and.. Using the ADC in the STM32 undersampling at 10.5 meg signal at 2 Msps.
Are you sure the STM ADC sample and hold is actually any good at 10 MHz ? 1st adjacent channel performance (signals that get through the crystal filter) will be problematic for the ADC because the SFDR / IMD performance of the ADC where the S&H is poor will be rather awful. Additionally, the stopbands of the first IF filter for a cheap radio have got to be at least 60dB down, otherwise strong off channel frequencies will be aliased down into the baseband... A good radio would be 120dB..... keep learning ! Nice work so far. Nicely explained in your blog. you should have been a teacher. cheers On 26/02/2015 9:08 AM, David Rowe wrote: > Hi Helmut, > > Can you please tell me how you worked that out? My next step is to add > gain to balance MDS and IP3 but not sure how you obtained those numbers! > > Yes the radio as it stands requires another design pass. At this stage > it is a "proof of concept" to test the novel features: such as the use > of a uC for most of the tuning, and extreme hardware simplicity. > > Thanks, > > David > > On 26/02/15 08:09, Helmut wrote: >> Hello David, >> >> a rough simulation of that SDR design predicts a rather deaf radio: Total >> noise figure = 38 dB, MDS=-95dBm @ 12,5kHz System BW, Input IP3 = -20 dBm. >> I would suggest at least a 20 dB preamp with high IP3 performance in front >> of the ADC. So you will achieve a MDS of -114 dBm. Sure no splendid value, >> but will detect some VHF signals, hi. >> >> 73, Helmut, DC6NY >> >> -----Ursprüngliche Nachricht----- >> Von: David Rowe [mailto:[email protected]] >> Gesendet: Dienstag, 24. Februar 2015 22:16 >> An: [email protected]; [email protected] >> Betreff: [Freetel-codec2] Simple SDR for VHF FreeDV >> >> Hello, >> >> To support VHF FreeDV developments I've been working on a really simple and >> very open SDR architecture for VHF radio: >> >> http://www.rowetel.com/blog/?p=3884 >> >> Glen and Matt - would appreciate you suggestions on appropriate input BPF >> filtering and a VHF mixer. Also pls let me know if you see any show >> stoppers in this architecture. >> >> Cheers, >> >> David >> >> ---------------------------------------------------------------------------- >> -- >> Dive into the World of Parallel Programming The Go Parallel Website, >> sponsored by Intel and developed in partnership with Slashdot Media, is your >> hub for all things parallel software development, from weekly thought >> leadership blogs to news, videos, case studies, tutorials and more. Take a >> look and join the conversation now. http://goparallel.sourceforge.net/ >> _______________________________________________ >> Freetel-codec2 mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> >> >> ------------------------------------------------------------------------------ >> Dive into the World of Parallel Programming The Go Parallel Website, >> sponsored >> by Intel and developed in partnership with Slashdot Media, is your hub for >> all >> things parallel software development, from weekly thought leadership blogs to >> news, videos, case studies, tutorials and more. Take a look and join the >> conversation now. http://goparallel.sourceforge.net/ >> _______________________________________________ >> Freetel-codec2 mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/freetel-codec2 >> > ------------------------------------------------------------------------------ > Dive into the World of Parallel Programming The Go Parallel Website, sponsored > by Intel and developed in partnership with Slashdot Media, is your hub for all > things parallel software development, from weekly thought leadership blogs to > news, videos, case studies, tutorials and more. Take a look and join the > conversation now. http://goparallel.sourceforge.net/ > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > -- - Glen English RF Communications and Electronics Engineer CORTEX RF & Pacific Media Technologies Pty Ltd ABN 40 075 532 008 PO Box 5231 Lyneham ACT 2602, Australia. au mobile : +61 (0)418 975077 ------------------------------------------------------------------------------ Dive into the World of Parallel Programming The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
