Spot on. What about desgining and building a "QRP" radio for digital use.
Its seems to me that some of the problems you mention are because the radio is made for many modes. What if the radio was just build for RTTY, PACKET, PSK31, PACTOR, etc? Instead of a 300-3500Hz audio bandwidth, it could be much tighter and desigend for the exact mode being used. After all, isn't that the way CW QRP rigs are desigend? They only have to work with a very narrow bandwidth. Charlie Crizer, KF4MNE Fairfax County (Alexandria) Virginia, US QTH: 38-47.96N / 77-05.17W - FM18kt [EMAIL PROTECTED] [EMAIL PROTECTED] - Winlink2000/Airmail -----Original Message----- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of jgorman01 Sent: Wednesday, September 20, 2006 10:23 To: digitalradio@yahoogroups.com Subject: [digitalradio] digital modes and THE RADIO I've been reading all the posts over the last several weeks about single tone/multi-tone, baud/bps, narrow/wide, etc. digital modes/modems. The one thing I see missing is any discussion of the actual RADIO's being used in these systems. Kind of funny in a digital RADIO forum populated by amateur RADIO operators. Perhaps I am just too impatient and the discussions will eventually end up discussing the radios being used. Some of my observations. Lots of discussions about specifications for different modems and their operation. I haven't seen any discussion about the corresponding specifications of the radios they are connected to. Just wonder how ham radio transceiver audio chains, mixers, filters, and RF chains, both transmit and receive, compare to the mil spec transceivers used with mil spec modems? Audio purists spend thousands of dollars on pink/white noise generators, equalizers, audio amps, speakers, etc. to insure flat responses. What kind of distortions do you think are allowed in ham radio audio chains. Are there amplitude/frequency variances introduced in the preamps and amps? Are there phase/frequency variations introduced in the mixers, amps, and filters? Do these have any effect on trying to cram high speed modem tones through the system? I suspect that there can be as much or more effects due to these variables as propagation introduces. Has anyone measured the difference between a $50,000 Harris HF tranceiver designed for this purpose and a $500 Icom tranceiver to see if the throughput is better? Perhaps I'm just an old fogey who still enjoys messing with and building radios and am not competent enough in the digital modes to add much to this discussion. However, I can assure you building a mic preamp or a receive audio amp that has a flat amplitude response over 300 Hz to 3500 Hz is no mean feat let alone the phase differences that can be introduced by using heavy feedback to acheive this response. I can also tell you from first hand experience that building a crystal filter without amplitude/phase variances is very difficult. I just wonder if some of this shouldn't also be discussed along with the "digital" side of the conversation. A system must have all of its individual components discussed and designed. The RADIO is a very important part of this. Jim WA0LYK 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 [Non-text portions of this message have been removed] 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/
