Limited range for PAW traffic - hardware issue?

[GeoffreyC]

I have a PAW classic that’s suffering from poor reception and transmission range for the PAW signal.
Typically I can see other traffic up to about 3-4km away, much more than that and they disappear from SkyDemon.   Talking to my flying buddy he says that he can only see my PAW signals for about the same range as well.
My PAW antenna has a 1m extension lead on it, enabling the antenna to be positioned in the nose of my flexwing.  I’ve tried connecting the antenna directly and didn’t make any appreciable difference so I don’t think its the lead.
Could this be a hardware problem with the PAW bridge board, or any other ideas?  I’d rather not have to buy a whole Rosetta to fix the issue (upgrade kits seem not to be available?), but the PAW range is definitely much less than it was last year when I toured on FlyUK and I would like to fix it.
Any ideas?

Thanks, Geoffrey

[exfirepro]

Hi Geoffrey,

Range limitation is usually (though not exclusively) an indication of a badly placed antenna - e.g. in a position where clear ‘line of sight’ is obstructed by part of the aircraft or occupant(s), though you say yours has been working fine until recently. Has anything else changed in the aircraft - e.g. new tablet mount fitted - which could be obstructing the signal?

What antenna are you using? Can you ‘borrow’ an antenna from someone else’s PAW and see if that improves your transmission/reception?

The other important thing to check before suspecting a faulty Bridge is that the PAW isn’t being ‘Throttled’ by a power supply issue. You can check this by looking at the ‘Uptime’ line on the Home Screen - please post a screenshot, which will also confirm your Software and Kernel Versions. A screenshot of your Configure Screen would also be useful.

It is possible that there could be a problem with your Bridge of course. If so, the Rosetta upgrade path is still available, just a short term problem with supply.

Let’s see if we can tie the problem down by eliminating all other possibilities first.

Regards

Peter

[Admin]

Hi Geoffrey

Let me add a couple of thoughts here

the PAW range is definitely much less than it was last year when I toured on FlyUK and I would like to fix it.

Is the installation exactly the same, or has anything at all changed ?
Things to consider are
- Power supply
- Power supply lead
- Antenna position

You also mentioned that the antenna was on a 1 metre extension, can I ask where you obtained the extension cable ?
do you know the loss of the cable ?

Are you seeing aircraft at only close range for PilotAware AND ADS-B - or maybe one or the other ?

Providing the following information can help us diagnose issues

1. Screenshot of Home Page
2. Screenshot of Configure Page
3. Copy of track flight where the behavior was observed.

Thx
Lee

[GeoffreyC]

Hi Lee and Peter, and thanks for such a swift reply and for your ideas.

Let me expand on my setup further.  I have a PAW classic fitted to my flexwing microlight.  PAW was mounted under the base bar, under the legs of the pilot.  The transponder antennae was mounted on the base bar in front of the battery (never had any issues with transponder receipt, can see right to the stratosphere!).
The PAW antennae has been in different positions in the front pod.  Mindful of the advice to try to avoid metal or human shielding it’s been on the side of the front pod, down at the end of the nose offset to one side, and cable tied to the front strut.

When I first got PAW (April 2016) I was impressed by the range it would pick other aircraft up over, but it was when I was on FlyUK in June 17 that I realised that it wasn’t consistently working as well as it used to.  I remember at the time it was sometimes playing up, sometimes crashing, sometimes losing connection to SkyDemon, and other times working perfectly.  I have screen shots from that trip showing other PAW planes 15 miles away and I also can recall other times when the range was down to just a few km.

When we were weathered in at East Fortune I spoke to Peter about the problem and tried to diagnose the issue.  I certainly flew at least one leg with the PAW antennae screwed straight into the PAW without the extension lead, and it didn’t make any noticeable difference.

Eventually after the trip and following Peter’s suggestions I traced the stability problem down to the power supply lead. I was using the PAW supplied 22AWG cable but over the year I’d used it the cable had obviously weakened and I found that wiggling the micro usb plug in the PAW I could induce the same drop-outs and loss of PAW.  Bought a new 22AWG micro USB heavy duty cable off ebay and the crashes disappeared.

But I think through all this time I have still had the limited PAW range issue.  I’ve noticed limited range in receiving PAW traffic and its only since I have moved the PAW to a new plane and been flying without the transponder fitted that my flying buddies had noticed the same issue with my transmission range.  With the transponder normally on they’ve been able to see me much further, but just with PAW on, they now can’t.

