Technical Tips for a Clean, Simple and Problem-Free VSAT Installation

Jul 12, 2023

Every very small aperture terminal (VSAT) installation should be done professionally and to the highest standard, no matter where the location is. But the more remote the site, the more critical it is that the installation is reliable and professional. This is because every additional visit to a hard-to-reach site, for maintenance or troubleshooting, is a challenge of its own. Additionally, in these areas, VSATs are often the only form of connectivity available so having a continuous and reliable satellite connection is vital, and at risk of sounding dramatic, can even be life or death. 

When it comes to installing and maintaining VSATs, there are many different aspects that need to be considered, from choosing the best site to deciding how to mount the antenna, proper use of cabling and waveguide, waterproofing, and reducing interference, and many other aspects as well. With the right technical know-how, good preparation, and the right tools, VSAT engineers can overcome common challenges to achieve a problem-free VSAT installation. And it all starts with choosing the best site for the installation. 

Selecting the right site 

Naturally, the VSAT dish needs to be positioned somewhere with a good line of sight to the satellites, and clear of nearby obstructions such as buildings or trees. It may be necessary to select a position off the ground, whether that’s on a building or on a mast, to ensure no obstructions. Usually, we look for an installation spot that has a good line of sight to all the satellites in Clarke's belt. But if you have to point to a high-elevation satellite, especially with a C-band link, it’s worth considering a location that will help to block potential interference caused by WiMAX and now also 5G. An antenna located within a blockwork walled structure (minus the roof obviously!) will be a good choice to minimize this type of interference. 

When choosing the best site to locate the dish, it’s also vital to consider potential year-round weather factors that might affect the installation. It may well be dry and still when the dish is installed but that doesn’t necessarily mean it’s like that all year. In areas prone to high wind, try to choose a location that is as protected as possible from winds but if that isn’t possible, then you might need to consider a wind-resistant antenna. We have also seen ground-mounted antennas affected by seasonal floods.

And if the antenna needs to be fixed on a rooftop, balcony, or other structure, that obviously needs to be strong enough to withstand the weight of the mount, antenna, and all the fixtures. If a roof will not allow any kind of rooftop installation and the low elevation poses a challenge for any ground-level installation, elevated platforms or tall masts are the best solution.

Another point to consider is to make sure access to the dish will be restricted. We don’t want unauthorized people to hang around there. It is also not safe for them (radiation) and not safe for the antenna. Sometimes antennas are installed in parking lots and not protected with a fence. And then, it is only a question of time till it will be hit by a passing vehicle.

Another critical point is to consider the cable run distance, between the antenna and the indoor modem. According to the distance, the right cable type should be selected.

And above all – SAFETY. It is the most critical aspect is to install the antenna in a place that will allow safe installation and maintenance both for the Field Engineer and nearby pedestrians.

Mounting the installation

Having decided where the installation will be placed, next it’s time to decide how to secure it so that the VSAT dish doesn’t fly away one day when the winds pick up. Deciding on the right mounting solution depends on the information available about the site. This is usually obtained from a site survey. Then it really comes down to judgment and experience. A non-penetrating mount (NPM) may be the best solution depending on the site. Because it’s relatively easy to dismantle, it’s a good choice for temporary sites where you may need to remove or relocate the installation. It’s also a good choice for rooftop installations because it sits on the surface rather than penetrating so therefore, does not damage the rooftop or the waterproof layer on the rooftop. Although easy to install and relocate, NPMs can be expensive, especially if the heavy metalworks need to be shipped overseas. A more cost-effective way, rather than shipping these mounts is to have them built and customized locally for installation. 

When using an NPM, there are three methods to make sure the VSAT dish will not turn into a “fly away” system. Usually, ballast is used to weigh the NPM down. The other two methods are tethering which involves securing the NPM with guy wires to a firm, strong structural element, and securing the NPM with bolts to the rooftop. Sometimes, it makes sense to use a combination of these measures. For instance, a number of blocks may be used as ballast and a couple of tethering points may be used as well for added stability. But an NPM won’t always be the best choice. It takes up a lot of space and if the construction of the building is poor, the required ballast might be too heavy for the rooftop. 

