--- jgorman01 <[EMAIL PROTECTED]> 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.
At least I am assuming a COTS radio, 300 to 2700 Hz audio bandwidth. That's what I have. > 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. So far....10%....- 20 dB at worst case. Should be better for complex modulation formats. > 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. If you stay near the center of the passband and shy away from the slopes, shouldn't create serious problems > 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? Maybe the performance difference does not justify the price difference...makes me remember the $500 hammer... > 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. Well, the problem in the past has been more of inapropiate modulation and coding formats rather than radio insufficiencies, in general. > 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. Of course. Certainly my old HRO or a Viking Valiant is insufficient for this. It is generally accepted that it takes a synthesized radio to start with. 73 de Jose, CO2JA __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com 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/
