I’ve been working on developing my own style home brew antenna. It’s a sort of fork from the theory of spider style, with some practical observations and tweaks mixed in on top of that basic style.
PiAware 3.5 is on a Raspberry Pi 2, with an FA orange dongle, and has an FA filter fitted to the input connector of the dongle. After that is about 5-6 metres of RG6 with as few connectors as I can manage (fewer still later this week hopefully)
Anyway, I had been getting the usual 150NM or so contacts the or so could extend to 3-4-5 hundreds in a few of the spikes.
Anyway, I grab data from this on my main desktop machine, and that done with VRS. After some serious setting up of that to get it reliable, I am seeing spikes of far greater distances, up in the 1700-2000NM range. I can track these for maybe 30 minutes sometimes. By then they are less spikes and more wedges pointing back to the RX location.
Oddly these are not registering at FlightAware on my stats page. Conversely I’ve seen stuff there in excess of 200NM which did not show in VRS. Obviously these are NOT MLAT contacts, but hard won by me and my design.
Why might these discrepancies exist?
VRS is getting it’s info from PiAware, so why isn’t FlightAware making use of the data I am collecting?
It is starting to feel a bit pointless collecting it to start with. Never mind how I’m starting to feel about all the effort I have put in to develop the antenna design. It is certainly not good seeing it dealt with in this way.
ian - whatever you see in 2000nm distance is nonsense. 200nm is usual possible - sometimes 300nm. if you are not on top of mt. everest and the ‘aircraft’ is at 300.000 feet altitude you can forget about this data from such a distance …
p.s. we all have these more or less meaningless spikes. i had lufthansa aircrafts that happily flew over germany according to all offical data - in vrs sitting on ground of african deserts
p.p.s. things like this can be e.g. wrong decoded messages, wrong gps-data in a real message, funsters that spoof ads-b data, and very very rarely real messages reflected by other aircrafts. anyways it has zero relevance to your antenna-design and even if very few were real signals - what’s the benefit? it were like getting five pixels from a japanese soap-opera on your tv-screen …
However, some of this “nonsense” can be tracked for maybe half an hour. As for altitudes, well certainly in the realm of 20,000-30,000 feet at times, but by no means all times, often lower still, so not out of the ordinary.
If PiAware had a range map for one’s Rx then one would not be compelled to use VRS for this facility. Having the facility in developing an antenna is pretty much a prerequisite for seeing how a design preforms.
Because I happen to indulge in DX listening, I am familiar with skip and grey line effects, and I would not be at all surprised if these are also some of the experiences I have seen. Knowing what I do know, I could not immediately allow myself to be terribly dismissive of all contacts.
As for spoofing, well yes, there are always idiots out there. It is hard to imagine what precisely is wrong with them, but they need a doctor’s considerations, not my speculations. Whatever, their actions are reckless.
My main thought is that as long as PA hands the data out to VRS then it must be FA editing/filtering my input, and that is of far greater concern, since that is not documented anywhere obvious, and so becomes deeply unhelpful to my endeavours; How can I trust what it shows?
if you feed raw data to vrs then vrs handles (and drops) probably false data. in dump1090 you can set the max range 300nm is the default setting. in vrs (options/raw-feed decoding) you find similar setting options.
ads-b messages you get directly from your dongle and pi - so there is no flightaware data-filter between your skyview and dump1090. mlat-data they can and do filter but obviously until now only few private-blacklisted ones.
just save the data from this ‘mysterious distances’ and later proof it against official data online from flghtaware, flightradar24, ads-b exchange etc.
i did antenna testing two years ago quite intensive. the vrs-range-plots are not really the best tool to see improvements. best is to use 2 setups side by side and determine differences live.
btw. i have not seen a selfmade antenna that was superior to one of these two. so if you want to have the best - go for this omnidirectional and this directional antenna:
Tom, I like your valiant attempt to help here, and really appreciated the input, but two set ups is not something I can really justify right now. Besides, I’d like to get one behaving above reasonable suspicion, before trying to justify such expense.
I must also point out that if I did do that, then I would clearly be guilty of gaming the FA rankings system surely? I doubt that would make a good or helpful decision.
… you can do this with one setup too. connect antenna1 for 5 minutes - make a screenshot from skyview. connect antenna2 for 5 minutes and make a screenshot. this way you have within 15 minutes a much better idea of what antenna is superior - than in days with the range-plots. they are nice to let others see your range - but a poor tool to test antenna setup
Well, there is only one antenna at any given time. I do run each design or tweak for maybe a few weeks to really understand how it behaves. Sometimes one will be so poor it’s obvious that it must come down again and a backward set is needed. If it’s just average then I understand it’s average but in the context of the current weather conditions, so trying for a week or two see a few other variations in weather than that can frequently surprise.
