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hangdoc

Wingtip light radio interference

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Hi

 

My new Foxbat A22LS has LED wingtip combined nav/strobe lights. They interfere badly with radio to the point it can't be squelched and they are effectively unusable. It has been inspected by a professional avionics person and he concluded there was direct interference from the light units via the radio aerial, not through the wiring etc. I am waiting RF chokes to clamp on the cables near the light unit, ones I have tried which are not VHF specific have made no difference. What is interesting is - one wing (the right) generates all the nav light interference when mounted on the right wing tip but generates strobe interference when mounted (upside down now) on the left wing and the left wing light does the same but opposite pattern. To me, that means the circuit boards themselves are probably generating the RF interference and some degree of internal (but incomplete) shielding is at work but then not so if the light is flipped. Probably has a direct line of sight to the antenna in the middle of the fuselage between the wings.

 

Any other Foxbat owners have this problem with the new LED lights? If so, did you solve it and how?

 

PB

 

 

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What brand are the strobes ?

They are "no brand", made in the Ukraine. Maybe aeroprakt themselves make them.

 

PB

 

 

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Hell yeah I have been talking to the agent, reckon he is getting sick of me. The ferrite chokes are being sent by him for me to try. I don't think they will fix it (but will try them of course). Doesn't sound like there are many foxbat owners experiencing this problem.

 

 

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No, they are the lights that came with the plane from new, now 23 hrs old.

Was the radio installation pre-installed by Aeroprakt?

 

 

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radio installed by the nz agent on arrival, wiring etc inspected by professional avionics expert and he concluded that the interference is getting in by the aerial not the wiring, suppressing it is proving a challenge. avionics dude recommended trying different brand lights but agent (understandably, cost wise), wants to try a fix, i just want them working correctly asap

 

 

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Hell yeah I have been talking to the agent, reckon he is getting sick of me. The ferrite chokes are being sent by him for me to try. I don't think they will fix it (but will try them of course). Doesn't sound like there are many foxbat owners experiencing this problem.

Hmmm... sounds like the old 'your the only one with the problem' routine to get yer to go away.

 

Years ago when them 912 engines first came out I had one that started to make metal in the filter. I had a knowledgable engineer look at the 'bits' and he took a guess at the gear box being the source. Upon enquires to engine supplier I were told it was the only instance they had ever heard of. I think it were a month later the factory put out a service advice about it and had replacement parts available. Apparently I weren't the only one.

 

Instead of faffing about, I would get the Foxbat dealer to send you two new strobe units to see if that fixes the issue. If it do - the warranty parts have been installed.

 

.

 

 

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As FB above. Putting the ferrites on the leads is just a patch, replacing the light units makes more sense. I'm assuming you have the same sort of 'trading standards' as we do this side of the Tasman. Currently the aircraft is 'not fit for purpose'. Pays to be hard-nosed in these situations or run the risk of getting walked over.

 

 

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have heard that at least one other foxbat in australia has the issue as they advised nz agent re. the chokes. have done some searching and seems LED lights can be noisey things (the boaties have issues) and other aircraft have it too (other forums). ultimately it may require replacements that have properly shielded circuitry and shielded wires (the ones running to the strobes are not shielded). will wait and see the result of the chokes....

 

 

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The light noise appears fixed. I fitted VHF chokes (from MGL) very close to the light itself with the wires looped through the choke. Cheap clip on chokes only did half the job. The MGL ones are VHF type and work really well. I know if only masks the problem but in reality, replacing the lights with ones that don't interfere/generate RF would require some work to the fibreglass tip to fit, just not worth it in my opinion. I will post some pics because I am sure there will be other Foxbat owners with the Aeroprakt LED lights fitted that will be getting noise. I had to cut the cable to thread through the choke and re-solder with heatshrink cover after. From the MGL website there looks to be a clip on version now that costs a bit more which would be a better option than cutting the wires. There may also be other chokes that work well too but I don't know for sure. I tried out my fix today and there really wasn't any noise at all, even weak radio signals had no overlying clicking or static noise from the lights. Hope this helps someone else.

 

Cheers

 

PB

 

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IMG_3058.jpg.91b50ef9985ab96e1d973ef04671a944.jpg

 

 

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So with a bit of time under my belt it appears the fix I used is only a partial fix. When the engine rpm is higher (5000 and above) the strobe noise clips through the squelch on the radio. Is also clips in at a higher freq (our chat channel, 133.375) regardless of the engine speed.

 

Any bright ideas short of different make of strobe (that would be a bit of a hassle to change the wingtip mounting holes etc)? I thought maybe replacing the unshielded cable with quality shielded stuff next.

 

PB

 

 

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How about they provide you with a couple of replacement units to try? As I said before, don't be too soft on the responsibilities of manufacturer/vendor.

 

 

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Yep totally agree they are not fit for purpose but trying 2 new units of the same manufacturer will be no difference, reason I say this is because the Australian Aeroprakt dealer sees the same issue there and "fixes" with chokes. Strobes from a different manufacturer probably would fix the problem but I bet would not be a direct fit to the existing tip fittings.

 

Cheers

 

PB

 

 

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