Author: admin

What do I choose? Tower or mast?

Main difference between towers and masts is comfort of use and amount of space needed for installation. There is an economy to consider as well. In general towers are more expensive than masts at the same height, but take up much more space. So decision here is: do I buy/rent more land and save on the construction (cheper mast) or do I buy more expensive tower and save on parcel size.

Some other factor is service cost. Masts need much more attention  – frequent servicing is advised, guy wires tension must be regulated, u-bolts changed, and finally if something goes really bad – the chance is that mast will fall down. Towers are less human dependent. We check bolts once in couple of years and see if welds are still okay and that’s it. It’s rather unusual for the tower to fall down even if badly injured.

Towers (especially T1000 series with internal ladder) are quite comfy to use. Range of additions like safety platforms, outer platforms make service people life on the tower even nicer. This is not the case with masts, especially other than M1000.

The final word here is about nature. In some regions (eg in Germany) you cannot use guy wired constructions due to risk for birds. Then tower might be the only possibility.

 

 

Are welded constructions any better than bolted?

A big communication towers form problems with transportation. For example Altruss H32 tower has base size of 4,5 by 4,5 by 6 meters. Not an easy piece to drag on a higway. Most of our constructions are hybrid  – lower sections are bolted, and upper (small ones) welded. Welded sections are quicker to install on site, and less things may go wrong with them during installation, but they are more prone to frost cracking, and welding errors. Bolted sections are little more expensive to manufacture and take more time to assembly, but transportation is cheaper and easier, plus there is nothing that may go wrong with them when assembled (bolts may become rusty after couple of years, but not much more).

As for stiffness (that is common concern) they perform the same. Bolted constructions show advantage when they are done with the job in one place (easier to disassemble and sell, or bring to another location)

 

What information matter when we brief you Altruss to make a mast for us?

Both masts and towers are quite resistant for vertical loads. Clients often ask us if a certain type of mast will carry some given weight of antennas in kilograms. The answer is nearly every time the same: yes sir. This is because for mast side loads are much more dangerous and influence the construction more. Side loads occur mainly because of the wind pressure on the antenna faces, and are directly proportional to their total surface. This is what counts.

For well designed mast the maximum Y axis  deviation from wind pressure is 1:100 of its height at max wind speed in  given wind zone. As you see for us the key information about your project is: location where the mast is going to be installed, and total surface of antennas you want to put on your newly bought truss.

 

How do we choose right height of the mast for radiolink?

The right height of radiolink antenna masts in telecommunication are connected with concept of so called Fresnel Zones.  Energy sent between radiolink antennas forms shape of a spindle (cigar like) with the biggest thickness in the midpoint between them. Points for antennas installation shall be found in the way that no obstacle gets into the Fresnel zone, otherwise the gain will be compromised (tree tops, houses, hill tops, or simply ground surface).

There are numerous online applets that let us calculate Fresnel zone thickness in given place between antennas. Having this information, plus maps and real terrain measurements let us find minimal mast/tower height that lets transmit all the energy between radiolink antennas.

 

Is mast stiffness importnat for me? What should I expect here?

Well in most cases stiff mast is a good mast, this is one of quality factors. Cheaply built masts are rarely stiff. Stiffness is mostly important for radiolink communication and satellite dishes (form of radiolink in fact) – where power beam is narrow and focused. Imagine a laser pointer that is aimed at a tower clock from outskirts of your city. Not easy to keep it steady pointed directly on the clock face… but fix it to the building and the beam will be glued to the point miles away.

In most countries masts are created to allow max deviation of 1:100 of its height. For 30 meters mast it is max 30 cm at the top! I would not call it a little, that’s couple hundred meters over 10 km. One of the cheapest ways to improve this is to top the mast with separation crown with additional set of guy wires.

Stiff masts are also nicer to service (you simply feel safer on one)

 

How welding technique influences the final product

Welding quality is a key to safe product in mast business – and we are serious about this. In Altruss we do weld only in TIG process and with best possible equipment by Fronius and Kemppi. On top of this we use certified rods by ESAB to all sensitive works and AirLiquide argon gas in 5th grade of purity. All welders are well trained, and their job is randomly checked, plus samples are destroyed to see if the weld had right amount of penetration.

Alternative to the TIG process is MIG – which is quicker, needs less qualifications, easier to master – but controll over weld penetration is inferior. In Altruss we use MIG process only for steel where above problems do not occur.

 

Why do I need separation crown?

The main reason to use separation crown is to separate antennas from each other accordingly to producer specifications. Antennas have backward radiation that may lead to interference and high noise bed. Because electromagnetic radiation force decreases with the square of the distance, even small separation is sufficient to improve the situation.

Second task of a separation crown is increasing the mast torsional stiffness (with additional set of guy wires). Truss masts are quite robust for vertical forces (inherit feature of a truss), average for horizontal forces (thanks to guy wires), and relatively non resistant for torsional forces (hence idea to help here). Twisting is most problematic during high winds and service jobs. This is especially problematic for radiolink, because it may interfere with or even break connection.

 

How do we attach antennas the smart way?

Telecommunication mast, as each truss construction has nodes or joints, that are the most robust places in the whole structure.  Every force we use on the mast shall concentrate around these nodes, no matter if during building or choosing a place for guy wire mounting points or finally when mounting antennas. The node is a place where cross members meet on the corner pipe.

 

 

Service of mast and tower, why sould I bother?

Masts and towers, both aluminum and steel are constuctions of high risk. Damage may cost loss in property or even life, so it is good to service your mast before it breaks.

Aluminum masts are resistant to corrosion, but not so much to frost cracking. Once each year, in spring preferably, qualified personel should chceck for any signs of frost damage. Any cracks found shall be welded, some poles echanged for new, and drainage patented. Altruss masts are well prepared to handle unwanted water, so less prone to frost cracking.

Second issue –  guy wires. In older installations it was usual to use 3 mm wires. Most of them were zinc-plated years ago and now are very fragile because of corrosion. We recommend usage of good quality guy-wires 1×19 type, minumum 4 mm made in Europe  – even for smallest masts.

Third thing is guy wire tension – this has to be corrected due to natural wire wear that results in wire lenght increase. Always chceck with mast producer what amount of tension shall be used. If possible measure it (some tensors have a gauge for this).

Aluminum towers are much more robust and require less work. All that has to be checked is: signs of frost cracking and corrosion to the bolts. Once in 5-10 years a verticality check is suggested (done by land surveyor). As gound under the towers settles unevenly the whole tower may change its centre of gravity. This can be changed with correction rings.

In case of steel constructions a anti-corrosion checek must be conducted, and any stained spots must be repaired. During u-bolts change (and other metal on metal components as well) we shall take under consideration electrochemical potential of used materials. High difference here may lead to amazingly quick corrosion that may be dangerous for the structure rigidity.