It seems that the MIL-STD/STANAG modems frequently use a variety of wavefoms depending upon the speed.
An example would be the STANAG 4539 suite of standardized waveforms. They are not all the same waveforms. Starting at 75 bps data modes it uses Walsh modulation and switches to BPSK at 150 bps, QPSK at 1200, 8-PSK at 2400 data and voice and then for faster voice up to 64-QAM at 12800 bps. This suggests that a highly adaptive modem may not necessarily need only one modulation type. STANAG 4285 is one exception and uses only PSK waveforms from 75 to 3600 bps. It is not easy to find much on the baud rate but I did find that the STANAG 4529 modem which is intended for 1240 Hz wide bandwidths (marine ship to shore) use 1200 symbols per second. This is what I have considered to be the baud rate. This is a "narrower" mode thus the slower baud rate. The one thing that comes across from comparing speeds vs. S/N is that there are really are no fast modems that can go down below zero dB. In fact, to get data rates of 1200 bps it is often around +10 dB. A lot of this information came from a web site from Rapid M a company in South Africa. 73, Rick, KV9U John Champa wrote: > Rick, > > Now that is some interesting research! More please. > > Thanks, > John > K8OCL > > ----Original Message Follows---- > From: kv9u <[EMAIL PROTECTED]> > Reply-To: [email protected] > To: [email protected] > Subject: Re: [digitalradio] Re: RSM2400 / MIL-STD-188-110 > Date: Fri, 16 Mar 2007 17:00:21 -0500 > > I was able to find some interesting data on poor channel performance of > the 110A modem from one company: > > http://www.etools.de/software/telekommunikation/komponenten/milstd188110a.htm > > Depending upon the BER you can tolerate, it appears that the 2400 bps > speed can only handle around +10 to +14 S/N dB. The slower bps rates can > work to around zero S/N. Te 150 bps shows something around -1 to -4. > > Another interesting specification is the the multipath tolerance. They > claim 6 msec at 2400 bps, 8 ms from 150 to 1200 bps, and 12 mec at 75 > baud. That seems to have good ability to cope with ISI. > > Now these are the bps rates. Isn't the baud rate the same 2400 baud, all > the time for this modem, contrary to what Bonnie claims? > > 73, > > Rick, KV9U > >
