12V when it is
fully turned clockwise (CW limit). Therefore voltage from the rotor will have to be
attenuated to 5 V by adjusting Pot1.
In other examples mentioned, rotators like the Kenpro KR-600RC or YAESU G-2000
may show a maximum voltage that is negative (-3.6V). Therefore the signal to the
ARS-USB board will have to be amplified to avoid losing resolution in the converter.
Polarity will also change from negative to positive. The is also accomplished by
adjusting the gain at Pot1.
The ARS-USB has a potentiometer for each input providing all of these adjustments:
Azimuth input:
Pot1 adjusts the Gain/Attenuation between 3-24V.
Elevation input:
Pot2 adjusts the Gain/Attenuation between 3-24V.
The insertion of the ARS-USB in parallel between the Rotor and the
Control Unit should not cause any error or modification in the readout of the
original instrument. The ARS-USB circuit presents high impedance at the J4
input.
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