3
\$\begingroup\$

We are currently developing a conceptual design for the renovation of Croatia's main RTV tower located on 1033 meter tall peak Sljeme at the Medvednica mountain north of Zagreb. The idea is to renovate and reopen its upper gondola for touristic purposes (as a revolving restaurant and viewpoint towards Zagreb metropolitan area, as it was initially intended) and to build another floor of apartments on the roof-top level of a lower maintenance and equipment gondola. Basically, the wish of the investor is to make it an important landmark of Zagreb and place its touristic purpose, which it was lacking since its construction ended in 1976, because it was only opened for public 2 years, above its primary function which is receiving, boosting and transmitting radio, ATC and television signals in a radius of approximately 100 kilometres.

However, after our social studies and researches, we determined that this investment would be absolutely useless because nobody considers it as an important landmark which tourists should, or would want to visit just because of that, considering its distance from the city and long drive to reach it. As you can see in the picture below, the body of this monstrosity is completely covered with antennas and aesthetically it looks unpleasant and way too much utilitarian. My problem is that I absolutely have no idea what these devices are. Are those receivers or transmitters?

Our concept and solution is as follows: we want to envelop the tower's central body, beneath the upper gondola and part of its lower gondola with organic, deconstructivistic "curtain facade" made out of highly perforated (ca. 60%) approximately 5 mm thick lightweight plastic composite material panels, to visually "hide" those antennas behind, and to give the tower a brand new vibrant composition mixed with LED lights for night light shows, which will make it very eye-catchy from Zagreb and all surrounding cities.

From my personal research and previous general knowledge about long-range radio waves, which are transmitted and received by this tower, is that this should not affect its performance, because of the wavelengths and frequencies of those waves as such, they would just slice through this median without reflection and deviation of direction with minimal losses in strength. There are also some radome plastic materials which we could use to implement this, in which antennas are usually covered and that could be used for this.

Is that all above correct, or will our intervention of this kind render the tower completely useless and we will leave half of Croatia without ATC, radio and TV broadcast coverage? Keep in mind that this is only a conceptual idea we are considering to implement, and it will anyways probably be rejected and scrapped by the investor. We just want to know if it's okay to go out publically with this project as we imagined, or will we embarrass ourselves proposing something as ridiculous as that? I'm still just architecture and civil engineering student with minimal knowledge in electrical engineering and stuff alike, so if someone could give me some advice or answer my doubts about the idea above, it would be highly appreciated. I am sending you a link to some public documentation and specifications about the tower and the channels types it is broadcasting.

Wikipedia: Zagreb TV Tower

Technical documentation with diagrams and illustrations: https://hrcak.srce.hr/file/18627

Recent image of the tower and antenna cluster it is equipped with:

enter image description here

The upper steel antennas painted in anti-collision red and white pattern are none of our interest, only the antennas installed on the platforms around the tower's central body. Can someone recognize what are those for, and can their path be obstructed with described panels above, without significantly influencing their work on a daily basis?

Many thanks in advance for your time and understanding, I would highly appreciate any feedback and thoughts about our idea and if it can eventually be implemented.

\$\endgroup\$
  • 1
    \$\begingroup\$ I don't think anyone would travel to the country side to look at the tower itself. The nicest part of such towers is the view from the tower. Even in places where the tower is easy to reach, the main interest is looking out of the tower. \$\endgroup\$ – JRE Aug 31 at 16:10
  • \$\begingroup\$ Too long, get to the point with the basic facts and ask a clear question. \$\endgroup\$ – Andy aka Aug 31 at 16:13
  • \$\begingroup\$ Not all of those antennas belong to the same operator. You'd have to get permission from all operators to put up panelling, and discuss signal loss and other potential problems with the engineers from all the the operators. Then after you got it all up you'd have to listen to the operators bitch about it and for normal people to complain about weak cellphone signals. \$\endgroup\$ – JRE Aug 31 at 16:19
  • \$\begingroup\$ @JRE Yes, I agree with you about that, but regarding the fact that 70% of residents below the age of 18 couldn't recognize this building when shown on a picture, and only 15% would recommend tourists visiting the tower in case of reconstruction, it is clear that this building has some serious issues while it is considered "landmark of the city"... Spending millions € on this while having 10 visitors a day definitely won't give investor what they are looking for. And we also want to use the wind, which is highly present up there in combination with those perforated panels to achieve acoustics. \$\endgroup\$ – Ivan Tahlin Aug 31 at 16:26
  • \$\begingroup\$ DO NOT use the wind to make noises around the tower. That's a perfect way to piss off everyone. If you make the construction workers angry while they are building your house here in Germany, they will install an empty beer bottle in the wall with just the mouth visible. It will be positioned such that it catches the wind. Your house will howl in the wind and drive you nuts. Don't do that on a large scale. \$\endgroup\$ – JRE Aug 31 at 16:31
1
\$\begingroup\$

