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RE: [RTrak] RTrak-HAB antenna thoughts

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  • Bruce Coates
    Hi Ben Most people use either a simple upside down 1/4 ground plane, vertical dipole or wire J-pole on the balloon. All these give good radiation patterns
    Message 1 of 36 , Jul 30 1:41 PM
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      Hi Ben

      Most people use either a simple upside down 1/4 ground plane, vertical
      dipole or wire J-pole on the balloon. All these give good radiation
      patterns sideways with varying degrees of a null directly below the balloon.
      I use a single vertical radiator with a single counterpoise which gives an
      odd shaped radiation pattern that doesn't have a null directly below it.
      For a mobile tracker my favorite is a simple 1/4 mag mount. A 5/8 will help
      receiving the signal once the payload is near or on the ground, but is has a
      strong null directly above it.

      The worst situation for reception will be when you are directly below the
      payload. The null on the payload and the null on your car's antenna will
      tend to add together and you'll notice a significant reduction is signal
      strength. I've heard this referred to as the "cone of silence".
      Occasionally it's enough to make it difficult to receive the payload. One
      option are to stay out of this area below the balloon. A simpler solution
      is to slap your mag mount on the side of the car. Really! I did this on
      one flight and my weak signal from directly above returned back to full
      scale.

      In short, you don't need any special antennas. Our balloon in mid
      Saskatchewan last weekend, running 300mW was heard in Manitoba, Alberta,
      Montana and North Dakota, all with no special antennas. I was also able to
      copy it about 80% of the time with my TH-D72 with a rubber duck at a range
      of about 40 miles.

      In short, keep it simple, try to keep 10 miles or more away from directly
      below the balloon and get creative if you need to like moving your receive
      antenna around. You may also want to take an extra hand held along so you
      can play with different antennas.

      73, Bruce - VE5BNC
      SABRE - http://ve5aa.dyndns.org/balloon

      -----Original Message-----
      From: RTrak@yahoogroups.com [mailto:RTrak@yahoogroups.com] On Behalf Of
      airsix73
      Sent: July-30-12 1:14 PM
      To: RTrak@yahoogroups.com
      Subject: [RTrak] RTrak-HAB antenna thoughts

      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



      ------------------------------------

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    • 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
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        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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