PilotAware
British Forum => General Discussion => Topic started by: Admin on September 30, 2015, 10:32:20 pm
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There have been testing reports of only achieving 1-2 mile range over the 868mhz frequency.
during early trials I was achieving max 25km range, so decided to investigate
I compared my original prototypes versus the latest prototypes, and modified the software to run RSSI checks, this allows the receiver to indicate the signal strength in dBm.
Comparing my old prototypes to the new, I was seeing a difference of 8dBm, that is significant!
The main difference was the use of an end launch SMA on the original, and pigtail on the latest.
As an experiment I soldered an SMA onto one of my newer prototypes, and the power loss was recovered.
I need to get back in the air with the modified prototypes to see what range I now see.
I have modded 6 protos so that is a good selection to try out.
So this may be the cause of the shorter transmit range.
It would appear at first glance that the pigtails are quite lossy
Thx
Lee
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I guess the loss depends on the quality of the mini coax cable used to make the pigtail. All coax must have some loss, in theory but I have found profound differences at some frequencies between cables that look identical. Unfortunately, the losses tend to intensify as we go up in frequency and I would expect 868 MHz to be verging on the critical zone.
Bill
Jodel D18, 19-4446, X-Air Std 19-3229
VK7MX
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So on the prototype you had the aerial soldered directly to the ARF board....or via an SMA connector on the board.
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So on the prototype you had the aerial soldered directly to the ARF board....or via an SMA connector on the board.
Hi
With the v1.0 ARF, I had an end launch SMA, soldered onto the board.
I have now done the same with the ARF 2.0, and this has made the RSSI numbers much better.
Incidentally, one of the pigtails had worked loose on one of my PAW, so in retrospect I think the SMA is a much more robust solution.
I will post some pictures later
Thx
Lee
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Not all is lost if thats the case...I guess these will solder in place of the pigtail connector......then a redesign of the ARF placement if using a slice or pod
http://www.aliexpress.com/store/product/SMA-Female-Jack-nut-RF-Coax-Connector-end-launch-PCB-Cable-Straight-Goldplated-NEW-wholesale/1861251_32329691707.html
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Pics would be good - am not sure what you mean by SMA or what to do - been using the stock aerials etc. so far.
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The link in the one I posted above is the connector which solders onto the end of the ARF where the pigtail connector currently is....this then plugs into the supplied antennae from the Ciesco....just means mouthing it so the end is in the plastic case.....so removing the pigtail wire connector completely
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I really don't much like the u.LF connectors that they use on the ARF as they have a very limited reconnection life and are really only useable with things like laptop wifi cards. The one on my original ARF will fall of just by looking at it though the pigtail with the last one I bought was better.
My concern with end-fed SMA is the lack of room in the small RPi case to use it successfully. Need to fit one and try it out as it may require a mechanical redesign as I wouldn't want the ARF supported purely off the SMA, knowing the standard of some soldering!
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Would be good to get comment from Wireless Things re this as it should be "fit for Purpose" which if it is attenuating the single that much it is not!
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Not all is lost if thats the case...I guess these will solder in place of the pigtail connector......then a redesign of the ARF placement if using a slice or pod
http://www.aliexpress.com/store/product/SMA-Female-Jack-nut-RF-Coax-Connector-end-launch-PCB-Cable-Straight-Goldplated-NEW-wholesale/1861251_32329691707.html
Hi
I used these
http://www.ebay.co.uk/itm/1-and-5pcs-SMA-female-jack-Panel-Mount-PCB-Solder-Connector-UK-SELLER-/271714107398?var=&hash=item3f436c4006
yours look better because I had to snip 2 legs off the connector
Thx
Lee
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Would be good to get comment from Wireless Things re this as it should be "fit for Purpose" which if it is attenuating the single that much it is not!
Antenna design & setup is a black art, this guide does exist
http://openmicros.org/index.php/articles/84-xrf-basics/289
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I've just ordered 20.....I'll let you know how it all works
Hopefully the mechanical strength coming from the fixing to the case....the dimension should allow it to sit on the underside of the slice of pod with a bit of jiggery pokery !!
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I've just ordered 20
Sounds like you may get a few requests to help relieve you of the additional 19 ;)
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As promised here are a couple of images
The original ARF1.0, and the ARF2.0
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Excuse my blatant ignorance, but is the advice to lose the little tail and solder direct? I'll have a go with my groundstation that I'm building if that's the plan..
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Lee have you managed a trial yet with the mod.....I know you mentioned the better transmission without the pigtail but I'm just wondering if there are any other issues with the ARF version 2.0.
When you did your initial testing was it all with version 1
Thanks
Brinsley
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I Plan to do some tests in the air this weekend, but what I can see is that the RSSI (Received signal strength indicator) value is 8dBm (dBi ?) better using an end launch SMA.
So I would say yes. this is a great improvement, but if you want to wait till I publish my findings after the weekend ....
When I release the next version of PilotAware you can configure your PilotAware to go into a test mode as either a Master or a Slave (you will need 2 units)
this will send a short packet of info from Master->Slave and then from Slave ->Master, the master will print the RSSI reported by the Slave, and the RSSI at the Master
Thx
Lee
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That's great news Lee, I'm currently building unit 2, so testing this would be great!!!
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That's a significant improvement Lee...I'll get on the case of changing over to the SMA's.....love the self test feature with two units....that'll make life easier testing......
Thanks again
Brinsley.
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Probably totally unnecessary on this forum but just in case, a caution to others looking to buy SMA sockets to replace pigtails. Both SMA plugs and sockets come in both male and female gender, so make sure you order the correct gender. The presence of a centre pin determines male gender, the presence of a centre hole determines female gender. Some newcomers to the use of SMA mistakenly consider the threaded portion of the connector to indicate that it is of male gender....
Bill
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I'm wondering if changing the connector on the board is removing the problem by getting rid of the small pigtail i.e. that its not the connector at fault but the pigtail cable / quality of the coax used.
Thus we may just need to swap that out to something like http://www.ebay.co.uk/itm/321730793221 (http://www.ebay.co.uk/itm/321730793221) the cable used seems a resonable spec if the ad is correct uses RG178 coax, from the spec http://www.farnell.com/datasheets/1504033.pdf (http://www.farnell.com/datasheets/1504033.pdf) the loss in the tail should be around 0.19db
thoughts?
I have ordered one to try, but I have only one PA unit, so if anyone is near King's Lynn and wants to meet up to try out the power test once Lee has that build out and the cable has arrived, let me know...
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I've done some measuring of the TX power levels with and without the pigtail, there is virtually nothing between them. So it looks like the issue is on the RX side, where attenuation will be the problem. This points at the pigtail as the culprit.
