Research Concepts RC2500 - Manual (Page 42)

RC2500 Antenna Controller Chapter 4 Inclined Orbit Satellites 35
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com
step 6 or by the PC program) using either the 0 or 1 key, and terminate the entry with the ENTER
key. Position the Antenna “On Satellite”.
11. If the receiver's AGC has NEGATIVE polarity (results of Step 6 or the PC program), go to step 12. If
the receiver's AGC has POSITIVE polarity, go to MANUAL mode and examine the signal strength for
the AGC channel that was not selected in step 7 or by the PC program. (SCROLL UP or SCROLL
DOWN until the channel number is displayed i.e. 2: ). If the signal strength reading for that channel is
greater than 10, adjust the OFFSET pot for that channel until the signal strength reading for that
channel is less than 10. To lower the displayed signal strength, turn the appropriate OFFSET pot
clockwise. Proceed to step 13.
Currently the AGC Channel Scroll feature is not supported
12. If the receiver's AGC has NEGATIVE polarity (results of Step 6 or the PC program), go to MANUAL
mode and examine the signal strength for the AGC channel that was not selected in step 7 or by the
PC program. (SCROLL UP or SCROLL DOWN until the channel number is displayed i.e. 2: ). If the
signal strength reading for that channel is greater than 10, adjust the OFFSET pot for that channel
until the signal strength reading for that channel is less than 10. To lower the displayed signal
strength value, turn the appropriate OFFSET pot counter-clockwise. Proceed to step 13.
Currently the AGC Channel Scroll feature is not supported
13. Connect the receiver's AGC output to the controller's AGC input (AGC1 or AGC2) chosen in Step 7
above or by the PC program. Be sure to connect the ground return of the controller to a ground on
the receiver. See figure 3.1 and the discussion of section 3.3.3.
14. Using a voltmeter clip the black lead to the RC2500 J1 pin 7 and the red lead to J1 pin 14 if using
AGC1 or J1 pin 13 if using AGC2. Adjust the OFFSET pot for the appropriate AGC channel until a
reading of your calculated Voffset is obtained. (See Step 9 or the PC program) To increase the offset
voltage, turn the OFFSET pot clockwise.
15. Adjust the gain pot for the appropriate AGC channel for a displayed signal strength of 650. To
increase the displayed signal strength, turn the GAIN pot clockwise for Vs positive with positive AGC
or when Vs is negative with negative AGC. Turn the Gain Pot counterclockwise for an increase in
displayed signal strength for Vs positive with negative AGC or when Vs is negative with positive AGC.
16. Now, readjust the Offset pot to show a reading of Voffset on the voltmeter described in Step 15. Re-
tweak the Gain pot for a displayed signal strength of 650. You may need to do this step 2 or three
times to get the values as close as practical.
17. Jog the antenna off of the satellite until the picture is just barely visible. Note the signal strength
value. Go to CONFIG mode and use the SCROLL keys to bring up either the AGC C Band
Threshold item or the AGC K/L Band Threshold item, whichever is appropriate for the frequency band
that the user has chosen to operate at (and has adjusted the pots at). Key in the signal strength
value noted above. Terminate the entry with the ENTER key.
AGC Threshold = ________________
4.4.1.2 Single Receiver - Dual Frequency Band Inclined Orbit Satellite AGC Setup
The setup procedure described above was for the case where a single satellite receiver is connected to
the controller, and the user is interested in tracking only satellites of a single frequency band (either C or
Ku). A slight increase in complexity occurs if the user must be able to track both C and Ku band inclined
orbit satellites. This is because the same AGC channel is used for both frequency bands, and therefore
the OFFSET and GAIN pot adjustments for that channel must be made so as to accommodate both
frequency bands. At the heart of the problem is the fact that the signal strength (as seen by the receiver's
AGC circuits) will vary with the frequency band selected due to differences in antenna gain, LNB gain,
and the differences in output power between C, Ku, and L band satellites.
The adjustment procedure for the dual band case is very similar to the single band case described above.
The following paragraphs describe the modifications required to adapt the single receiver - single band
procedure, to the single receiver - dual band case.
1. The procedure is similar to step 1 above except that the user should align the antenna with a strong
C band and a strong Ku (or L) band satellite. The installer should then choose the largest of the two
(or three) levels as the “On Satellite” voltage.