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Re: RTrak-HAB antenna thoughts

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  • airsix73
    Thank you all for your advice! I didn t expect so many responses, all of which have been great. Jason, what teflon coax are you using? Can you recommend a
    Message 1 of 36 , Aug 2, 2012
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      Thank you all for your advice! I didn't expect so many responses, all of which have been great.

      Jason, what teflon coax are you using? Can you recommend a supplier? Thanks

      Ben

      (Hope this message posts. Been having some trouble. Sorry if duplicate.)



      --- In RTrak@yahoogroups.com, Jason KG4WSV <kg4wsv@...> wrote:
      >
      > Something to keep in mind is the temperature rating for the insulation
      > on the exposed material, and the fact that the payload will experience
      > various amounts of turbulence, especially at burst.
      >
      > At one point we had standardized on roll-up J-poles (standard
      > commercial grade RG58 with typical PVC insulation combined with 300
      > ohm twin lead). We experienced some failures because the PVC
      > insulation became brittle (temperatures are usually -40C or lower).
      > When this brittle PVC got hit too hard during turbulence it broke,
      > allowing the conductors to short, at which point we lost the tracker
      > signal.
      >
      > My standard now is to use milspec teflon insulation for any cabling
      > that is outside the payload.
      >
      > We've also had antennas get ripped off completely, so that our
      > radiator was about 1" of coax center conductor left unshielded. This
      > is not terribly efficient on 2m. :| We managed to find that one by
      > predicting the landing location, finding some high ground near the
      > predicted location, and listening with a yagi and a D7. Even then we
      > probably would not have found it if it wasn't hanging in a tree.
      >
      > -Jason
      > kg4wsv
      >
    • 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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