[AMRadio] GG 813 Linear in GE Ham News


Donald Chester k4kyv at hotmail.com
Sun Oct 9 09:43:58 EDT 2005


>A standard carrier reading wattt meter (think 'Bird') should not move, when 
>the carrier is modulated to 100%.  A PEP reading wattmeter (it's my opinion 
>that you can *not* find one that reads accuratly enough) willl only show 
>that the rig -is- being modulated, but not if it is being over-modulated, 
>causing distortion and splatter and being rather un-neighborly to others on 
>near frequencies..

A field strength meter should not move when the carrier is modulated to 
100%.  It is designed to read AVERAGE carrier voltage.  If the final stage 
has good modulation linearity, the average carrier voltage doesn't change up 
to 100% modualtion.

A true average-reading wattmeter will read increased output with modulation. 
  The power output includes carrier + sideband power.  1000 watts carrier 
output should read 1500 (average, or mean) watts out with 100% sinewave 
modulation.

With a thermocouple rf ammeter in the line, the rf current at the output 
should show a 22.5% increase with 100% sinusoidal modulation.

Many rf output meters actually read rf voltage output and therefore show no 
upward kick with modualtion.  An rf ammeter is a thermal device which does 
not average the output, so it will show an upward kick with modulation.  
Square the current increase to get the percent power increase.

Don k4kyv





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