PilotAware
British Forum => Technical Support => Topic started by: GeoffreyC on April 23, 2019, 08:01:18 am
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.
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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
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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.
On the power supply itself, ... I will rectify and fly PAW with the sole device on the Anker ...
Geoffrey
Update on my PAW limited range problems ...
I have now wired in a separate dedicated Anker Powerdrive 2 and now only run PAW from this with a 50cm 20AWG connector cable.
The PAW antennae extension cable has been removed and the PAW antennae directly connected to the bridge board and Brian Montilla kindly lent me a spare PAW bridge board so I've been trying it out on a couple of flights to see if these changes together fix my problems.
The short answer is no, I'm not convinced that it entirely has. With Brian's bridge board in my classic I have been able to see other traffic up to the side of my flight path a maximum of 8 miles away, which is better than I had, but whilst flying today following Jinx who has a Rosetta I found several times that the signal disappeared after about a mile to mile and a half separation.
I appreciate that antennae positioning and attenuation can have a significant effect on signal strength, so its either that I need to extend the antennae again on a pigtail lead, or its the antennae itself that is the root cause of my problems. My PAW classic is currently mounted on top of the battery on the QuikR base tube, so its underneath the flexwing front pod. The antennae is connected straight to the PAW, no extension lead, so is in front of me and behind the glass cockpit and all its electronics.
Although its not connected to any metal parts I am wondering whether the electronics up front is part of the problem and I need to get a pigtail and mount the PAW antennae under the QuikR windscreen or underneath the pod where it can get more 'clear air'?
If so, is there a recommended source of SMA M/F low loss extension leads?
Thanks, Geoffrey
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Just like electrics is understandable in a plumbing sense, RF engineering can be related as low frequency light!...
Envisage a transmitting RF antenna as being a point of light source, or in the case of our dipole, a light stick. Anything metallic in its vicinity is going to cast a shadow and absorb some of the 'light'. In a perfect world, we want no shadows, or at least the smallest possible. This is acheived by keeping the light source as far away from parallel metal parts as best as possible.
Obviously this isn't easy if you cannot install the antenna outside of the aircraft, so finding the best location to allow the most 'light' to get out (and in) for the job you want it to do is still an element of trial and error but using the above analogy is good as a starting point!
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With Brian's bridge board in my classic I have been able to see other traffic up to the side of my flight path a maximum of 8 miles away, which is better than I had, but whilst flying today following Jinx who has a Rosetta I found several times that the signal disappeared after about a mile to mile and a half separation.
Hello Geoffrey,
Did Jinx loose your position at approximately the same range (1 to 1.5miles) or were you visible on his display at a greater range?
Deker
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With Brian's bridge board in my classic I have been able to see other traffic up to the side of my flight path a maximum of 8 miles away, which is better than I had, but whilst flying today following Jinx who has a Rosetta I found several times that the signal disappeared after about a mile to mile and a half separation.
Hello Geoffrey,
Did Jinx loose your position at approximately the same range (1 to 1.5miles) or were you visible on his display at a greater range?
Deker
I didn't check with Jinx, but from when I tried range checks with Brian on a previous flight, we lost each other at about the same time.
Geoffrey
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Geoffrey,
That sounds very like simple screening to me - this is very common to the rear with flexwings due to a combination of ‘non RF friendly’ objects - Pilot/passenger/luggage/pylon/engine/radiator/trike suspension/etc. getting between the antennas and the ‘targets’. 3-axis get a similar problem to the front and below due to the firewall and engine, hence why we normally suggest the coaming or underneath for their antennas.
Our priority is generally early warning to the front (highest closing speed) and trying to optimise antenna positioning to get as good to the rear as we are able, relying on incoming aircraft from the rear being picked up before they get into any ‘blind spot’.
