[Elecraft] Small QRP antenna
Jim Brown
jim at audiosystemsgroup.com
Thu Dec 29 23:41:22 EST 2016
On Thu,12/29/2016 3:07 PM, Bill Johnson wrote:
> Having "only" 5 watts doesn't change the need for proper termination and
> antenna match.
By proper termination, I think you're thinking about SWR and a match to
the transmitter. This thread is several days and 20+ posts old, but I
think I remember that the intent of the original poster was for portable
operation. But I could be wrong. :)
There are two reasons for low SWR and "matching." One is to get the
transmitter to provide power to the transmission line. If the mismatch
is too high, the transmitter will "fold back" (reduce its drive to
reduce its output power) to protect itself. Providing that match is the
function of an "antenna tuner."
The second reason is to reduce loss in the line due to a mismatch. The
SWR in a transmission line is determined entirely by the match between
the antenna and the line. It is NOTHING to do with the match between the
transmitter and the line. In typical QRP portable setups, transmission
lines are rarely long enough for loss to matter, so the match between
the antenna and the line usually doesn't matter. And the antenna tuner
takes care of match at the transmitter so that the output stage can
supply its full power.
73, Jim K9YC
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