Thinking much the same, I had some new pigtails delivered today but they have sent me male not female. Hunting around I don't have a gender changer, so these need to get swapped.
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I'm getting this with a master / slave config in the log...
ARF-SER: (24) aSSRSSIS-025aMMRSSIM-22 or sometimes 23...
Is that good / bad??
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I'm getting this with a master / slave config in the log...
ARF-SER: (24) aSSRSSIS-025aMMRSSIM-22 or sometimes 23...
Is that good / bad??
I am getting figures of about -020 at a range of about 30ft.
Do you have the pigtail or SMA, and how close are your units ?
Thx
Lee
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I have pigtails and they're directly above each other, separated by one floor...
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I have pigtails and they're directly above each other
I don't think your hair style will have much, if any, effect on it ;D ;)
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I found power source issues today... My battery pack doesn't seem to provide enough juice and the PA unit kept crashing. Once I plugged it into the aircraft it was rock steady.
Still didn't pick up anyone, or my home ground station, but I think that crashed today.
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hi Lee,
Was there any update on the testing you were planning to do?
Cheers,
SM.
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hi Lee,
Was there any update on the testing you were planning to do?
Cheers,
SM.
Unfortunately Long Marston had both runways closed due to the 'International Jet Meet', so unfortunately not :(
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When I release the next version of PilotAware you can configure your PilotAware to go into a test mode as either a Master or a Slave (you will need 2 units)
this will send a short packet of info from Master->Slave and then from Slave ->Master, the master will print the RSSI reported by the Slave, and the RSSI at the Master
I gather that this is now possible, but please can anyone tell me how to configure two units to perform this test?
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On the latest software you can config each unit to be master and slave for testing via the config on 192.168.1.1
You get the power levels in the logging after setting them both up like that embedded in the log messages
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On the latest software you can config each unit to be master and slave for testing via the config on 192.168.1.1
Thanks, I see that now, under Serial.
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I now have 2 PAWs with the SMA soldered mod so if possible will fly one with another on the ground tomorrow and look at range - will report back.
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Flew my pilot aware with a ground based unit also switched on and monitoring.
Airborne pilotaware detected by ground until about 7nm while ground based unit was lost by airborne unit at about 2nm. Supect limited by power supply as using a iPhone type battery recharge pack on the ground unit. Airborne unit powered by a high power battery with a 2amp outlet and short,15cm, usb cable.
I'm also ads-b out transponder equipped and range of detection not an issue.
Overall pleased with the detection range of the Of the pilot aware signal provided it's only a power supply issue with the ground based unit.
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One of the things that will make a vast difference to range, both for ADS-B and for PAW, but especially for the latter, is antenna location. For those of us flying all metal aircraft this has to be an important consideration. For example, the obvious place, on the instrument coaming will mean that signals will be profoundly attenuated below and behind the aircraft. This is not so much a problem for ADS-B, where we are only receiving but for PAW that means that a following aircraft won't see our transmissions and nor will we see his.
This got me thinking about where to put the antennas. From an engineering perspective it is quite easy to have the antennas wherever you want them, either on coaxial cable extension leads or by remoting the dongle with a USB extension cable. If we are flying a PtF aircraft then in principle we can put antennas wherever we like. More difficult for C of A aircraft unfortunately.
For ADS-B reception it is probably fair to say that most stuff will be above us, at least for the time being. As more GA aircraft get ADS-B capability this will change. ADS-B transmissions from the aircraft transponder are at considerably higher power, in the order of 200W peak power typically, so we can afford some losses. An antenna on the fuselage roof should be sufficient for good all round coverage and it might even be that one on the coaming will be adequate. As an aside, transponder antennas are always mounted on the aircraft underbelly because they are transmitting to and receiving from the ground-based radar. We, of course, are listening to the aircraft's interrogation replies rather than the ground radar.
For PAW transmission/reception things are more tricky. The transmit power is quite low so we cannot afford much attenuation. An antenna on the roof and another on the underbelly coupled to the ARF via a coaxial power splitter cable would do the trick but is awkward to engineer and probably somewhat OTT. It's definitely something we need to think about to gain maximum benefit from PAW.
Finally, I'd like to open up the Pandora's box of RF interoperability. We have an ADS-B receiver operating on 1090MHz and a PAW transmitting on 868MHz. It's a fair bet that the front end of the ADS-B dongle isn't the most selective of receivers and a nearby transmitter, albeit 200MHz away, might well swamp the ADS-B dongle's front end. The general rule of thumb here is to keep the antennas out of each other's near field, usually considered to be 2-3 wavelengths. At 1000MHz the wavelength is 30cm, so ideally the ADS-B and PAW antennas should be at least a metre apart to be on the safe side. It would be fairly easy to do some tests to see whether this is a real problem or not.
All this is a bit theoretical but it's based on decades of RF engineering work as well. As we gain real life experience we'll get a better handle on the performance issues and how to fix them. It would be interesting to hear other pilots' thoughts and experiences.
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Westmorland Flyer
I could not agree more. you are spot on with my thinking too. Dare I say it, but a nice little read is the setup of the antennas in the installation manual of the P**** F***M Remember they have been hear before .
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My twopennce worth.
I fly a Europa so composite, with the Pilot Aware on the front parcel shelf with the two antennae about 10-15cm apart..
Shielding would be me or the engine and I wasn't doing anything other than flying away and back and not exploring the polar diag.
Certainly I was also seeing other ADS-b traffic up to 30nm at EGLL as well as 2-3 nm away so I concluded that no immediate effect of swamping of the PAW ADS-B receiver by the PAW 868 and I also switched on my own transponder and that had no swamping impact on the PAW ADS-B reception with transponder antenna at 8-10 foot away.
By no means scientific but just my initial observations. More flights intended and also considering better antennae which I'll construct as Dipoles with the correct length and separation mounted in the fuselage.
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Very interesting Alan, thank you. It's particularly encouraging that the transponder doesn't mess with PAW ADS-B reception, as that is a seriously high power. It tends to suggest that the dongle front end is reasonably bulletproof, although, of course at 8-10ft away the inverse square law is doing its thing quite well too.
I've been thinking some more about this and I reckon that by far the best place for the antennas is in the wing tips, which are almost always composite, even on all metal aircraft like my Sportcruiser. ARF on one side and ADS-B on the other side, probably vertical dipoles, as you suggest, should give near enough 360 degree coverage and be well away from other noise sources.
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Hi John,
Sounds like a lot of very lossy coax, weight and difficulty to me!
