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/
 



Reply via email to