[UK-CONTEST] Output power

[G3RAU at aol.com]

In a message dated 31/01/2012 17:14:17 GMT Standard Time,  
tony at llewellyns.freeserve.co.uk writes:

Can  someone please explain to me as a non HF contester how it is legal to 
be  using  " Acom 1000 at around 600-700w from the amp. " at any time let  
alone during a contest.

Regards
Tony  G8ONK



It is the Laws of Physics Tony.  If you want to deliver 400w to the  
antenna end of a feeder you have to put more than 400w in at the drive  end, 
unless you use a theoretical zero loss feeder, which obviously doesn't  exist.  
To work out just how much extra power you need to put in, you have to know  
the feeder loss, and this is usually measured in dBs.  Let us say the  
feeder loss is 3db, then the power needs to be increased by 3dB.
It  can be shown mathematically that this means the drive power needs  to 
be 800 Watts.  
It is as easy as that, just increase power to match the feeder loss  and 
achieve 400w at the antenna. 
A 3dB loss is nothing in some situations, so it is all perfectly legit  and 
nothing to worry about.
73
Derek G3RAU