Problem with receiving signal from satellite Thuraya-3

Hi,

I am trying to collect signal from Thuraya-3. Here is the setup I used:

  • USRP N210 + WBX
  • LNA with 30dB gain (ZHL-1217MLN)
  • Iridium Antenna (I don’t have specific antenna for Thuraya right now.
    Since Iridium and Thuraya frequency bands are quite close, I suppose it
    would work more or less)

Center frequency: 1530MHz
Sampling rate: 10MHz

From the spectrum (attached), I can see the Inmarsat signal, but no sign
of
Thuraya signal. Anyone has suggestion about how to receive the thuraya
signal?

Best regards,
Cheng C.

On 01/28/2014 09:14 PM, Cheng C. wrote:

Sampling rate: 10MHz


Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Is the Thuruya signal spread spectrum?

On 01/28/2014 09:14 PM, Cheng C. wrote:

Sampling rate: 10MHz


Discuss-gnuradio mailing list
r[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Interesting. That amplifier is basically a power amp, rather than a
receiver amp, and the noise figure isn’t stunning, and 1.5dB.

On 01/28/2014 09:24 PM, Cheng C. wrote:

Hi,

I think it’s TDMA/FDMA, not spread spectrum. Each channel is about 30KHz.

Best regards,
Cheng C.

Make sure that you’re tuned to the correct frequency, and that your link
margins are adequate. It could be that your antenna has insufficient
gain for the signals coming from Thuruya. The Iridium birds are
strong, and also in fairly low orbits.

You might need a real LNA at those frequencies–a GPS LNA would work,
except that you’d likely have to remove the 1575MHz filter.

Cheng,

The resources I’ve read say that the downlink is 1525-1559 MHz, which is
a
ways off from Iridium’s frequency of 1616-1626 MHz.
This would suggest that you should find a different antenna, like this
one
which covers both bands:

http://www.northernaxcess.com/satellite-communication-products/satellite-accessories/antennas/thuraya-antennas/sattrans-thuraya-hemi-omni-antenna/

-John

Also, apparently, the two systems have opposite polarization:

http://www.peter2000.co.uk/aviation/satcomms/3G1216RL-P-XXX-X.pdf

-John

Hi,

I think it’s TDMA/FDMA, not spread spectrum. Each channel is about
30KHz.

Best regards,
Cheng C.

On Wed, Jan 29, 2014 at 10:14:19AM +0800, Cheng C. wrote:

From the spectrum (attached), I can see the Inmarsat signal, but no sign of
Thuraya signal. Anyone has suggestion about how to receive the thuraya
signal?

Are you aware of OsmocomGMR[1]? It’s a project that is aimed at
receiving the Thuraya signals. Although, AFAIK, so far only Thuraya2 was
received, due to the physical location of the people involed.

Kind regards,
-Alex

[1] http://gmr.osmocom.org/trac/

Hi,

Are you aware of OsmocomGMR[1]? It’s a project that is aimed at
receiving the Thuraya signals. Although, AFAIK, so far only Thuraya2 was
received, due to the physical location of the people involed.

No, no we got some Thuraya 3 reception as well.

Dimitri had some vacation in Asia and he of course had packed SDR and
antenna for the trip :slight_smile:

This is the map with the spot beam we captured :

http://bit.ly/nInTOi

The green ones are Thuraya 3. (Each spot beam reports its own GPS
center location in the broadcast channel).

Cheers,

Sylvain

The polarisation loss in your case might be 30 dB. Have a look into
that.

Regards,
Vanush

Hi,

From the spectrum (attached), I can see the Inmarsat signal, but no sign of
Thuraya signal. Anyone has suggestion about how to receive the thuraya
signal?

Several issues to improve :

  • Your antenna has the wrong polarization, this will definitely kill
    your signals
  • You can also try more directional types of antenna like described
    here : https://gmr.osmocom.org/trac/wiki/Receiver_Setup
  • Ideally if you have some GSM1800 nearby, it’s good to have a filter
    as those signals tend to swamp / saturate inputs when amplified …

fwiw, I have had some success receiving thuraya by using a GPS antenna
and just using a big metal surface as a reflector (to swap
polarization).

Cheers,

Sylvain

Hi all,

Thanks! I’ll give it a try once I get a LHCP antenna.

Best regards,
Cheng C.

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