[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] Mode-S/ADS-B and UAT

From: Andrew Rich
Subject: Re: [Discuss-gnuradio] Mode-S/ADS-B and UAT
Date: Mon, 6 Dec 2010 19:33:10 +1000

I have been doing Mode S with a DSO accessed via the USB port and the video out on an SBS-1

Using LINUX to decode the samples.

Set trigger. and download

- Andrew -

----- Original Message ----- From: "Eric Cottrell" <address@hidden>
To: <address@hidden>
Sent: Monday, December 06, 2010 11:10 AM
Subject: [Discuss-gnuradio] Mode-S/ADS-B and UAT


I was emailed by a few people off list that are interested in the Mode-S/ADS-B code. I am still working on it.

I got the DPD Productions antenna just before Thanksgiving, but it was too windy to put up right away. Sitting on the first floor in the middle of a wood frame house, the antenna was picking up aircraft from 40 to 140 miles away depending on direction. I could not see low altitude aircraft to the south of the nearest busy airport, which is eight miles south. 44 feet above the ground on my roof is a different story and I can see aircraft from 150 to 210 miles depending on direction. Although the DPD antenna is higher gain, I do not get the same level of interference as the colinear. The DPD antenna is suppose to be a narrow bandwidth antenna. I tried the wideband preamp with the DPD antenna and had the same problem with the noise floor rising and decreasing range.

I bought a SBS-1 last week. It is a commercial Mode-S/ADS-B receiver that is smaller than the USRP. The sensitivity seems slightly better. It could handle the wideband preamp better with just a slight decrease in range. I am currently working on providing a port 30003 compatible output for my receiver. Then I can use Planeplotter and can compare my code to the SBS-1.

My nearby major airport has a ASDE-X system for monitoring aircraft and vehicles on the airport surface. It appears they are installing an ADS-B Multilateration system as I get a couple of the sensors. They use DF18 (Non-Transponder Extended Squitter) and just send an ID and Multilateration status. Two of them ID as STEST123 with the category of Fixed Ground/Tethered Obstacle. The third recently appeared with an ID of PTEST123. The SBS-1 also picked up the IDs so it can decode at least some DF18 formats.

I want to do a UAT receiver and was planning a trip to Philly to look at the TIS-B/FIS-B ground segment transmissions. I got a surprise when I found out the New England area has TIS-B/FIS-B services. Someone did a demo of a receive only system. The TIS-B service only transmits if there is a ADS-B aircraft using UAT in the area. Being able to receive TIS-B would be good because it includes non-ADS-B aircraft. There is also cross-linking of UAT and Mode-S so ADS-B aircraft on Mode S ADS-B should show up on UAT.

It is an iPhone application using a separate UAT receiver costing $1100.

I looked at the 978 MHz UAT frequency and think I see the signal but it does not completely match up with the specifications. The system uses slightly over 1 megabit per second FSK with a over 600K shift. I see what looks like the mark frequency, but instead of the space frequency I get another signal at the center frequency (978.0 MHz). If I use a simple PLL FM detector flow graph with a scope sink I do see what looks like a bitstream. The current plan is to get my laptop updated and setup, then go mobile. I suspect there is a transmitter at a nearby airport.

73 Eric

Discuss-gnuradio mailing list

reply via email to

[Prev in Thread] Current Thread [Next in Thread]