Sometimes, the best or only place for the installation is on the ground. It’s important to remember that not all soil is the same. Some soil is not stable, and this can result in the antenna tilting and losing points. This problem can affect both penetrating and non-penetrating mounts. One possible solution is to build a solid and stable platform, where a NPM or king post can be securely installed on top. When preparing the mount for the antenna, it’s also important to use a mast in the right diameter. Even the slightest movement will degrade the performance and might cause adjacent interferences. Everything needs to be very tight, very strong, and very stable.

With an NPM, the base obviously needs to be wide enough to stabilize the installation. The required size of the base will depend on several factors including the available space, antenna size, and the weight of the NPM. It’s wise not to rely only on the size of the base and its weight to stabilize the antenna. For added stability, it’s worth placing ballast blocks on top of the base and tethering it with metal guy wires. But how much weight needs to be added to the base as a ballast? If you have a big antenna in a highly exposed windy area, you’ll need to add a lot of ballast over a wide area. Putting ballast in a small area doesn’t work because it’s less effective and might result in too much weight in one place. It’s much better to spread the NPM and ballast wider. 

Choosing the right antenna

So, do you opt for an offset antenna, a standard parabolic antenna, or maybe a batwing antenna? That would depend on the requirements of the installation because each antenna has its pros and cons. Starting with the offset antenna. Although it’s a type of parabolic antenna, an offset antenna differs because the true elevation is higher than the mechanical elevation (the actual position and angle dish faces). It’s important to know the correct offset and to know how to calculate the elevation for proper pointing. Usually, the offset between the true and mechanical elevations is around 17 or 23 degrees. Offset antennas have several advantages and may be a better choice for some installations. One advantage is, it provides easier access to the feed system, and another is that it can be positioned lower than an actual line of sight would require. 

Let’s now consider batwing antennas. They may be more complicated to install than parabolic antennas and are likely to be more expensive too. For this reason, they’re less common than regular parabolic VSAT dishes. They are however sturdier so may well be a better option in areas with extreme wind load. Batwing antennas also have a smaller mechanical profile, so tend to be better in tighter spaces. It’s also said that they filter out surrounding interferences because the beam is narrower, although we’ve not measured it ourselves in the field.

As a passive component, a VSAT dish can serve for many years, even after it’s long since stopped looking bright and clean. Having said that, what can happen over time is that the dish’s performance can start to degrade because of the poor condition of the surface, causing the reflector to reflect less and absorb more. Additionally, degradation over time can happen when the dish geometry is less than optimal. This may happen over time as a result of the boom slightly sinking due to the weight of the feed and especially the heavy block-up converter (BUC).

Achieving good grounding

Static electricity, surges, and lightning can damage different components and circuits, so every electrical device needs to be grounded to mitigate damage or eliminate it completely. Most of the time, we just plug our electrical appliances into the wall socket without thinking about grounding. We take for granted that the third pin (the grounding) is connected somewhere. But this is not always the case. Some remote or old structures have no structure grounding and the electrical socket grounding is not connected. External grounding is then very much needed.

Independent grounding points can be prepared by placing layers of charcoal and salt which increases the conductivity of the ground. After the grounding rod has been placed, it’s important to measure the overall resistance to check that the grounding is effective. If grounding is overlooked, it can be critical. Neglecting to connect the system to a good grounding point will commonly lead to an eventual hardware failure, usually of the BUC or the modem. Additionally, when an indoor unit (IDU) is connected via interfacility link cable (IFL) to the outdoor unit (ODU), it is sometimes critical to pare the grounding of the IDU and the ODU.

Skew of the feed system

In linear-polarity feeds, the position of the feed system is seldom straight and, most of the time, it should be rotated. The rotation depends on the satellite's longitude and the VSAT location, as well as the required polarity. Fine-tuning the feed skew is vital and its position also needs to be checked during the activation process, in the peak and poll process to be precise. Failing to position the feed system correctly will lead to poor performance of the VSAT system and, much worse, will cause interferences at the opposite transponder. 

