Interesting plot, but nowhere near what I would find useful for my particular needs. Hence I had to go elsewhere for that. I’m trying to come up with a better build for an antenna here and that is obviously far too granular for that.
So, you are saying that PiAware elects not to send it in the first place? Just for the clarification?
As for whether it’s junk or not, I have no definite conclusion yet. I’ve been asking a mate if he got it on his two set ups and he did (several tens of miles from my site). So we are at least getting the same junk, which might mean it is quite possibly something to contemplate, I think. I’ve long since realised that I don’t have ALL of the answers every time, but I can elect to try and understand each time.
Yeah, piaware does not forward the position to FA. dump1090 will still be forwarding the raw message which is why you might see it in VRS et al.
It’ll be a bad transponder giving you the bogus positions - there are a surprising number out there that just transmit garbage - correctly formed messages containing a completely wrong position.
Microwave signals are pretty much line of sight, you’re not going to get 2000NM with the transponders / receivers used.
so it seems i am not the only getting unrealistic range plots. check 1 from VRS and one from ModeSmixer.
note VRS clips the polar at ~ 360nm. in both case when I coss-checked position with FA and it matched.
maybe has to do something with MLAT receivers ‘exchanging/relaying data directly’ to each other ?
or the Prostick Plus is that good that…‘reads between the …lines of sight’ ;=)
OK, thanks for that clarification. It helps to know which bits are real and which other bits are poor observation on my part!
Yes, that has been among my thoughts. One in particular was being a bit of a devil in that the false very closely mimicked truly possible and even bordered on looking likely. Luckily it has tipped it’s hand and shown me some truly implausible at last.
I’d like to gain better experience in knowing where the line might sensibly be drawn. I’m not too familiar with this frequency band yet, and also not sure how the differences will present themselves at any given time.
First instinct says grey line is known real. Well, that’s fair enough, however given any actual situation, one must consider whether what is seen is more grey line or more airline schedules. Not always easy to pick them apart when they happen to coincide as they often can.
I’m looking to make my set up attentive, yet not over keen to hear a contact which isn’t there, or worse, which is really somewhere else.
maybe has to do something with MLAT receivers ‘exchanging/relaying data directly’ to each other ?
There are a couple of things going on here:
you can participate in mlat even if you only receive, say, one message a minute from an aircraft; and these can be short (56-bit) messages which are more likely to be received than the long (112-bit) messages used for ADS-B positions. In contrast to get a position from ADS-B you need to receive a pair of position messages within 5 seconds of each other. So the effective range for mlat can be larger.
the mlat server will continue to send you results for a couple of minutes after you last participated in a result (to help smooth out some of the randomness of which aircraft are requested / which messages actually pair up) which can also extend the range
For mlat positions you’re not receiving the position from the aircraft, you’re receiving it from the FA servers, so range from the receiver to the aircraft is not an issue - it’s all about when the FA servers decide to give you positions.
If you’re interested in antenna range you probably don’t want to plot mlat positions as part of that.
exactly what i am trying to do !
it makes sense, because i ONLY get MLAT that far. so it is safe to say that
if equipment was ‘over-performing’ i would have received normal targets too at that range.
That’s probably the next step for me. I haven’t optimized my current setup yet. Being an opportunistic Dutch guy who thinks that he sees equipment stacked in such a way that it could be for permanent storage: would you consider selling the Yagi and possibly one of Guenthers antennas?
