Great information, Tony. Just the kind of real world stuff that we need. By the way, although there are similarities between the systems, it is interesting to note that:
AOR is a 50 baud OFDM system using 36 DQPSK carriers. For voice it uses AMBE2020 which I think is the same voice codec as in the D-Star system. The error correction for voice is Golay/Hamming, but with data it uses convolutional/Reed-Solomon. WinDRM uses between 29 to 57 COFDM QAM carriers, with QAM variable between 4-QAM and 64-QAM, with most of the main channel running on 16-QAM unless conditions are very good. If I understand it correctly, based upon symbols/frame (of 400 milliseconds), the baud rate must be similar except depending upon certain modes it may be 37.5 or 50 baud. So this seems to make sense. The AOR has training pulses and that might make it more robust plus the carriers are further apart in most cases compared with WinDRM and maybe that helps with more difficult conditons. However, the samples of audio really did not impress me very much and unless there was some other compelling reason for using DV on HF, it would seem difficult to warrant a move toward this technology. From what I can gather in talking with the digital SSTV folks, they have not moved toward DV when chatting back and forth when sending their images. 73, Rick, KV9U Tony wrote: >All: > >Performed a few informal path simulator tests with the AOR-9000 modem and >WinDRM. I used two laptops and Moe Weatley's PathSim. > >I wanted to first test each mode for sensitivity without any ionospheric >distortion. I used direct-path and slowly increased the white noise. > >I found that the decode threshold for WinDRM is much the same as what I've >experience on HF; about 8db signal-to-noise ratio. Going lower than that >will cause WinDRM to stop decoding completely. > >The decode threshold was lower with the AOR modem and it would still decode >down to 7db SNR with a hint of distortion. > >Degrading the SNR further down to 5db and then 3db would cause the signal to >become increasingly garbgled. It was interesting to still make out some >words at 3db SNR! > >Polar path distortion is always tough on digtial so I thought I'd try >Pathsims high-latitude simulation. > >WinDRM did very well with mild high-lat destortion and 13db SNR. On the >other hand, the AOR signal didn't do as well and would drop-out often. > >These simple tests are not counclusive, but I think it's safe to say that >the simulator can show certain mode characteristics that may show up on the >air to some degree. > >The AOR modem may hang-on a little longer than WinDRM as the signal fades; >albeit with some distortion and garbled decode, while WinDRM may handle >ionospheric distortion somewhat better. > >I have the clips if anyone is interested. > >73 Tony KT2Q > > > > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
