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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
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
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