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Vario - Radio interference


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This is an Odd question....

I connect my Vario to my head set made by Loescher. A great set of coms with noise cancelling mic. I connect my Vario with the stereo lead for the I phone. This helps me listen to the Vario while flying thermaling

Every thing is fine if i have my vario plugged in on its own the radio is fine when its connected on its own... But when i have them both connected and press the PTT on the radio my Vario goes wild.

First i thought it was the radio sending a signal/current down too the Vario. I added a couple of suppressors (one way things) given to me by a mate who is fairly good with electronics.. This didn't stop it.

I disconnected everything and pressed the PTT again everything was fine until i got close to my Vario. It did the same thing sending the Vario wild. the Vario is fine at a distance of over foot until i connect the them together again.

How do i stop this interference.



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Hi Mark,

What people don't realise with a hand held radio is that the operator/pilot is acting in some fashion as part of the antenna system that the radio is working into.

If you connect a perfectly balanced dipole or similar then there will be very little RF 'leaking' around the body of the radio.

With a typical setup on a paramotor, with a short inefficient antenna on the radio, the body of the radio is acting as the 'ground plane' in conjunction with the flexible antenna. The radio is normally mounted close to the body so some absorption of RF is coupled into the operator.

As an aside that is why hand held radios are limited to 5W output.

When you connect another lead to something else then some of this RF that is on the 'earth' or equivalent ground plane is conducted into the other connected equipment.

As Notch says the only cure is to keep the vario away from the source of RF.

It may be possible to put a block on the RF getting down the lead by winding the lead through a ferrite ring, you would probably need quite a few turns of cable, so if your cable is short that could be a difficulty.

If you would like me to pop you a ferrite in the post to try just shout.



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  • 2 weeks later...

Hi Alan Notch

Thanks for the replies...

I have no issue with the radio vario when separate.. Just when connected..

The radio fits inside my harness pocket when i am thermaling and using the Vario together..

Barry holleran said about a ferrite ring.. But was not sure it would work...

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Hi Mark,

The only way I can think of removing the interfernce down the wire would be an optoisolator of some sort. But I am pretty sure that it would require some power from each circuit.

Perhaps Alan can comment, if I get a spare moment I will see if I can work out a diagram. But to be honest I am not 100% sure it would work.

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