..maybe it is "obviously" :-) OFDM has been tried for DV and it works (see WinDRM available at n1su.com) but it has issues for the HF ham radio operator. Try it.. it needs CODEC2!
OFDM is being used very successful/y with "EasyPal" a picture transfer program for HF that has been in use for several years now with near 24 hour activity worldwide across many of the hambands. Listen for it on 14.233kHz. Mel ----- Original Message ----- From: "Gregory Maxwell" <[email protected]> To: <[email protected]> Sent: Thursday, December 06, 2012 10:25 AM Subject: Re: [Freetel-codec2] OFDM for FreeDV? > On Wed, Dec 5, 2012 at 6:39 PM, Bruce Perens <[email protected]> wrote: >> I did a talk at Lawrence Berkeley Lab today. Because the group I am >> working >> with does a lot of things that look very close to radio, I showed Mel's >> recent video as an example of an Open Source project where we are doing >> real >> science. >> >> I got one technical question privately afterward, which is why aren't we >> using OFDM? This was prompted by the visibility of guard-bands between >> our >> carriers. >> >> Maybe this is an area for some future Open Source developer. Do you think >> it >> has the potential to further reduce our spectrum use? > > The main challenge with OFDM for amateur use is that the PAPR goes up > substantially with many carriers. > Even when your linearity is good (it certainly isn't for all ham gear, > but thats a prereq for OFDM) most ham gear is peak power constrained. > So poor peak to average ratio translates to lower output power. > > There are techniques to address this stuff. Some may be patented > though. See also my post in the thread "PAPR and handheld operation" > on this list and the following responses. > > Though sure OFDM is _obviously_ the way to go, after solving/ignoring > all other issues! :P > > ------------------------------------------------------------------------------ > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > Remotely access PCs and mobile devices and provide instant support > Improve your efficiency, and focus on delivering more value-add services > Discover what IT Professionals Know. Rescue delivers > http://p.sf.net/sfu/logmein_12329d2d > _______________________________________________ > Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
