Category Archives: Aviation

Scanners set up for monitoring/tracking aircraft

I un-mothballed a number of my old trusty-rusty Radio Shack PRO-2052 scanners for monitoring aircraft operations here in the valley.

With the new VHF/UHF multireceiver antenna setup, it’s very easy to have a number of scanners all running in parallel so that I don’t miss as many conversations and handoffs.

Here’s the stack of scanners: the top is ZAB (Albuquerque Center); the middle is Phoenix area TRACON; the bottom has both KSDL (Scottsdale airport) and KPHX (Phoenix Sky Harbor airport) in there so that I can monitor either or both.

I put different color LEDs for the display backlights. Yellow is top; orange is middle; red is bottom.

NIST WWV and Canada’s CHU

I have been working on the “long-wire” antenna that’s only about 10′ above the ground, and buried in the oleander hedge. It’s 110′ long, and fed about 10′ from one end. There’s an SGS tuner out there, but it’s currently not active, so it’s kind of hit and miss.

I programmed in the Central East Pacific HF aviation channels, but haven’t heard anything yet on them. With an antenna like this, I think I’m asking a lot.

I also programmed in all the WWV/WWVH/CHU time broadcast frequencies, more as a sounder than anything else. If I can hear one or more of these, that gives me a very rough idea of how well the antenna is working.

Tonight, I can hear CHU (Ottawa, I think) on 3330 kHz, at about -92 dBm. WWV (male voice, so Fort Collins) is running about -71 dBm on 2500 kHz, -93 dBm on 5000 kHz. Don’t hear a darned thing on 10000 kHz. But it is 4 hours after local sunset.

And, while you were asking “what’s the format for the beeps and boops on WWV?” I grabbed this handy-dandy quick guide from their site.

So now you know.

Hey – I think I might just be hearing WWVH (woman’s voice) on 10000 kHz. But the path is really poor.

American AAL1920 ADS-B Capture

Living next to a large hub airport, and having a good view ADS-B-wise of the airport and a to 200+ nm around it, I get to see flights come into PHX, unload and load, then take off. Case in point: AAL1920.

The route it’s currently on is LAX-PHX-MIA. My ADS-B receiver first heard its beacons when it climbed over the Santa Ana mountains in Orange county. It’s now approaching Deming NM and it should drop off my display very soon.

aal1920_A

Total time recorded is almost 2-1/2 hours, and nearly 9000 position reports.

When zoomed in on Sky Harbor, the path is

aal1920_b

What I find interesting is that as the plane was on final landing to the east (right), it did a little bump in the path just a few miles before the runway. Why? Avoiding a PHX PD copter? Dunno.

aal1920_c

Once it landed (rwy 8R), it taxied to the even-number side of the A15-A30 part of Terminal 4. Kinda looks like gate 16 or 18.

After loading up its passengers, it taxied out and took off to the east on runway 8L.

Nice filter for 1090 MHz ADS-B site

Over a year ago I decided that I needed some good filters for ADS-B reception on mountaintops. Not that I had an immediate need, I didn’t have anything on a mountaintop, but I suppose I had a little extra cash and felt excited to be able to imagine a good ADS-B receive site atop an Arizona mountaintop (or hilltop) location. So, I drafted up what I thought would be a reasonable spec and went into Alibaba to find a filter manufacturer to build one. I ended up with 5 filters, all exactly to my spec, and for a bargain price (well, relatively speaking).

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Above is the finished ADS-B receiver assembly, complete with Raspberry Pi, RTL-SDR 1ppm TCXO SDR dongle, a eBay-purchased LNA, an eBay-purchased 12 vdc to 5 vdc DC-DC converter, and some coaxial cabling (also from eBay). The black square in the center of the image is the 1090 MHz filter, and it’s a quite good one.

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It’s a straightforward cavity filter, a little aluminum brick with fine performance.

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Solid out of band rejection, and I suspect around -100 dB ultimate rejection. The SA just doesn’t have the range to see it.

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While the signal of interest is only a MHz wide, I wanted a filter that was wider so that temperature and mechanical variation would never haunt me, and I wanted a low bandpass loss (the above shows less than 1 dB loss) across the band.

