Loading ...
Sorry, an error occurred while loading the content.
 

OT2/FT1900/j-pole in the Plane

Expand Messages
  • Pete Howell
    Thanks for the thoughts on polarization - it has been considered, but the j-pole is a cheap, easy, no-drag install in the plane, and in practice it works
    Message 1 of 3 , Jul 6, 2014
      Thanks for the thoughts on polarization - it has been considered, but the j-pole is a cheap, easy, no-drag install in the plane, and in practice it works better than predicted.  The RV group has over 100 of these flying with great results using some very low power/light weight microtrak units.   I previously had that a microtrak with the same antenna and did not get the dropouts that I see with the current setup, thus my question.   I am running the lowest power possible on the 1900.

      I will make sure the audio in is disabled and see if that helps - thanks again.

      --

    • Jason KG4WSV
      ... Wow, with that many in use it could even be worth it to set up ground support (igate ) with a horizontally polarized antenna. A digi would need separate RX
      Message 2 of 3 , Jul 6, 2014
        > On Jul 6, 2014, at 9:14 AM, "Pete Howell pete.howell@... [tracker2]" <tracker2@yahoogroups.com> wrote:
        >
        > The RV group has over 100 of these flying

        Wow, with that many in use it could even be worth it to set up ground support (igate ) with a horizontally polarized antenna. A digi would need separate RX and TX antennae.

        -j
      • James Ewen
        On Sun, Jul 6, 2014 at 8:14 AM, Pete Howell pete.howell@gecko-group.com [tracker2] ... While the theoretical calculations are sound,
        Message 3 of 3 , Jul 6, 2014
          On Sun, Jul 6, 2014 at 8:14 AM, Pete Howell
          pete.howell@... [tracker2] <tracker2@yahoogroups.com>
          wrote:

          > Thanks for the thoughts on polarization - it has been considered, but the j-pole
          > is a cheap, easy, no-drag install in the plane, and in practice it works better
          > than predicted.

          While the theoretical calculations are sound, as you have observed,
          the 20 dB hit is a non-issue when airborne. The line of sight path to
          any station on the ground can easily handle 20 dB of path loss without
          a problem. The j-pole antenna fits easily within the wing, and
          presents a zero drag installation, with no worries about affecting
          aircraft performance.

          One could easily argue that people driving cars need to install their
          vertical antennas on top of 60 foot poles to overcome the many dB of
          attenuation caused by local LOS obstructions such as other vehicles,
          buildings, and trees. By mounting the antenna 60 feet above the
          vehicle many of these obstructions would be cleared, and a much better
          chance of being heard by the local digis would be achieved. Of course,
          there might be some vehicle performance issues, such as not being able
          to drive under and obstructions on the roads.

          The j-pole in the wing works well enough to provide the communications
          desired, similar to a vertical mounted on a ground vehicle.

          > I previously had that a microtrak with the same antenna and did not get the
          > dropouts that I see with the current setup, thus my question.

          Program an offset into the radio for a quick and dirty test. Make the
          radio listen somewhere else, and transmit on 144.390. (ie 144.990
          -600) Of course, any of these solutions makes your tracker operate in
          the blind, which means you have a very good chance of clobbering other
          users on the ground. When you are flying at altitude, you have a very
          large outgoing footprint, as well as a large incoming reception area,
          as you are most likely very aware.

          As with any airborne APRS tracker, the preferred path to use is a zero
          hop path. Digipeaters are designed to be stations with antennas
          mounted at 100 or 200 feet HAAT (some are much higher, others even
          lower) such as to provide large area coverage that can be used by
          ground based assets to increase their area of influence. Those
          vehicles with poor antenna height and lossy paths can only communicate
          over a few miles to other similar stations. They send signals to
          digipeaters to increase their area of influence to a few dozen miles.

          An aircraft flying at even 1000 feet AGL will be able to influence a
          much larger area than a ground based digipeater, so it really doesn't
          make much sense to ask a digipeater with less coverage area to repeat
          a signal that already has been heard over the whole area that is
          covered by the digipeater. From the lofty vantage point of an airborne
          platform, APRS trackers will generally be heard by many i-gates,
          giving ample opportunity to get to the APRS-IS stream.

          Pete, you're now running a very powerful APRS tracking platform. It
          has many advantages over the MicroTrak for your type of operation. You
          should look at setting up altitude based profile switching. You can
          change your operational characteristics based on the altitude you are
          at. Many people object to flying a no-hop path because they want to
          use a normal terrestrial path when on the ground. This unit can do
          just that. You can have a WIDE2-1 path when on the ground, and a
          no-hop path when airborne. This means you get good coverage when down
          low, and don't cause network congestion when up high. With the profile
          switching, not only can you change your path, but also the QUIET time,
          which would allow you to operate politely down low with a path, while
          ignoring incoming noise and using a no-hop path up high. It looks like
          you fly in an area with ground altitude around 1000 feet or so.
          Program profile switching to occur about 1000 feet AGL, or at about
          2000 feet ASL.

          One other thing I noticed is your minimum turn time looks to be set to
          5 seconds. Do you need to be updating your position every 5 seconds
          during turns? It makes for a very nice track when turning on final,
          but it does make a fair bit of noise on the channel. You put out 8
          packets in one minute while turning from downwind to short final at
          Anoka County- Blaine Airport on Friday.

          --
          James
          VE6SRV
        Your message has been successfully submitted and would be delivered to recipients shortly.