covered with antennas and aesthetically it looks unpleasant and way too much utilitarian.

… I heartily disagree, but that's just a matter of taste.

My problem is that I absolutely have no idea what these devices are. Are those receivers or transmitters?

These things are antennas; some are used for receiving, others for transmitting, most for both.

  • The red longish ones look like common 2G/3G/4G cellular antennas.
  • The smaller rectangular antennas might be the same
  • The large dishes on the left of the tower pointing into roughly the same direction are probably satellite dishes pointed at geostationary satellites.
  • The "drum-like" round ones are high-directivity microwave antennas for stationary point-to-point links. They provide such things like giving cell towers elsewhere an uplink to the cell provider's backbone, or directly attaching factories to company networks, or are the link used by a radio station to bring the radio signal to the broadcasting tower. They are also dish antennas, but in a protective housing with a relatively RF-transparent shield against weather in front.

Then there's things I can't assess:

  • There's the big, dark-gray "sphere" on the lowest level. That's probably a radom, i.e. a housing for a movable antenna. The fact that it's dark might indicate it's actually usually used in naval or military applications. It might be tracking a satellite, or ships on the sea, or troops on the move.
  • The second level has these gigantic "cut-off tubes"; I've never seen something like this; these might be military high-bandwidth antennas, but that's pure speculation.

We want to envelop the tower's central body, beneath the upper gondola and part of its lower gondola with organic, deconstructivistic "curtain facade" made out of highly perforated (ca. 60%) approximately 5 mm thick lightweight plastic composite material panels, to visually "hide" those antennas behind, and to give the tower a brand new vibrant composition mixed with LED lights for night light shows, which will make it very eye-catchy from Zagreb and all surrounding cities.

First of all: you're asking the wrong folks. These platforms have been rented out to companies operating these antenna systems, and all hinges on them agreeing to your plans – it's very unlikely a touristic attraction would ever generate as much revenue as the infrastructure is worth here. If at all possible, you need to have goodwill of whoever owns these platforms they rent out, and political support from above. The operators have rented the platform with guarantees about unhindered line of sight, with power reliability levels, and with a guarantee that the antennas are easy to access for maintenance, and access to the antennas is strictly regulated.


Then: I like the idea, aesthetically :) !

So, plastic will absorb RF, and that will be hard to sell to the people using these antennas. However, that effect scales with the percentage of that plastic that's actually holes, and there's worse and better plastics, so there's potential for compromise. However, expect things to become more expensive than thought.

Then: "Composite" is a bit too vague. There mustn't be any metal in front of these antennas. That rules out the possibility of putting LEDs directly in front of them.

Apropos in front: Human workers mustn't accidentally happen to end up in the beams of these dishes. That's microwave. In your microwave oven, you use that to cook soup.

So, all in all, I don't think that putting something in front of these antennas is actually feasible, and especially politically much less feasible then technologically. I still think your concept could work – just exclude the platforms from the enclosing, and maybe work with conformal light projection on these surfaces. The operators don't get a word about which pictures are projected onto their antennas :)

\$\endgroup\$
  • \$\begingroup\$ Thank you very much for all the explanations, thoughts and suggestions, I really appreciate your time and efforts helping me out with this issue and looking deeper into it. Based on your explanations I think it is better to continue without these panels, I will implement what the investor asked and will try to do something else that won't interfere with the antennas there at all. \$\endgroup\$ – Ivan Tahlin Aug 31 at 17:51
  • \$\begingroup\$ ice buildup may be a problem. \$\endgroup\$ – analogsystemsrf Sep 1 at 4:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.