A poor or non-professional installation will often fail to fine-tune the polarity of the feed, and this causes an accumulation of interferences and significant losses to the industry, so must be avoided.

Laying correct cabling

No matter how big or small the dish, what bandwidth is provided, or what technology or frequency band is used, it’s pretty much guaranteed that you’ll need to run an IFL cable. The problem is, you just can’t tell how easy or complicated this will be until you’ve done a site check. Some types of buildings and some countries require installers to follow specific codes and procedures which can make the process more complicated, while other times, running the cable can be quite simple. 

Installers also need to decide between cable and waveguide. And in some cases – even a fiber link could be the best option. In a cable, the attenuation and distance ratio is very high at higher frequencies. In some installations such as one running on Ku-band, the RF frequencies attenuation would be too high if run in a cable. When possible, it’s better to have the active component as close to the RF segment as possible; this could be done by connecting the low-noise block (LNB) directly to the feed system. The LNB also converts the signals to the much less attenuated L-band that runs over the cable to the modem. 

Sometimes, the BUC is mounted directly on the feed system. But when a high-power BUC is used, it’s not always possible to connect it directly to the orthomode transducer (OMT) because of the BUC’s weight and dimensions. Attenuation in the waveguide is significantly less than the attenuation in the cable, so in these types of installations, a waveguide is used to carry the RF signal to the BUC, which is mounted on the dish boom. Even a flexible waveguide has its limitations though. When working with it, it’s important to allow gentle and moderate banding radius to avoid cracking the interior metal part of the waveguide. The danger is that it may appear satisfactory on inspection of the outside but could be damaged on the inside as a result of too much twisting and bending. 

Of course, it’s not just cabling above ground that needs care and consideration. Damage from rodents can cause serious problems to underground cabling so cables should always be run in protective tubes with tube entrances sealed. When troubleshooting and testing, you’ll often need to identify a cable or confirm cable continuity. A quick trick to do this is to connect a terminator to one end of the cable, and then use a multimeter to beep the tip ring of the other end of the cable. And voila!

It's important to futureproof the installation by leaving spare cables. Leaving some slack cable will allow the satellite to be shifted to a higher elevation in the future if required. Leaving a spare cable will also help if a connector has to be replaced. It’s also worth leaving some spare cable inside as well as outside so that if necessary, it’s possible to move the modem from one position in the room to another. But while some spare cabling is a good idea, it’s important not to leave too much slack because this will cause unnecessary attenuation to the system.

 Use the right tools

The importance of using the right tools for the job can’t be overstated. Many of the issues that arise during or after an installation can be avoided if the right tools for the job are used, and used correctly. There are far too many cases of engineers attempting to use a compass to point to the right azimuth, but actually, a compass is one tool the VSAT engineer can do without (because of magnetic variation and deviation). Put simply, magnetic variation is the difference between the magnetic north of the Earth and the true north. This variation changes from one place on earth to another, and additionally also changes over time. Magnetic deviation is the compass reading an error due to iron and magnets nearby. So, if you happen to be using a compass near the steel construction of an antenna, you won’t get a good reading. Additionally, pointing the antenna in an accurate manner with the compass is another difficult and frankly useless task. 

So, while a compass may be an invaluable tool for hiking across a mountain, it’s not the right tool for installing a VSAT system. What you really need is a good inclinometer, used correctly We’ve seen many field engineers placing their inclinometer (if they have one) in all kinds of funny places on the antenna. When in fact, unless stated otherwise in the manual, the only good place to place the inclinometer and measure the elevation is behind the dish. Next, calculate the offset, set the elevation correctly, and you will find the satellite in less than 5 minutes.

The next vital tool for any VSAT field engineer is a spectrum analyzer. It’s an essential tool for troubleshooting, as well as for some site surveys and installation scenarios. A spectrum analyzer allows you not only to point the antenna to the satellite, but it can also help you identify interferences, and their characteristics and analyze the carrier you need to work with. There are also other important uses such as measuring attenuation on cables and checking for 10Mhz reference signal. 

