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  1. #1
    Airfield Ops Gramac's Avatar
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    Poor Radio Transmission

    Hi,

    My flexwing (GT450) is fitted with a relatively new radio but the transmissions are poor/weak although the reception is fine. Any suggestions of what may be the issue? The radio is a YAESU FTA-750. Thanks.


  2. #2
    Co-Pilot Martin Watson's Avatar
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    First off you need to find out if your transmitted signal is weak or if your transmission has poor audio quality.
    If signal weak, suspect the antenna and it's feeder cable and connectors.
    If poor audio, suspect the cables and connectors between microphone and radio.
    It's worth trying things in different configurations - what's it like using a rubber duck antenna? - what happens if you bypass the intercom unit?
    It's very unlikely to be a problem actually in the radio. Always with things like this check how good all the connections are first.
    HTH
    Martin
    BMAA 5370


  3. #3
    Airfield Ops Gramac's Avatar
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    Thanks Martin. It is definitely a weak signal as ATC reported this to me. I will strip the aerial out this weekend to ensure it is OK. I suspect the aerial was fitted when the aircraft was new ten years ago, so maybe time for an upgrade? I have seen the two MicroAvionics ones but is there any other alternatives suitable for a flexwing?


  4. #4
    Co-Pilot Martin Watson's Avatar
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    Ah right. The aerial itself is probably fine (it's just a piece of metal the right length after all). Things to go over carefully are all the connections, plugs, sockets, and ground connection (where a wire joins to the metal frame of the aircraft). If it's ten years old you may also find the coaxial cable to the aerial has deteriorated and needs replacing (the insulation between the inner conductor and the copper braid breaks down or gets water in it).
    Any corrosion anywhere is a sign that things need a clean up.. Radio frequency signals need clean bare metal connections to get through.
    Martin
    BMAA 5370


  5. #5
    Airfield Ops Gramac's Avatar
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    Thank you. I will work backwards from the aerial to ensure everything is clean and serviceable.


  6. #6
    Captain andy dixon's Avatar
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    If you are using a microavionics interface make sure all the internal switches are set right.....if in doubt take a pic and send it to microavionics and ask them, or give them a call and they will tell you how the 12 switches should be set.

    Plan "B" try someone else's radio.
    disclaimer....as per 2010 European libel act....these are my thoughts only and may not represent the thoughts or actions of any person /company/group/manufacturer named in this article/Internet posting


  7. #7
    Captain andy dixon's Avatar
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    "The dude" on this forum uses a yaesu trancever and he mends electronic stuff for a living ( and he's been a sound engineer for a good 30 years) may be worth sending him a private message.
    disclaimer....as per 2010 European libel act....these are my thoughts only and may not represent the thoughts or actions of any person /company/group/manufacturer named in this article/Internet posting


  8. #8
    Co-Pilot goldrush's Avatar
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    If the foregoing fails, then the best thing really, is to beg borrow steal.. or even buy a 50 Ohm VWR meter which covers the airband frequencies such as at about 40.
    http://www.ebay.co.uk/itm/AVAIR-AV-2...AAAOSwLEtYfSVu

    (the old CB radio meters WILL NOT DO)..

    Then follow the instruction.
    A Vswr reading of, or less than, about 1.5:1 is fine... anything above about 3:1 is "dangerous" to your transmitter.

    Try it at both frequency ends of the airband frequencies.
    If the ratio is much higher at the high frequency end......... the antenna is too long... chop an 1/8th or so off and try again.

    Beware that occasionally the length of cable, if its length happens to be at a multiple of the transmitted wavelength may well "mess up the reading".. so always keep the leads between the VSWR meter and radio short.
    Hope it helps
    Wally Hayward


  9. #9
    Airfield Ops Gramac's Avatar
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    Thanks. Eddie Cartwright from MicroAvionics hangars at the same strip as me. I will get his opinion.


  10. #10
    Co-Pilot goldrush's Avatar
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    Always pays to go to the local guy who "knows about such things"
    Wally Hayward

  11. The Following User Says Thank You to goldrush For This Useful Post:

    Martin Watson (12-10-17)


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