Chris
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Not really. Modern low loss coax such as LMR-240 would only lose around 1.5 to 2dB along the length of a wing and that would be more than made up by using a full size dipole out in the clear rather than the whip. Weight? Around half a kilo for both wing lengths. I do agree it's a lot of faffing around and I only said it was the best location, not the easiest. I wish I'd thought of it when I was building JONL!
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I once made one of these for my flexwing, just had it tapped to the inside of the pod. It seemed to work fairly well.
http://www.xplorer.co.za/wonder-whip/index.html
Any reason not to make and use connected to the ARF?
By my calcs i think the antenna legs only need to be around 320mm.
Thoughts please!
Thanks Brian
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The wonder-whip is just a slightly oddly realised dipole but its performance would certainly be significantly better than any whip antenna, especially at air band frequencies. More conventional dipoles have two identical elements, fed at the centre with coaxial cable that emerges perpendicular to the elements. For the frequencies we are dealing with the dipole is small and can be easily fabricated using single sided printed circuit board.
For 868MHz the wavelength is 34.5cm, so each quarter wave element is 8.6cm. We need to allow for a velocity factor of around 0.9 (signals move more slowly in wires than in free space), giving an element length of 7.8cm.
At 1090 MHz, for the ADS-B antenna, the same calculation yields an element length of 6.2cm.
Dipoles made to these dimensions would hugely outperform the rubber ducks that come as standard. Maybe that's not needed for the ADS-B side but for the P3i component I think the effort is likely to be worthwhile.
Someone with PCB making facilities could make these antennas quite trivially. Or a bit of DIY work with some PCB material, a scalpel and a soldering iron would yield the same result.
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Would be interesting to see results if someone if someone could make some up.
Am sure there would be takers to buy them too.
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I'm planning to make a PCB 868MHz antenna with which to do some trials. Trouble is that around these parts there are no others playing with PAW yet, so I'm going to have to make a second unit to act as a test rig. I'm on the case!
Question for Lee: what do I need for a cut down system to just do P3i Tx/Rx? Can I get away with just an RPi and ARF module or do I also have to have WiFi, GPS, ADS-B? My thinking is to have the cut down unit on the ground somewhere and then fly around it with a complete PAW in the cockpit to see what happens.
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If I were you I'd make a complete 2nd unit - easy to sell on after am sure.
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Just been up for a short 15 minute flight to do some air - ground testing. I ran:
- One unit on the ground, in the back of my estate car in open space on the airfield. 20AWG cable + 2 amp cig lighter + GPS dongle.
- 2nd unit in the aircraft, big charge pack power + 20AWG cable + Skydemon for GPS input. Aircraft is metal and PAW was on the floor of the a/c.
Both units have the baro chips and both also the soldered SMA connector on the ARF.
Performance of the ARF side was very disappointing :( I lost the ground unit about 900ft in the climb out. A pass over the airfield at 1300ft AGL clearly in direct line of sight of the car showed nothing. Short final - nothing. Taxying in, picked up the ground unit again.
A bit stumped as to what to do now - was hoping the soldered SMA would give great results ???
I'll try some master-slave diagnostics later on the ground with both units being the master in turns - does anyone have good figures for the power expected for a given distance between units ?
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Was the ground unit inside the car? If so then I'm surprised you got it at all! Your airborne unit on the floor was stuck deep inside one Faraday cage and if the ground unit was inside another Faraday cage, i.e. your car, then I would have said all bets were off.
800MHz is quite good at going through walls, foliage, etc. but won't go through metalwork however much power we run. Really, the antennas have to be in the clear to have a chance of working. If you put the ground unit on the car roof and the airborne unit on the instrument coaming then I think you'll get better results.
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Thanks, yes it was. The thing is, that's exactly the setup 2 metal aircraft with PAWs will often have. A lot can't / won't fit antennas to the outside, esp CofA aircraft. I don't really have instrument combing to speak of in the RV4 either to put it on - it's cozy in there! ;) Hmmm - I didn't realise it was going to be that bad :-\
The ADS-B freq seems fine but I guess the transmission power is much higher as well.
I'll see what I can do about positioning it higher up at canopy level next time and hope to do some air-air tests soon which should be a bit more realistic.
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You're exactly right on that Ian, which is why I raised the point in that long missive a couple of pages back in this thread. PAW is really only running very low power. Not sure how much but my guess would be no more than 200-500mW peak power. Compare that with the 200W peak output that even fairly basic Mode A/C/S transponders are running, to an external antenna at that, and you can see that were dealing with several orders of magnitude difference.
The solution is going to lie in innovative antenna design/placement. One thing that would certainly be worth investigating is stick-on antennas that can be (temporarily) attached to a cockpit window. Like the stick-on rear window car radio aerials of yesteryear. As the antennas are so small, they would be barely noticeable. Biggest issue is getting a reliable connection to them.
Fl*** (I gather we dare not speak its name here) has the same limitations but pretty well all gliders are composite, so relatively transparent to 800MHz wirelessry. Power Fl*** is a completely different beast and does require external antennas for exactly the reasons we are discussing here.
We have some good RF engineers amongst our number... a solution will be found!
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:)
btw. Do you think the "10s of kms" range claim of 2 ARFs is in any way realistic ? (assuming in free air and line of sight) either with the stock pigtails+antennas or with something else ?
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Free space and line of sight? Certainly. Probably even more. The challenge is getting both of those characteristics in all directions at the same time :)
Years ago I remember playing with some early solid state kit on 1300MHz. Probably only running 50mW or so we were able to establish comms between two line of sight hilltop locations over 20 miles apart without too much difficulty.
The little wireless wiggles don't get worn out too quickly in free space but they don't like banging their heads on lumps of metal!
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This is a massive flaw. Frankly the PAW needs to be capable of transmitting through the metal skin of a CofA a/c...
Stupid question but the ARF card is high power? So why don't we just bump up the power?
Hopefully Lee can add something to this discussion
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A wouldn't say that exactly. Don't panic yet. There's also a bit of a question mark over the soldered SMAs.
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DON'T PANIC!! DON'T PANIC!! DON'T PANIC!! DON'T PANIC!! DON'T PANIC!!
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Ok. Ok. I'll chill. I'll fly over mig29's field on Thursday and check out air/ground reception.
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This is a massive flaw. Frankly the PAW needs to be capable of transmitting through the metal skin of a CofA a/c...
I do hope you are joking? ???
No radio transmitter, no matter how powerful, will transmit through the metal skin of anything.That's why all your aircraft's antennas are on the outside. It's how a kilowatt of high energy microwaves can cook your food without cooking you at the same time.
No flaw... just the laws of physics at work. Fortunately there are solutions.
