jgorman01 wrote: > Ok, folks, surely there are several of you who know what your rigs > design is. What do some of the newer, higher priced and lower priced > rigs use in their audio chains for amps and preamps? Do they have > sophisticated feedback networks to equalize the amplitudes over the > passband or are they simple amplifiers?
No, just simple amplifiers as far as I know. AFAIK, only the higher end radios, with DSP audio processors and DDS carrier generators do some response compensation. > Jose, I am not arguing that there aren't better ways to do things. > What I am saying, is that amateur radios have not always done it the > best way, but instead the most inexpensive way. Perhaps some of the > newer more expensive rigs have better solutions but I'll bet the > lower end ones don't. Jim, I know. I did redesign a few things in my old Swan 700S, a low end radio, and I would qualify some of them as plain stupid mistakes. One of them was feeding the microphone preamp from the screen grid of the transmit mixer. Beautiful audio...only while receiving. When transmitting, voltage dropped and audio linearity suffered a lot. It DID improve just by finding another place to tap the voltage from. It worked far better on digital by tapping the audio before the audio power amplifier.... The AFC was ME... The FT-757 I got later really eased my life. > What does your current rig have for an audio chain prior to the > balanced modulator? It has a custom thick film IC. >Is it optimized to handle wide bandwidth > multi-tone digital signals, and not just in the audio but through > out? If not, then the decision on what modem design would be > recommended must take this into account. I believe it does not, considering it is a well designed but OLD radio, from the late 70's. Nevertheless, it behaves quite well, even on Pactor (I, II, III....). It was a piece of old junk I brought back to life. It was well worth the effort. Using the RIGHT audio input level is very important. I built my own interface with two transformers and an optocoupler. Thunderstorms here are not child's play. I am using a salvaged, 10K to 600 ohms broadcast quality transformer on the TX side. > If one of the objectives is wide acceptance, then one must take into > account the capabilities of a wide number of amateur radios. Yes, and also, as W4LDE said before, we must face our role as operators, as not everything is plug and play. A couple of weeks ago I found a DX station on 20 attempting his first QSO's on PSK31, with a very broad signal, some 600 Hz wide and -9 dB IMD. I suggested him to backoff his soundcard output....he just closed the mic gain a bit, reduced power, but the signal stayed as wide as before, indicating a choked up mic preamp. Finally, I desisted, fearing I would soon be impolite... 73 de Jose, CO2JA __________________________________________ XIII Convención Científica de Ingeniería y Arquitectura 28/noviembre al 1/diciembre de 2006 Cujae, Ciudad de la Habana, Cuba http://www.cujae.edu.cu/eventos/convencion 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/
