Alignment of the Simulsat antenna with the desired satellite arc is only the first part in optimizing Simulsat performance. Once the antenna is aligned, each feed must be carefully peaked to ensure that the feed placement coincides with the focal point of each satellite transmission. Along with the actual peaking procedure, there are several steps involved to ensure that a feed is successfully peaked or re-peaked.


FEED PEAKING TOOLS AND EQUIPMENT

The first step in feed peaking is to ensure that you have all the necessary equipment and information. The following is a list of items that are needed for peaking feeds in a Simulsat.

  • 5/32” and 3/16” hex keys. We recommend ball-end hex drivers because of their ability to access socket head screws at odd angles. For peaking 2° spaced feeds, long-handle ball drivers make the job easier.
  • 5/16" and 7/16" wrenches.
  • Felt tip marker.
  • Feedbox spacer bars. Spacer bars are available from ATCi.
  • Ladder or a bucket truck.
  • Satellite receiver.
  • Video monitor.
  • Low noise block down-converters (LNB).
  • Spectrum analyzer.
  • List of desired satellites.

Note: If an ATCi TE900 spectrum analyzer is used, a satellite receiver and video monitor are not required because this analyzer has satellite receiver and video monitor functions.


FEED PEAKING PRELIMINARIES

If possible, peak feeds in the early morning or early evening. Sunlight can make it difficult to see the analyzer display and the video monitor. When it has been determined that daylight and weather will permit, commence with the feed peaking. An important part of peaking Simulsat feeds is to set up the peaking tools and equipment in or on top of the feed box. This way you can get immediate feedback during peaking and zero in on the peak more quickly and accurately. Prior to moving feed assemblies up to the feedbox, firmly fasten the filters, (if any), and then the LNB's to the feed assemblies and then lightly tighten the elevation, focal length, and polarity adjustments of the feed assemblies. Set the feed assemblies to the side in the feedbox. You are now ready to begin peaking feeds.

FEED PEAKING

Simulsat feed assemblies allow adjustment in azimuth, elevation, focal length, and polarity.

LOCATING SIGNALS

Frequently, the first thing to be done after setting up is to locate the desired satellite(s) in the feedbox. Your view of the satellites looking into the feedbox is the same as your view of the satellites in the sky looking at the satellite arc. General feed locations can be found by connecting a bare LNB to a spectrum analyzer and scanning in the feedbox. When looking for feed locations this way, be careful to keep the LNB polarized correctly. The LNB should be held so that either the long or short sides of the rectangular entry port of the LNB are parallel with the sides of the feedbox. Occasionally a satellite will have carriers on only one polarity. In this case, you may need to try scanning the feedbox for each polarity. Certain satellites have distinct signatures and can be easily located.

Once a satellite is located, you can gauge where satellites are in its vicinity. In the Simulsat-5 feedbox, 1° of satellite longitude is equal to approximately 2" of azimuth travel in the feedbox. For a Simulsat-7 antenna, 1° of satellite longitude is equal to approximately 3" of azimuth travel in the feedbox.

After finding the desired satellite, use a marker or a moistened finger to make a mark in the feedbox window to facilitate relocating the spot with the feed assembly. You can now do a quick check of this location to make sure you are on the right satellite.

Set the elevation adjustment of the feed assembly to approximately where you expect to get a peak. Secure the focal length adjustment of the feed assembly. A good starting point for focal length is approximately 1" closer than the feed assembly's maximum travel away from the reflector. The polarity will usually be just about at right angles to the feedbox. Loosen the track bar fastening screws. Connect the analyzer to the feed, and briefly peak the feed.

The carrier levels in the analyzer display (and the acoustic level indication of the TE900) will rise as the feed approaches the best location and fall as the feed is moved away from the best location. Locate the feed where the carrier levels are at their highest. (Note: See 3.3. The highest carrier level is not always optimal.) Seat the feed assembly into the feedbox tracks. If you are using a TE900, switch to the receiver mode, or if you are not using a TE900, connect the feed to a receiver and monitor, and verify the satellite by checking the programming being received against the program listings of a satellite TV publication. Once satisfied that you are on the right satellite, you can begin peaking.

