[BC] Re:50 Kw AM and 1 5/8 line

[Xmitters@aol.com]

In a message dated 2/20/07 12:00:42 AM Central Standard Time, 
broadcast-request at radiolists.net writes:

<< On Monday 19 February 2007, Xmitters at aol.com wrote:
 >> You have to remember that the 250 kW peak power that you mentioned is peak
 >> Envelope Power, which is defined as the equivalent unmodulated power that
 >> has the same voltage as the amplitude modulated carrier at peak crest of
 >> modulation.
 
 <But of course.  Basic stuff.>

Indeed it is. I have met people that believe that peak power and peak 
envelope power is the same thing. Basic yes. A misunderstanding can be costly.
 
 >> Even at this [506kW]
 >> figure, we have not considered  the required headroom for possible VSWR
 >> excursions for this system yet. All of the 50 kW AMs that I have
 >> seen/worked on, either use three inch rigid coax or four inch andrew air
 >> dielectric.
 
 >Certainly one needs to think about the VSWR as well.  But have you tried 
 >1-5/8's at 50kW to see what it would do?

Nope, no need to. I already know the line's ratings will be exceeded at 125% 
positive crest modulation. None of my employers ever had the funding for 
experiments designed to verify what theory clearly demonstrates; I go by what the 
manufacturer says and don't push that envelope (no pun intended). In an 
emergency, I would do anything. I would however, tend to run with less carrier and 
more modulation if I had an emergency line that could not handle full power.
 
 > Anyone here using 1 5/8 foam feedline for their 50 kW AM plant ? If so, you
 > have more guts than I have.
 
 I know of a 25KW using 1-5/8's.  And for that application it is sufficient.
  >>
I'm sure it would work well in such an application.


Jeff Glass
Northern Illinois University