Quoting jgorman01 <[EMAIL PROTECTED]>: > Op amps may very well be a good solution for a very linear > amplifier. However, my point is how many current amateur radios use > this much more expensive solution in their audio chains?
You would be surprised to find them used in many ham transceivers in the last 20 years. > My transceivers are dated, as I suspect many hams are, but not so old > that they couldn't have used op amps for a very fine wide bandwidth > amp. I'll be honest, I also don't know what kind of phase shift > problems op amps will have even if the amplitude variations are > minimized. > On the other hand, it has been a while since I investigated op amps > and they had some issues. At the time, there were none offered that > could deal adequately with a balanced modulator (RF mixer) either > because of the toroids used in a balanced modulator nor could they > provide the +7 dBm or higher powers needed for this purpose. I think that power is the least important issue in a balanced modulator. For some time MC1496's, diode quads and CMOS switches have given very good carrier suppression and high linearity, which are key issues for a balanced modulator, delivering about 0 dBm. Power can be raised with an amplifier stage after the balanced modulator. At this point, I would not sacrifice any of those parameters for power. > Bipolars were the best solution for this type of need. In addition, > power supply requirements, i.e., +12/-12 volts to get good common > mode rejection was also needed. The available devices nowadays have solved many of those limitations, including devices designed for a single supply. Besides, it is not that difficult to generate the -Vee voltage with a small switching regulator inside a shielded case. Jose, CO2JA ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program. __________________________________________ 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/
