Several flights with PAW this week

[DavidC]

I have a home-built PAW based on the RPi 1 rather than RPi 2 but with the production RF bridge using SkyDemon on an iPad.
After a few flights, I'd make some observations.

Generally, it picks up airliners at 10 to 40 thousand feet, and up to 100 miles away. Rarely been close enough to see anything other than vapour trails. Useful to confirm it's working though, and I know I can configure those out.

Have seen (onscreen) very few aircraft. Very occasionally they are shown with hash marks before and after the registration; sometimes just the six digit hex code; mostly with the normal registration. Do the hash marks mean anything - ie PAW? Attach screenshots of both for the same aircraft.

The Wi-Fi link goes down intermittently. I found this happened more often in one aircraft than others, perhaps due to more interference. SkyDemon stops navigating and I've typically just unplugged/replugged the power cable to reset PAW, and it starts working again in a couple of minutes. In those cases, I've more often just given up and reverted to the iPad GPS.

Powered by a compact ANKER battery - claimed 10,000mAH capacity - seems to work quite happily for 4 hours or more. I have an inline USB power meter and it shows 0.4A during normal operation, so it should last for ages. I even left it running over a lunch stop once, and it wasn't a problem.

It does let you spot traffic some distance off - say 2-3 miles - which you probably wouldn't have seen before. I've attached a screenshot and photo of one we saw crossing above us. It wasn't a close enough to be a threat at any time.

There is a natural tendency to focus on spotting the aircraft shown on your screen. You really have to remember that 90%+ of aircraft won't show up and be disciplined to retain your normal scan. But if something is converging (including out of sight from below) then it is helpful.

The long/large antenna that I have really don't fit easily on the combing. The unit overall is much more clunky/fragile than a single fully enclosed FLARM box, and I may revisit how to package it up. Perhaps smaller antenna could be used, but I haven't really explored the options.

One of our aircraft has ADS-B out installed. I was surprised I couldn't pick that up easily when it was in the circuit - it only briefly showed up rather than all the time like airliners. Perhaps this was the orientation (can't "see" though the engine).

Lastly, I have flown about six different aircraft in the last few weeks. It would be really nice to have a simple method of selecting the correct hex code instead of looking it up and entering fresh each time. I'm using 160307 software version, so apologies if that's already been addressed.

[JCurtis]

If you leave those plug in USB power monitors on all the time you may get issues. They cause a voltage drop by their design and the additional connections also cause a drop.   It's possible the PAW supply voltage is lower than it should be and as a result you will see all sorts of weirdness.

[exfirepro]

Hi David,

The hash marks mean it is a PAW equipped aircraft using the same 'Group ID' as yourself (on the Configure Screen - PAWGRP by default but you can set something else e.g. for fly outs set your club name and all your club aircraft - and only those with your group ID will show the hash brackets).

SkyDemon can drop out if you swap between screens a lot, e.g. to look at the PAW traffic screen. This then presents when SD is reselected as "The connection to your GPS has been lost'. Reselect 'go flying' , 'use FLARM' and it should come back up. Not saying this is the reason but might be.

I use a similar Anker battery - should be fine, but you need to make sure you are using a heavy enough power cable (at least 20awg is required).

Points noted re getting sucked in by the screen. With use, you will do this much less.

Be careful about randomly changing antennas. The long fat one is the PAW P3i transmit antenna. It is a 'tuned' end-fed 1/2 wave dipole antenna. If you want to change it, I would suggest the centre-fed dipole as sold on the hardware site. Only use a shorter 1/4 wave if you can fit it to a metal ground plane.

The other (shorter thin) antenna is for 1090mHz ADSB / Mode S reception. It can be cut down if desired to about half its length without any serious side effects, but don't cut it any shorter as this might affect the efficiency of the Mode S alert triggers. There are threads on here which will show you how to cut this antenna and its coax feed cable down if you do a search.

I also have ADSB out. GA ADSB is lower power than commercial airliners, but you should still pick it up to st least 25/50 miles in the air. As you say yourself, it may have been screened from you in the circuit.

The question of changing hex code between different aircraft has been raised before, but so far no simple solution has appeared. If any of the aircraft you want to use your PAW in are ADSB out or have transponders make sure you do set the hex and ID (Reg) correctly or you will get false alerts from your own aircraft.

Looking at your screenshots you are seeing a good variety of contacts. IIRC G-OXFB is ADSB out, #G-AWKD# is definitely PAW as is probably 40179F and G-EEGU may be either ADSB, or PAW with the group ID changed from the default. The best way to check this is by reference to your traffic screen. See this thread (amongst others)

http://forum.pilotaware.com/index.php/topic,419.msg5447.html#msg5447

Hope this helps clarify things.

