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Squealing headset


Ben Longden
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Anyone with a clue on how to fix this problem?

 

I use an Altronic headset (six months old and well cared for) and have had little trouble with them until the past couple of weeks.

 

Whenever I hit the transmit button, I get a feedback squeal.

 

This is also transmitted...

 

I worked out the headset cable length is about 1/4 wave of the CTAF frequency, and noted the plug point is at the back of the centre console, and close to the antenna.

 

I did chat with the company I bought them from, and he has noticed a problem with Tecnams in this respect. The headset works fine when plugged into the 172 or any other AC.

 

My initial thought was to toss them out of the cabin, but on reflection, I thought of putting a couple of loops in the cable or attaching a toroidal coil to the cable as an RF choke.

 

Any techies out there with any other suggestions?

 

Ben

 

 

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I had this problem but it was only when using a Vertex 150 radio with a GPS running at the same time. It doesn't always do it.

 

I was told that handhelds are not designed to be used in airccraft, which has me wondering why the manufacturers sell them with headset adaptors and advertise their use.

 

Ian Borg

 

 

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Guest Ken deVos

Hi Ben

 

I have a similar problem in the Jabiru J160 when I use my Altronic headset instead of the ones supplied in the a/c.

 

Perhaps it's a clue to your situation, but the only way to reduce but not eliminate the squeal is to turn up the headset volume and turn down the intercom volume, then adjust the radio volume to suit.

 

A friend who owns an older Jab LSA55 (these a/c do not exhibit the problem) advised that to cut costs in the J160, the microphone and headphone wires are not separately shielded (ie the two wires are now routed in the same cable). This has the potential to cause signal feedback from the headphone to mic.

 

Why does this problem not present with the a/c supplied headset? I suspect the problem stems from the higher impedance of the Altronic headphones which is made worse when the headphone volume is reduced and worse again when the intercom volume is increased.

 

Anyone with a clue on how to fix this problem?I use an Altronic headset (six months old and well cared for) and have had little trouble with them until the past couple of weeks.

 

Whenever I hit the transmit button, I get a feedback squeal.

 

This is also transmitted...

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I had a good yarn with Ron from Skysupply whom I bought the headset off, and after describing the symptoms, the first question he asked.. "are you flying a Tecnam?"

 

It turns out that the Altronic headsets and Tecnams seem to have a difference of opinion, and that in all his years, the Tecnam is the main aircraft to pose this issue today.

 

The problem is because the headset cord acts as an aerial for the headset, and is literally being swamped with radio frequency from the main antenna only a metre or so away.

 

So, I quickly thought about my Yr 12 Physics, and thought of an RF choke.. or a few loops in the headset cable.

 

I did an experiment today.. I took along my headset, one Altronic from Air Shepp and another spare, very well used set and did a test on the ground.

 

Both Altronics squealed when the PTT was keyed. The bashed up one didnt. Then I used my set, and made a short coil of three turns in the cord.. hit the PTT and no squeal.

 

As its a bit difficult to fly and hold the now shorter cable in a coil, Ive invested $3.98 from DSE in an RF choke, consisting of a pair of magnets to clamp around the cable instead.

 

 

All in all, a cheap and painless way to solve the problem.

 

Ben

 

 

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Guest Ken deVos

It sounds like a logical fix Ben. I'll try it in the Jabiru next time I get a chance.

 

Just one question though, where on the cable did you locate the filter?

 

 

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Guest Nelson Smith

I chased this problem in an sp Jabiru for 3 years.An A200 icom without seperate intercom, and Altronic headsets.I seperated aerial and headset cables, fitted the rf chokes and when I thought I had it licked, the squeal would appear on a higher or lower frequency.Under pressure from my partner,(the pilot in command) I bit the bullet as one often does, and equipped the SP with BOSE.They are magic,and there is no sign of the elusive squeal.This will take some time to pay off the browney points

 

 

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Guest AusDarren

Isn't it the way things go.. after spending $$$ to get a fix you hear of someone else resolving the problem for $3.98..

 

I do remember years ago having a discussion with Phil Ainsworth, then at Jabiru, now running Microair, about headsets, and performance. He maintained that the Jabiru being all composite was very different to a typical all metal light aircraft. and it was important to match 'horses for courses' so to speak. At the time he recommended the Flightcom Blackhawks as being the best for the Jabiru with the ICOM radio.

 

Regards,

 

AusDarren

 

 

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