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<blockquote data-quote="s-band" data-source="post: 1159569" data-attributes="member: 407744">[USER=369937]@Terryl[/USER] Don't give up with Satdump, is can be reliable, I used it continuously for a month or more when STA was close. Most of the following is based on other use of Satdump but I found an RTL stick and looked at that. One problem is that there is no IQ correction to remove the zero term in Satdump's pre-demod plot hence the big spike in the middle on your plot. It appears that NOAA is present there but you need to adjust the FFT length, try 65k, and sample rate or decimation so you see about 500kHz. Then play with the FFT levels to get a better view (i.e. expand it vertically). Other SDRs (e.g. Airspy, Pluto, USRP) seem to have inherently better IQ balance than the RTL hence lower DC term.The examples in [USER=415308]@ozumo[/USER] 's link show IQ correction enabled on the SDR++ plots and DC blocking (METEOR). In the case of Satdump, it might be better to offset the wanted signal to clear the DC spike in the middle. Remember that the RTL only has 8 bits resolution so it has&nbsp; restricted dynamic range and needs careful amplitude adjustment to keep it in the sweet area. Don't use AGC.</blockquote>

[QUOTE="s-band, post: 1159569, member: 407744"] [USER=369937]@Terryl[/USER] Don't give up with Satdump, is can be reliable, I used it continuously for a month or more when STA was close. Most of the following is based on other use of Satdump but I found an RTL stick and looked at that. One problem is that there is no IQ correction to remove the zero term in Satdump's pre-demod plot hence the big spike in the middle on your plot. It appears that NOAA is present there but you need to adjust the FFT length, try 65k, and sample rate or decimation so you see about 500kHz. Then play with the FFT levels to get a better view (i.e. expand it vertically). Other SDRs (e.g. Airspy, Pluto, USRP) seem to have inherently better IQ balance than the RTL hence lower DC term. The examples in [USER=415308]@ozumo[/USER] 's link show IQ correction enabled on the SDR++ plots and DC blocking (METEOR). In the case of Satdump, it might be better to offset the wanted signal to clear the DC spike in the middle. Remember that the RTL only has 8 bits resolution so it has restricted dynamic range and needs careful amplitude adjustment to keep it in the sweet area. Don't use AGC. [/QUOTE]

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