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So I have a 1.5 m by 1.5 m window. Through it, I have a number of spatially separated ~10 cm wide "beams" coming from local repeaters.

It looks something like this:
Picture of my window with reception areas marked

Outside of the marked areas, I have absolutely no reception of local repeaters and inside of them, it's relatively good.

Unfortunately, I can't use the traditional methods of solving the issue by placing an antenna at the roof.

So are there any antenna types that could be helpful in this case?

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  • $\begingroup$ What antenna did you use when you determined these areas of good reception? What frequency band(s) are you talking about here? $\endgroup$ – Dave Tweed N3AOA Jun 25 '16 at 14:37
  • $\begingroup$ @Dave Tweed I used a telescopic antenna (AL800 clone) for 2 m and a rubber ducky (SRH771) and quad loop for 70 cm. $\endgroup$ – AndrejaKo Jun 25 '16 at 14:55
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    $\begingroup$ If you're getting such widely-varying signal strengths within the space of the window, you're suffering from some strong diffraction effects. What kind of conductive surfaces are nearby (including on/inside the wall)? It would be interesting to see how the pattern changes a few meters in front of or behind the window. $\endgroup$ – Dave Tweed N3AOA Jun 25 '16 at 15:02
  • $\begingroup$ @Dave Tweed Well the thing is, entire area visible from my window is blocked by buildings. I'm basically looking into a type of inner court-yard. I do have an interesting building in front and a bit to the side of the window. Its metallic roof is visible as well as an elevated porch that has metallic railings and stairs going to it. Maybe the railing is acting as a sort of diffraction grating? I'll try to trace out the internal and external propagation, but it's going to be a bit difficult. $\endgroup$ – AndrejaKo Jun 25 '16 at 15:44
  • $\begingroup$ can you open the window ? do you have access to the outside of the window ? can you get a cable outside the window ? can you mount anything outside the window-surroundings ? did you measure anything outside the window... these questions would help us to determine if you can use an external antenna... as well as patterns outside the building. $\endgroup$ – Edwin van Mierlo Jun 29 '16 at 8:02
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I think you'll find this problem isn't so easy to analyze or solve. What you have are not spatially separated beams, at least not in the sense that there's a beam of signal going through those specific areas in your window.

The reason is the same reason why individual atoms can't be imaged by an optical microscope: diffraction. Anything small relative to the wavelength of light (or RF radiation, which is just a much lower frequency of light) can't be resolved.

So what you are observing when you stick your antenna in the window and get good reception there isn't that you've placed the antenna in a "beam". Rather, it's just in that particular spot, you've just happened to find a local maximum in the diffraction pattern.

The orientation of the antenna also plays a role, since unlike visible light from the sun or an ordinary light bulb which is incoherent radiation, radio radiation is mostly coherent. This means (among other things) it has a particular polarization, and if you don't match that polarization with the antenna, you'll experience signal loss.

This diffraction pattern can be perturbed by anything with electrical properties different from free space anywhere within a few multiples of wavelength. Unfortunately this means it's not feasible to design an antenna that will "catch" all those signals. Remember they aren't really beams anyway. Simply adding an antenna will perturb the system.

My advice? Trial and error, just as you'd adjust a TV antenna. There's no guarantee you'll find one antenna and orientation that works well to receive all the signals.

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  • $\begingroup$ Let's not get into circular polarization, shall we...? $\endgroup$ – a CVn Aug 6 '16 at 21:05
  • $\begingroup$ @MichaelKjörling circular polarization is a special case of combined and horizontal polarization where the two are in quadrature. $\endgroup$ – Phil Frost - W8II Aug 7 '16 at 15:49
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You should be more specific as I am not quite sure if I got it right.

Distance in centimeters does not matter. What matters is beam angles.

What you should do is to choose location where you want to set antenna. Then measure angles of each repeater using some directional antenna.

Calculate angle between beams of the most left and most right repeater. That angle is minimum beam angle of antenna you need. You may use wider beam antenna.

Pay attention that for repeaters you have to use vertical polarization, meaning if you use Yagi antenna it should be set vertically. Yagi antenna charts are usually drawn for horizontal set antenna, you have to take that in count.

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  • $\begingroup$ I'm sorry, this is not what I'm asking. What I'm trying to figure out is what type of antenna I should use that has a large "reception" area. Basically, the volumes in which I can receive certain repeaters are very small and non-overlapping, so I'm looking for an antenna type that might be able to receive as many of them as possible without moving. $\endgroup$ – AndrejaKo Jun 25 '16 at 16:00
  • $\begingroup$ That is exactly what I explained how to calculate beam width needed so single antena can get them all. $\endgroup$ – Pedja YT9TP Jun 25 '16 at 21:11
  • $\begingroup$ I get that part, but what I'm looking for are wide-beam antenna types in general that I could look into. $\endgroup$ – AndrejaKo Jun 25 '16 at 21:14
  • $\begingroup$ You can use two elements antennas like beam, moxon, or HB9CV. iof to wide the just chose something with more directivity elelemnts. How you measured what you measured? What antenna you used? What was exact method of measurement? $\endgroup$ – Pedja YT9TP Jun 26 '16 at 5:27

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