Another aspect, much more trivial though still very painful, is using the right-hand tools for each installation. Vise grip and adjustable wrench are wonderful tools, but they might damage the hardware and will fail to properly snug it to the right torque. Proper spanners should be used. Same for the tools used for attaching the connectors to the cables. These should be professional and match the cable and the connector type. We have seen all kinds of improvisations, with one common thing: Their poor performance compared with using official tools and the right procedures.

Waterproofing to reduce attenuation

As we all know only too well, water and humidity attenuate RF signals and some frequency bands are more affected by this than others. The degradation effect from water and humidity is noticed immediately. Water and humidity can also crawl into the cables and attenuate the electrical signals. If this happens, the degradation of the electrical signal is noticed gradually, during weeks and months of slow and continuous reduction of its parameters. This is why waterproofing is so important. Poor waterproofing will result in water ingress which will eventually result in the entire cable having to be replaced, not just the connector. 

Also, the feed system itself is required to be waterproofed. Though usually there is no need to apply special waterproofing on the OMT itself, we do need to pay attention to the feedhorn window. Birds (especially crows) like to stand on them and poke them with their beak. Eventually, the membrane will be torn, water will penetrate the feedhorn windows and also all kinds of fauna will be happy with a new warm shelter. If the membrane was already torn and water got in, it will be necessary to change the membrane and make a good seal with special silicones. To do this, it’s important to first dry everything well, including the feedhorn and the OMT, next remove the LNB and dry, then replace the cables with new ones and waterproof everything.

Water attenuation is not the only cause of interference. While interference affects all bands, C-band is highly sensitive and prone to interference. It can be caused by many different factors which can make it difficult to identify the source and resolve. Sometimes interference can be a result of other satellite links that have been poorly installed and aligned. Other causes include terrestrial microwave point-to-point links, 5G, radars, and also many other factors. When faced with interference on site, it’s really a case of working through different possible solutions until you find a satisfactory one. If troubleshooting an existing installation, the location of the antenna may not be optimal, so it’s always best to start by studying the site and finding the best location for the antenna. It may also be worth considering building a shelter to block the sources of interference. Installing a filter is yet another option. Sometimes, it can even be difficult to find a solution. This is where experience and even instinct can go a long way. 

It's also important to reduce thermal noise as much as possible because it can interfere with the signal being transmitted. The performance of different components can vary with temperature, and generally, colder temperatures are better than hot. This is because the electrons of hot components have more "fuzzy" movement, which translates into noise. As the temperature of components increases, so does the thermal noise. This can be a major problem when pointing an offset antenna to a satellite with a relatively low elevation. This can cause the feed system, including the BUC and the LNB, to be very close to the ground, which means it absorbs the radiated heat from the surface. In a hot climate, this can degrade the performance so much that it causes the link to be unusable during the hot hours of the day. It’s well worth considering this effect when siting the equipment. 

With offset antennas with a low elevation pointing, it is worth considering a reverse installation, meaning the boom will be above the reflector. But not all antenna models support this option, and it can cause some difficulties during installation and maintenance.

Summing up

Satellite communication is not only about fancy GUI, advanced modulations, FEC, and protocols. It’s also about metal, blocks, cement, and plastic. It’s important to prepare well for installations so that you don’t have to improvise because that will invariably lead to poor-quality installations. Whether an installation is intended to be permanent or temporary, for the best quality of the link, the work should always be carried out to the highest standard. Any cable that needs to be run requires a properly protected conduit and should be secure, and every antenna requires a stable, safe, and long-lasting mount with a ballast heavy enough to prevent dish movement. All connectors need to be waterproofed to prevent humidity from leaking in, and all bolts need to be well secured to prevent even the smallest unwanted movement. 

Even though developments in the last 10 years or so have made VSAT installations much easier, it’s still critical that a professional is on-site to carry out or supervise the installation. To choose the right location, to reason the best cable run path, to make sure the mast is plumbed, and to ensure that all work is done according to good standards. And there are even more aspects that we didn’t even touch here, wishing to avoid overwhelming the reader. Such as choosing the right types of connectors and adapting techniques, in-door modem mounting and location strategies, in-door cable run considerations, and more and more. But all these fields lead to the same conclusion: Proper knowledge, proper tools, and proper procedures lead to proper results.

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