Author Topic: Radio interference  (Read 497 times)

JCurtis

Re: Radio interference
« Reply #15 on: September 13, 2020, 12:01:03 pm »
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.

Code: [Select]
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
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB power without the RF interference. Approved for EASA installs under CS-STAN too.

steveu

Re: Radio interference
« Reply #16 on: September 13, 2020, 12:24:23 pm »

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.

JCurtis

Re: Radio interference
« Reply #17 on: September 13, 2020, 05:55:47 pm »

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.
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB power without the RF interference. Approved for EASA installs under CS-STAN too.

Merlin29

Re: Radio interference
« Reply #18 on: September 14, 2020, 10:52:39 am »
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?

JCurtis

Re: Radio interference
« Reply #19 on: September 14, 2020, 11:09:48 am »
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.
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB power without the RF interference. Approved for EASA installs under CS-STAN too.

Merlin29

Re: Radio interference
« Reply #20 on: September 14, 2020, 02:41:22 pm »
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?
« Last Edit: September 14, 2020, 02:43:51 pm by Merlin29 »

JCurtis

Re: Radio interference
« Reply #21 on: September 14, 2020, 05:06:25 pm »
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.
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB power without the RF interference. Approved for EASA installs under CS-STAN too.

exfirepro

Re: Radio interference
« Reply #22 on: September 14, 2020, 09:51:45 pm »
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
« Last Edit: September 14, 2020, 10:17:14 pm by exfirepro »

Merlin29

Re: Radio interference
« Reply #23 on: September 15, 2020, 10:19:52 am »
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.

JCurtis

Re: Radio interference
« Reply #24 on: September 15, 2020, 11:37:32 am »
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.
Designer and maker of charge4.harkwood.co.uk, smart universal USB chargers designed for aviation.  USB power without the RF interference. Approved for EASA installs under CS-STAN too.

exfirepro

Re: Radio interference
« Reply #25 on: September 16, 2020, 09:18:31 am »
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).
« Last Edit: September 16, 2020, 10:13:47 am by exfirepro »

Merlin29

Re: Radio interference
« Reply #26 on: September 16, 2020, 10:12:03 am »
Thanks Peter.