Spring 2023 SBN Ground Station Repointing Guide

On January 24, 2023, NOAA released Service Change Notice 22-77, describing the change of relay satellite for all SBN services (NOAAPort and NWWS) from Intelsat’s Galaxy 28 to the newly launched Galaxy 31. For ground station operators, this move is non-trivial in that the location of Galaxy 28 is geostationary over 89°W, and Galaxy 31 is geostationary over 121°W.

The current transition schedule requires ground stations to switch to the new satellite on a relatively tight schedule:

  • 5 Feb 2023: Galaxy 31 illuminated
  • 10 Feb 2023: Ground Station Transition Begin
  • 31 Mar 2023: Ground Station Transition End
  • 3 Apr 2023: Galaxy 28 decommissioned

This guide is intended to help operators who are not familiar with repointing a satellite dish to provide the information to a professional satellite technician.

Note: This guide was prepared for SBN ground station operators to be able to provide information to their professional satellite technician to repoint a satellite reflector for SBN reception. UCAR is in no way responsible for injuries, damages, loss of data, loss of income, loss of life, or other issues that may arise from the use of the information herein. Lightning, wind, heavy equipment, heights, and all other dangers associated with construction, satellite communications, and satellite reflector maintenance are a serious threat to life and potential injury. UCAR in no way indorses anyone not trained and experienced with to perform any of the tasks outlined in this document, rather, this document is meant to act as the starting point for a Statement of Work for an operator to hire a professional to perform such work.


Assumptions made in this guide include the following:

  • The reflector is attached to the mount in an “Az/El” mount paradigm
  • The mount is anchored without the use of a motorized actuator
  • The reflector is pole-mounted
  • The Novra S300N has been configured for the new satellite (see Novra S300N configuration, below).


UCAR SBN reflector
Figure 1: UCAR SBN ground station reflector.
(Click to enlarge.)

In this example, we step through the process of repointing the current SBN reflector at UCAR's Foothills Laboratory in Boulder, Colorado (Figure 1).

Using a GPS, cell phone, or Google Maps, determine the latitude and longitude of the satellite reflector that will be repointed.

For our example, the latitude is found to be 40.03721°N and the longitude is -105.24192°E.

Searching the Internet will yield several on-line satellite pointing calculators. For this example, we use the Satellite Signals home page, which can calculate results for all aspects of the repointing.

Providing our latitude and longitude as inputs, and using the current satellite, Galaxy 28 at 89°W, as our control, the current look angle and polarity tilt will be used to make relative changes.

Guide Location:
40.03721°N latitude.
-105.24192°E longitude.

Galaxy 28:
89°W longitude (geostationary).

Current Azimuth:
155.64° from true North.
150.19° from magnetic North.

Current Elevation:
40.73° above the horizon (or “level”).

Current Polarization tilt at peak signal:
-18.41° from LNB housing horizontal (clockwise) if viewed from the front.

Galaxy 31:
121°W longitude (geostationary).

Current Azimuth:
203.68° from true North.
198.24° from magnetic North.

Current Elevation:
40.9° above the horizon (or “level”).

Current Polarization tilt at peak signal:
17.91° from LNB housing horizontal (counterclockwise) if viewed from the front.

Note: For determining the change in azimuth, it does not matter if you use true North or magnetic North, but pick one and always use the North reference selected.

In this example, the repositioning data above require the following changes:

Azimuth delta: 48.04° to the west
Elevation delta: rise 0.17° above horizon
Polarization tilt delta: 36.32° 
(counterclockwise, viewed from facing the reflector)

If there is more than 1° change in elevation, it is best to start by changing the elevation first. Select a section of the mount or part of the dish that is flat, and using a magnetic declinometer, note the starting angle before loosening any hardware.

Elevation adjustment
Figure 2: Protractor set for elevation adjustment.

On most pole mounted reflectors, the elevation is changed by loosening and rotating nuts on an elevation rod. It may be necessary to loosen bolts and nuts very slightly at pivot points, but only enough so the dish will move. It is important to loosen the nut in the direction of the adjustment, first. In the case of raising the dish, loosen the bottom nut, and then tighten the top nut to follow the bottom nut. The goal is to change the elevation by the delta as calculated from the current position and the position needed to point to Galaxy 31.

Elevation adjustment key points
Figure 3: Elevation adjustment key points.

