>
>RF design is not such a complicate matter, in theory, what's difficult
>is to deal with and to realize objects that doesn't introduce too many
>unknown parasitic parameters so modifying, in practice, the original
>(or supposed) electrical configuration. The difference between skilled
>and non skilled RF designer is mostly in the knowdledge of the above
>reality and in the ability to choose a configuration, or a device,
>that's not adding uncontrollable complications to the amplifier.
? Well put.
>The problem with non professionals when building or dealing with RF
>amplifiers (not necessarily power amplifiers) is not "to see" the
>presence of inherent parasitic parameters in a circuit or, more
>frequently, in the way those amplifiers are then effectively built or
>modified by the amateur, a way that often introduces a number of
>parasitic parameters and messes everything.
? true
>A good device, like a Gaasfet transistor with large gain and stability
>at several GHz, has no problem at all to be controlled at much lower
>frequencies and risks of self oscillations are virtually absent if also
>the external circuit around the Gaasfet has been designed and realized
>in a proper way, all the above story do not only apply to solid state
>but is also valid for vacuum tube amplifiers.
>On the other end, a badly designed tube (more frequently older tubes,
>but not only) with a low gain already at 30 MHz can still have enough
>gain (at some nearby VHF) to start parasitics when their internal
>construction is not the good one to insure stability and the external
>ciruit does nothing to fix such type of problems.
>
? Good point.
cheers, Mauri
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|