Yes, you're almost dead one what I was trying to say. You just can't ignore such an important part of the system by just assuming that the RADIO (any ham radio) will perform in the manner you wish. What are the requirements for a RADIO to optimally handle the modem signals being discussed? You have to know this side of the equation before being able to decide upon modem characteristics. I just pointed out some of the audio issues. There are many other amplitude/phase variations introduced in each stage of a tranceiver from if/rf amps, to filters, mixers, etc. And, you must take into account that not only does a transmitter introduce these but the receiver does also. So, in essence, you can double some of the variables. Jim WA0LYK --- In digitalradio@yahoogroups.com, KV9U <[EMAIL PROTECTED]> wrote: > > Jim and group, > > Any modems that are used for amateur radio, hardware or software, > generally would need to be compatible with the kind of equipment that we > use in order to enjoy wide adoption. It is true that some ham equipment > will not work well with modes that require fairly stable frequencies. > > Another thing that I came across in my web searching was that amateur > equipment generally has group delays that make it difficult to even > employ some of the modems we have been discussing. > > I wonder if any of the modem experts might comment on that. > > 73, > > Rick, KV9U > > > jgorman01 wrote: > > >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 > > > > > > > > > > > > > > > > > > > > > > > > > > >
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/
