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jvierine / chirpsounder2

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a frequency bias of around 3.053KHz #3

Open niuniu1138 opened 3 years ago

niuniu1138 commented 3 years ago

Hi,I'm using a receiver x300 and ubx with 12.5MHz center frequency, 25MHz sample rate and GPSDO.

thor.py -m 192.168.10.2 -d "A:0" -y "TX/RX" --clock_source 'gpsdo' --time_source 'gpsdo' -c ch1 -f 12.5e6 -r 25e6 -g 0 /dev/shm

I read the h5 data using matlab and found that there is a frequency bias of around 3.053KHz in all the data, why is this? Is it because my parameter setting is wrong?

One more question, how can I know where the ionogram I receive is emitted from?

Thanks!

alexchartier commented 3 years ago

The ubx has a listed minimum frequency of 10 MHz: https://www.ettus.com/all-products/ubx160/

Your command targeted 0 - 25 MHz. I'm not sure what happens inside the radio if you do that - I'm surprised it didn't give an error. The solution would be to install a LFRX daughterboard (https://www.ettus.com/all-products/lfrx/). If you happen to have a BasicRx, you could use that (but in that case you have to specify a band starting at/above 1 MHz, e.g. centerfreq = 13 MHz, samplerate = 25 MHz). If you stick with the UBX, you could record 10-20 MHz. That could show the upper part of some of the sounders. [https://www.ettus.com/wp-content/uploads/2019/01/prod_lfrx_01_lg-650x630.jpg]https://www.ettus.com/all-products/lfrx/ LFRX Daughterboard 0-30 MHz Rx | Ettus Research, a National Instruments Brand | The leader in Software Defined Radio (SDR) - Ettus Research - The leader in Software Defined Radio (SDR) | Ettus Research, a National Instruments Brandhttps://www.ettus.com/all-products/lfrx/ Overview The LFRX daughterboard is a low-cost daughterboard that provides direct access to the ADC inputs. www.ettus.com

[https://www.ettus.com/wp-content/uploads/2019/01/UBX_160-Large_2-1200x630.jpg]https://www.ettus.com/all-products/ubx160/ UBX 10 MHz - 6 GHz Rx/Tx, 160 MHz BW - Ettus Researchhttps://www.ettus.com/all-products/ubx160/ The UBX-160 is a wide bandwidth transceiver for the USRP Software Defined Radio (SDR) platform. The UBX-160 provides 160 MHz of bandwidth and 10 MHz to 6 GHz frequency coverage. www.ettus.com

From: niuniu1138 @.> Sent: Tuesday, June 15, 2021 2:09 AM To: jvierine/chirpsounder2 @.> Cc: Subscribed @.***> Subject: [jvierine/chirpsounder2] a frequency bias of around 3.053KHz (#3)

Hi,I'm using a receiver x300 and ubx with 12.5MHz center frequency, 25MHz sample rate and GPSDO.

thor.py -m 192.168.10.2 -d "A:0" -y "TX/RX" --clock_source 'gpsdo' --time_source 'gpsdo' -c ch1 -f 12.5e6 -r 25e6 -g 0 /dev/shm

I read the h5 data using matlab and found that there is a frequency bias of around 3.053KHz in all the data, why is this? Is it because my parameter setting is wrong?

One more question, how can I know where the ionogram I receive is emitted from?

Thanks!

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jvierine commented 3 years ago

The UBX might also have a tuning offset. I think the true center frequency is stored in the metadata by thor.py. I rely on the value in the .ini file. I’ll see if I can change the code to use the center frequency in digital rf.

niuniu1138 commented 3 years ago

Thank you very much, I will go find the LFRX daughter board to test it.

And I also want to know,where the ionogram I receive is emitted from? Thank you.

alexchartier commented 3 years ago

The program only calculates virtual range of the signal, but the different sounders use different chirp-rates. In most cases, you should be able to figure out which ones you are receiving from that. If you can attach an ionogram and tell us where you are, we could help identify it

From: niuniu1138 @.> Sent: Thursday, June 17, 2021 8:08 AM To: jvierine/chirpsounder2 @.> Cc: alexchartier @.>; Comment @.> Subject: Re: [jvierine/chirpsounder2] a frequency bias of around 3.053KHz (#3)

Thank you very much, I will go find the LFRX daughter board to test it.

And I also want to know,where the ionogram I receive is emitted from? Thank you.

— You are receiving this because you commented. Reply to this email directly, view it on GitHubhttps://github.com/jvierine/chirpsounder2/issues/3#issuecomment-863183905, or unsubscribehttps://github.com/notifications/unsubscribe-auth/ABCK6UGSJID2W6WKNZCYIBLTTHQTDANCNFSM46WRVZDQ.