Author Topic: Radio interference  (Read 7176 times)

Merlin29

Radio interference
« on: September 12, 2020, 11:08:01 am »
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.

Merlin29

Re: Radio interference
« Reply #1 on: September 12, 2020, 11:14:13 am »
In case you ask we are using Anker PowerCore 13000 Power Bank - Compact 13000mAh

steveu

Re: Radio interference
« Reply #2 on: September 12, 2020, 12:03:20 pm »
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.

Merlin29

Re: Radio interference
« Reply #3 on: September 12, 2020, 12:53:16 pm »
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?



steveu

Re: Radio interference
« Reply #4 on: September 12, 2020, 01:28:12 pm »
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.




Merlin29

Re: Radio interference
« Reply #5 on: September 12, 2020, 01:38:39 pm »

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.

JCurtis

Re: Radio interference
« Reply #6 on: September 12, 2020, 02:34:37 pm »
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. ?
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB Type-A and USB-C power without the RF interference. Approved for EASA installs under CS-STAN too.

Merlin29

Re: Radio interference
« Reply #7 on: September 12, 2020, 03:07:01 pm »
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.

Merlin29

Re: Radio interference
« Reply #8 on: September 12, 2020, 09:48:04 pm »
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.

exfirepro

Re: Radio interference
« Reply #9 on: September 13, 2020, 09:49:45 am »
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

JCurtis

Re: Radio interference
« Reply #10 on: September 13, 2020, 10:15:50 am »
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.
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB Type-A and USB-C power without the RF interference. Approved for EASA installs under CS-STAN too.

Merlin29

Re: Radio interference
« Reply #11 on: September 13, 2020, 10:51:06 am »
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.


JCurtis

Re: Radio interference
« Reply #12 on: September 13, 2020, 10:54:21 am »
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?
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB Type-A and USB-C power without the RF interference. Approved for EASA installs under CS-STAN too.

steveu

Re: Radio interference
« Reply #13 on: September 13, 2020, 10:56:13 am »
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.




Merlin29

Re: Radio interference
« Reply #14 on: September 13, 2020, 11:10:43 am »
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.