I’m just following the rules of the community and this has. Been on my mind for the past few days . I used to be able to listen into law enforcement and even automated the process but they upgraded their system and encrypted their system.

Now I’m theorizing how I can track law enforcement different ways one of which is using a direction finding system. i could super technical and order a bunch of parts and have a desktop running all the time or I can try to dumb it down with analog composition.

I think it’s cool that you can add AC with a ring of iron and winding wires in a specific way (the other way will subtract it)

    • fullsquare@awful.systems
      6·
      4 days ago

      Transformers in antennas are just transformers, but you have to use ceramic cores (ferrites) that would be right for your band. I think that what you might be trying to do would be wideband antenna of some sort, but for UHF which is likely in this case, I’d recommend you some kind of log-periodic antenna instead (it just works, directional) or some kind of spiral antenna (it just works, nondirectional). You can make both of these at home

      • PixelPilgrim@lemmings.worldOPEnglish
        2·
        4 days ago

        Apparently the police operate from 850-860 mhz range and I could use adcock antenna to to get good accuracy and with their frequency being so high wavelength only has like 1% variance. I’m still locked into 2 SDRs for each antenna pairs in the adcock arrangement (I actually think I’d get 2 legitimate directions because SDRs can’t match phases). The tldr is adcock doesn’t play well with SDRs on paper

        I forgot what log-periodic antennas were. it would be better to use directional antenna on a swivel mount and record the highest amplitude at a given angle. As I add antenna I can pick designs with directionality and add sensitivity

        • fullsquare@awful.systems
          4·
          3 days ago

          wait, it sounds like you want to use something called four square antenna, but it’s usually only made for HF. you’d have to rework it significantly for microwave region http://tm1o.free.fr/4SQ/80m/en_ver_final4-sq_03_04_15.pdf instead of transformers you’d have to use segments of transmission lines with right impedances and some directional couplers, gives direction immediately, no need to compare phase between different SDRs

        • fullsquare@awful.systems
          2·
          3 days ago

          Or if you want to get more involved, make a couple of 3el yagis, make a small phased array out of these by plugging them in a directional coupler or 4x4 butler matrix and this will get you two or four receiving directions in a 90 degree segment. If you only want to use that small segment you don’t need a LPDA, regular yagi would be fine