RESEARCH CONCEPTS RC2000C Manual page 38

30 RC2000C Az/El Tracking Antenna Controller
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/L Band Threshold - This is similar to the C Band Threshold described above, except it
pertains to Ku or L Band. If the signal strength is above this value when the receiver is tuned to a
Ku or L band satellite, the controller assumes that a satellite signal is present.
The signal strength is displayed when MANUAL, TRACK, SETUP, and LIMIT modes are active. In
MANUAL, TRACK, and SETUP modes, the signal strength of the AGC channel that corresponds to the
strongest received satellite signal is displayed. In LIMIT mode, the signal strength of both AGC
channels is displayed (the first value corresponds to AGC1). The signal strength is displayed as a
number in the range of 0 to 1023. Note that in MANUAL, TRACK, and SETUP modes, the maximum
signal strength that can be displayed is 999. A signal greater than 999 is displayed as '***'. The
displayed value takes into account the setting of the AGC Polarity Flag. In other words, a greater signal
strength value always corresponds to a stronger received satellite signal.
Single Receiver - Single Frequency Band Inclined Orbit Satellite AGC Setup
The following paragraphs describe the setup procedure for the simplest case - only one receiver and
controller AGC input are used, and the user is tracking only C band (or only Ku or L band) inclined orbit
satellites.
1. Align the antenna with a strong satellite (geostationary or inclined orbit) of the proper frequency
band. 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.
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.
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.
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.
5a. If the receiver's AGC has NEGATIVE polarity, go to step 5b. If the receiver's AGC has POSITIVE
polarity, go to LIMITS mode and examine the signal strength for the AGC channel that was not
selected in step 3. If the signal strength reading for that channel is greater than 10, adjust the
OFFSET and GAIN for that channel until the signal strength reading for that channel is less than 10.
To lower the displayed signal strength turn the OFFSET pot clockwise and the GAIN pot counter-
clockwise. Be sure not to turn the controller off while the controller is in LIMITS mode, or else the
limits that have previously been set will be corrupted. Proceed to step 6.
5b. If the receiver's AGC has NEGATIVE polarity, connect a jumper from the controller's unused AGC
input channel to connector J1, pin 11. Go to LIMITS mode and examine the signal strength for the
AGC channel that was not selected in step 3 above. If the signal strength reading for that channel
is greater than 10, adjust the OFFSET and GAIN pots for that channel until the signal strength
reading for that channel is less than 10. To lower the displayed signal strength value, turn the
OFFSET pot counter-clockwise and the GAIN pot clockwise. When this is accomplished proceed to
step 6.
6. In the next few steps of the procedure, the OFFSET and GAIN pots of the AGC channel connected
to the receiver's AGC output are adjusted so that the 'off satellite' signal strength value is between
50 and 100 and the 'on satellite' signal strength value is between 600 and 700.
Research Concepts, Inc. • 9501 Dice Lane • Lenexa, Kansas • 66215 • USA
Chapter 4 Inclined Orbit Satellites
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