30 kHz filter for satellite reception

[Botox200]

Since the decoding of earth-orbiting satellites, like NOAA, is unfortunately not planned, it would be nice if the audio reception on FM could be supplemented with a 30 kHz filter.

[Mainstreamlos]

I want HackRF Portapack H2+R4 Mayhem with CLPD: QFP100 and LTK8002D Audio amp and WM8731L QFN Codec. Is this the latest version with most compability, or did anyone recommend another version? I hope anyone can help me.

Do you have the H2-R4 Model with the Codec above? Is this model the latest version or is there a newer one? Please let me know. I made some screenshots of the model I mean.

Thank you

Regards Jan Bensch

[gullradriel]

@Mainstreamlos open your own issue or better go read the wiki if not done and ask on discord :-)

@botox200 30Khz on NFM or WFM ?

[Botox200]

30kHz on WFM would be great. Thank you.

[Brumi-2021]

Hi @Botox200 , I captured many times NOAA APT with other equipments and also some other digital weather satellites .

But do you need FM audio demodulated WAV signal or do you need I,Q, captured signal ? I guess that you need audio FM demodulated, and feed it to WXtoImg . But I do not remember , our recorded audio sampling rate will be ok for you , or you will convert if needed ? And why you need 30 or 40 Khz ? Maybe 30Khz is ja litle too small , not ? did you try to record current BW = 200Khz , the 137 Mhz , or it is really too much bandwith and getting too much adjacent noise ? Cheers Cheers,

[Botox200]

Well, thinking of a 30 kHz (or 40 kHz) bandwith demodulated WFM mono signal, recorded in a .wav file for later feeding WXtoImg or similar. 200kHz won't work. So, this might be the equipment:

[Brumi-2021]

Hi @Botox200 , i see . Here in that link , it says BW 34Khz .

It can be done adding a BW filter 34Khz inside WFM, but now I am quite busy. Then if anyone can implement it now, perfect . If not I will try to consider it for next weeks . cheers ,

[Brumi-2021]

Hello @Botox200 are, you available through discord ? Are you familiar about unbrick your unit with DFU ? I got a preliminar binary version , but you may need two steps to write it , due to my different compile gcc version.

8th of may 23 Forget my previous comments about two steps and the preliminar version. I already released yesterday the final tested version. Is it available in today’s nightly. I think to capture the sat from lower angles you may need some extra LNA with SAW filter or a better antenna . But please check with your current setting and report to us .

Chears,

[Brumi-2021]

Hi @Botox200 , did you tried that requested feature ? It is already applied in latest nightly. How is going ? Did you had time to check it? We will appreciate your experience feedback. Cheers

[Botox200]

Hi @Brumi-2021 I will flash and test the new firmware this weekend.

Thank you for your commitment. Great.

[gullradriel]

Be sure to flash last nightly so most of the app that can will have the options

[Botox200]

I've flashed the ROM and testet the function with NOAA15. I could hear a clear satellite sound. Unfortunately when pressing the RECORD button the system crashed. A second attempt to record the signal was successfull, but the volume level of the WAV audio file was too low for WXTOIMG.

[Brumi-2021]

Hi @Botox200 , i also tried to capture this weekend some high elevation NOAA APT pass (>70°) but just with simple default telescopic antenna , and I could not hear anything.

All my previous successful experiences was always with different set up: RTL2838U + external 137 Mhz LNA + good circular polarization QFH antenna.

Then in your case , you already have a better antenna than me , but I think that you will still need to add some additional LNA 137Mhz (better with SAW filter) . That is my opinion.

Cheers

[Botox200]

Works with the latest version. The recorded audio file can be decoded with noaa-apt.

[Brumi-2021]

HI @Botox200 , glad to hear it !!! What was the difference compared to previous week end that did not work ?
Now different satellite NOAA18 or 19 ? Or better antenna position ? Or less background noise changing sat freq ?

I guess that you used AMP 1 ,, Gain maybe 32 - 40 and adjusting VGA to not saturate + WFM filter of 40 Khz

Cheers

[Botox200]

hi @Brumi-2021 The difference was using the latest Nightly Release 2023-05-19. However, I don't think that was the main reason.

Rather it was the fact that I decoded the .wav file with noaa-apt instead of importing it to (x)wxtoimg. In noaa-apt the .wav file is decoded first, and than - in a second step - is processed into an image.

noaa-apt https://noaa-apt.mbernardi.com.ar/

Thank you for the feature.

[Brumi-2021]

Ok, @Botox200 thanks for the update . Congratualtions your first NOAA APT decoding step!.... I started same as you , catching small pieces of the pass. You still have room to improve to capture the max. 15 min of the max. pass.

FYI , But after improving the system , this was captured with cheap RTLSDR + LNA with SAW filter + QFH antenna , several years ago.

Cheers,