I like to use 0805 series, at higher frequencies, I see 0603 and smaller
sizes being used. As far as carbon comp resistors, they are the best
through-hole components for RF, at least up to a certain point. True, they
can and do change value over the years, and they can absorb moisture.

Pete

"james" wrote in message
...
On Sat, 24 Feb 2007 18:01:09 -0600, "Pete KE9OA"
wrote:

+++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
+++
*************

And carbon composition should be avoided. They absorb moisture and
change resistance with time. I have seen to many 100K carbon comps
measue around 60K with time. I would aviod them like the plague.

I have worked with chip components for over 20yrs. I stay away from
the samllest one unless the board density constraints or the design
dictates it.

james
james




+++"Frank Gilliland" wrote in message
om...
+++ 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.
+++
+++
+++
+++