Steve brings up a very important point, one I learned the hard way,
too. I now tell my friends, especially those very confident of their "3
KW" rated tuners, that any gradual change in SWR while the key is down
is a sign that the tuner is having trouble inside. Look for heat, don't
be surprised, it can happen in lots of surprising circumstances and may
be a sign of other problems that need to be fixed (shorted coax comes to
mind). I have heated up (and melted) coil forms on "3 KW" tuners with
100 watts to my surprise. Just occasionally watch the SWR for "creep"
and start problem solving when it appears. Keep the VOM nearby :-) .
Clark
WA3JPG
On Wednesday, January 8, 2003, at 04:36 AM, n4lq wrote:
line? Once I burned up a torroid coil in a TS-940's tuner trying to load
an 80m dipole on 160m. The tuner was seeing a very low impedance thus
the
current through the little coil was quite high. With a big tuner, you
would not notice the heat but those little torroids will get blazing
hot,
change value and the swr will creep up as you transmit.
Maybe next time it starts acting up, remove the lid and check for hot
parts. If you find this to be true, try adding a quarter wave length of
feedline and see what happens.
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