[AMRadio] shunt

Rick Brashear rickbras at airmail.net
Fri May 5 17:46:13 EDT 2006

I think maybe my concerns are not being understood.  I realize with 1000 
watts and a 50 ohm load a 5 amp meter would be ample, if not ideal.  
However, if the load were to become mismatched for some reason the 
current could easily soar, immediately trashing the meter.  The proposed 
shunted meter (which obviously was not a good idea) was to provide 
headroom in the event of a problem.  It's quite possible during the 
process of tuning that the current would be considerably higher than 
when at resonance, even if the output wattage were only 500 watts.  Once 
in operation a 5 amp meter would work best as the accuracy would be much 
better than that of a 25 amp meter.


Mike Dorworth, K4XM wrote:

>  If I'm not mistaken the BC-939 antenna coupler used with
>>the BC-610 transmitter uses a 15 amp meter in the antenna output
>>circuitry and the BC-610 is capable of only 400 watts carrier.
>Again it is still I squared R so at a TWO OHM load and 15 amps you would
>indeed have 450 watts. The way the BC-610 ran mobile is into a 15  foot whip
>so the resistance could be perhaps as low as 2 ohms, negelecting ground loss
>which is in series BUT the BC 610 is looking into a fifty ohm load into the
>tuner and the meter should be looking at the  output.  mike

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