attn Jim Weir

Discussion in 'Home Builders and Sport Pilots' started by fruitfly, Apr 30, 2016.

  1. fruitfly

    fruitfly Filing Flight Plan

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    Hello Jim, I enjoy reading your articles in kitplanes. I am building a sportcopter lightning gyro and am installing a fl760 radio and I was wondering about antenna options.There isn't any ground plane surfaces since it is tube construction,but it does have a instrument pod made of fiberglass that is 18" x 12". Could I put a ground plane inside the pod and mount the antenna on top or would there be a problem with the electrical panel causing noise. The machine also has a 2 stroke engine. Sport copter has a steel whip mounted on the frame of there tandem trainer and it seems to work ok. Also, where is a good place to find a swr meter? Thanks for any advice.
     
  2. wilkersk

    wilkersk Line Up and Wait

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    I'm not Jim. But, I'm a retired avionics guy.

    A welded steel tube fuselage makes an excellent ground for a vertically polarized 1/4 wave length VHF aircraft antenna. Just properly ground the antenna base to a metal grounding tab on the fuselage structure per the manufacturer's installation guide, no need for a separate ground plane. A serviceable vswr meter can be purchased from any online Ham radio website, or even on Amazon.com. You may have to futz around to come up with the right connector adapters. But, it can be done without too much trouble.
     
  3. flyingron

    flyingron Touchdown! Greaser!

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  4. denverpilot

    denverpilot Taxi to Parking

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  5. fruitfly

    fruitfly Filing Flight Plan

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    Thanks for the info,the sport copter tandem has a steel whip mounted on the front of the frame and it seems to work fine.
     
  6. weirdjim

    weirdjim En-Route

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    What he ^^ said. Here is a neat trick for a cheap VSWR meter: http://www.kb6nu.com/no-vhf-swr-meter-no-problem/
     
  7. fruitfly

    fruitfly Filing Flight Plan

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    Thanks for the reply. It is hard to find a meter for the air band frequencies.
     
  8. flyingron

    flyingron Touchdown! Greaser!

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    Eh? VHF SWR meters for the powers involved (less than 100W) can be bought outright new for less than $50.
     
  9. denverpilot

    denverpilot Taxi to Parking

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    My most recent Bird 43 (of three) with a complete set of slugs from DC to daylight only ran me $100. Granted, it was a bit of a steal at that price, but they're out there.
     
  10. wilkersk

    wilkersk Line Up and Wait

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    The Bird meters are nice if you're a shop tech and need expensive tools. But, for this application, I'd think it'd be acceptable to just get a good radio check and let it go. If a base station can her you loud and clear, power out is acceptable. After all, this isn't a $5,000 radio installation on a rich guys Bonanza.

    If you have to have a SWR meter for a 16 watt VHF radio, just get the Workman model 104. Its $50 on Amazon.
     
  11. fruitfly

    fruitfly Filing Flight Plan

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    Thanks, I ordered a 104 2 days ago for about that price.
     
  12. denverpilot

    denverpilot Taxi to Parking

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    I've never found quality tools to be a bad investment. Especially when maintaining something that costs 1000x more.
     
  13. flyingron

    flyingron Touchdown! Greaser!

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    Yeah, but aviation antennas are pretty broadbanded (and they don't cost much more than the $50 meter) and he's just checking for his ground efficiency. You could feed his 14/28v transistor final comm radio into a dead short and while it wouldn't radiate well, it won't damage the radio.
     
  14. denverpilot

    denverpilot Taxi to Parking

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    Who cares if it's damaged? The test is to find out that it's actually working. $100 is cheap to do the job right. I spent $22 on burritos for two tonight.

    Oh well. Options. Folk can do as they please. I just offered that the cheap tool isn't saving that much.
     
  15. flyingron

    flyingron Touchdown! Greaser!

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    You were lucky you could find a used Bird for 10% of what it cost new, but that doesn't change the fact that a $40 new in the box VHF SWR meter would do exactly the same thing in this situation that the Bird does. Because you made some obtuse point about the value of the com radio, my "damage" comment was trying to guess what point you were trying to make.