"MRW" wrote in message
ps.com...
Hi everybody! I want to mount a dipole FM antenna on top of a three
story building. My transmitter will be located in a room in the
bottom
floor. Has anyone have experience in this?

I know that I will get some signal attenuation with that long of a
coaxial cable (100 meters). If my cable has a characteristic
impedance
of 50 ohms (matching the output impedance of the transmitter), will
it
adversely affect my transmission?

I was reading my electromagnetics book and it mentions that
depending
on transmission line length the cable might look like an inductor or
capacitor.

========================================
That the cable will look like an inductance or capacitor is a load of
nonsense. Change the books you've been reading. Don't read the
comics.

For minimum loss in the cable the input impedance of the antenna
should be approximately the same as the cable impedance.

If the cable loss is 3dB then half of the transmitter power will be
lost in the cable. Check the cable manufacturer's specification for
actual loss per unit of length.

Very approximately, if the diameter of the coaxial cable is doubled
then the loss in the cable, in dB, will be halved.

On the other hand, if 3/4 of the Tx power is lost in the cable, then
depending on the distance to the customers' receivers, it might not
matter very much. Everything depends on the required service area of
the transmitting station. There's not much point in buying expensive
cable to radiate 100 watts if 25 watts with cheap nasty stuff is good
enough.

Think in terms of your bank balance.
----
Reg, G4FGQ