Reflector damage – The surface of a Ku-band antenna is often about +/- 20 one-Thousandths of an
inch.
It can usually not be repaired. And even if it is repaired, it must be retested for compliance after the repair. Leave this up to a professional.
Considering its size and how hard it is to replace a reflector, this means it is very expensive. Some antenna systems cost as much money as you will make in six to nine months. Don't ever forget that.
On my first day on the job in television, photographer David Coleman looked at me and pointed at a piece of umbilical cable, “Do you see that? It's easier to replace you than it is to replace that cable.” I often wonder what he would say about a 40-Thousand dollar dish.
Feedhorn support damage – Generally, feedhorn supports can be repaired, reformed, or rebuilt. This
will be difficult if the feedhorn is part of the folding or deploying mechanisms.
These days, getting proper replacement parts from the manufacturer or having a complete retrofit done to the antenna is often the only way to make a repair that will maintain compliance in a damaged or old dish.
The FCC has declared a few dishes are no longer compliant, now that satellites are living closer together (3 degrees has now become 2 or less degrees between some satellites). If this is the case, it would be sad to see the dish destroyed or thrown away. Even a small DirecTV or Dish Network dish is useful for something and could be used as a downlink dish. See what you can do to donate the dish to a small TV station or sports bar. There are still a lot of FTA (free to air) broadcasts available. If you take it to the factory for repair, they may recycle the dish in another way.
Once you or a professional has replaced feedhorn supports, the centering of the feedhorn and the focus must be checked.
Microwave absorber panel damage – In Ku-Band's infancy, many dishes did not even meet 3º
compliance (they must now be 2º compliance) because they were built for C-Band transmission, so they were outfitted with microwave absorbing materials to help the dishes maintain their sidelobe compliance. Many of them also used microwave absorbent material in the center or the feedhorn mount to prevent any secondary reflections off the feedhorn or the feedhorn supports.
This issue has been largely solved now that most Ku-Band and some C-Band trucks use an offset dish, where nothing is in the way of the outgoing or incoming beams once they reflect off the dish.
If this absorbing material is used on a dish you are operating or maintaining, be sure to keep the material clean and free of dirt. And replace the pads when they get old or worn out.
Positional system damage – Absolutely no horizontal play is allowed in the antenna system. This
should be checked regularly. If you have a cable driven antenna, you should be aware of whether or not the cables have slipped (if the dish won't stow, that's a pretty good sign!).
Some antenna positioning systems can be “flexed.” Try it out when you aren't transmitting: Push on the edge of the dish (don't force it). When you let it go, does it return to the original position? If so, then you are fine and there is no play in the system.
Many antenna positioning systems have gears, ball bearings, cables, or jam blocks with support screws that loosen up over time of being bounced down roads and shaken up by the wind. These things need to be checked regularly, and tightened if necessary.
• On one occasion while uplinking in Wichita, Kansas our truck was hit with a wind shear, the type that
can take down an airplane. It was a beautiful day, not a cloud in the sky, then bam, we all grabbed onto something and it felt like we'd been bumped hard by a bus. There was a loud thump on the roof of the truck.
I and jumped out of the truck to find that the wind sheer had shoved the offset dish so hard, it slipped through the grasp of the cables (said to withstand 80 mile and hour winds). The feed support came slamming down onto the roof. The dish did exactly what it was designed to do. Instead of bending the dish, it allowed the dish to slip instead of holding it there to be bent. However, it took a long time to convince the dish it was now in a different place. The dishes often need to be moved back through this tension, by loosening the cables and slipping the dish through them, or you can have soft limits removed from their programming, or if you are lucky, you might be able to manually move the dish like I did.
Always have a backup plan, and figure out what you can do when technology fails you. It keeps you on top of your game, and you won't panic when the worst happens to you.
Feedhorn damage – The feedhorn is a very critical part of the satellite antenna. Leave the repair up to the manufacturer, and only attempt repair if you know it has not changed the manufacturer's
specifications. A crack might only need repair with JB Weld. However, this should only be your last option. Damage to the waveguide going into the feedhorn can often be repaired by professionals who know how to repair waveguide. There are many of these professionals around the country. But make sure this person knows what they are doing. Don't just take the part to a farm welder.
Antenna stabilization damage – All uplinks need to have a means of stabilizing the antenna, the
truck, or the van.
These stabilizers need to be in perfect working order. Stabilization is important not only for the optimum operation, but it is also important because it eliminates interference.
If the truck, van, or flypack is not stable, small movements are amplified by the antenna itself or the antenna's feedhorn stabilizer. The downlink can lose your signal, and you can cause interference from your swinging dish.
The most common stabilizers used in trucks and vans are hydraulic and hand-crank levelers used for uplinks, production trailers, Recreational Vehicles (RV), and various utility trucks.
Maintaining these stabilizers is often a full-time job in itself. Understand how to use them, how to fix them, how to replace them, and if you have hydraulic jacks, know how to clean up after them should they blow a hydraulic line.
Spectrum Analyzer or Monitor damage – The uplink system must have a spectrum analyzer or
spectrum monitor connected to the receive system.
The analyzer must be able to display all 500 MHz of the Ku-Band and/or all 500 MHz of the C-Band. Usually this can be done with the same monitor.
The analyzer or monitor must also be of sufficient quality to identify the satellite and the various types of satellite traffic, digital or analog traffic. And it must also be capable of displaying a 2db per division or greater expansion (able to zoom in or magnify) for the purpose of fine-pointing.
These requirements do not mean you will have to spend boatloads of money. The application is a modest one, in that you are only verifying satellites and signals. But this equipment must be well built enough to withstand the abuse of travel. Two of the most popular brands today are Tektronix and Avcom.
System indicators and control damage – The uplink chain and all of its components must power up
in a safe, non-radiating state and power down in the same safe way.
Indicator lights on baseball switches and indicators for power should be driven from sensors and not control circuits or remotes. Waveguide baseball switches should use telemetry contacts to give the true status of the switch. However, even engineers who design these switches promise that every switch, no matter how well it will built, will someday fail. You just don't know if that will be today, or 1,000 years from now.
Any automatic system running antenna control, crosspol control, or waveguide control must give a continuous indication of its status or you must visually be able to see these things with your own eyes.
Switches and indicators critical to all of these processes, especially RF power must have a visually obvious way of indicating in some way whether the equipment is operating or has failed. LED lights are the preferred choice because of their longevity and ease of replacement.