[mcdonaldREMOVE TO ACTUALLY REACH [email protected]]

Don Pearce wrote:
On Mon, 25 May 2009 11:40:48 -0500, "mcdonaldREMOVE TO ACTUALLY REACH
wrote:

Scott Dorsey wrote:

You want goofy, look up where the 50 and 75 ohm transmission line
standards came from...

That's not goofy. The impedance of free space is (about) 75 ohms, as
is, not accidentally, the impedance of a matched dipole antenna.


The impedance of free space is 377 ohms (120 pi)

You are of course right! I had a brain lapse! I was equating FOLDED
dipole to plain dipole. It's bad getting old!


Minimum loss (at which copper loss and dielectric loss cross) comes at
about 67 ohms. There are cables at that impedance, but I've never seen
one.




I've actually used them. I've also used the 125 ohm lines,
and even 250 ohm rigid ones (with teensy inner conductor held
in place with nylon fishing line.

Doug McDonald

Doug McDonald