[Amps] Where is power measured ?

[Jim Thomson]

Someone mentioned that in the US, the power is measured at the back of the amp. 
Your rules don't stipulate where it's actually measured.  Dave Leeson, and other's,
contacted FCC officials, and the FCC said it was reasonable to measure the power at the
load, IE: ant feed-point.  US broadcast TX are measured at the feed-point, or close to it, not the
output of the amp at base of tower.  

.5db of feedline loss = 10% LOSS.   1 db = 20 %loss    2db =  37% loss   3db = 50% loss 

IMO, most folks will have at least .5db loss..and a lot more on the upper HF bands...esp 
with the typ 140-400' length's of coax used.  So the next time you tell the fella on the other end of the
qso, that ur running 1.5 kw.... stick a pep meter at the top of the tower, and get your friend on top
to give you the real story....via his 2m FM hand held. 

I know  a few folks  who actually did that procedure, [including myself]....and got a REAL eye opener...with the dismal
results.   Broadcast TX manufacturer's  have factored line loss into the equation. [ ditto with cell sites, commercial vhf/uhf]

With just 2db of feed-line loss,  you require 2380 watts OUTPUT..to get 1.5 kw at the ant. 

OK, all the above  might be a moot point.... but your typ 30-46 lb plate xmfr, when run at it's  max CCS ratings,
typ has a high internal temp.   If you want a real 1.5 kw at the feed-point.. you really need a 2 kw output rated amp...
which will require a 3.5 kva CCS  hypersil xmfr..which will weigh 60-64 lbs..and will  STILL  run hot when maxed out.   

When Roger  was trying to calculate duty cycle on ssb/cw/rtty  etc,  you forgot to toss in the IDLE current. 
Unless EBS is used, that will throw your calcs way off.  That 2 x hole QRO /Commander amp with the russian
tetrodes does not use EBS...and the pair of tubes idles at a whopping 450 ma.....and 675 ma  for the 3 x hole
version of the same amp.  The heath idles at 180 ma.  The stock drake amp idles at 230 ma.  Don't forget
processed SSB, or ssb  with a lot of low freq content in it, like essb.  That will increase the duty cycle by a 
whole bunch.  Ham Amp makers want to stuff small xfmr's  into table top amps.  IMO, the B+ supply should
be in a separate box.... on the floor, behind the desk.  Then the weight is split between RF deck..and B+ supply.
The HB  folks have the advantage they can configure any way they want.

Jim  VE7RF