PilotAware
British Forum => Technical Support => Topic started by: Merlin29 on September 12, 2020, 11:08:01 am
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Hello. We are using PAW in our GT450 flexwing. The setup is as per the guidance. PAW is in the nose of the aircraft with antennas pointing vertically down and powered by the recommended Anker Powerbank. We are getting significant radio interference on certain channels. It is constant noise as if the squelch needs increasing but you could increase the squelch to max and it wouldn’t go away and probably block all transmissions. We are certain it is the PAW as if we disconnect the power then the noise goes away to a clear sound. Plug it back in and the noise returns within 30 seconds. It’s not all channels. Examples of where we’ve had constant noise is Brize Radar 124.275, Halfpenny Green 123.005, Compton Abbas 122.710 and emergency 121.500. When i flew to Halfpenny Green transmissions were still coming through but noise all other times. Other places then not hearing anything other than noise. Installation was approved by BMAA Inspector. What can we try as we can’t really fly with it at the moment.
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In case you ask we are using Anker PowerCore 13000 Power Bank - Compact 13000mAh
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Just out of interest, how big is the capacitor across your rectifier/regulator?
There has been some debate in the past about whether the capacitor should the the P&M value of 2,200 micro Farads, or whether it should be the Rotax value of 20,000 micro Farads.
Having said that, it's probably EMC issue as some channels are affected more than others.
Side issue. A PilotAware person will be along to answer the question properly in a moment.
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Sorry, not having any electronics knowledge I don’t know the answer to your question!
One other bit of info that might be useful is that when an iPad and PAW plugged into Powerbank the noise issue happens. When just an iPad no noise. When just a PAW noise. Would this indicate interference coming from PAW unit itself rather than Anker power bank?
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Sorry, not having any electronics knowledge I don’t know the answer to your question!
One other bit of info that might be useful is that when an iPad and PAW plugged into Powerbank the noise issue happens. When just an iPad no noise. When just a PAW noise. Would this indicate interference coming from PAW unit itself rather than Anker power bank?
OK, understood, so the PAW isn't electrically connected to the aircraft at all? In which case it's an EMC/ radio frequency interference problem.
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OK, understood, so the PAW isn't electrically connected to the aircraft at all? In which case it's an EMC/ radio frequency interference problem.
Correct. Not connected to the aircraft system.
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Sorry, not having any electronics knowledge I don’t know the answer to your question!
One other bit of info that might be useful is that when an iPad and PAW plugged into Powerbank the noise issue happens. When just an iPad no noise. When just a PAW noise. Would this indicate interference coming from PAW unit itself rather than Anker power bank?
Depends on the battery level of the iPad when you had it connected. Try the same test with the iPad below 80% and active with the backlight turned up.
Is the PAW connected to anything, intercom etc. ?
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Sorry, not having any electronics knowledge I don’t know the answer to your question!
One other bit of info that might be useful is that when an iPad and PAW plugged into Powerbank the noise issue happens. When just an iPad no noise. When just a PAW noise. Would this indicate interference coming from PAW unit itself rather than Anker power bank?
Depends on the battery level of the iPad when you had it connected. Try the same test with the iPad below 80% and active with the backlight turned up.
Is the PAW connected to anything, intercom etc. ?
I will have to test the iPad below 80%. PAW not connected to anything else other than Wi-fi to iPad running SkyDemon.
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Just reviewing channels where we’ve had ‘noise’ - anything around 120-124 MHz. Higher channels such as safety.com 135.480 and microlight freq 129.035 and Popham 129.805 all fine.
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Sorry, not having any electronics knowledge I don’t know the answer to your question!
One other bit of info that might be useful is that when an iPad and PAW plugged into Powerbank the noise issue happens. When just an iPad no noise. When just a PAW noise. Would this indicate interference coming from PAW unit itself rather than Anker power bank?
