Posted by
Ron D'Eau Claire-2 on
May 17, 2005; 4:48am
URL: http://elecraft.85.s1.nabble.com/Simple-Method-for-Measuring-Tuner-loss-with-reactive-loads-tp378394p378396.html
Stuart K5KVH wrote:
He (Frank Witt) measured the Johnson Matchbox, and found although a good
balanced tuner, it did not match all impedances and work on all of today's
bands. -Stuart K5KVH
-----------------------
E.F. Johnson specified the "Matchbox" tuners for 3.5 to 30 MHz. Over that
range, the Johnson specifications say they were capable of matching antennas
showing feedpoint impedances of 50 to 1200 Ohms into balanced lines and 50
to 2000 ohms into unbalanced lines.
1200 ohms is not especially impressive when feeding the "all-band doublet"
type of antenna with open wire line. The impedance can easily exceed this
value.
On the lower end, 50 ohms is no great value either. Short antennas can
easily show impedances below 10 ohms.
So, while the venerable "Matchbox" ATU's were very good, they definitely
couldn't "load up the bedsprings" as we used to say in praise of a tuner
that could load anything!
Ron AC7AC
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