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The only "real" tests are air to air, which is after all the intended environment.
Recently I was picking up a flyby on my ground test unit and based on the lat/long reported the transmitter was about 3.2nm (5k) away at 1750ft.
I think I had the power turned down on my unit at the time as I was tinkering with some stuff so I wasn't detected.
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Stupid question but the ARF card is high power? So why don't we just bump up the power?
It's only 'high power' in the sphere of Licence-free ISM transmitters. 500mW (or half a watt) isn't exactly high-power but compared to most hand-held or integrated transmitters used for telemetry signalling in the ISM band, it is.
Theoretically, the ARF at the settings configured by the PAW transmits at the maximum allowable for that frequency, but whether all of the licensable power is actually getting to the antenna is a moot point and really needs some specialist test kit to check it out accurately. Also could do with checking how well the transmitter locks to the set frequency and whether there is any sort of drift or variance.
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No I'm not.
The low cost portable nature and ‘bring your luggage with you’ concept does imply this needs to be possible.
If it can't penetrate one layer then surely if an antenna is mounted underneath an a/c the anyone above and behind will not see the signal will they as that will mean penetrating at least 2 layers??
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3.2nm (5k) away at 1750ft. .
I'd be MORE that happy with those numbers providing I can have the antenna in the cockpit.
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3.2nm (5k) away at 1750ft. .
I'd be MORE that happy with those numbers providing I can have the antenna in the cockpit.
Well mine was sitting in an upstairs window, not sure where it was in the aircraft.
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If it can't penetrate one layer then surely if an antenna is mounted underneath an a/c the anyone above and behind will not see the signal will they as that will mean penetrating at least 2 layers??
That's essentially correct. It's why, for example, transponder antennas are mounted on the underbelly, so that they can be seen by the radars on the ground. At lower frequencies, e.g. air band, the problem is less severe because the aircraft is relatively small in wavelength terms. So we can get away with mounting air band antennas on the top of the fuselage of a small aircraft.
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Ok. Ok. I'll chill. I'll fly over mig29's field on Thursday and check out air/ground reception.
There's a reasonable chance I will be flying overhead his field on Thu (tomorrow) too !
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Has anyone tried any of the slightly larger antennae coupled with the ARF?
This sort of thing? (http://www.ebay.co.uk/itm/868MHZ-915MHZ-GSM-3G-Small-99-UK-Omnidirectional-High-gain-Antenna-7DBI/171802354402?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3D9e2308c353d94ce38cc7f76002e0fa07%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D291141186807)
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Has anyone tried any of the slightly larger antennae coupled with the ARF?
This sort of thing? (http://www.ebay.co.uk/itm/868MHZ-915MHZ-GSM-3G-Small-99-UK-Omnidirectional-High-gain-Antenna-7DBI/171802354402?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140122125356%26meid%3D9e2308c353d94ce38cc7f76002e0fa07%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D291141186807)
Hi Paul,
I purchased one of these a while back, when I test the power, the RSSI numbers get worse, I suspect the loss in the cable is greater than the gain in the antenna. Bear in mind its a pretty long cable
Thx
Lee
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I flew a low orbit on mig29's field earlier. My paw (uses the ARF, shield with sma by jcurtis) was behind the seat. I flew directly over Gerry and I got and indication of his device at -0.5 but was almost directly overhead before it appeared. To be host a little title disappointed but if I only get 500ft warning from a p3i target I'll take that as it's better than no warning at all.
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Russ Hi!
Thanks for flying over. Only to compound your disappointment and mine...I got NO indication or target from you.
Both my PAW could see each other. I did a very crude on the ground check of range.
With one unit in the car and the other on table outside the Hangar i managed to maintain target for about 250Metres line of sight whilst driving away.
When Unit placed on car roof and then driven up strip I got about 450Metres until out of line of sight.
Bit perplexing.
Used ARF Shield and SMA soldered to board on one and standard early build for other.
ADS-B worked OK with Medi-Vac Helicopter picked up at 700' AGL at 15NM.One target in North Sea! About 175NM to the East?
Tomorrow the RV6 goes to Thruxton and I'll put one Unit into it and have tracked from the ground and see what those results will be.
Regards
Gerry
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I purchased one of these a while back, when I test the power, the RSSI numbers get worse, I suspect the loss in the cable is greater than the gain in the antenna. Bear in mind its a pretty long cable
Yes, I feared that, especially as I received my ARF (with shield) today and found that the supplied antenna is reasonably large to start with.
Though it may be better having this (or other) antenna up high rather than trying to use the PAW on the floor of the aeroplane with the antenna attached directly to it.
Regarding the announcement about the ARF today, have you measured the output power into a dummy load? It looks awfully small. When I was looking to build something similar, I looked at some 500mW modules from China and they seemed rather bigger than this module.
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Wow. That was a fairly steep turn I would have thought there would almost have been line of sight between units as I turned back towards you. :-\
Well. Ads-b showing in skydeamon is better than nothing ....
Looks like a lovely field you have there.....
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To be host a little title disappointed
???
The productive test playing up again?
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868Mhz realistic requirements............
Realistically we require 868 to establish rock solid 2 way contact air to air at a distance of 5 miles anything more is a bonus.
ADS-B units are designed as Air-Ground even the small units run 130Watts into a compromise antenna to give a design range of 150miles.
Is it possible to achieve this using the 868 band? I believe it probably is but we would need to utilize the maximum permitted power output in the High 868 500mw and use a descent antenna eg. a v- rabbit or at least a dipole for those that have ground plane problems...
So are these parameters achievable and is it permitted?
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Well, when everything works, we're getting 5 miles plus with 63mW (or is it 100mW?) and the rubber antenna stuck on the coaming.
We're allowed 500mW.
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Frank makes some very valid points, notably the three orders of magnitude higher power run by transponders and the fact that the antenna (external!) is looking at the ground. 868MHz is only marginally better at getting through "stuff" than 1090MHz, so most of the gain has to be made elsewhere, either by power or by antenna design/location. Power is severely limited by license conditions, so the only option available to us is to improve the all-round visibility of the antenna and (perhaps) its gain.
A dipole is quite small (span about 17cm (6.5")) and it's easy to construct. A ground plane antenna is nearly as good and only half that size but needs metalwork to work against. The real problem is where to put it, so it can see all around. Atop the tail fin is fairly good, as is a composite wing tip but both require lengthy coaxial cable runs, potentially losing some of the benefit through cable losses. A ground plane antenna on top and one underneath the fuselage would work very well but is difficult to engineer and to integrate (power splitters and so on).