I have done considerable experimentation with antenna types and positions to try to minimise these effects, with varying results. Fitting ‘horn-dipole type’ antennas up the sides of the trike windscreen is pretty effective. I have also tried standard PAW/Rosetta end fed (sleeve) dipoles in the same positions on 0.5m, 0.75m or even 1metre SMA extension cables. (I made up my own cables, but you can buy them from www.wifi-Antennas.co.uk - just be careful to specify SMA Male to SMA Female - NOT RP (Reverse Polarity) SMA - which are for WiFi Routers.)
I am currently testing a set of PAW ‘Rohan External Antennas’ mounted underneath the back edge of my fibreglass pod, with a plastic laminated aluminium foil ‘ground plane’ inside - under the pod bag, which so far seem to be giving positive results. I can, however, only fit the antennas in this position because my transponder antenna (which would otherwise overwhelm the 1090 Receiver) is fitted right at the back of my ‘skirt’. This installation seems to be bearing fruit so far, but I only fitted them last Thursday and testing so far has been limited to a weekend flight through to Gigha and back. First impressions, however are good, but it’s early days - I need to do more testing.
Best Regards
Peter
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Geoffrey,
That sounds very like simple screening to me - this is very common to the rear with flexwings ...
I have done considerable experimentation with antenna types and positions to try to minimise these effects, with varying results. Fitting ‘horn-dipole type’ antennas up the sides of the trike windscreen is pretty effective. I have also tried standard PAW/Rosetta end fed (sleeve) dipoles in the same positions on 0.5m, 0.75m or even 1metre SMA extension cables. (I made up my own cables, but you can buy them from www.wifi-Antennas.co.uk - just be careful to specify SMA Male to SMA Female - NOT RP (Reverse Polarity) SMA - which are for WiFi Routers.)
Peter
Thanks Peter,
I agree, it sounds potentially like shielding, and with a flexwing you have limited places to put things. Brian has his PAW antenna on the pod nose, in place of the radio antennae that used to be mounted there. I don't like that option as its something to catch the bar on when de-rigging the wing off the trike (unlike your luxury hangar in East Fortune we are all semi-rigged at Sandy).
I have a short SMA MF antennae extension lead so will try putting the PAW dipole under the windscreen and see what that does for me. Agree with your comment about prioritising oncoming traffic and the RF shielding that occurs with engine/people if you're flying behind, I'd just like it if I can get more than a mile or so of range. With the antennae inside the nose pod behind the glass screen electronics I felt it wasn't ideal but was trying to eliminate other cause of my problem by going for a vanilla installation.
Looking on wifi-antennas they only appear to have a 1m standard cables https://www.wifi-antennas.co.uk/1-metre-extension-cable-standard-range-sma-male-to-sma-female.html (https://www.wifi-antennas.co.uk/1-metre-extension-cable-standard-range-sma-male-to-sma-female.html) not low-loss ones. eBay only had 16 foot long ones and Amazon 10-15cm. I'll try with the one I've got and see what happens.
Geoffrey
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Looking on wifi-antennas they only appear to have a 1m standard cables https://www.wifi-antennas.co.uk/1-metre-extension-cable-standard-range-sma-male-to-sma-female.html (https://www.wifi-antennas.co.uk/1-metre-extension-cable-standard-range-sma-male-to-sma-female.html) not low-loss ones. eBay only had 16 foot long ones and Amazon 10-15cm. I'll try with the one I've got and see what happens.
Geoffrey
Geoffrey,
Those ‘Standard Cables’ are made from CLF200 coax, which is pretty low-loss at PAW frequency - well below 0.5dB per metre at 869MHz, so certainly worth a try in 1m or even 2m lengths. They will also make them for you in custom lengths, though the price will of course be dearer.
Let us know how you get on.
Regards
Peter
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I have a short SMA MF antennae extension lead so will try putting the PAW dipole under the windscreen and see what that does for me.
I’ve mounted the PAW antennae under the lower front windscreen with my eBay extension lead.
Unfortunately no-one else with PAW active when I went flying on Saturday so wasn’t able to test the effectiveness of this setup. Did see a couple of ground stations so I know its working.
Will try again with more aircraft !
Geoffrey