Hi Merlin,
I’m a bit confused by the above statement. You start by saying that the noise happens when you have [both] PAW and your iPad plugged into the [same] powerbank, which could (as Jeremy suggests) be due to a low charge level iPad grabbing lots of power and causing the PAW supply to go low voltage. For this reason we recommend NOT running a second device from the same (battery or low power) source as PAW. This would show as a voltage ‘Error’ or ‘Warning’ and Throttle = ‘throttled’ or ‘warning’ in the Status line on the PAW Home Screen. Can you check this?
You then go on to say ‘With just an iPad no noise. With just a PAW noise.’ so are you saying that you get the interference whether or not the iPad is connected to the [same] powerbank - i.e. all the time?
I certainly experienced white noise interference in the early days when running a homebuilt PAW and a low charge tablet (android or iPad) from the same powerpack or poor quality aircraft power supply, but the noise always went away if the charge lead was removed from the tablet or if left to its own devices, when the charge level in the tablet got high enough to reduce the current draw.
I now use a Charge2 / Charge4 setup, so no longer have this problem. I do, however, also experience higher than desirable ‘white noise type’ interference on certain frequencies, such as Newcastle Approach (124.380), Leuchars Approach (126.500) and in some areas on Safetycom (135.480), but hadn’t associated this with PAW, as other frequencies such as East Fortune (118.755) and Edinburgh (118.705 and 121.205) are completely clear.
I am away from home this coming week and definitely not flyable up here at the moment anyway, but will investigate further when I get back home.
In the meantime, it would be worth trying a clip-on ferrite noise suppressor (available in various sizes from Amazon or e-bay) on the power lead where it goes into your PAW to see if this cures or reduces the problem. If it does help, you can try adding a second one in tandem as this can improve things further.
Regards
Peter
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Hmm, interesting...
How close is the ADSB RX antenna to any aircraft radio antenna?
It would be interesting to know if you disconnect the coax to the ADSB RX antenna (from the SDR) if it stops. Leave the SDR in and working though.
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Hi Lee, thanks for your reply. To confirm when we were not running an iPad at all then the noise was still present. I didn’t check the PAW home screen but will do some tests. I will also get some ferrite beads as someone else has suggested this.
JCurtus - the radio antenna is at the back of the aircraft on the rear suspension leg. The PaW aerials are at the very front. So some distance.
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JCurtus - the radio antenna is at the back of the aircraft on the rear suspension leg. The PaW aerials are at the very front. So some distance.
Any of the RF cables run together at any point?
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Just reviewing channels where we’ve had ‘noise’ - anything around 120-124 MHz. Higher channels such as safety.com 135.480 and microlight freq 129.035 and Popham 129.805 all fine.
Is there a harmonic thing going on here? 8th harmonic?
869.5MHz / 8 = 108.6785MHz.
This might explain why lower frequencies are worst affected.
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JCurtus - the radio antenna is at the back of the aircraft on the rear suspension leg. The PaW aerials are at the very front. So some distance.
Any of the RF cables run together at any point?
Not the RF cables as the we are using the built in antennas in the Rosetta.
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Is there a harmonic thing going on here? 8th harmonic?
869.5MHz / 8 = 108.6785MHz.
This might explain why lower frequencies are worst affected.
Nope, don't think so...
Looking at a real time view of the airband frequency directly connected to my PAW Bridge, it does generate some noise in the band but they are very low power.
Plus this only transmits roughly every 1.7s, so won't cause an issue. At worst you might hear a click, but the transmission is only a few milliseconds anyway, probably not enough to break the squelch of the radio.
I suspect these are derived from the internal clock reference of the bridge, as they don't corospond to the 896.5MHz of the bridge transmission itself.
1,119.999069 MHz,-46.85 dBm
2,134.819625 MHz,-42.38 dBm
3,135.321334 MHz,-28.35 dBm
4,135.493453 MHz,-20.72 dBm
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Plus this only transmits roughly every 1.7s, so won't cause an issue. At worst you might hear a click, but the transmission is only a few milliseconds anyway, probably not enough to break the squelch of the radio.
Thanks, that might explain a very small click whilst testing a few days ago.
