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

From: DOHA
Subject: Re: [Discuss-gnuradio] Mode-S/ADS-B and UAT
Date: Sun, 17 Apr 2011 23:57:58 -0700 (PDT)

hello eric
i was searching for your mode s ads b code in gnu radio so pleas can you
send it to me .


Eric Cottrell wrote:
> 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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