Resistors can have complex impedances, especially film resistors. Carbon
film resistors can get by up to 30MHz or so, and metal film resistors
shouln't be used above 10MHz. The problem with these devices is that they
consist of a sprial etched resistance material that has a fair amount of
reactance as you go up in frequency.
Carbon composition resistors are preferable in RF applications, but even
their lead length becomes too reactive at higher frequencies.
Nowadays, we use 0603 or smaller size components at higher frequencies. 0402
geometry is presently being used at higher frequencies, with 0201 size soon
to become the norm. This is what I have been working with for the last
couple of years.

Pete

"Frank Gilliland" wrote in message
...
On Mon, 19 Feb 2007 19:12:33 GMT, james wrote
in :

On Sun, 18 Feb 2007 18:24:33 -0800, Frank Gilliland
wrote:

+++Conjugate match is needed for maximum power transfer.
+++
+++
+++IMPEDANCE match... for maximum power transfer. A 'conjugate' match is
+++when the impedances are complex, which isn't always the case.
***********

I have found that it is rare in the real world that impeadances are
not complex. Outside transimission lines, there is little that is not
complex.


You just said that resistors have complex impedance and transmission
lines are flat.


Then again when you conjugate match, the imaginary part of
the complex impedances is nulified and you are then left with the real
part.


Reactances don't just disappear. They create a current between the
source and load that must be assessed to see if it is going to cause
any problems. Sometimes it doesn't and sometimes it does.