Telamon wrote:
In article ,
"Brenda Ann" wrote:

"Telamon" wrote in
message
...

6 1/8 inch is what most radio stations use?

Pretty common for FM and TV stations.. not so much for AM. IIRC, 1520
in Portland used 3" Heliax for 50KW.

Someone wrote that 50 ohm was standard. Why am I seeing 75 ohm
components then?

Dave wrote:

75 Ohm has lower loss for long runs, but requires extra matching
sections, usually at both ends.

Sorry to rain on your parade...but to follow your own (lack of) logic:

The "extra matching sections" you talk about (at each end) would add
*more* loss than you would gain by using your -supposedly- lower loss 75
ohm cable.

Also, 75 ohm cable does not inherently have less (or more) loss than 50
ohm cable. *Loss* is dependent on the dielectric used, the materials
used and the construction (size) of the cable, no matter what the impedance.

Finally, AFAIK, 50 ohms has been traditionally used for AM/FM/SW
transmitters while 75 ohms is used for CATV distribution.