[AMRadio] Legal-Limit tuner advice....?


John E. Coleman (ARS WA5BXO) wa5bxo2005 at pctechref.com
Fri Aug 18 12:01:05 EDT 2006


	That's ODD:

	I've always found it to be a problem the other way around.  Where
they don't like to match low Z such as 100 Ohms or lower.  but it can be a
problem at higher Z if the feed point is reactive where the total length of
the ant and the feed line do not come out close to a quarter wave multiple
at the High Z length.  My experience is mostly on 80, 40 mtrs.  I used a
dipole of 120 ft. center fed with 60 feet of 600 ohms line made with #12
wire and spaced about 6 inches.  The voltage and Z for the feed point was
about as high as it gets at that point, maybe 5000 ohms.  The arc pulled
from the feed point of the Matchbox tuner was about the same as the arc from
plate end of the tank coil in the rig.  As a mater of fact, the feeders
needed to be pulled away from the composition roof edge just before going to
the tuner mounted under the edge of the roof, to prevent dialectic heating
and melting of the composition roof material.  So I know the Voltage was
high.

John, WA5BXO

-----Original Message-----
On Behalf Of uvcm inc.
Sent: Thursday, August 17, 2006 10:27 PM

   I have a Johnson kw matchbox, it is very limited if the impedance goes
above 1000 ohms.
It will not match my double extended zepp below 2:5:1
I am going to build one as soon as I decide on a very good design using
vacuum caps
Brad KB7FQR






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