Research Concepts RC2000A - Manual (Page 99)

RC2000A Dual Axis Antenna Controller Appendix I 2.6x Addendum 99
down resistor. This means that if one of the AGC channels is unused, its input is pulled to ground.
This can cause problems if the AGC Polarity Flag specifies negative polarity, because an input of
zero volts (ground potential) corresponds to the strongest possible satellite signal. For this case the
installer must place a jumper from connector J1, pin 11, to the unused AGC input channel and
adjust that channel's potentiometers (after negative polarity has been specified) so that its signal
strength value is 0. J1 - pin 11 has a potential of 5.7 volts.
2. AGC C Band Threshold - When the receiver is tuned to a C band satellite and the signal strength
is above this value, it is assumed that a satellite signal is present. The same threshold is applied to
both AGC channels.
3. AGC K Band Threshold - This is similar to the C Band Threshold described above, except it
pertains to Ku Band. If the signal strength is above this value when the receiver is tuned to a Ku
band satellite, the controller assumes that a satellite signal is present.
The signal strength is displayed in MANUAL, REMOTE, SETUP, and LIMIT modes. In REMOTE,
SETUP, and LIMIT modes the signal strength is displayed to the right of the ‘S:’ banner. In these
modes the value displayed will be the greater of the AGC1 or AGC2 channels. In MANUAL mode the
user can use the Scroll Up and Scroll Down keys to display either the greater of the AGC1 or AGC2
channels (‘S:’ banner displayed), AGC1 (‘1:’ banner displayed), or AGC2 (‘2:’ banner displayed).
The signal strength value is represented as a number in the range of 0 to 1023. The displayed value
takes into account the setting of the AGC Polarity Flag. In other words, a greater signal strength value
on the display of the controller always corresponds to a stronger received satellite signal.
2.1 Controller AGC Potentiometor Adjustment
The following steps guide the installer through the pot adjustment process in an installation that will
operate at a single frequency band. If the controller is being interfaced to a receiver that will be used for
both C and Ku band, the procedure given below must be modified slightly. The modifications to the
procedure for the dual band case are described in section 2.1.2.
2.1.1 Single Frequency Band Potentiometer Adjustment
The following steps are performed when the controller is in MANUAL mode.
1. Align the antenna with a strong satellite (geostationary or inclined orbit). Place a voltmeter on the
receiver's AGC output, measure and record the voltage. In the description that follows, the term 'on
satellite' will be used to refer to the antenna aligned with a strong satellite.
Note that if both AGC inputs will be utilized, record the ‘on satellite’ voltage for both receivers.
2. Jog the antenna off of the satellite so the antenna is looking at nothing. Measure and record the
receiver's AGC voltage. In the description that follows, the term 'off satellite' will be used to refer to
this case where the antenna is positioned well off of any satellite, looking at nothing.
Note that if both AGC inputs will be utilized, record the ‘off satellite’ voltage for both receivers.
3. If the difference between the two recorded values is less than 1 volt, connect the receiver's AGC
output to the controller's AGC1 input. Otherwise, connect the receiver's AGC output to the
controller's AGC2 input. Be sure to connect the ground return of the controller to a ground on the
receiver. See figure 3.1.
Note that if both AGC channels will be utilized, connect the Signal Strength output of the receiver
with the smaller ‘on satellite’ – ‘off satellite’ voltage difference to the controller’s AGC1 input.
Connect the other receiver’s Signal Strength output to the controller’s AGC2 input.
4. If the AGC voltage associated with the 'on satellite' case is greater than that of the 'off satellite'
case, the receiver has POSITIVE AGC polarity (otherwise the receiver has NEGATIVE AGC
polarity). Go to CONFIG mode and use the SCROLL keys to bring up the AGC Polarity Flag item.
Key in the proper polarity using either the 0 or 1 key, and terminate the entry with the ENTER key.
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