[Elecraft] dB

[G3VVT at aol.com]

There you go Jim shooting yourself in the foot straight off by referring  
your dB to power!
 
> and I increase my transmitter power by 4:1 (6 dB)............ 
 
Of course the two entities voltage and power are mathematically related,  but 
unless you say to what reference you are using, they can be somewhat  
meaningless. In the 17 years I spent in the Cable TV industry pre the advent of  
satellite technology, the dB was always related to voltage at 75 ohms and was  
understood to be so. The only occasion I remember using dB related to power was  
when using multiple phased antenna arrays to work out the total output as the  
gain was increased by a ratio of 3dB in power every time the number of 
separate  arrays was doubled.
 
With a sideways shift into telecoms for the last 20+ years I had to  start 
thinking about dB related to power where 4 times gain or  loss when related to 
power is 6dB as you say. The same 4 times gain or  loss is 12dB when related to 
voltage as used in Cable TV. Irrespective  of how the measuring systems for 
the two industries work, they are  calibrated in dB relative to the system you 
are working with and as such are not  directly compatible, thus making a 
reference when referring to dB gain or loss  essential.
 
Perhaps a topic to be discussed further off the Elecraft Reflector if  needed.
 
Bob, G3VVT