Conversely, lowering the pointing angle entails loosening the top nut, and then turning the bottom nut to follow the top nut. Once you have changed the angle as seen on the protractor by the desired delta, snug, but not tighten, the adjustment nuts and any loose pivot points.

Pole mounted reflectors normally adjust azimuth by rotating the entire dish on the pole after loosening the collar bolts. Before committing to the azimuth change, take the time to make witness marks of the current reflector position (figure 4).

Azimuth witness marks
Figure 4: Make initial witness marks.

Next, measure the circumference of the pole (not the collar). Most pole mounted collars are 12” or 18” long, although the Comtech 3-piece reflector has a collar that is 48” long. Regardless, the circumference needed is of the pole that the collar sits on, which, on the Comtech, will be close to the ground.

Measure pole circumference
Figure 5: Measure pole circumference.

In this example, the pole has a circumference of 536mm. Knowing the angle of the direction change needed to repoint to Galaxy 31, the arc distance change on the pole can be calculated:

Rotating the collar to repoint to Galaxy 31, west of the current satellite, results in an arc distant change of 71.53mm.

Measure new location
Figure 6: Measure to the new location.

Final azimuth preparation entails scribing a second witness mark on the pole, to which the collar (and thus whole dish) will be rotated to acquire Galaxy 31.

Target witness mark
Figure 7: Apply target witness mark.

Mount collars will have three or four sets of bolt pairs equally spaced around the collar that secure the dish at the correct azimuth. In this example, there are three sets of two bolts. We suggested that only one set of bolts be loosened, and only loosened enough to allow the dish to rotate, but not rotate freely.

Azimuth adjustment
Figure 8: Bolts for adjusting azimuth.

With assistance, push the reflector in the direction that will bring the collar mark in line with the 121°W pole witness mark. Snug the bolt only slightly. With assistance, use Novra monitoring software tool (see Novra S300N configuration below for details), and note the Carrier to Noise ratio (C/N). Very slightly, push the reflector to the left (as viewed from behind the dish), and note changes to the C/N. If the C/N decreases, push the reflector back to the right in small increments. Allow the Novra statistics to sample over 10 seconds at a minimum with each slight move before pushing the reflector again.

Continue moving the reflector in small motions, noting an increase/decrease in the C/N, with the goal to move the reflector to achieve the highest C/N. Once the highest C/N has been located, make witness marks on the collar and pole, separate from other witness marks, as the final azimuth position for Galaxy 31.

Tightening tip
Figure 9: Nudge reflector to the right before tightening.

Stonie’s Tip: On pole mounted reflectors, tightening the collar bolts to lock down the reflector will result in the reflector moving from the intended “peaked” position. This is due to the bolts being tightened “biting” into the pole and walking the collar away from the intended location. To overcome this potentially frustrating aspect, once you achieve the peak C/N from the Novra monitoring tool, push the reflector slightly to the right, viewed from behind the reflector, before starting the tightening process. When the bolts are tightened, they will bite and walk the collar to the left, and with practice, will put the collar back to the optimal witness mark.

Once all collar bolts are confirmed to be tight, return to the elevation rod peaking process. Lower the elevation angle very slightly, and again, note the C/N reading from the Novra monitoring tool. Adjust the nuts on the elevation rod until the highest C/N reading is achieved. At that point, tighten all nuts and bolts, both on the elevator rod itself, as well as all pivot points. This concludes the base reflector repointing and attention will now turn to the polarization tilt.

Not all reflector feedhorn/scalar ring assemblies allow for adjustment in polarity other than horizontal to vertical, but in discrete relation to the reflector. However, for those scalar ring/feedhorn assemblies that allow adjustment, additional peaking should be considered.

Polarization tilt angle
Figure 10: Measuring initial polarization tilt angle.

As done previously, it is best to start with a reference of what the LNB’s polarization tilt angle is initially. Use the bolt heads on the LNB as stops for the edge of the protractor to insure an accurate reading of the angle.

Loosen the set screw(s) for the feedhorn and rotate counterclockwise (viewing from within the reflector) the delta angle calculated earlier. For Boulder, this was 36.32° in total from the initial position. Snug the set screw(s), and with assistance, record the C/N reading from the Novra monitoring tool. Note that while a person is standing or in front of the reflector, the C/N will be lower than it was when the azimuth and elevation were adjusted. Maintain the same physical location of the operator adjusting the polarity until final peak.

