Yea, nice work David. What SNR do your simulations say the modem will work to, BER =1/50, BER = 1/1000 ?
I reckon, for a readability of 3/5 you will get the following on a decent radio T sky=290k, NF RX = 627k (a reasonable VHF receiver without any thing fancy) Ttot = 917k analog FM '25k' : -123dBm (assumption - 4dB CNR requirement) codec2 GMSK , linear radio, SSB passband : -130dBm (assumption - 6dB CNR requirement) 3/5 difference = 7dB. 5/5 readibility : analog FM '25k' : -119dBm (assumption - 8dB CNR requirement) codec2 GMSK , linear radio, SSB passband : -127dBm (assumption - 8dB CNR requirement) 5/5 difference - 8dB. note- my assumptions of 6 or 8 dB CNR req for codec2 gmsk. I'm assuming you are not coherently detecting But, David, if you are going to use a SSB radio, then why not QPSK ? That will be good for another 3dB, perhaps, depending on how hard you want to push your amplifier. The advantage of GSMK is the use of a non linear amplifier, given. g On 6/02/2015 9:46 AM, David Rowe wrote: > Thanks Glen - I have replied to your comment on the blog post. > > Cheers, > > David > > On 06/02/15 08:40, glen english wrote: >> You can't compare apples for apples this way, at least not as these >> things are used in the REAL WORLD >> >> It is IMPROPER to compare an analog and digital system on SNR because >> they are very different beasts. Of course the digital will outperform >> the analog system one it get sa lower BER. >> >> The test should be , at what power level can you achieve a readability 5 >> conversation ? , at what power level can you achieve a readability 3 >> conversation ? >> The power level requird should be normalized for a 0dB noise figure (so >> the front end of the receiver system is taken out of the equation) >> >> Why ? because that is how we use our radios. >> >> however >> >> I have no doubt that with a modem operating with a SSB radio, it will >> outperform the FM radio hands down. >> >> >> On 6/02/2015 7:04 AM, David Rowe wrote: >>> Daniel, VA7DRM, and I have been doing some tests using GMSK, Codec 2, >>> and real radios. It appears we are getting at 10dB gain over Analog FM >>> and 1sts gen DV systems: >>> >>> http://www.rowetel.com/blog/?p=3856 >>> >>> - 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 >>> Freetel-codec2@lists.sourceforge.net >>> 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 > Freetel-codec2@lists.sourceforge.net > 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 Freetel-codec2@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freetel-codec2