For all the time that the PAW was in the other flexwing I powered it with a standalone battery brick.  This probably contributed to the failure of the power lead as the brick was loose in the footwell and thus the cable would move around.   Since moving to the new flexwing I have powered PAW with an Anker Powerdrive 2 USB cigarette socket adaptor and the plan is to wire it in more permanently with an Anker mounted in a box and fused to the plane.

PAW antennae is currently cable tied to the bottom of the front strut.   The antennae extension lead came from ebay, its about 1/2 m long.

Attached are photos of the config and other screens and I will PM three trace files to Lee.  The first one shows the problem quite clearly as I climb out of Sandy and lose contact with the other PAW plane on the ground.

Thanks, Geoffrey

[GeoffreyC]

Don't seem to be able to add attachments to PM's so here are three trace files with a buddy showing the problem of him disappearing.

Cheers Geoffrey

[exfirepro]

Hi again Geoffrey,

Not necessarily the only problem, but the 4th screengrab clearly shows ‘Throttled=0x50000, which indicates that the CPU of the Raspberry Pi is being throttled due to a low voltage issue. This will either be due to the power source or the cable (which should by the way be minimum of 20AWG, which is thicker than 22AWG). The standard cables are available from www.juicEbitz.com

This may well be the source of your inadequate range.

When you say your antenna is cable-tied to the front strut, I take it you mean hanging down vertically from it clear of the metalwork.

Regards

Peter

[GeoffreyC]

Yes I noticed it said throttled on the last screen shot as well.   Earlier it wasn’t showing this but the last one did show throttling.

I’ll have a look at the power lead and maybe try the power brick again, see if it reduces the throttling.  What does 0x50000 mean - bigger numbers = lots of power issues or what?

I’ll also try and borrow another antennae from a working PAW to see if that shows the same issues.

And yes, its cable tied to the side of the front strut.   In my Quantum I finally got round to getting the PAW installation mod done and my inspector didn’t like the way I had the PAW antennae free hanging (held on with a sticky pad and loop cable tie) in the front of the nose.  Said it was at risk of being knocked or coming free.  So cable tying to the front strut is my attempt to appease him.     Appreciate its close to the aluminium tube but if it were shielding I would think it would be omni-direction shielded on one side which isn’t the case.

Cheers

Geoffrey

[Ian Melville]

In the Hex number 0x50000 there are several binary flags.

Type out in full binary =
0000 0101 0000 0000 0000 0000  Binary
^                                                ^
Bit 23                                          Bit 0

Bits 16 and 18 have a flag which can be looked up in the table
Bit : Flag message
0   : under-voltage
1   : arm frequency capped
2   : currently throttled
16  : under-voltage has occurred
17  : arm frequency capped has occurred
18  : throttling has occurred

So in the value of 0x50000 you have:
16  : under-voltage has occurred
18  : throttling has occurred

[GeoffreyC]

Thanks Ian, so these flags are showing “it has happened since boot up”, not “its happening now”.

I was fixing a cooling system leak so running the engine up to near cruise power for periods of time on the ground yesterday.  I can try with the power bank and in flight to see if I can spot how often the throttling/under voltage is occurring, but it might be a bit hit and miss - is this identifiable from the trace logs, or maybe a future enhancement to show frequency/occurrences/percentage or similar to aid in debugging power supply issues?

Geoffrey 

[Admin]

Thanks Ian, so these flags are showing “it has happened since boot up”, not “its happening now”.

Hi Geoffrey
Its difficult to catch the 'its happening now' flag, this is samples every 100ms, but the data is updated every 2 seconds so unless it is caught at the right time, it is not seen. Bear in mind that the transmit pulse is about 6ms wide, and this is the critical current draw period

Also 22AWG is not sufficient, minimum 20AWG is required (smaller the number, thicker the wire)

Thx
Lee

[GeoffreyC]

Its difficult to catch the 'its happening now' flag, this is samples every 100ms, but the data is updated every 2 seconds so unless it is caught at the right time, it is not seen. Bear in mind that the transmit pulse is about 6ms wide, and this is the critical current draw period

Also 22AWG is not sufficient, minimum 20AWG is required (smaller the number, thicker the wire)

Thanks Lee,

I went back and checked my eBay purchase history and the item was described as "USLION 50cm 1m 2m 20AWG Micro USB Fast Charging Cable Samsung Galaxy Data Lead", so should be OK?  I'd mis-remembered it as 22AWG.

