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Thread: Radio interference

  1. #1
    Member Settling in
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    Radio interference

    Hello Dynamic owners and anyone else who reads this forum

    Can anyone help with a radio interference problem that can be heard at

    A 250.00 reward is being offered by YLAC for anyone who can give advice that solves the problem.

    The problem is random, interemittent interference that starts after an incoming transmission ends as a low level rythmic chirping sound that gradually increases over 5-10 seconds to a very loud continuous noise which can only be made to stop at squelch level 10 or by changing frequency. The receive flag in on in the radio LCD display so the problem is RF interference. On some flights there can be 5 or 10 minutes between problems, but on others the problem can be nearly constant. Radio is a Filser ATR500 and the antenna is a Commant CI 122. The radio has been changed and all electrical connections checked included the earthing of the antenna ground plane. The problem only occurs in flight and cannot be made to happen on the ground. As the Dynamic is an all carbon fibre aircraft electrical bonding seems a possibility and if anyone agrees, can they suggest where to start?

  2. #2
    Banned Banned500 Club
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    A Lancashire lass settled in Essex
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    Radio interference

    Suggest this wiki article for starters
    http://en.wikipedia.org/wiki/Motorboating

    Joan

  3. #3
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    Radio interference

    Joan

    Thanks for the suggestion and an interesting read. Tried some of the ideas in the article but no luck

    Latest is as follows

    A different type of radio was tried and the existing radio was run from a separate 12v battery not connected to the aircraft and the co-axial cable has been thoroughly checked for electrical faults. A long flight using many frequencies from 118.05 to 130.55 showed interference on 118.05, 120.62, 123.60, 122.70, 124.07. The squelch was set at 6 throughout the tests (Note: 10= max and 2 -3 normal on similar radios). I cannot be 100% on this as the problem is intermittent, but so far it has never occurred on the ground even with the engine running and all avionics switched on?

    The interference has now been isolated to some form of RF being generated in the aircraft, as a test with a hand held Icom radio running on its own battery produced the same interference? The transponder and GPS have been eliminated from this, so does anyone have any ideas where/what to look for next. High on my suspect list is a 12v to 12v convertor made by Filser to protect the transponder from transient voltage spikes often associated with the Rotax charging arrangement which uses a Ducati regulator which itself is on the suspect list? Also as the aircraft is constructed from carbon fibre I also wonder if static build up across non electrically bonded parts might be an issue but if so why only this aircraft as the other 15 in service have no such problems?

  4. #4

    Radio interference

    Are you using the built-in intercom on the radio or an external intercom?

  5. #5

    Radio interference

    How about the hobbs meter Malc?

  6. #6
    Member Settling in
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    Radio interference

    Hi Jon and Phil

    Thanks for your comments on the interference problem.

    Just wanted to let you and the other readers of this group know, that I am no longer working with YLAC - Lets just say due to difficulties in dealing with the boss and I am sure you all know who that is and can therefore read between the lines, given the previous history of my predecessors, who all suffered the same problem?

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