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[Discuss-gnuradio] Mode-S/ADS-B and UAT
From: |
Eric Cottrell |
Subject: |
[Discuss-gnuradio] Mode-S/ADS-B and UAT |
Date: |
Sun, 05 Dec 2010 20:10:37 -0500 (EST) |
Hello,
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.
http://www.youtube.com/watch?v=NmYrUGxRC88
It is an iPhone application using a separate UAT receiver costing $1100.
http://www.skyscope.net/
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] Mode-S/ADS-B and UAT,
Eric Cottrell <=