SIMULSAT FEED PEAKING PROCEDURE

When peaking feeds, the highest signal indication on an analyzer does not always correspond to the optimal performing location of the feed. The noise present has a profound effect on performance. (Note: The most prominent noise feature is frequently a peak of interference from an adjacent satellite.) As such, the optimal performing location will be the location where the difference between the noise and the carriers is the greatest. Also, adjustments made to each plane of motion of the feed assembly impart slight effects on the other planes of motion. It is recommended to go carefully through the following steps, and then repeat them giving particular attention to optimizing the difference between the carriers and the adjacent noise in the spectrum. Peaking the feed while paying attention to a particular transponder may be helpful if that transponder is troublesome.

Step 1
Begin with the feed assembly set up the same as in verifying the location of the feed. That is, set the approximate elevation, secure the focal length and polarity, and loosen the screws that secure the azimuth of the feed assembly. If necessary, adjust the distance between the feedbox tracks using the spreader bars. The feed assembly should move easily on the feedbox track. Connect the desired polarity LNB on the feed to the spectrum analyzer.

Step 2
Hold the feed assembly slightly above the feedbox track and move it side to side. The carrier levels in the analyzer display (and the acoustic level indication of the TE900) will rise as the feed approaches the best location and fall as the feed is moved away from the best location. Locate the feed at the best performing location. Make sure that you have not peaked the feed onto a side lobe. Seat the feed onto the track. Mark the track adjacent to the feed assembly track bars on each side of the feedbox. Repeat the process using the track marks as a reference. When the feed is at its best location, secure the feed onto the tracks. If tightening the screws causes the feed to move, use a screwdriver wedged between the track bar and the feedbox side to hold the feed assembly in place during tightening.

Step 3
Peak the elevation by zeroing in on the best spot. Make a reference mark on the feed assembly side bars relative to the feed assembly scalar. Repeat the process using the mark as a reference. When you are satisfied that the feed is at its best location, secure the elevation.

Step 4
After setting the azimuth and elevation, adjust the focal length of the feed by moving the feed assembly in and out. Frequently, the focal length adjustment shows less dramatically on the spectrum analyzer, but can still be very important to optimizing the feed's peak. In some cases, particularly for Ku feeds, the best performance will be found farther away in focal length than the standard feed configuration allows. If this appears to be the case, the feed assembly rack can be modified to allow the feed to be secured farther out. Call ATCi for information.

Step 5
Adjust the polarity by rotating the waveguide portion of the feed assembly. Set the polarity so that adjacent polarities are nulled. In 2-degree adjacent situations, the adjacent satellite peak will frequently not completely null.


SIMULSAT FEED PEAKING PROBLEMS

There are many things that can make feed peaking difficult: terrestrial interference, sun outage, LNB failure, bad connectors, inclement weather, satellite center of box status, and more. Following are some additional suggestions to address problem feeds:

  • Check all connectors and splices, especially those in the feedbox, for signal leakage with a bare LNB connected to a spectrum analyzer. Scanning for leakage of L-band frequencies can be done by connecting a rod antenna (1/2-wave dipole) that can telescope between 3-3/4” and 6” with a line amplifier to a spectrum analyzer. Connectors are also potential sources for signal ingress. Replace or wrap aluminum foil around problem connectors.
  • Canting or angling the feed can sometimes help with problem feeds.
  • Sometimes what appears to be un-nullable cross-polarity is actually adjacent satellite co-polarity. You will need to use a spectrum analyzer to see this. If the adjacent carrier is causing problems, the feed should be peaked viewing both carriers on the spectrum analyzer, trying to maximize the difference between the two carriers instead of just trying to maximize the desired carrier's peak. The greater the difference between the desired carrier and an adjacent carrier, the cleaner the pictures. Using a receiver with a narrower bandwidth or adjustable bandwidth that can be narrowed can also help. Adjacent satellite carriers are 20 MHz away from each other. Sometimes a 36 MHz bandwidth receiver (± 18 MHz) sees too much of the adjacent carrier.
  • Different combinations of equipment will perform differently. For a problem transponder, try different combinations of receivers, LNB's, and feed assemblies.

Your Simulsat feeds should now be optimized for problem free operation. If undesirable issues persist, please feel free to contact ATCI for more in depth troubleshooting.