If we accept that most risks come from straight ahead give or take 30 degrees then we can get away with something in the cockpit, e.g. on the coaming, but that will be severely compromised in other directions, especially behind and below. It is something of an intractable problem and not something we have had to worry about in the past with other types of avionics. If this was a simple problem we'd have fixed it by now!
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True 5 miles Is possible with around 90mw I think the ARF is capable of. What we need is a Rock Solid signal even when theres line of sight issues cockpit positioning etc.
Theres only a 25khz section of the band that permits 500mw can someone confirm the ARF is transmiting in that section.
Given 400+ mw and a half decent antenna that negates the need for decent ground planes unless you have a metal aircraft and want to start cutting holes in it... (not forgetting Mod Status) I believe 5miles minimum certainty contact is achievable.
Assuming licence restrictions are OK we need a bolt on narrow band amplifier accepting the input of the ARF module or even the XRF which would be cheaper. Shouldnt be too difficult I wouldn't have thought except for cooling issues if running a continuous amp.
Another thought is how good is the ARF receiver would a decent antenna and a preamp work or would we swamp the ARF RX.
Light bulb has just gone off..... must contact a friend who used to work in this field designing kit for the mobile phone network and P2P communication systems....
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True 5 miles Is possible with around 90mw I think the ARF is capable of. What we need is a Rock Solid signal even when theres line of sight issues cockpit positioning etc.
Theres only a 25khz section of the band that permits 500mw can someone confirm the ARF is transmiting in that section.
Given 400+ mw and a half decent antenna that negates the need for decent ground planes unless you have a metal aircraft and want to start cutting holes in it... (not forgetting Mod Status) I believe 5miles minimum certainty contact is achievable.
Assuming licence restrictions are OK we need a bolt on narrow band amplifier accepting the input of the ARF module or even the XRF which would be cheaper. Shouldnt be too difficult I wouldn't have thought except for cooling issues if running a continuous amp.
Another thought is how good is the ARF receiver would a decent antenna and a preamp work or would we swamp the ARF RX.
Light bulb has just gone off..... must contact a friend who used to work in this field designing kit for the mobile phone network and P2P communication systems....
Yes, the ARF operates within the licence free ISM high power band.
The ARF is two products combined. An SRF module (the small square board) which is the actual Tx/Rx IC and is a transmitter in it's own right. This SRF is mounted to another PCB with a combined Tx Booster and Rx high gain amplifier. This assembly is called ARF by WirelessThings. Basically it is a TI CC1101 & CC1190 loosely following the TI reference design. The only thing that can be done with the ARF module is antenna choice. The TI reference design and the associated documents state the limitations of the design, they are part of the 'low cost' Ti Sub 1GHz chipset range. Other variants are available that can run at higher powers - these are often deployed within the certified modules available from various (huge) companies.
The last RF stuff I was really involved that I can mention with was the deployment of AirWave for the Police, that is all based on TETRA. The implementation was "fun", especially the integration into everything else. Ah, the memories....
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Yes, the ARF in PAW is using the "high power" (sic) bit of the band. What we need and what we can get are unfortunately likely to be poles apart once metalwork gets in the way. The problem with bolting on amps (transmitter or receiver) is the need for T/R switching so that both can use the single antenna. All is possible, of course but the technology isn't commonplace (i.e. cheap). The ARF already has a PA-cum-RF amplifier that includes the T/R switching fabric. (Edit - I see that Jerry has covered some of these points whilst I was doing my one fingered typist trick.)
I'm working up to an experiment. I shall place PAW #1 in the visual control room at my local airfield, then trundle off with PAW #2. In the aircraft I shall have a) the standard whip antenna lurking on the coaming, b) a dipole taped to the canopy, and c) a quarter wave ground plane antenna protruding through a convenient hole in the underside of my aircraft's all metal fuselage (don't ask...!). I'll then do some tests, flying from and to the airfield with the different antenna configurations. All I need is for it to stop raining... should be an interesting test.
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I did some highly scientific testing tonight... :P
Tests
10ft apart
No aerials on either - IS 77 IM 70
1 stubby aerial horizontal – IS 88 IM 57
2 stubby aerials horizontal – IS 69 IM 41
2 stubby aerials 1 hoz 1 vert – IS 65 IM 35
2 stubby aerials vertical – IS 52 IM 23
1 stubby, 1 long both vertical – IS 46 IM 23
2 stubby vertical + adptr - IS 75 IM 47
I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.
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Interesting test. If the antennas are cross-polarised (e.g. one horizontal, one vertical) then with everything else equal you will see a marked reduction in range. It doesn't greatly matter whether the antennas are horizontal or vertical but they both need to be the same. Usually vertical is preferred because that gives a 360 degree horizontal radiation pattern.
What is the "long" antenna? How long is it and is it just an end-fed whip or perhaps a dipole or something else? Perhaps you could post a picture. Longer isn't necessarily better - resonance is the name of the game. The adaptors shouldn't make any difference.
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Long: https://www.wirelessthings.net/868-915-mhz-rubber-duck-antenna
Short: https://www.wirelessthings.net/868-915-mhz-small-rubber-duck-antenna
Adapter: http://r.ebay.com/HPKFIv
I was surprised the adapter made a difference... I also think I've buggered one of my ARFs as it doesn't seem to be responding now...
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I did some highly scientific testing tonight... :P
Tests
10ft apart
No aerials on either - IS 77 IM 70
1 stubby aerial horizontal – IS 88 IM 57
2 stubby aerials horizontal – IS 69 IM 41
2 stubby aerials 1 hoz 1 vert – IS 65 IM 35
2 stubby aerials vertical – IS 52 IM 23
1 stubby, 1 long both vertical – IS 46 IM 23
2 stubby vertical + adptr - IS 75 IM 47
I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.
Hi Stephen,
There is clearly a marked difference in the two units when all should be equal, in particular here
2 stubby aerials horizontal – IS 69 IM 41
2 stubby aerials vertical – IS 52 IM 23
just out of interest, I know it is hassle, are you able to unplug your ARF and swap, I would expect the two readings above to be the same for master and slave but they are wildly different!.
I have become so dissatified with the ARF :-(
Thx
Lee
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Working on it...
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Ah... when i say horizontal, I mean tip to tip, not broadside to broadside.
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Got it. The long one is the standard one supplied with the ARF and it should out-perform the stubby quite noticeably IF you can get it vertical. Both would work considerably better with a ground plane.
It's possible that the 90 deg adapter is U/S but I'd have thought it unlikely. Check that the coaxial centre pin is correctly locating with the centre socket on the adapter. If you have a test meter you might also check for centre pin continuity and that the centre pin is not shorting to the screened casing.