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Plus this only transmits roughly every 1.7s, so won't cause an issue. At worst you might hear a click, but the transmission is only a few milliseconds anyway, probably not enough to break the squelch of the radio.
Thanks, that might explain a very small click whilst testing a few days ago.
I'd be surprised if it was the PAW as the power output is very low and short, many strobes (even LED ones), will often be heard on the radio. Easy to test, just turn them off and see if it stops.
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Did some testing this morning. Flew without PAW and iPad connected to power and all was fine with the radio. On the ground I plugged in the PAW to power tuned to Brize Zone. Within 30 seconds the white noise came back. I disconnected power to the PAW and the noise went away. I did the same with my iPad which was <80% charge. No power to PAW and power to iPad. The same thing happened. Obviously with both connected to power the noise is present. There didn't seem to be any PAW difficulties with running PAW and iPad, the home screen showed everything green throughout. No throttling issues.
So I guess this indicates the Anker Power Supply at fault, even though it is a recommended one? One other thing to note, the power supply cable for the PAW runs alongside the RF cable for a short distance.
The ferrites should arrive later. Would it be prudent to fit one to each end of PAW cable? Also, it would be good to run iPad from same Powerbank as for long trips it is needed! Maybe a shielded cable for ferrites again? Whilst I am at it, a ferrite on the radio power supply?
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Did some testing this morning. Flew without PAW and iPad connected to power and all was fine with the radio. On the ground I plugged in the PAW to power tuned to Brize Zone. Within 30 seconds the white noise came back. I disconnected power to the PAW and the noise went away. I did the same with my iPad which was <80% charge. No power to PAW and power to iPad. The same thing happened. Obviously with both connected to power the noise is present. There didn't seem to be any PAW difficulties with running PAW and iPad, the home screen showed everything green throughout. No throttling issues.
So I guess this indicates the Anker Power Supply at fault, even though it is a recommended one? One other thing to note, the power supply cable for the PAW runs alongside the RF cable for a short distance.
The ferrites should arrive later. Would it be prudent to fit one to each end of PAW cable? Also, it would be good to run iPad from same Powerbank as for long trips it is needed! Maybe a shielded cable for ferrites again? Whilst I am at it, a ferrite on the radio power supply?
If none of the PAW kit is wired to the aircraft I doubt adding a ferrite will help much, it seems to be radiated RF from the power bank. Did you leave the cable for the PAW connected at the power bank, and just remove it from the PAW itself? I *might* be conducted RF using the cables as an antenna, so a different length one might help and adding a ferrite as close as possible to the power bank. If it doesn't seem to help, try looping the power cable to get two passes through the ferrite if you can.
Can you move the power bank away from any installed kit and see if things improve?
The other option is to look at how the RF is getting into the radio. If it's breaking squelch then it's probably seen as via the antenna, so check the connections and grounding between the antenna and radio. If it's just headset noise, then it could get betting into the intercom, so again check for properly screened and grounded connections.
Without poking around with some near field probes it could be hard to track down.
Alternatively, try a different power bank if you have one available.
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Update.
The ferrites arrived today and I went to the airfield to fit them. I added one to each end of the PAW supply cable. Instant result. Noise gone! I plugged the ipad back in and noise returned so added a pair to the iPad supply cable. Another result. Noise stops.
Before fitting the ferrites I tried moving the battery away from the trike keel tube. This had some success also, so I might try permanently relocating this at a later date.
This was all tested on the ground. True test in the air needed. One of our syndicate is flying later so might know more.
Thanks all for the advice so far.
One further question I have is that the noise doesn't start until 30 seconds or so after power 'switched on' to PAW unit. Does it start drawing more power from the USB Powerbank as the different modules within the Rosetta start up?
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Update.
The ferrites arrived today and I went to the airfield to fit them. I added one to each end of the PAW supply cable. Instant result. Noise gone! I plugged the ipad back in and noise returned so added a pair to the iPad supply cable. Another result. Noise stops.
Before fitting the ferrites I tried moving the battery away from the trike keel tube. This had some success also, so I might try permanently relocating this at a later date.
