Appendix I Signal Strength Peakup; Signal Strength; Controller Agc Potentiometor Adjustment; Single Frequency Band Potentiometer Adjustment - RESEARCH CONCEPTS RC2000A DUAL AXIS Instructions Manual

Antenna controller

Table of Contents

RC2000A Dual Axis Antenna Controller Appendix I

To implement the peaking algorithm, the controller requires an analog input which indicates the strength

of the received signal. Such a voltage is generated within a satellite receiver, and is referred to as an

AGC signal (Automatic Gain Control). On many receivers this signal is available at a terminal on the

back of the receiver. On satellite receivers this signal may also be referred to as a 'Signal Strength' or

'Tuning Meter' output. An AGC output typically varies in proportion to the received power of the

transponder which the receiver is currently tuned to.

The controller has the provision to process two channels of AGC information. This means that two

receivers can be connected to the controller (at least one receiver is required to implement peakup

function). The two channels are referred to as AGC1 and AGC2. The controller uses the stronger of

the two as its AGC input. Each channel has separate gain and offset potentiometer adjustments. The

installer uses the pots to transform the receiver's AGC signal swing into a range of values which is

easily measured by the controller.

In addition to the potentiometers, there are three CONFIG mode items which are related to the AGC

system. The three items are ...

1. AGC Polarity Flag - This flag indicates to the controller whether a stronger satellite signal

corresponds to a higher AGC voltage (positive polarity) or a lower AGC voltage (negative polarity).

Both AGC channels must have the same polarity. Each AGC channel contains an internal pull

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.

1.1 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.

1.1.1 Single Frequency Band Potentiometer Adjustment

The following steps are performed when the controller is in MANUAL mode.

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