Today I found this strange device which seems like a DIY construction to me and I wanted to know what it is and what it does. It is connected to the lightning rod and it is also grounded to many points. Also, the thick black wire is going straight to an apartment. It is located near the lightning rod at the rooftop of the apartment building that I live. So can someone recognize this?

PS. I had more photos but I couldn't upload them cause of reputation restriction.

the metal tube on the right is the lightning rod

enter image description here

  • 1
    I have no idea what anyone could possibly be attempting with this, but have you tried asking the landlord? – keshlam Nov 11 '16 at 5:47
  • No I didn't want to be curious to him because I thought it could be something illegal or so. – poloapolo Nov 11 '16 at 5:53
  • Unless you weren't supposed to be on the roof in the first place, go ahead and ask. The worst that will happen is he won't tell you. – keshlam Nov 11 '16 at 15:07
  • I'm voting to close this question as off-topic because it isn't about home improvement. – isherwood Nov 11 '16 at 16:00

This is most likely some type of homebuilt radio antenna such as used in amateur radio.

  • The “lightning rod” — which, note, is not actually directly grounded as a lightning rod was, but appears to be insulated from the ground or roof — is one antenna element.

  • The connections to ground serve as the other antenna element.

  • The “thick black wire” is coaxial cable for carrying the RF signals between the antenna and the radio receiver or transceiver.

  • The glass and copper device visible inside the box looks like a vacuum variable capacitor, which can be used as part of a matching network to match the electrical characteristics of the antenna to those of the cable. I can't tell from the photo what else might be in the box (which is presumably there to keep rain off).

It looks like it could have been built a lot less messily, but its maker may have other priorities or not want to spend money on better tools and parts.

Further questions on amateur radio and radio technology in general are welcome over at Amateur Radio Stack Exchange!

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