Goodness. This took a long time to get posted! Bonnie already answered the question very well. regarding OFDM, etc.
>From: "John Champa" <[EMAIL PROTECTED]> >Reply-To: [email protected] >To: [email protected] >Subject: RE: [digitalradio] First digital voice QSO ! >Date: Sun, 01 Oct 2006 13:36:12 -0400 > >Is what I am hearing true? That BPL has no affect on digital voice! > > > >From: "Andrew O'Brien" <[EMAIL PROTECTED]> > >Reply-To: [email protected] > >To: <[email protected]> > >Subject: [digitalradio] First digital voice QSO ! > >Date: Sat, 30 Sep 2006 21:06:27 -0400 > > > > > >I think John W2FS and I completed our first digital voice HF QSO this > >evening. > > > >John and I had a QSO on 14.236 MHz , USB. today September 30, 2006 from > >2315 to 2329 UTC.. We used WinDRM as the software, a SDR 1000 Flex > >radio, and ye olde Kenwood TS440. This involves digitalizing the signal > >via free soundcard based software , transmitting the data, and decoding >the > >data at the receive end. There is a 1-2 second "lag" as the >encode/decode > >processing takes places but otherwise the conversation is similar to any > >other voice QSO. > > > >We are rookies and this , and need to adjust the audio levels somewhat, > >However the audio quality using this mode is far superior to the normal > >analogue HF SSB signals. The process uses a 2.5 kHz bandwidth , SSB. > > > >Here is proof of my end of the QSO > > > > > > > > > >The above picture indicates reception of W2FS with a signal to noise >ratio > >of 22.5 , using 10 watts. (we live about 100 yard from each other !) >Using > >Mode B , 16=Amplitude Quadrature Modulation (16QAM) and the MELP codec. > >The waterfall in the picture above is best described by the WinDRM >software > >help file. > > > >Receive Waterfalls > >There are two waterfalls, the 'classic" waterfall with its sweep from the > >bottom of the display to the top. The OFDM spectrum will be shown with an > >even intensity level across its 2.3 or 2.5 KHz band width. Typically, >some > >change in intensity at the bottom and top of the spectrum (darker area) >may > >be seen but should not affect performance. Within the waterfall, three > >frequency pilots (carriers) of slightly higher intensity can be seen. >They > >stand out in the waterfall because they have higher gain (transmitted at > >twice the power). These pilots are modulated with known fixed phases and > >amplitude which optimize DRM's performance for initial synchronization > >duration and reliability. The high-lighted red markers of the >waterfall's > >sweep indicate where these pilots are located when the transmitter and > >receiver DC offsets match. The "moving" waterfall moves from top to >bottom > >with the red marker's indicating the position of the pilot signals > >remaining fixed at the top of the display. The moving waterfall adds a > >visual method to monitor the health of the decoded signal in the form of >a > >vertical line on each side of the waterfall spectrum. During the >decoding > >process, green vertical lines indicate data is being received without > >errors and red lines indicate errors were received (segments lost). >These > >green/red indicators move with the spectrum instantly showing when and > >where data errors occurred. The horizontal line across the top of this > >display indicates the bandwidth of the OFDM signal. The signal in the > >waterfall should fully extend the width of this indicator. > > > >John and I did this at our first attempt, so it is not a very difficult > >process. I had the software configured in less that 5 minutes. IF I can > >do it, everyone else will find it a no-brainer ! > > > >If you would like to give it a try, the free software can be found at > >http://n1su.com/windrm/ the software also decodes digital pictures sent > >via HF amazingly well. > > > >Let me know if you need help. > > > >Andy K3UK > ><< w2fsdv.gif >> > > 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/