This was all tested on the ground. True test in the air needed. One of our syndicate is flying later so might know more.
Thanks all for the advice so far.
One further question I have is that the noise doesn't start until 30 seconds or so after power 'switched on' to PAW unit. Does it start drawing more power from the USB Powerbank as the different modules within the Rosetta start up?
Good news and interesting, it would appear to be conducted EMI from the Powerbank. I hope they haven't been tinkering with the design...
A Raspberry Pi starts off with quite a small power draw, which goes up as it boots. So it could well be delayed with the PAW until everything is up and running.
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Hi Guys,
Still following this with interest, though as I said earlier I’m away from home this week visiting our daughter and Grandkids for the first time since January.
Good to hear you are having positive results from fitting the ferrites. I echo Jeremy’s advice on PAW current draw and its effects. It certainly sounds as if the powerbank is generating EMI as power draw increases towards its design maximum, which could simply be a consequence of the design rather than a ‘fault’. Although powerbanks are generally reliable devices, we have to remember that they are designed to charge phones and tablets, not to power devices such as PilotAware long term - which is where Jeremy’s Charge2 and Charge4 devices come into their own - very highly recommended by the way - (and of course very grateful for Jeremy’s expert assistance with this type of problem).
I will take a look at the actual model of Anker Powerbank you are using and see if that gives any pointers.
Please keep us posted of developments.
Regards
Peter
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Thanks all. Maybe the charge 2 /4 might be a road to go down in future, especially as I would like to do more touring. Was put off by the cost and installation hassles! Flying last night my friend reported noise was occasional but much better.
Does anyone know of a shielded USB / lightning cable for the iPad? Found one on Amazon but out of stock.
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Thanks all. Maybe the charge 2 /4 might be a road to go down in future, especially as I would like to do more touring. Was put off by the cost and installation hassles! Flying last night my friend reported noise was occasional but much better.
Does anyone know of a shielded USB / lightning cable for the iPad? Found one on Amazon but out of stock.
The USB specification requires shielded cables. However, your milage may vary depending on the source. Genuine Apple cables will be shielded up to and including the connector. Bargain cables may not have any shielding at all, or the braid shield may not be connected to the actual USB connectors.
The descriptions on the likes of Amazon and eBay are, in many, many, circumstances not related to what physically arrives.
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Thanks all. Maybe the charge 2 /4 might be a road to go down in future, especially as I would like to do more touring. Was put off by the cost and installation hassles! Flying last night my friend reported noise was occasional but much better.
Does anyone know of a shielded USB / lightning cable for the iPad? Found one on Amazon but out of stock.
Hi Merlin,
In my experience, Charge2 / Charge4 are definitely worth the price. Since fitting mine, I have never had any power issues (except when my microUSB connector became loose in the PAW socket as reported elsewhere) and have never regretted the purchase.
You can buy excellent replacement and supplementary cables direct from JuicEBitz (who make the standard cables supplied by PilotAware) at https://www.juicebitz.co.uk They also do first class ones for iPads with right-angled ‘lightning’ connectors with a 20AWG power cable and in a range of colours - I recommend the 0.5m or 1 metre ones. We don’t recommend using longer ones as they might cause voltage issues, depending on what they are being fed from. I shouldn’t really publicise this, but if you use the code ‘LOY10’ at checkout, you should get a 10% discount and free postage, so don’t be frightened to buy a few while you are on (I use them for virtually all my cable needs now).
Regards
Peter
Edit: p.s.just checked the site and see they are doing a 20% discount on their Premium Apple MFI Certified Lightning Cables in all 3 lengths (though not the right-angled ones).
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Thanks Peter.
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Hi all,
Reviving this thread, hope it's OK as we can avoid repeating all the good advice.
Not my aircraft, but I have an interest. I fly it from time to time.
912 Quantum.
PAW on top of the tank, RHS.
PSU is a Charge 2.
USB cable supplied with PAW.
Intercom - Microavionics. Radio - A6 MkII.
