If you know the Er (dielectric constant), and the thickness if the
substrate, here is a nice website to calculate microstrip impedance...

http://www.microwaves101.com/encyclopedia/calmstrip.cfm

FR is basically just G-10 but fire retardant. G-10 is generally
considered OK up to about 1 GHz. Duroid has a higher Er and thus
thinner boards can be used and this will make a 50 Ohm line narrower and
reduce the line's radiation.

Scott
N0EDV

wrote:
Sometimes, at work, I need to make, or have made, an RF PCB board to
test an RF part. For example, a surface mount 2-way power divider, up
to say 4 GHz. We have regular g10? copper clad, a PCB millimg machine.
Is a 50 ohms trace about .1 in wide in this material? What is
advantage of FR and Duriod? Is TXLINE a good program to determine
trace widths? Any good books on RF boards?
Any tips would be very appriciated.

--
Scott
http://corbenflyer.tripod.com/
Gotta Fly or Gonna Die
Building RV-4 (Super Slow Build Version)