My present one is fair at nearby, surprisingly better a little further out and then tapers down as one might expect, but on a day like yesterday for example, there was a large drop in humidity, both local and for some distance further out. There was a clear sky, good sun, and also higher pressure than in preceding days. Unsurprisingly it turned in some very good distance results. My Shortwave did better too as one would expect. Modest power transmitters up to 8 thousand miles away were there to be heard against my expectations. Station idents showed these not to be spurious.
Skip and grey line are real. It does happen in radio, it is much discussed and documented all over the net. We use radio for this hobby, so no surprise odd things turn up from time to time. I don’t and will never rely on that, but it’s just one more bit of the overall picture. If people rush to dismiss it then how would any of us ever learn more? They’d be missing out on one aspect of the fun too!
Sometimes when listening to shortwave, there is a 10 watt non directional Tx in Brazil, I am frequently astonished by how well the audio makes the trip at grey line time. They happily play out some great acoustic guitar tracks too!! All of this on a modest random longwire antenna I sort of threw together, and which is not really all that long anyway!
Crikey Tom, that’s a lot of money! More than I would spend in all probability!
My present antenna has cost me a massive £10.00p at the very most!
Mine don’t look anything like as good, but I like the way it is interesting to me in it’s own little way.
If I had those setups, I’d keep them indoors an maybe polish them so they always look their best, when I look at them, and I would probably stare at them for hours on end! Truly impressive they are!
ian - all those aren’t in use anymore - the radarcape was just placed at my house for their mlat-testing.
i now have just setup number 3 - with not too bad results https://flightaware.com/adsb/stats/user/TomMuc
cheers
tom
p.s. and this is my favorite setup to play with now
Tom, you have a wonderful location! I bet that feels good. The antenna is a big surprise!
My location is totally rubbish, but I’m always up for a fairly reasonable challenge. The location here definitely gives me one of them! I would not wish it on my worst enemy, but finding ways to beat it is the challenge! Much fun when it goes well too.
What is the big red lump on that set up? Do you have a page with more details perhaps?
exactly - the fun is to get the maximum at one given location. and yes i was simply quite lucky with the reception here at my house in the south of munich. the big red lump is the battery that feeds the raspberrypi zero and dongle. this is a fully ads-b receiver running dump1090 - antenna, dongle, computer and battery. here and below you find some of my tinkering: Post your PiAware setup - #152 by TomMuc
hehe - yes the zero is tiny (and cheap). anybody can do things with lot of money - but the real fun is to get it done with little money. that attracts me most and is simply magic what this tiny zero with a chaep dongle is able to do with antirezs and objs extremly smart dump1090 software
Tom,
you know, I like your ‘cute’ setup. Now I have a PiZero too, installed the PiAware 3.5 image and everything works well. Now I’m waiting for the (again) availabilty of SiTech Solar Panel;it’s announced for mid september.
I agree - it’s really amazing, what’s possible for really small money: take
a PiZero,
a standard DVB-T stick (you have to install specific RTL-software),
a home brewed (DIY) antenna (e.g. spider),
dump1090 software (PiAware image or whatever) and
register your PiZero with FA to get MLAT,
that’s it …
but again ensure that the battery-pack must match the varying power-input from a solar panel and moreover must be able to use the maximum power the solar-panel is able to harvest. otherwise the battery would not load at all or would miss the advantage of best hours of the day while using only partial loading power …
i just used the yagi in addition to my omnidirectional antenna while the whole setup was in the attic. now my omni-antenna is mounted on the roof (as low as possible) and i get the data from their runway without the need of the yagi. my house sits on a small hill but in direction to the airport a hill about 150feet higher than my position sits in-between. with the yagi i was able to overcome this obstacle even from inside the attic. if i were you i’d give the yagi a try - there is a real chance to get the signals even when there is no direct line of sight. btw. the airport next to me is not a major airport there are about 30 starts and landings per day: Funny - what's that? Alco-Test for helicopter pilots? - #3 by TomMuc
using the yagi now i could get about 50-100 aircrafts per day (maybe some more) additionally from czechoslovakia far away - but i’m not really interested in these flights over there …
There is a basic polar range plot on the stats page.
Positions that are implausibly far from your configured receiver location (2000NM is implausible, that data is junk) are discarded by piaware, so you won’t see them in FlightAware’s data.
I doubt that would make a good or helpful decision. 
All of this on a modest random longwire antenna I sort of threw together, and which is not really all that long anyway! 