Best Regards

Peter
Mode S Development Tester

Edit: Just noticed you say you are still running software version 20160307. I would definitely recommend an update to the latest software. The current version is 20160530, though you will have to use the manual update method in the first instance as auto-update is not available from the version you are running. This will definitely improve stability, so should help with your Wifi issues, though you won't get the full functionality as Mode S detection and the audio alerts are only available if running on a Pi2B. If in doubt as to what to do see the Pilotaware Operating Manual here...
http://www.pilotawarehardware.com/dl/PAWOperationManual.pdf
and have a read at this thread...
http://forum.pilotaware.com/index.php/topic,465.msg5923.html#msg5923

Peter

[DavidC]

Thanks for the suggestions and clarification. I will update the software but leave the antenna as is for now. I've attached a photo of the kit sitting on the front combing - it's really far from ideal from an RF perspective due to size of antenna and multiple cables rather than a single compact unit. I really like the format of the US based Flightbox which is completely self-contained.

I only used the inline USB current meter for testing at home, not in the air. Hadn't thought too much about how it would affect output voltage.

I have just acquired a Pi2B on eBay so may also upgrade to use that, for which I understand I'll need to buy a full annual licence key. Not sure I want too many vague alerts popping up all the time, but I suppose I can switch that feature off if it's bothersome.

ANKER battery still only half empty after a full 4 hours use yesterday. For the very small size (half the size of the PAW), that's more than enough.

Re aircraft spotted: G-AWKD = 40179F. PAW displayed both at different times for the same PA-17 aircraft. G-OXFB is an Oxford Aviation Academy PA34 Seneca training aircraft. G-EEGU is a Norwich based PA28 which almost certainly has ADS-B out because its flights on Flightradar24 are logged in full, including through take-off and landing (normally that bit isn't show because need to receive Mode S from multiple ground stations simultaneously to figure out where the aircraft is).

[DaveStyles]

Hi David,

Just looked at your implementation.

The placement of the small (ADSB) antenna really isn't critical and can be put just about anyhow you like.

But  the P3i one really needs to go vertical to work well.

If that's a bit hard considering it's attached to the box, there are some horn dipoles in the hardware store that are on a lead, have a sticky tab and can be mounted remotely from the processing box.

By the way, the Flightbox you reference above is an ADSB RECEIVER ONLY. Which is why it's aerial placement isn't important and you can just throw it in the rear luggage compartment. Receiving ADSB is the easy bit ! We could make it like that, but it wouldn't work ! (unless you only want to receive ADSB that is).

[exfirepro]

Hi David,

As Dave S says, the P3i antenna is the critical bit for plane to plane operation with other PAWS. The replacement antenna he is talking about is the one I suggested to you yesterday. An alternative would be to simply turn your Pi case round the other way so the P3i antenna is towards you. The antenna will then fit in the vertical orientation without significantly affecting your view and will be out in the clear away from any aircraft metalwork - all good!

The battery pack can be tied to the Pi with cable ties or simply elastic bands (yours will fit easily underneath the Pi) and I have found these short right angled cables work well...

http://www.ebay.co.uk/itm/221712730771?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

...these particular ones which I bought came from China but only took about a week.

The ADSB cable can be simply coiled and shortened with a couple of small cable ties or tie wraps (as you have done already). This makes a really neat little package which will sit fairly still on the coaming of most aircraft, but with the antennas vertical. Please give it a try - you won't be disappointed.

Regards

Peter

[Ian Melville]

Re aircraft spotted: G-AWKD = 40179F. PAW displayed both at different times for the same PA-17 aircraft.

Guilty as charged Was that Wed or Thursday?

[DavidC]

Guilty as charged Was that Wed or Thursday?

Wednesday around 11am.

[Ian Melville]

Have to double check my logs. Thought I only got a hit in the afternoon from a Eurofox. I was in the Enstone circuit, and in the Shipston-on-stour area to do a bit of hooning  around during late morning.

[Ian Melville]

Hi David,
Yes I did get some transmissions from you, assuming you were '402375', which you have used as both your Flight ID and Hex ID. Flight ID would normally be your call sign. G-AZWS?

Max distance we got was 6km, min 3km. That is well down on the only other target I have seen whilst airborne, which is over 22Km.

Still trying to work out where we were.

[Admin]

Hi Ian, David

Max distance we got was 6km, min 3km. That is well down on the only other target I have seen whilst airborne, which is over 22Km.

This is almost certainly down to the Antenna position as discussed earlier in the thread.
David, I think the Centre Fed Dipole would be a much better option for your configuration
(assuming you cannot place an external antenna, which is the best solution)

Thx
Lee