Category Archives:Q&A
Aluminum masts, truss masts, aluminum towers, radio towers, communication towers, stage constructions and trusses, truss solutions, advertising constructions, radio masts, communication masts, architectural solutions, Wifi networks, LTE, WLAN

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 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.

 

Fresnel ilustracja

 

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.

 

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 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.