Positions v's planes


#1

Hi all. I am running piaware and have done a lot of work improving system so I now regularly see flights to 350-400 km. What does surprise is that nearby systems reporting a lot less positions consistently see more planes. This is all about the challenge of improving the system for me so interested in any suggestions on how I can capture and analyse data to work out what may be going on.

Phil


#2

A brief overview of what equipment you are using might help. What type of antenna? Any filters? Amplifier? What type of cable? Where is the antenna located? The more details you can provide, the better we can come up with ideas to help you increase your stats.

Cheers!
LitterBug


#3

Ok. Coaxial co linear at about 50feet in air. Direct coax run of RG213u into a 20db amp at base with 950mhz cut-off. Will be installing 2nd pre-amp at base of antenna within next few weeks with saw filter and determine if I then remove bottom Pre-amp or pad it out to reduce gain.
What I am looking for is any way of comparing data between nearby users to determine flights I am not seeing so I can address issue. I have option to put antenna higher but am not sure that is the solution.


#4

Cable is actually lower loss then RG213 - from memory specs were midway between RG213 and LDF450 - but it’s up to the job. Antenna is above roof line on two storey house.


#5

The positions/planes ratio is very dependent on the software that’s feeding. You will see e.g. quite different results from the same setup via Planeplotter vs. piaware/dump1090. This is just because they aggregate the raw messages according to different sets of rules.

So make sure you’re comparing apples with apples when comparing to nearby sites.


#6

It also depends on the kind of polar diagram your antenna produces. I have a quite narrow beam to the north east which crosses a lot of air corridors so I see lots of flights for only 5 or 10 minutes therefore the reports per flight are very low. In the other direction there are fewer flights but I see them a lot longer.


#7

thanks - great info and I would be interested to know more about the impact this has on stats. I am guessing planes = planes but positions are reported greater with piaware? only a guess. Several of the users I was comparing with are planespotter. thanks again.

Phil


#8

Rustytwig. I wonder what antenna you are using to have that type of antenna pattern and whether you are using any software to plot that?

I am relatively confident my antenna is as close to being omni - directional as possible and the drop off I see in certain directions are due to mountain ranges in those directions. Certainly worth looking into a bit further though. I do notice that I have planes cross the outer limits of my coverage (350-400 km) that get tracked but not identified.

thanks again

Phil


#9

Hi Phil,

I’m one of those nearby systems. I’ve watched your tracking increase since you started logged flights pretty much at the same time as me.

You’re now seeing about 10% (80ish) more flights than me but about 50000 more positions a day.

I have a 6 or 8 (I can’t remember which one I built) segment co co mounted above the roof line on a single story house.

Craig


#10

Great to see you here Craig - I follow your stats closely. I have the antenna now at about 50ft which improves reception pattern but introduced considerable feed line loss. I have put a 20db amp at the antenna feed point.