Dawn CONTROL-1500A Manual page 37

CONTROL-1500A Single Axis Antenna Controller
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.
The following procedure describes AGC1 and AGC2 potentiometer adjustment for a dual band
installation.
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.
DAWNco • 3340 S. Lapeer Rd • Orion, MI 48359-1320 • Ph (248) 391-9200 • Fax (248) 391-9207 • sales@DAWNco.com
Chapter 3 Installation/Setup 30