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horsefeathers

"Phantom" radio reception

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Hi Guys.

 

I've got a problem with my radio(s) in my Jabiru.

 

I get random "phantom" receptions on my radios - the receive light turns on, and I get loud audio at the same time - 5 to 30 seconds, sometimes longer

 

I can receive transmissions from other aircraft when this happens, so it doesn't just blank out the radio completely

 

It happens on the inbuilt MicroAir, and a battery operated Vertex handheld radio, at the same time

 

Squelch has no effect on the noise.

 

This has been happening for a few weeks now.

 

Points to consider are:

 

  • Other planes that I fly with/near me do not receive these "phantom" transmissions
     
  • Inbuilt radio is a MicroAir 760, model M
     
  • I have a handheld radio (Vertex VXA-220) in the aircraft with me, battery operated, which receives these "transmissions" at the same time as the MicroAir, so it seems that the aircraft is generating some extraneous random noise
     
  • I can receive other aircraft transmissions while the phantom transmissions are occurring, so does not appear to be related to the problems that MicroAir report with a faulty electronic component
     
  • Squelch has no effect
     
  • Nothing has been altered on the plane in the last few months
     
  • Jab engine 2200
     
  • Battery is about 6 months old, and is charging OK (14.2 Volts)
     
  • Noise seems to reduce after about 20 minutes flying, but can still occur at times
     

 

 

Any ideas on what may be causing this?

 

 

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Have a read about skip. Of course the burst of audio could be someone giving their radio a quick test.

 

 

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Try loading your aircraft electrical system differently and see if it changes.

 

eg, lights and strobes, elect fuel pump off.....or "on"...

 

I always had intermittent static with my engine at high revs and in hot weather. Never any other time.

 

I changed from passive to anr headsets and it's gone......

 

 

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Skip the skip. Unlikely at VHF.

 

Do you have a USB supply for anything in the aircraft? I would suspect that if squelch is opening {without any voice signal) then it is likely to be RF interference.

 

 

  • Agree 1

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Skip occurs on the old 27 mhz c.b band, somthing about that freq bouncing of the ionosphere, don't think it happens on vhf.

 

 

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High angle 'skip' using the occasional enhancement of the 'E' layer known as 'Sporadic E' can have effect into the VHF range. It renders very strong signals, but generally does not last long at the higher frequencies. I have used it on the amateur 144mHz frequencies, achieving distances in excess of 2000 kms. Atmospheric ducting can also work very well at VHF frequencies. However the OP has already said that it was only his equipment that was receiving the signals.

 

Conditions are not that conducive to Sporadic E so early in the summer.

 

 

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I received very strong VHF signals from Darwin, and could communicate both ways, while I was on the Kimberley north coast 400Nm away. But then I was in the eye of cyclone Rachel at the time. Never experienced it on VHF at any other time but it was normal on HF and other low frequencies - usually the chatter from Indo fishermen using frequencies illegally would drive you so nuts you just turned the HF off.

 

So - unless you were in some very rare atmospheric conditions at the time then it's probably not a skip event. Since your handheld received at the same time it's not a MicroAir problem either, so the likelihood is that someone was actually transmitting what you heard, from nearby, or you were transmitting to yourself, so to speak.

 

You're saying loud 'noise', so I guess it's not voice or detectable words? So - what kind of noise? Feedback squealing?

 

Since you have two radios on at the same time might they be feeding back into each other ...?

 

 

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As summer starts to roll around "skip" can start..although on VHF its not really skip it is more like ducting or Sporadic that is happening. Also something else can be causing a image into your radios. if you have another item in the aircraft that has a strong local oscillator it can cause a image to appear in the IF of your radios. Most likely if they are other aircraft radio transmissions it will be ducting or if you can find those originating transmissions and they are far emough away in frequency from what you are listening on then it can also be an image issue. There are filters in your radios and they have a positive and a negative side. Your radio is designed to only look at one side but if a transmission is 10.7mhz away the other side and is reasonably close it can come through your radios. There are other images it just depends on what your final IF is (IF=intermediate frequency)

 

 

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Thanks all for your suggestions, but especially to [B]@Bluboyz[/B], a new member, who has provided an extensive list of possibilities to try out. If I get a resolution, I'll be sure to post it here.

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Skip the skip. Unlikely at VHF.Do you have a USB supply for anything in the aircraft? I would suspect that if squelch is opening {without any voice signal) then it is likely to be RF interference.

I agree. Also, do you fly with an tablet or phone? If so, make sure the wifi is turned off. I found that cured the phantom receptions I was getting.

 

 

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If you turn one radio off does it still happen to the other?

 

 

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I only started carrying the hand held radio to confirm the phantom reception was caused by an external source to the inbuilt radio, and not a fault with the MicroAir itself. The noise continues with the handheld turned off.

 

And yep, the intermittent noise continues even when I don't carry phone and iPad with me.

 

Hopefully will get down the airport this weekend to try out everyone's suggestions

 

Cheers

 

 

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