Research Concepts RC2000A - Manual (Page 101)

RC2000A Dual Axis Antenna Controller Appendix I 2.6x Addendum 101
‘Threshold value is applied to both channels for operation at a given band. There are unique
‘Threshold values for each band.
2.1.2 Dual Frequency Band Potentiometer Adjustment
The setup procedure described above was for a single band antenna system (either C or Ku). A slight
increase in complexity occurs dual C and Ku band operation. 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
and Ku band satellites.
1. Align the antenna with a strong C band satellite. Place a voltmeter on the receiver's AGC output,
measure and record the voltage. This voltage will be referred to as ‘RCV1 - on satellite – C band'
where ‘n’ is 1 or 2 depending on which AGC channel is used. In a similar manner, align the
antenna with a strong Ku band satellite. Record the receiver voltage. This voltage will be referred
to as ‘RCV1 – on satellite – Ku band’.
Note that if both AGC inputs will be utilized, record the ‘on satellite’ voltages associated with the
other receiver ‘RCV2 – on satellite – C band’ and ‘RCV2 – on satellite – Ku band’.
2. Jog the antenna away from any satellites so the antenna is looking at nothing. Measure and record
the receiver's AGC voltage. Refer to these voltages as ‘RCV1 – off satellite – C band’, ‘RCV1 – off
satellite – Ku band’.
Note that if both AGC inputs will be utilized, also record the ‘off satellite’ voltages for the other
receiver … ‘RCV2 – off satellite – C band’ and ‘RCV2 – off satellite – Ku band’.
3. Choose that band that has the greatest difference between the ‘on satellite’ and ‘off satellite’
voltages. If the difference between the two 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.
5a. If two receivers are interfaced to the controller proceed to step 6. If the receiver's AGC has
NEGATIVE polarity, go to step 5b. If the receiver's AGC has POSITIVE polarity, from MANUAL
mode use the Scroll Up/Scroll Down keys to 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. Proceed to step 6.
5b. If the receiver's AGC has NEGATIVE polarity and only one receiver is interfaced to the controller,
connect a jumper from the controller's unused AGC input channel to connector J1, pin 11. From
MANUAL mode use the Scroll Up/Down keys to 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(s)
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. The
Research Concepts, Inc. • 5420 Martindale Road • Shawnee, Kansas • 66218-9680 • USA www.researchconcepts.com