With no radio connected, clean as a whistle listening to intercom on headset.
With radio connected, and using the stock Quantum aerial on the nose, splats every 1-2 seconds. Splat is worst on frequencies round about 122.210 MHz. Does not go at highest squelch setting.
Splat in line with LED flash on the PAW, need to look more thoroughly tomorrow, but I'm guessing L1.
Swap Quantum installed aerial for rubber duck, problem gone, but this could just be lower gain of rubber duck.
L1 flash must be because of ground station about 40 metres away?
USB cable hit with ferrite beads, no change.
Three things to worry about:
Weather stops me testing outside, and so the engine is not running. This could be a problem that is user generated. Battery on conditioner so top quality. Next test with engine on.
L1 flash green means RX, so is the next thing to turn off the ground station and see if the fault clears?
Home page says fine but occasionally no 1090, it's in the hangar so why would there be?
Aircraft not mine so not 100% sure of wiring.
Thoughts please?
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What is the Quantum installed antenna?
Is it a suitable antenna for the frequency?
Can you put a meter across the connector of the antenna and measure its resistance between the centre pin and connector housing?
If the A6 is on battery power, does it still happen? If not, try a ferrite on the power lead to the A6, as close to the A6 as you can get it, looped a couple of times through it if possible.
It can't see it being on the PAW receiving data from the ground station, unless it then replies, which is feeding back.
Is this anywhere near Cambridge?
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What is the Quantum installed antenna?Is this anywhere near Cambridge?
Unbranded AFAIK, commonly used without problems by a fairly significant fleet.
Is it a suitable antenna for the frequency?
Based on my experience of other Quantums, yes, never had a VSWR meter on it though, but it works well. How well tuned to airband it is, another matter. Selectivity could be a problem.
As the rubber duck aerial doesn't suffer the problem my initial thought is that it's something in the aerial installation.
Can you put a meter across the connector of the antenna and measure its resistance between the centre pin and connector housing?
Will do, forgot to do that, I've already checked for continuity on centre and screen, and screen connected to ground plane.
If the A6 is on battery power, does it still happen?
Yes.
If not, try a ferrite on the power lead to the A6, as close to the A6 as you can get it, looped a couple of times through it if possible.
I'll ferrite the lead anyway, got some...
It can't see it being on the PAW receiving data from the ground station, unless it then replies, which is feeding back.
That's what I thought, but I was getting to the end of my fault find, and couldn't remember LED allocations. However, I'm only seeing a green flash, but not viewed directly. Common sense says, as you indicate, that it should flash green then on TX red, and the synchronicity of the red flash with the splat would have me convinced.
Is this anywhere near Cambridge?
Not really, Kent.
Big thanks for your pointers.
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So do you put the rubber duck antenna on the connector for the Quantum antenna, or disconnect the A6 from the aircraft wiring and fit it direct?
Is the radio connected to the intercom, and does the radio still splat if on the aircraft antenna but not connected to the intercom?
Is the PAW audio connected to the intercom too? If so, does the splat go away if this is disconnected?
Any cables (any type) in close(ish) proximity to the PAW antenna?
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So do you put the rubber duck antenna on the connector for the Quantum antenna, or disconnect the A6 from the aircraft wiring and fit it direct?
I fit the rubber duck to the BNC output on the radio, thus bypassing the aircraft aerial install completely, so direct.
Is the radio connected to the intercom, and does the radio still splat if on the aircraft antenna but not connected to the intercom?
The radio is connected to the intercom. I didn't think to disconnect the radio from the intercom but leave it connected to the aircraft antenna. I will do this.
Is the PAW audio connected to the intercom too? If so, does the splat go away if this is disconnected?
The PAW audio was connected but only later to see if it would make the problem worse.
So, the problem exists when the PAW is not connected to the intercom for audio injection.
Any cables (any type) in close(ish) proximity to the PAW antenna?
Not that I can seen but I need to re-check the route for the radio audio in/out lead.
The radio RX indicator comes on when the splat is heard.
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I will take a look at the actual model of Anker Powerbank you are using and see if that gives any pointers.
