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Old 4th Nov 2018, 8:00 pm   #47
G6Tanuki
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Join Date: Apr 2012
Location: Wiltshire, UK.
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Default Re: RF power meter calibration

Quote:
Originally Posted by Bazz4CQJ View Post
As an aside, quite lot of amateurs are using ATU's made by MFJ. These are certainly built to a tight budget, but generally seem to be assessed as OK for 100W. Most models have a Power Out/SWR meter fitted. I searched the internet yesterday looking for comments on how accurate those meters might be; found absolutely nothing!

B
You need to define the mode used in order to get any sense of power.

"Key-down" on a CW transmitter might give you 100 Watts for a while; the same transmitter delivering un-speech-processed SSB voice might only deliver 15 Watts or so averaged over a few seconds.
This is why ham transmitters often overstate their output on SSB; the duty-cycle is low so they can get away with heatsinks that allow them to deliver '100W PEP' in sideband service but only 25 Watts in continuous-carrier modes like FM, double-sideband-and-full-carrier AM, or RTTY/Digital modes.
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