[Amps] Where is power measured ?

[Jim Thomson]

Date: Wed, 6 Apr 2011 08:52:11 -0400
From: "Paul Christensen" <w9ac at arrl.net>
Subject: Re: [Amps] Where is power measured ?


97.3(b)(6) and 97.313(b) require that maximum allowable power occur at the 
transmitter output (aka, "TPO").   I prefer it that way rather than the FCC 
start regulating power based on ERP or EIRP.

Paul, W9AC 

## I stand corrected.  After some research, it appears that part 97 has been revised. 
Back in the mid 90's, it didn't specify back of amp, or at the ant.  Some FCC types
said back of amp, some said at the ant. The new version of the rules appears to just clarify
exactly where it's measured.  Perhaps that's so the FCC fellow doesn't have to climb to the
top of your tower with his bird in tow.  So it appears you folks got screwed....again.  Your 
current AM rules state 1.5 kw pep out.   That implies 300-375 w of cxr.  Any of those old
plate modulated AM, ham rigs  from the 50's  would do an easy 800 w  cxr.... and 3200-4000w
pep out.  

## measuring at the feed-point or at the back of the amp has nothing to do with ERP 
In canada, it sez... "across an Z  matched load" .   The load is at the ant..so that's where
it's measured. That only factor's in feedline loss..and nothing more.  Ant gain has nothing to do
with it. 

Jim  VE7RF