I'll try a different antennae if I can borrow one and try to see if I can correlate the throttling warning in more detail.   I have also thought, I have my iPad plugged into the same Anker Powerdrive 2 so will try removing that from the equation.

I'm still leaning towards an antennae/bridge problem rather than power as the PAW is stable and shows transponder traffic OK, its just PAW traffic it has a range problem with.   Having said that though, in one (of 3) flights on Monday and one (of 3) on Saturday SkyDemon lost contact with PAW and I had to turn the iPad Wifi off and on again to reconnect and restart navigation.  So maybe not quite as stable as it was.

Geoffrey

[Admin]

Ok, that is the issue, the ipad will suck all the power, we have seen this issue before, I am sure we have noted this somewhere
Thx
Lee

[exfirepro]

I went back and checked my eBay purchase history and the item was described as "USLION 50cm 1m 2m 20AWG Micro USB Fast Charging Cable Samsung Galaxy Data Lead", so should be OK?  I'd mis-remembered it as 22AWG.

Geoffrey,

Can you confirm what length of replacement cable you bought? 50cm and 1m should be OK, but even at 20AWG, 2m can cause issues.

I'm still leaning towards an antennae/bridge problem rather than power as the PAW is stable and shows transponder traffic OK, its just PAW traffic it has a range problem with.   Having said that though, in one (of 3) flights on Monday and one (of 3) on Saturday SkyDemon lost contact with PAW and I had to turn the iPad Wifi off and on again to reconnect and restart navigation.  So maybe not quite as stable as it was.

Geoffrey

An antenna/Bridge problem won’t cause SkyDemon to disconnect. This would most likely be due to a dodgy WiFi dongle or a power issue. Can you confirm exactly what error message you got on SkyDemon? (If you are running the newer versions of SkyDemon, you will be aware that it now gives different messages for ‘loss of gps’ and ‘Device offline...’ (= WiFi Disconnect).

Regards

Peter

[Paul_Sengupta]

And yes, its cable tied to the side of the front strut.   In my Quantum I finally got round to getting the PAW installation mod done and my inspector didn’t like the way I had the PAW antennae free hanging (held on with a sticky pad and loop cable tie) in the front of the nose.  Said it was at risk of being knocked or coming free.  So cable tying to the front strut is my attempt to appease him.     Appreciate its close to the aluminium tube but if it were shielding I would think it would be omni-direction shielded on one side which isn’t the case.

Note this is bad. Very bad. An antenna needs to be completely clear of any metal objects to work properly. If it's up against something metal, it'll not only shield it, but it will couple with it and completely change the characteristics of the antenna. Since this antenna also transmits, it can also damage the transmitter due to a high VSWR. Since you report that connecting the antenna directly to the PAW gives the same results, it may be because the bridge board is damaged due to this.

First thing to ensure is that the antenna is completely in the clear. After that it may be worth trying another bridge board.

[GeoffreyC]

Note this is bad. Very bad. An antenna needs to be completely clear of any metal objects to work properly. If it's up against something metal, it'll not only shield it, but it will couple with it and completely change the characteristics of the antenna. Since this antenna also transmits, it can also damage the transmitter due to a high VSWR. Since you report that connecting the antenna directly to the PAW gives the same results, it may be because the bridge board is damaged due to this.

First thing to ensure is that the antenna is completely in the clear. After that it may be worth trying another bridge board.

Thanks guys for your suggestions and comments.  I have removed the extension cable from the PAW and re-attached the PAW antenna directly to the PAW (that's currently velcro'd on top of the battery under the nose cone).  When I next go flying I will try it again.

I take your point about the metal of the (aluminium) front strut could change the characteristics of the antenna, maybe this needs to be more explicit in the instructions (although is ages since I read them so maybe it does).   What sort of separation from metal objects is recommended?   It could be difficult to have a decent separation AND to secure the antenna in such a way that it can't be liable to move to the satisfaction of my inspector.

On the power supply itself, I can't believe I was so dumb on this.  I'd always run the PAW off a separate external battery so it had a good stable power supply.  On fitting to the new plane I wanted to improve on this and so temporarily plugged in an Anker Powerdrive 2, and then stupidly used the spare USB socket for my iPad moving map.  I will rectify and fly PAW with the sole device on the Anker - which is my intended configuration once I wire in the second Anker for use by PAW only.

And Lee, it was a 50cm USB 20 AWG cable I bought.

Geoffrey