I have a blind friend who can't put anything outside, and is restricted to antennas near the window in his apartment. Luckily he lives closer to the top, which helps with range a little bit. He has a VoIP linked repeater at his apartment and while I was range testing, I had little success getting in to it from anywhere greater than a mile from the apartment.

Currently, he has a 5/8*5/8 magmount 70cm antenna on some copper strips on the windowsill but I wouldn't think that is a very good ground plane. I am thinking of building an antenna for him to attempt to improve performance for his apartment repeater, I am thinking about wire antennas I could hang up or something. Does anybody have any suggestions?

  • $\begingroup$ Shouldn't this type of "Looking for Suggestions" question be moved to Amateur Radio Chat? $\endgroup$ – W8AWT Feb 23 '15 at 1:15

A 70cm halfwave dipole is only 35cm long. That's a bit over a foot. Just do it!

  • $\begingroup$ True but will a half wave actually work very well? We are aiming for a very high gain antenna putting all the energy out horizontally not up in the sky $\endgroup$ – Skyler 440 Feb 22 '15 at 21:51
  • 1
    $\begingroup$ A vertically-oriented dipole radiates horizontally (scroll down to the first 3D color illustration). $\endgroup$ – Pete NU9W Feb 22 '15 at 23:11

For an omnidirectional antenna, books will often suggest a 5/8 wavelength vertical antenna for lowest angle of radiation and highest gain (as compared to an ideal antenna, isotropic). The issue with using a vertical or dipole antenna indoors is much of the energy is radiated inside the room and depending on the building/room construction, the signals might pass through (albiet attenuated a bit) or it might not pass thru and be just wasted.

You need to shift your focus to other antenna designs, directional antennas. They are designed to have high forward gain, but very low backward (and side) gain. Remember the front-to-back ratio in the exams? You will probably benefit more from a directional antenna (i.e. an Uda-Yagi) pointed out the window but herein lies a problem. Repeaters are really meant to use omnidirectional antennas, using a directional antenna make your system relatively deaf to other signals comming from other directions. This is a big compromise for your repeater system.

I suggest you also study the use of antenna modelling SW (i.e. MMANA, NEC, MININEC) so that you can understand what the antenna is designed to do and customize the antenna to fit your needs.


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