The ARF stops ackling if there isn't a usable GPS signal - that caught me out to begin with. Might that be the problem?
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I did some highly scientific testing tonight... :P
Tests
10ft apart
No aerials on either - IS 77 IM 70
1 stubby aerial horizontal – IS 88 IM 57
2 stubby aerials horizontal – IS 69 IM 41
2 stubby aerials 1 hoz 1 vert – IS 65 IM 35
2 stubby aerials vertical – IS 52 IM 23
1 stubby, 1 long both vertical – IS 46 IM 23
2 stubby vertical + adptr - IS 75 IM 47
I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.
Hi Stephen,
There is clearly a marked difference in the two units when all should be equal, in particular here
2 stubby aerials horizontal – IS 69 IM 41
2 stubby aerials vertical – IS 52 IM 23
just out of interest, I know it is hassle, are you able to unplug your ARF and swap, I would expect the two readings above to be the same for master and slave but they are wildly different!.
I have become so dissatified with the ARF :-(
Thx
Lee
As the Master always seems lower than Slave, have you tried to swap Master and Slave settings over and see what the results are?
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JCurtis, I think you make the combined board with the thingy soldered onto the board direct with the baro thingy... that one is the master... I'm working on getting one back up and working.
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I've not used this setting in PAW, are these RSSI values -ve? In general RSSI numbers are better the closer to 0. You would be better to have the units further apart when testing, or in different rooms so there is some attenuation between them, 10 feet isn't that far even at the power of the ARF.
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Yes negative, I was just making it easier to read...
Starting to lose the will to live with this... I can only get a reading off the long one (that comes standard) if I hold the tip with my fingers.
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Jeremy is correct, I made my measurements 30ft apart.
I got numbers if -020 on each
Thx
Lee
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Went and put it one in another room, now just getting a dollar sign...
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Went and put it one in another room, now just getting a dollar sign...
That sounds like the settings are wrong at one end a $ is the start of a standard p3i serial packet
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All I did was unplug it and plug it in again in another room... I'll have to check but the will to live walked out a few minutes ago and I went to the fridge to get a beer...!!
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I see where youre coming from :)
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I'm away from Friday, I may have some time tomorrow to test further, but I'm not sure as I need to pack and depart at 4am... Otherwise I'll test again when I'm at home.
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A thought, can the ARF board be remote mounted with the antenna and the control cable run back to the Pi, no coax needed, we could also do with decent antennas especially with the flex wigs as we don't won't stray bits n pieces going through the prop.
Nick
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Yes, the ARF in PAW is using the "high power" (sic) bit of the band. What we need and what we can get are unfortunately likely to be poles apart once metalwork gets in the way. The problem with bolting on amps (transmitter or receiver) is the need for T/R switching so that both can use the single antenna. All is possible, of course but the technology isn't commonplace (i.e. cheap). The ARF already has a PA-cum-RF amplifier that includes the T/R switching fabric. (Edit - I see that Jerry has covered some of these points whilst I was doing my one fingered typist trick.)
I'm working up to an experiment. I shall place PAW #1 in the visual control room at my local airfield, then trundle off with PAW #2. In the aircraft I shall have a) the standard whip antenna lurking on the coaming, b) a dipole taped to the canopy, and c) a quarter wave ground plane antenna protruding through a convenient hole in the underside of my aircraft's all metal fuselage (don't ask...!). I'll then do some tests, flying from and to the airfield with the different antenna configurations. All I need is for it to stop raining... should be an interesting test.
I'm not sure what alternatives to the ARF Lee may be considering. If these do not achieve any improvement in transmit power, I wonder if a narrow band ( or even broad band) power amplifier connected to the ARF TX output, might be the way to go (dependent also on TWF's experiment described above).
My thoughts are;
1) Existing ARF antenna retained and used for ARF receive (and low power TX) as at present, via the end feed SMA connector.
2) ARF pig-tail coax connected to ARF output U/FL connector (effectively "T" ee'd off (1) above), and connecting to power amplifier input, via cable's SMA female end.
3) Amplifier output connected to additional antenna (for high power transmit).
4) Separate (high power i.e. 450 mw) antenna and existing ARF antenna gets around Tx/Rx switching referred to by TWF.
Is this too much of a bodge, could it work? Would the "T" reduce the ARF receive sensitivity? I consider the two TX antennas could assist "position diversity" as called for, if connected to PAW using coax cables.
Regards,
Chris
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A thought, can the ARF board be remote mounted with the antenna and the control cable run back to the Pi, no coax needed, we could also do with decent antennas especially with the flex wigs as we don't won't stray bits n pieces going through the prop.
Probably, yes. The ARF only needs a few connections and none of them are carrying seriously fast data, although noise immunity might be an issue with only 3.3V signalling levels. You would probably also remote the 3.3V regulator to reduce the issue of voltage drop. Decent quality coaxial cable and short runs would be a simpler solution.
I'm not sure what alternatives to the ARF Lee may be considering. If these do not achieve any improvement in transmit power, I wonder if a narrow band ( or even broad band) power amplifier connected to the ARF TX output, might be the way to go... <snip>
Perhaps although it seems like a complex solution that is only fixing one half of the problem. Really we need the Tx AND the Rx to be able to work better and there is only one common component to that problem: the antenna. That said Lee's work on a replacement for the ARF is important because the 500mW would be handy to have and because of the apparent variability in Tx (and possibly Rx) performance between units.
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Yes, the ARF in PAW is using the "high power" (sic) bit of the band. What we need and what we can get are unfortunately likely to be poles apart once metalwork gets in the way. The problem with bolting on amps (transmitter or receiver) is the need for T/R switching so that both can use the single antenna. All is possible, of course but the technology isn't commonplace (i.e. cheap). The ARF already has a PA-cum-RF amplifier that includes the T/R switching fabric. (Edit - I see that Jerry has covered some of these points whilst I was doing my one fingered typist trick.)
I'm working up to an experiment. I shall place PAW #1 in the visual control room at my local airfield, then trundle off with PAW #2. In the aircraft I shall have a) the standard whip antenna lurking on the coaming, b) a dipole taped to the canopy, and c) a quarter wave ground plane antenna protruding through a convenient hole in the underside of my aircraft's all metal fuselage (don't ask...!). I'll then do some tests, flying from and to the airfield with the different antenna configurations. All I need is for it to stop raining... should be an interesting test.
I'm not sure what alternatives to the ARF Lee may be considering. If these do not achieve any improvement in transmit power, I wonder if a narrow band ( or even broad band) power amplifier connected to the ARF TX output, might be the way to go (dependent also on TWF's experiment described above).
