PiAware Setup in good location tracks poorly


#1

Hi, I’m very new to this and decided to setup a PiAware. I used the current img so I’m running 1.18 right now. In in new Rochelle, NY 40.909749, -73.783208 in a high rise, on the 38th floor. I have my antenna on a window ledge, floor to ceiling windows, with a line of sight East to South. No obstruction whatsoever yet I’m tracking VERY poorly. I recycled an old domain of mine if you want to see live data dclairity.com/
Also my stats are flightaware.com/adsb/stats/user/marc2912 I’m trying to see if anyone has any recommendations on what this could be caused by.

EDIT: Also I am using the dongle per the how to: amazon.com/gp/product/B009U7WZCA as my antenna.


#2

If you’re using that stock antenna, it will not have very good performance at all. I was able to cut off the antenna to the proper length for the 1090MHz frequency and it does work better, however it’s not any better than the two antennas I have that were built for this purpose.

There could also be some coating on the windows that impacts its performance.

Also, it’s possible that you’re receiving some various radio signals from cell/tv/radio towers that is over driving the dongle and causing it to have a hard time to see the ADS-B signals. A proper filter should help that if it’s the case (and if it’s a good filter, it wouldn’t hurt anything by installing it)


#3

Do you have any recommendations for alternate antenna I could use with the Pi? Same for filter. As I said totally new to this.


#4

minicircuits.com/pdfs/VBFZ-1065+.pdf

Band pass filter

I have another post about this from the other day. You can look at.


#5

See this multiple page thread regarding antennas. viewtopic.php?t=19517

Marty


#6

thanks marty


#7

How much difference did the filter make in number of aircraft or positions reported?


#8

I know how a bandpass filter functions. Build a few in my ol’ college days when “borrowing” pay cable was a simple analog hack.

How does the bandpass filter help dump1090? Does is only pass the 1090MHz’ish range thus reducing out of band noise that otherwise ‘swaps’ the receiver with interference?


#9

That is correct.


#10

The biggest bang might be a better antenna before a filter. If you have some copper (e.g. from a solid electrical cable) lying around, try making your own. I made a version of the collinear antenna below over this past holiday vacation. It only required a ruler with millimeters & a few bends.

tech-software.net/1090_ant_02.JPG
martybugs.net/wireless/collinear.cgi

Also keep the coaxial length to a minimum. The gain is only a few decibels at best, and probably approaches 0 in 50 feet.

My antenna is on a 4th story roof in Brooklyn. It hears squitters from aircraft at altitude as far north as Stamford, south almost to McGuire AFB. That’s only about 45 miles, but it’s pretty impressive for a relatively low antenna in one of the densest urban environments. On the 38th floor, you should get some crazy range! (albeit directional)


#11

I’d suspect the ADSB signal is being swamped by something else - a filter may be the answer.

The stock antenna with a R820T dongle on the 8th floor inside a fixed (single glazed) window, Birmingham UK on a Pi gave me about 150nm.

Could always take the rig out of town and run it on a car cigarette lighter power converter to see if the range looks reasonable.


#12

Your SDR is being swamped by other signals, most likely below 1GHZ, such as commercial radio(FM) and television. While the Mini Circuits bandpass filter is a good choice, you’ll probably see very good results form using a high pass filter such as the Mini Circuits SHP-1000 or NHP-1000. These show up on eBay quite often.

The insertion loss from the HP-1000 high pass filters is also quite low (under 0.5dB) at 1090 MHz, lower insertion loss than bandpass filters. Either will also provide some protection for your SDR input.

Try a high-pass filter, or a band pass filter between the antenna and your SDR.

Technical details –

The simple SDRs have a wideband variable-gain low-noise amplifier (LNA) followed by a detector which sets the LNA gain. This means that the LNA gain is set by the strongest set of signals present at the LNA – typically broadcast TV and radio, and not 1090 MHz! Throwing away those strong unwanted signals is important, as that lets the LNA amplify signals we’re interested in.

Since most of these signals are below 1GHz, a high-pass filter does a good job. This still leaves the SDR susceptible to cellular signals in the 1800-1900 MHz range, but a lot of SDRs are already falling off at those frequencies.

cheers–

Bob K6RTM


#13

Thanks guys. I tried to make a coax antenna and really no difference . I see planes fly right next to my window where I could probably see the tail number with a pair of crappy binoculars and it doesn’t seem to notice those half the time. I’ll try the filter next and let you guys know if it makes a difference.

Marc.


#14

At least for rtlsdr dongles, this is only true if you turn on the tuner’s AGC - otherwise the gain is manually controlled. dump1090 will default to manual max gain unless you tell it otherwise.

(Of course manual gain doesn’t help you because setting the gain high enough to amplify the Mode S signals enough just means that the strong signals saturate the LNA…)


#15

I have to agree with other posters: if the antenna is indoors glazing on the window can have a significant impact on performance. The windows I have at home and in my office significantly attenuate 1 GHz and above signals. In fact, moving the ADS-B antenna away from the window (during initial setup) into more a central location at home (wood structure) resulted in a lot more packets being received.

The other issue is being 38 stories up - you’re SDR dongle is probably being subject to a lot of strong signals - possibly both locally (like cell sites) as well as other nearby high power transmitters. Back in the late 1980’s I participated in a ham radio event on the top of the UN building in NYC (if I remember correctly something like 52 stories) and every band required extensive filtering to be able to receive anything - we were in the RF soup, so to say.

If you can solve your antenna / signal issues I’d assume you should be able to decode a ton of traffic especially that across the sound and Long Island.

Bob W1QA