Slightly rotate the feed to the right, note the increase or decrease in the C/N. If increasing, continue to rotate, incrementally, in that direction until the C/N decreases. Likewise, if the C/N decreases, go the opposite direction. Once the C/N has reached the highest level, secure the set screw(s) without overtightening.

On aftermarket feedhorns, it is also possible to adjust the focal length of the feed by sliding it forward or out of the scalar ring with the set screw(s) only snug (but loose enough to allow feedhorn movement). This process is the same as the other peaking processes and can help attain a further gain in signal strength or decrease in noise.

Once satisfied that the peak C/N has been obtained, confirm the coaxial connections are watertight, all items loosened during the repointing are retightened, and replace zip ties with fresh zip ties or Velcro to prevent movement of cables on or around the dish. Wind induced movement in cables produces inadvertent RF noise, and cable hygiene goes a long way to further reduce noise sources.

Novra S300N configuration

The following information for configuring the Novra S300N satellite receiver has been provided by NOAA.

NOAAPort ingest:
-- Symbol Rate: 30 Msps
-- RF Frequency: 1130 MHz
-- PID(s):  101
-- FEC Type: DVB-S2
-- Modulation/Coding: 16PSK 2/3
-- ISI: 18
NWWS ingest:
-- Symbol Rate: 30 Msps
-- RF Frequency: 1130 MHz
-- PID(s):  201
-- FEC Type: DVB-S2
-- Modulation/Coding: QPSK 1/3
-- ISI: 2

One method to reconfigure the Novra is to save off the current Novra configuration, edit the resulting xml file with the items that need changed, and then reload. The Novra supplied Linux “cmcs” utility can be downloaded here:


Using the "cmcs" utility:

$ cmcs -list
S300N   IP address: MAC: jj-bb-aa-zz-yy-xx

$ cmcs -ip -pw  -save mynovra.xml

Edit the resulting mynovra.xml file for RF Frequency:

    <NETWORK ReceiverIP="" SubnetMask="" DefaultGateway="" StatusDestinationIP="" StatusDestinationPort="6516" IGMPFilter="OFF" />
        <SIGNAL RF="1130" SymbolRate="30000" AutoSR="OFF" GoldCode="0" SearchType="DVBS2" MODCOD="2/3 16APSK" ISI="18" />
            <LNBSpec LOFrequency="0" PolaritySwitchingVoltages="13 &amp; 18" HiLowBandTone="22" />
            <LNBControl Power="ON" Polarization="Horizontal/Left" Band="High" LongLineCompensation="ON" />
        <CARRIER_TO_LO>Carrier Freq. &gt;= L.O. Freq.</CARRIER_TO_LO>
        <TRANSPORT_STREAM PIDS="Selected">
            <PID Number="101" Processing="MPE" />
            <PID Number="102" Processing="MPE" />
            <PID Number="103" Processing="MPE" />
            <PID Number="104" Processing="MPE" />
            <PID Number="105" Processing="MPE" />
            <PID Number="106" Processing="MPE" />
            <PID Number="107" Processing="MPE" />
            <PID Number="108" Processing="MPE" />
            <PID Number="150" Processing="MPE" />
            <PID Number="151" Processing="MPE" />
            <PID Number="NULL" Processing="RAW" />
        <IP_REMAP_TABLE Enabled="false" RemapSourceIP="false" />

Then reload the configuration:

  $ cmcs -ip -pw  -load mynovra.xml

Note that since the only parameter being changed here is the signal RF frequency, you could skip editing the configuration XML file by hand and use the cmcs command to change the parameter directly:

$ cmcs -ip -pw  -rfreq 1130

(The method you choose to change this value is up to you. There is no need to both edit the XML file and use the command with the -rfreq parameter.)

Finally, to monitor the signal strength, use the cmcs command:

  $ cmcs -ip -pw <password> -shsat

    Satellite Interface Settings:

      Receiver MAC Address:   jj-bb-aa-zz-yy-xx
      Receiver Mode:          DVBS2
      Frequency:              1110.0 MHz
      Symbol Rate:            30.000 Msps
      ModCod:                 2/3 16APSK
      Gold code:              0
      Input Stream Filter:    On
      Input Stream ID:        18

      Signal Lock:            On
      Data Lock:              On
      Uncorrectable Rate:     0/Second
      Packet Error Rate:      0.0000e+00

      Carrier to Noise C/N:   15.2dB
      Signal Strength:        -53 dBm

If you have questions about this example satellite receiver repointing process, please contact support@unidata.ucar.edu.


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