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Re: RTrak-HAB antenna thoughts

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  • airsix73
    Just wanted to follow up and let everyone know we pulled off a successful 1st balloon project. The RTrak-HAB performed well. In fact it survived a very hard
    Message 1 of 36 , Sep 5, 2012
      Just wanted to follow up and let everyone know we pulled off a successful 1st balloon project. The RTrak-HAB performed well. In fact it survived a very hard landing. I didn't mess around with profile or frequency switching just to be safe.

      One thing I'm scratching my head over is that although I configured it for "WIDE2,1" it was not picked up by a single repeater. I used APRSISCE running on my laptop with a Verizon mobile wifi hotspot to act as an iGate from my chase-vehicle. That worked great, but I'm puzzled that it was ignored by the rest of the APRS community. There are plenty of repeaters around that certainly heard it.

      I ended up going with a vertical dipole which worked very well until roughly 100,000ft at which point we couldn't get out from under the doughnut and started missing packets. We were roughly 12 miles off to the side, but that was no longer enough distance. Our highest-altitude packet came in at 124k and change. Based on our rate of climb at that point and the time-stamp on the video we hit a bit over 126,000ft roughly 3 minutes later.

      Here is a bit of video from the last 1:30 before burst. Thanks for the help with antenna design!

      http://www.youtube.com/watch?v=GRqrnh_ySNs&feature=g-upl

      -Ben


      --- In RTrak@yahoogroups.com, "airsix73" <ben.messinger@...> wrote:
      >
      > Hello,
      > I'm preparing my first balloon launch and trying to decide on antennas for the mobile ground station as well as the balloon. I'm a new ham, and nervous about keeping a strong enough signal over 25-30 miles with just 350mw transmit power and random orientation. Suggestions?
      >
      > For best front-to-back ratio there are some really neat antenna designs (patch, bi-quad with reflector, yagi, 2 and 3 element quad) but they aren't very conducive to balloon work!
      >
      > For those of you who've done this before, what are your recommendations? I'm sure I'm over-thinking it, so I'd love to hear what others have done with success.
      >
      > Thanks!
      >
      > Ben
      >
    • Keith VE7GDH
      Ben KF7VZR (got that from a June 22 message) wrote... ... Deviation is important. If it s too high (within limits) nearby stations may still be able to decode
      Message 36 of 36 , Sep 6, 2012
        Ben KF7VZR (got that from a June 22 message) wrote...

        > My documentation says nothing about TX audio level...
        > They've both been played with...

        Deviation is important. If it's too high (within limits) nearby stations
        may still be able to decode the tones. Distant ones where your signal
        is weaker may not be able to. You have probably heard this on a voice
        repeater or even on simplex. A distant and noisy station can be copied
        via a repeater if he backs off from the mic. If he starts shouting, the
        deviation goes up. More energy is outside the passband of the receiver
        and eventually the signal is too noisy to copy or the squelch might
        even close. If you are simplex, you can try opening your squelch. If
        you are on a repeater, you're out of luck. It's the same with packet.
        You are better off having the deviation set properly. It can be done
        by ear, but a deviation meter or service monitor would be better.
        Lacking one, just crank the deviation all of the way up and then
        start turning it down. When it starts to sound quieter, turn it down
        some more. It will get you in the ballpark, but checking the actual
        deviation would be better.

        Perhaps you could check the actual deviation before you change
        anything. So... could over-deviation explain why only one iGate
        heard you?

        73 es cul - Keith VE7GDH
        --
        "I may be lost, but I know exactly where I am!"
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