Please keep us posted of developments.
Did you ever get chance to look at this Powerbank and see if there is an issue with this model. I would like to buy a secondary powerbank as I think I left it plugged in after I flew yesterday! Would be good to have a spare anyway!
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Update
So do you put the rubber duck antenna on the connector for the Quantum antenna, or disconnect the A6 from the aircraft wiring and fit it direct?
Is the radio connected to the intercom, and does the radio still splat if on the aircraft antenna but not connected to the intercom?
Update based on JCurtis pointers:
Inner/screen on coax measured, open with AVO.
Radio set to Headcorn, 122.210
Radio with rubber duck on its own battery, unconnected to aircraft in any way = perfect
Radio with aircraft antenna on its own battery, unconnected to aircraft power or intercom = badly splatting
Looks like antenna.
Second unattached radio with rubber duck tested as receiving Headcorn, radio with aircraft antenna just splatting at the same time, none or minimal RX.
Antenna cable inner and screen measured for continuity, now with two pairs of hands we can see the screen to the ground plane is intermittent sometimes, continuity at best.
Remove far end of cable, at termination with ground plane. Clean up and re-attach. Re-measure. Not intermittent.
Problem solved.
Nothing to do with the PAW. Unfortunately, a fault that appeared at the same time as the install, most likely because of disturbance.
Everything put back to intended config as per destructions.
Now working. SkyDemon integration tested.
Final test soon after everything is 100% tidied up and ready to fly. Ferrite beads on USB cable to PAW, and A6 DC power entry.
I have printed out the page with the location of L1 and L2, fault finding LEDs, and also the two pages of trouble shooting help in the manual. Both pages have been laminated and stored with the aircraft.
Suggest anyone with a Quantum do this with the main wiring diagrams too.
Big thanks to JCurtis for help.
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Thanks for the update, good news.
Many, many, similar things end up down to poor grounding/bonding.
You could probably remove the ferrite too, save the weight ;D
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Nothing to do with the PAW. Unfortunately, a fault that appeared at the same time as the install, most likely because of disturbance.
Surely you mean Fortunately :P
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I will take a look at the actual model of Anker Powerbank you are using and see if that gives any pointers.
Please keep us posted of developments.
Did you ever get chance to look at this Powerbank and see if there is an issue with this model. I would like to buy a secondary powerbank as I think I left it plugged in after I flew yesterday! Would be good to have a spare anyway!
Hi Merlin,
Many apologies - I thought I had replied to this. If it is the PowerCore 13000 Model: A1215, I have two of them (as well as 3 of the larger PowerCore 20100 version and a couple of the smaller PowerCore 10000 version). They all perform well with PilotAware.
Hope this helps
Best Regards
Peter
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Nothing to do with the PAW. Unfortunately, a fault that appeared at the same time as the install, most likely because of disturbance.
Surely you mean Fortunately :P
Ha, ha...
No, faults appearing are always unfortunate.
It's fortunate that the problem was not PAW, but that's a different thread.
Unfortunately, the problem has come back, and the aerial will need more reseating, or IMO, replacing.
The aircraft owner would like to fly with the rubber duck aerial as a short term solution. I say no, replace the existing aerial with the right thing.
However, the fault has returned even with the rubber duck aerial because he uses screens on the dash, and the big Samsung tablet to the right of the centre part where the radio is also interferes with the radio. This was proved by moving the radio, the Samsung tab within 15-20 cm of the radio interferes. With the PAW and the rest of the plane switched off, still the same result.
It would't affect me because I would only fly with PAW audio, and a Garmin 76S on the dash. Yes, I'm a dinosaur. My phone would log on SkyDemon, but would be in the pod bag.
I'm therefore after an aerial similar to the original that would fit a P&M Quantum and would go in the same position on the Nose. I have started a new thread to avoid taking this one off track:
Click here for Flexwing pilots - replacement for nose mounted aerial in P&M Quantum/Quik? (http://forum.pilotaware.com/index.php/topic,1956.0.html)