Behind the filter is a run-of-the-mill eBay wideband LNA with a 1 dB NF, and somewhere around +30 dBm IP3. The RPi is running the most current version of FlightAware’s PiAware, rev 3.0.4, and supports just about any off-the-shelf USB SDR dongle.

After setting it up, it looked like I needed to reduce the overall gain a bit, so I discovered how to go into dump1090 and change the gain from “automatic” (really not, I think it’s just max) to 42 dB. That gave me best range and most received a/c.

The antenna for the site is a FlightAware fiberglass stick, about 12′ above the ground, mounted on the side of the tower.

HeyWhatsThat_30aug16Coverage seems to be pretty close to the model generated by HeyWhatsThat.com (above). The blue line is the 40,000′ contour, while the orange line is the FL300 contour.

24 hours or so of actual flight logs produces the following plot, which is more or less pretty similar to the HeyWhatsThat plot.

ADS-B_Measured_30aug16

The primary notch in the pattern, in the SE, is the higher part of the ridge on which the radio site sits. It ends up blocking any coverage of flights in and out of Tucson, over 110 miles away, until said flights get to FL300 or so.

It will be interesting to see how the coverage shapes out over the next few weeks – I hope that it will get up near the top of all the local receive sites in performance.

ADS-B Update

Installed an ADS-B receiver up on White Tank Mountains over the weekend. Coverage seems pretty darned good, and I lose a/c only when they’ve gone about 1.5° below the theoretical horizon.

Below is a screenshot of the display. The a/c out beyond the 200 nm range ring are all at FL300 or greater, but at least according to heywhatsthat.com, they’re all significantly below the local horizon from White Tank.

RPi_WT_29Aug16_1027

Also seems that I have about a 10 dB dynamic range on the receiver. Signals are never stronger than about -1.6 dBFS and I always lose the a/c when the signal drops below about -12 dBFS. Using HeyWhatsThat.com, it’s very apparent when it drops out.

Here’s AAL110 headed NE from LA. I lost it as it was about due east from Cedar City UT.

AAL110_29aug16_1055

The RSSI is below the minimum required for this particular station to decode successfully. Not that the a/c is over 220 nm distant, but it’s at FL410. So why did it suddenly fade out? HeyWhatsThat gives an indication.

AAL110_29aug16_1055_HWT_profile

From this plot, it’s obvious that the a/c, even at 41k feet altitude, is well below the local horizon and the actual path is probably ducting or multiple knife edges. Either way, it seems to explain for me why I can’t hear farther than this even with the receiver atop a significant “hill” in the Phoenix area.

ADS-B Receiver for mountain-top comms site

Monitoring aircraft via ADS-B is a terrific hobby and super easy to do. I get to have a display here that shows sometimes hundreds of aircraft (both commercial and general aviation) out to about 200 miles from the house.

ADS-B_screencapture

The above screen capture was from my Raspberry Pi running PiAware and connected to a homebrew 1090 MHz antenna up on the roof of the house. Nothing special in the setup, but look at the range! A/C at altitude are hearable out over the Grand Canyon and into California. Occasionally I get a/c into or out of Mexico, and I can see traffic in the southwest corner of New Mexico.

I’m planning to put one of these receivers on a local hilltop, about 3000′ above my house and the Valley floor, and yesterday installed the antenna on a temporary mount on the tower at the site. I connected it to my most recent ADS-B receiver setup, seen below, and was awestruck at the coverage. Was seeing a/c over Los Angeles and Albuquerque!

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It’s a bit tricky to put a cheap SDR dongle anywhere near radio transmitters, and the hilltop that I was on is loaded with them. In fact, the building in which I have some current monitoring equipment is only 50′ away from a huge comms tower with dozens of two-way radio antennas, and a lot of potential interference. The ADS-B receiver antenna is right in the center of the picture, on the end of a piece of unistrut attached to the tower legs. In the background, nearly a dozen towers bristling with antennas.

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The secret to success is a very good filter in front of the SDR receiver. That black square near the middle of the picture is exactly that. It’s a custom-made cavity filter, only 50 MHz wide, centered at 1090 MHz. Extremely sharp rolloff and ultimate rejection about 100 dB. Really helps the RTL-SDR receiver.

However, I wasn’t able to leave the receiver up on the hill yesterday, I was troubleshooting other issues and didn’t have time to set up the network connection to my receiver. Next time I will hopefully get it installed and on the air!