RESEARCH CONCEPTS RC2000C Manual page 37

RC2000C Polar Tracking Antenna Controller
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 which 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
which 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 LIMIT mode and examine the signal strength for the AGC channel which 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 SCALE pot counter-
clockwise. Be sure not to turn the controller off while the controller is in LIMITS mode, or else the
limits which 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 LIMIT mode and examine the signal strength for the
AGC channel which 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 SCALE 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.
Note that the GAIN and OFFSET adjustments are implemented using 20 turn pots. A lot of turns may
be required.
7. Go to MANUAL mode, position the antenna 'off satellite', and adjust the OFFSET pot (for POSITIVE
polarity receivers) or the GAIN pot (for NEGATIVE polarity receivers) so that the signal strength
reading is about 75.
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas 66218-9680 • USA
Chapter 4 Inclined Orbit Satellites
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