My thoughts are;
1) Existing ARF antenna retained and used for ARF receive (and low power TX) as at present, via the end feed SMA connector.
2) ARF pig-tail coax connected to ARF output U/FL connector (effectively "T" ee'd off (1) above), and connecting to power amplifier input, via cable's SMA female end.
3) Amplifier output connected to additional antenna (for high power transmit).
4) Separate (high power i.e. 450 mw) antenna and existing ARF antenna gets around Tx/Rx switching referred to by TWF.
Is this too much of a bodge, could it work? Would the "T" reduce the ARF receive sensitivity? I consider the two TX antennas could assist "position diversity" as called for, if connected to PAW using coax cables.
Regards,
Chris
Not sure this would work, the additional amplification would probably slightly alter the phase of the signal, so you could make things worse for receivers at shorter range as the two signals contend. Any additional amp also needs to know when to turn on & off, that signal is available on the ARF board to tell the CC1190 what mode it's in but not easily accessible. An Amp will just amplify until you tell it otherwise, the carrier will still transmit.
Other modules exist, Lee and his team are looking at options, for me any replacement should be certified for a number of reasons including repeatable quality. Certified doesn't mean expensive, they can be had for within a few £'s of the ARF. The big players in this area make them by the truck load for use in all sorts of things, saw a few at an electronics show last week and that was on one stand. Whats also handy is the offer of assistance with antenna selection and/or design to get a good match where needed.
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Hi TWF and Jeremy,
I agree regarding antenna efficiency and position, however I think a big part of Lee's original concept for PAW was one of portability, particularly for renters or users of certified aircraft where mod approvals for installing antennae is for PAW difficult or undesirable.
I'd assumed the TX carrier is switched off whilst the ARF is in Rx mode due to Tx/Rx switching in the ARF. Accept phase differences between TX signals potentially a problem.
Regarding replacement for ARF, just a little bit concerned over ability to talk to Pi and amount of reprogramming this might mean for Lee. Accept your comments over certified performance. If a suitable device with appropriate output power and input sensitivity can be found this is likely to be a big step forward for PAW.
(Reading open micros.org description of ARF/SRF including TI admission about unpredictable behaviour, had me slightly concerned and made me wonder if some of the variability the testers are seeing might be caused by such factors as well as RF propagation issues)
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I'd assumed the TX carrier is switched off whilst the ARF is in Rx mode due to Tx/Rx switching in the ARF. Accept phase differences between TX signals potentially a problem.
Yes, it is, the CC1190 on the ARF flips between Tx and Rx based on a signal received from the small SRF board on the ARF module. When in Rx is operates as a high gain receiver, when in Tx a power amp. If you add anything external to the ARF to try and boost things etc. it would also need to 'see' these control signals to be able to switch the amp on and off.
(Reading open micros.org description of ARF/SRF including TI admission about unpredictable behaviour, had me slightly concerned and made me wonder if some of the variability the testers are seeing might be caused by such factors as well as RF propagation issues)
I've not seen that admission, but would not be surprised if production variances caused enough of a problem to explain some of the oddities.
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Have people run a scanner where they are testing to check what else is transmitting and at what duty cycle ?
Trouble with 869.4Mhz is 500mw could end up the base level.
example:
http://xlsystems.co.uk/html/869mhz.html (http://xlsystems.co.uk/html/869mhz.html)
If a few of those were within 10 miles or so....
just a thought.
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I too have only heard my PAW(s) but I live in a very rural area, my nearest neighbour 400m away, so I wouldn't expect to hear anything that I hadn't generated myself.
The 868MHz ISM band is, however, free for all to use and it's inevitable that as time goes on this relatively new allocation will become busier. At 2000ft we'll be able to pick up ground-based systems over a wide range. The main thing that will help to reduce the problem is the very short duty cycle that most, if not all these devices will be using.
It would be instructive to take the scanner flying some day!
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Have people run a scanner where they are testing to check what else is transmitting and at what duty cycle ?
Trouble with 869.4Mhz is 500mw could end up the base level.
example:
http://xlsystems.co.uk/html/869mhz.html (http://xlsystems.co.uk/html/869mhz.html)
If a few of those were within 10 miles or so....
just a thought.
Yes, and around Cambridge there is something else either on 869.4 or very close by. From memory it transmitted briefly every couple of minutes.
User the ISM band the duty cycle can be no more than 10% (per hour) so that shouldn't be an issue. A device can transmit for a total of no more than 36 seconds in any given hour.
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I was wondering about "interference " from other ISM sources. Am I being overly simplistic in my thoughts that when PAW receives transmissions from non-PAW sources, data will be unrecognisable as not conforming to PAW protocols, therefore nothing is output to display or otherwise?
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...the ISM band the duty cycle can be no more than 10% (per hour) so that shouldn't be an issue. A device can transmit for a total of no more than 36 seconds in any given hour.
10% would be 360 seconds but perhaps there is an overarching limit of 36s/hour as well, effectively making the long term maximum duty cycle 1%?
Edit: I see on further investigation that the P3i protocol has a 2.5% duty cycle, meaning it is transmitting for a total of 90 seconds/hour. From what I can tell there are two parameters: an overall duty cycle of <10% and, separately, a maximum single transmission time of 36s.
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I was wondering about "interference " from other ISM sources. Am I being overly simplistic in my thoughts that when PAW receives transmissions from non-PAW sources, data will be unrecognisable as not conforming to PAW protocols, therefore nothing is output to display or otherwise?
Yes, the packet protocol (packet length, CRC) should ensure that non P3i packets are discarded although I am not clear how reliable that would be when there is lots of different traffic. Hopefully there is also lots of data field integrity checking as well, so any non-P3i packets that do manage to pass length/CRC muster are ignored.
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...the ISM band the duty cycle can be no more than 10% (per hour) so that shouldn't be an issue. A device can transmit for a total of no more than 36 seconds in any given hour.
10% would be 360 seconds but perhaps there is an overarching limit of 36s/hour as well, effectively making the long term maximum duty cycle 1%?
The rules give a maximum single length of a transmission to be 36 seconds, with a min 3.6 second gap between. There are various tables around with all this stuff in.
I was wondering about "interference " from other ISM sources. Am I being overly simplistic in my thoughts that when PAW receives transmissions from non-PAW sources, data will be unrecognisable as not conforming to PAW protocols, therefore nothing is output to display or otherwise?
The ARF will ignore transmissions if they are not on its 'net', in the ARF setup there is a PANID setting - unless it gets the same ID it simply throws the packet away and Lee never even sees it. I believe they also throw the packet away if it fails a CRC check too, again before Lee even sees it in PAW. Current this is set to the default of 5AA5 so it's possible if someone else is using an ARF with the default too Lee may see some packets that don't relate to P3i.
