Hello Kristoff, Hmmm, I can see how inverting audio would be a trap when driving a FM system - it would deviate the wrong way.
Couple of questions: 1/ What other parameters is GMSK sensitive to, for example how about the mapping of sound card audio levels to FM deviation,, of HP/LP filtering of PC sound card audio? 2/ On a PC based VHF system, is there a we can include tuning tools so people can make sure their transmitted signals will be compatible (e.g. waveforms deviating the right way)? I understand specifying a certain USB sound card is one way. 3/ What is the relationship with GMSK and channel bit rate on a PC-FM radio system? For example does halving the bit rate get us a 3dB performance increase in terms of BER? Thanks, David On Mon, 2012-05-21 at 22:16 +0200, Kristoff Bonne wrote: > Hi Daniel, > > > Well, the situation now is that Peter -who is also on this list- has > started to work on a proposal for a bitstream format. > > > Hardware-wize, the most easy thing to do now, is just use a > "soundcard" modem on a PC or some kind of development board. > > One interesting way to do this is as done by the "freestar" project > which use a PC and an external USB audiofob which is known to work > well. > " http://www.va3uv.com/freestar.htm > > That's also the approach I use for my gmsk modem (which is actually > largely based on the gmsk encoder/decoder software part of the > "pcrepeatercontroller" project of Jonathan G4KLX); but -in my case- it > runs on a ARM development board. > See http://villazeebries.krbonne.net/hamstuff/?p=106 for some info on > it. > The advantage of using an external USB audiodevice is you do not have > to deal with different behaviour of the PC-based audio devices. (e.g. > the audio device on my laptop actually inverts the audio it receives > and sends). I also tested a griphin iMic with mixed result. > > Of course, this is only one approach. One other way would be to use > some kind of chip with embedded ADC and with sufficiant CPU power as > the standalone gmsk modems do. > > > As I focus myself on "modem" part in this, my goal now it to get > something ready so we can start experimenting. As everybody has a > computer anyway, I think it makes sence to make that the main > development platform at this stage. > Porting it to other platforms can be done latter. > > We'll start with something very simple: 4800 bps -what we already > have- and minimal processing in the modem: only deal with > syncronisation and -for the rest- just pass everything transparent. > This would enable other people to experiment with things like FEC, > interleaving, scrambling, ... etc. without having to change the modem > part. The goal is gather some knowledge and experience so what modes > make sence and what do not, > > In the mean time, we can look into a version of the modem at other > speeds (2400 bps, 2000 bps, 1600 bps, ...). > > > > > 73 > Kristoff - ON1ARF > > > > > > > On 20-05-12 22:19, Daniel Mundall wrote: > > > We've designed a digital 10w 2m radio that we're just testing at the moment. > > Any input would be great. > > Have a look at hamcell.com > > 73's > > Daniel VA7DRM > > Sent from my iPad > > > > On 2012-05-20, at 1:00 PM, Kristoff Bonne <[email protected]> wrote: > > > > > Hi Matthew, > > > > > > > > > Well, I try not to look to much at that radio or else I might have to > > > find yet another excuse if my wife asks me why I need "yet another radio". > > > (I just bought a 2m/4m portable and a "modified CB" station to monitor > > > our new local 10 meter repeater one week ago). > > > :-) > > > > > > > > > Anycase, the goal is to have a something so that people can experiment > > > with it with as less hardware requirements as possible. > > > My preference would be just a basic radio interface board and a couple > > > of USB audio-fobs that are known to work well. > > > > > > We first need to gain some experience with this. What modes or speeds > > > work best, etc. > > > I also had a request of somebody to think of possible issues to use this > > > over satellite links. That's also an interesting thing to look at. > > > > > > > > > > > > 73 > > > Kristoff - ON1ARF > > > > > > > > > On 20-05-12 16:38, Matthew Pitts wrote: > > > > Kristoff, > > > > > > > > Sounds good, and I knpw of a transceiver that we could use this with > > > > that will be available later this year. In fact, we could do something > > > > a bit more complex, as far as coding and it should easily handle it. > > > > > > > > http://www.nwdigitalradio.com > > > > > > > > Matthew Pitts > > > > N8OHU > > > > > > > > > > > > > > > > ------------------------------ > > > > On Sun, May 20, 2012 10:24 AM EDT Kristoff Bonne wrote: > > > > > > > > > Hi, > > > > > > > > > > > > > > > We are looking into the possibility to create an additional modem for > > > > > codec2, but for VHF/UHF frequencies. > > > > > > > > > > As a first "proof-of-concept", this would be to convert my gmsk modem > > > > > to > > > > > a new format to carry codec2 voice. This would have the advantage that > > > > > the hardware requirement to run this would be minimal. > > > > > > > > > > > > > > > > > > > > Sofar, I see two options: > > > > > - A 2400 bps modem: > > > > > This would be quite sufficient to contain codec2 voice (at 1400 bps), > > > > > additional syncronication patterns + some additional data and even an > > > > > options 2/3 FEC for the voice part. > > > > > > > > > > - A 4800 bps modem: > > > > > This would then give even more headroom, e.g. tu use a 1/3 FEC for > > > > > voice > > > > > (which would make it much more robust) and still have headroom for > > > > > syncronisation patterns and some additional data > > > > > > > > > > > > > > > > > > > > The 2400 bps modem would have the advantage of the lower bandwidth > > > > > (better S/N ratio, better suited for e.g. bands with limited > > > > > bandwidth: > > > > > 10 meter, 4 meter). > > > > > The 4800 bps modem would have the advantage of the better FEC. > > > > > > > > > > > > > > > Does anybody have a comments on this? > > > > > > > > > > > > > > > > > > > > 73 > > > > > Kristoff - ON1ARF > > > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > > > Live Security Virtual Conference > > > > > Exclusive live event will cover all the ways today's security and > > > > > threat landscape has changed and how IT managers can respond. > > > > > Discussions > > > > > will include endpoint security, mobile security and the latest in > > > > > malware > > > > > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > > > > _______________________________________________ > > > > > Freetel-codec2 mailing list > > > > > [email protected] > > > > > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > > ------------------------------------------------------------------------------ > > > > Live Security Virtual Conference > > > > Exclusive live event will cover all the ways today's security and > > > > threat landscape has changed and how IT managers can respond. > > > > Discussions > > > > will include endpoint security, mobile security and the latest in > > > > malware > > > > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > > > _______________________________________________ > > > > Freetel-codec2 mailing list > > > > [email protected] > > > > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > > Live Security Virtual Conference > > > Exclusive live event will cover all the ways today's security and > > > threat landscape has changed and how IT managers can respond. Discussions > > > will include endpoint security, mobile security and the latest in malware > > > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > > _______________________________________________ > > > Freetel-codec2 mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > ------------------------------------------------------------------------------ > > Live Security Virtual Conference > > Exclusive live event will cover all the ways today's security and > > threat landscape has changed and how IT managers can respond. Discussions > > will include endpoint security, mobile security and the latest in malware > > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > > _______________________________________________ > > Freetel-codec2 mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 > > > > > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ Freetel-codec2 mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
