Gnu Radio and Mode S (1090 MHz)

GNU Radio
1

Hello

Sorry if this is a duplicate.

I am using my digital scope to capture data and pipe it to a flat file
where I can look at it in LINUX (gdsh USB and perl)

I am attempting to decode 1090 MHz transponder signals.

I know what I am looking for. ( I do this for a job)

I am on the hunt for better hardware and software to do the job under
LINUX.

I simply need a faster better capture soluition that will allow me to up
the through put of my signal analysis.

Can someone suggest ? I see some work has already been done on gnu-radio
in this area.

At the moment I am processing csv capture files from the scope.But it
takes seconds to grab the data from the scope.

Does gnu-radio have a module or code that would let me sample and save ?
I can do the rest. Maybe a scope function ? samples vs time.

The data rate is 1 MHz for Mode S.

I have the 1090 MHz receiver, actually got 2. SBS-1 with video out
(0-2Volts)

Here are some captures I have done so far.

http://vk4tec.no-ip.org/adsb_gds1022/

Would the USRP and some LINUX code help me out ?

I can program, in perl, python should not be too hard to grasp. C, so so
.

Here is my website

Andrew R. VK4TEC

17/03/2010

2

Andrew,

Eric C. has written a complete Mode S receiver for gnuradio, using
a USRP with a DBS-RX daughterboard. I also use a 1090MHz SAW filter and
an LNA in my setup to get better results. Eric’s software has not been
ported to the current gnuradio architecture and uses the older “blks”
interface.

I rewrote Eric’s software from scratch last spring to achieve better
processing at lower sample rates, and to use a more optimal bit slicer
for coping with FRUIT. I haven’t released the software yet – it is
working with the latest gnuradio trunk, but I haven’t gotten around to
cleaning up the code to the point where I’m not embarrassed to look at
it.

It sounds like you’re more interested in sampling data that you already
have in demodulated PPM form, from a receiver you already own. If that’s
the case, the USRP is probably overkill, but it will certainly work if
you use an LFRX as the front end board. If you add the DBS-RX to the
USRP, you’ve all but obviated the need to use the SBS-1 you have in your
current setup.

Nick

I know what I am looking for. ( I do this for a
allow me to up the through put of my signal analysis.

http://vk4tec.no-ip.org/adsb_gds1022/

17/03/2010

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3

Thanks Nick

I have some more questions if I may

  1. What determines the bandwidth of the daughter boards for USRP ?
  2. Where do you connect if you want to bypass the RF board and connect
    at
    base band ?
  3. Will I be able to achieve what I want to achieve on openSUSE linux ?
  4. When you talk about “code” what language ?
  5. What is a trunk when you talk about gnu ? is that the software base ?
  6. I assume I can get an RF board and do 1030 MHz as well ?
  7. Can I use perl to do any of this ?
  8. Would someone be able to guide me through this.
  9. Is a “PC” suitable and quick enough to keep up with the signals ?
    Does
    the USRP and code lag or is there plenty of time left over ?

Andrew

----- Original Message -----
From: “Nick F.” [email protected]
To: “gnuradio” [email protected]; [email protected]
Sent: Wednesday, March 17, 2010 9:11 AM
Subject: RE: [Discuss-gnuradio] gnu Radio and Mode S (1090 MHz)

Andrew,

Eric C. has written a complete Mode S receiver for gnuradio, using
a
USRP with a DBS-RX daughterboard. I also use a 1090MHz SAW filter and an
LNA
in my setup to get better results. Eric’s software has not been ported
to
the current gnuradio architecture and uses the older “blks” interface.

I rewrote Eric’s software from scratch last spring to achieve better
processing at lower sample rates, and to use a more optimal bit slicer
for
coping with FRUIT. I haven’t released the software yet – it is working
with
the latest gnuradio trunk, but I haven’t gotten around to cleaning up
the
code to the point where I’m not embarrassed to look at it.

It sounds like you’re more interested in sampling data that you already
have
in demodulated PPM form, from a receiver you already own. If that’s the
case, the USRP is probably overkill, but it will certainly work if you
use
an LFRX as the front end board. If you add the DBS-RX to the USRP,
you’ve
all but obviated the need to use the SBS-1 you have in your current
setup.

Nick

I know what I am looking for. ( I do this for a
allow me to up the through put of my signal analysis.

http://vk4tec.no-ip.org/adsb_gds1022/

17/03/2010

Hotmail has tools for the New Busy. Search, chat and e-mail from your
inbox.
http://www.windowslive.com/campaign/thenewbusy?ocid=PID27925::T:WLMTAGL:ON:WL:en-US:WM_HMP:032010_1=

4

On 03/16/2010 10:52 PM, Andrew R. wrote:

Thanks Nick

I have some more questions if I may

  1. What determines the bandwidth of the daughter boards for USRP ?

The bandwidth is limited by the data rate back to the computer, so with
the USRP1 you get 8 MHz of RF BW, and with the USRP2 you get 25 MHz.
The exception is the TVRX daughterboard which has SAW filters that limit
you to 6 MHz.

  1. Where do you connect if you want to bypass the RF board and connect
    at base band ?

Use the LFRX daughterboards instead. They give you baseband inputs.

  1. Will I be able to achieve what I want to achieve on openSUSE linux ?

Yes

  1. When you talk about “code” what language ?

C++, Python, or using GRC which is a graphical design system.

  1. What is a trunk when you talk about gnu ? is that the software base ?

Yes

  1. I assume I can get an RF board and do 1030 MHz as well ?

Yes. The DBSRX will receive that frequency, as will the WBX and RFX900/

  1. Can I use perl to do any of this ?

Probably not.

  1. Would someone be able to guide me through this.
  1. Is a “PC” suitable and quick enough to keep up with the signals ?

Yes.

Does the USRP and code lag or is there plenty of time left over ?

Not sure what this means. People have done what you are trying to do
already and it works.

Matt

5

Thanks Matt

I am making good progress as I teach myslef to decode Mode S using a DSO
and
perl

  •                                                                *
  • Mode S decoder using Digital Scope and perl on openSUSE LINUX *
  • Andrew R. - March 2010 *
  •                                                                *

Sample rate 10MS/s
Max sample 71
Cut off 35.5
Array is 4000 points
Trigger on point 1094
Start count 1096
Pre-amble Match
DF starts at 1176
DF value 17
Type ADS-B squitter
Address 75008F
FT value is 11
Type Airborne Position NUC = 7 25 m < HPL < 185.2 m
(0.1nm)

----- Original Message -----
From: “Matt E.” [email protected]
To: “Andrew R.” [email protected]
Cc: “Nick F.” [email protected]; “gnuradio”
[email protected]
Sent: Tuesday, March 23, 2010 3:07 AM
Subject: Re: [Discuss-gnuradio] gnu Radio and Mode S (1090 MHz)