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Yes, it is, the CC1190 on the ARF flips between Tx and Rx based on a signal received from the small SRF board on the ARF module. When in Rx is operates as a high gain receiver, when in Tx a power amp. If you add anything external to the ARF to try and boost things etc. it would also need to 'see' these control signals to be able to switch the amp on and off.
I've not seen that admission, but would not be surprised if production variances caused enough of a problem to explain some of the oddities.
[/quote)
1) I'm not sure why one would need to switch the amplifier on and off. During Rx cycle there would be no TX signal at amplifier input as CC1190 has flipped away from TX mode, therefore no TX carrier.
Amplifier input correctly terminated, so presumably no transmission or spurious output to TX antenna.
2) worth looking at openmicros.org webpage concerning ARF/SRF. Looked it up when Lee pointed to it concerning PAW master slave RSSI tests. The transceivers can act in very odd ways, largely inhibited by Wirelessthings firmware update, but sometimes requiring re-flashing of memory by WT.
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If we accept that most risks come from straight ahead give or take 30 degrees then we can get away with something in the cockpit, e.g. on the coaming, but that will be severely compromised in other directions, especially behind and below. It is something of an intractable problem and not something we have had to worry about in the past with other types of avionics. If this was a simple problem we'd have fixed it by now!
Not convinced the threat is from 30 degree either side of dead-ahead. I would hope that most pilots would spot something in this area sooner or later. Under noses, above high wings and below low wings, I would consider the greatest threat due to not being spotted? A vertical dipole would be blind to an aircraft directly above or below e.g. on approach.
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How do you graft on of these onto a PA28?
:)
(https://upload.wikimedia.org/wikipedia/commons/8/80/FuG_220_and_FuG_202_radar_of_Me_110_1945.jpg)
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It never comes from dead ahead...
https://www.youtube.com/watch?v=H4TuJM3uuzY
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HI All, I have successfully built two units at the weekend. Thanks to excellent documentation and advice on the forum both fired up first time with just the ADS-B In fitted. I did some initial testing in an RV9 over East Anglia and was gaily spotting the big jets heading into and out of Stansted, Norwich and even London at 2000' over Diss - see pic.
https://www.dropbox.com/s/u0g2dnujcchezk4/IMG_0164.PNG?dl=0
Later when back on the ground I was still picking up a/c over Belgium - seems extraodinary - is that norm
https://www.dropbox.com/s/mhqfuo3ofgh102l/IMG_0165.PNG?dl=0
When my ARF and Jeremy's shield arrived I fitted and again fired up great. First test was at my desk in Fulham and again good results with ADS-B In.
I was interested to see one a/c turning onto finals at LCY (2000') and it had a course marker attached
https://www.dropbox.com/s/2sd8cp085egm4m5/IMG_0166.PNG?dl=0
- does that mean I was receiving Mode S data? I understand that Mode-S on its own only transmits Reg and Height info on the ES - what should I expect to see on Skydemon for an a/c in that mode only (i.e no connection to a GPS source)
Keep up the good work
Cheers, Rod
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Good stuff Rod. It makes me realise just how much busier upper airspace is down in your neck of the woods - around here I might see as many as six ADS-B aircraft at at any one time between, say, Manchester and Glasgow!
ADS-B uses the Mode-S transponder transmitter, which is quite high power and is intended to give a range of up to 200 miles, albeit to a high gain radar head, so yes, what you're seeing is to be expected.
An aircraft squawking Mode-S without extended squitter will not show at all on the current PAW system because there is no positional information available for PAW to plot where it is. The identity and altitude are actually transmitted as part of the Mode-S response, not in the extended squitter. With ADS-B out, GPS position data are provided to the transponder and it is that information that is broadcast in the extended squitter.
I don't know why SD sometimes attaches a velocity vector (track marker) to aircraft. I too have seen it occasionally. Perhaps it's to do with being at low altitude or lower speed? Does anyone know?
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Hi Rod,
That has got to be one of the busiest screenshots I have seen so far
Thx
Lee
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Thanks John - so it seems to Squitter or to Extended Squitter that is the question!
I am fortunate enough to have access to a nice Cardinal with a Mode-S Transponder and G430 for further testing but it has not yet undergone the upgrade to connect the two together (for fear the avionics chaps will mess up both!) so not sure how useful that will be at the moment.
One more question - am I correct in assuming that PAW even with an ARF will also not pick up true F****M traffic as that has a different transmit protocol? Lee has just been very clever in utilising the existing SD F*****M interface to enable PAW to show ADS-B and (when available) ARF contacts? Or am I missing something?
Hope the weather clears and everyone can get some flying this weekend
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One more question - am I correct in assuming that PAW even with an ARF will also not pick up true F****M traffic as that has a different transmit protocol?
Correct
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An aircraft squawking Mode-S without extended squitter will not show at all on the current PAW system
I don't know why SD sometimes attaches a velocity vector (track marker) to aircraft. I too have seen it occasionally. Perhaps it's to do with being at low altitude or lower speed? Does anyone know?
Kind of. If you have vanilla S mode S AND a PilotAware with the same hex code configured being picked up by a 2nd PAW, your reg (from the Mode S) will be used in preference to the hex code when displayed in SD! A neat side effect of Lee's s/w implementation. It takes the reg from the mode S and position from the PAW. My testing with a Funkwerk shows that this happens even if the transponder is in STBY mode.
I think it shows the vector if the aircraft in question is a potential conflict e.g. similar altitude (?)
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My testing with a Funkwerk shows that this happens even if the transponder is in STBY mode.
That's curious and I don't understand how it can work, as on standby the transponder is not squawking and should be producing no RF output at all. I'd like to hear more!
8) I just thought - it's probably because you were squawking earlier and PAW has remembered the ICAO code to callsign pairing from then.
I do agree it's a very handy facility. Of course it relies on Mode-S interrogation from the ground, which means there aren't so many places up here where it'll work!
I think it shows the vector if the aircraft in question is a potential conflict e.g. similar altitude (?)
Ah yes, that makes sense.
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My testing with a Funkwerk shows that this happens even if the transponder is in STBY mode.
That's curious and I don't understand how it can work, as on standby the transponder is not squawking and should be producing no RF output at all. I'd like to hear more!
8) I just thought - it's probably because you were squawking earlier and PAW has remembered the ICAO code to callsign pairing from then.
It may be a bug in the transponder s/w but I think STBY just means it's not transmitting a squawk not that it's not transmitting ADS-B messages. It was a surprise to me too!