Has anyone encountered this problem before? My 7 year old OMNI VI+
(option 1) has developed a problem with drawing excessive current on 15
meters. All other bands behave normally, but on 15 meters, I can only
show 80-85 watts output before the power supply over-current circuit
trips. This OMNI has always been a bit "touchy" on 15 meters into
anything less than a near perfect match, but I have always been able to
put out 100 watts into a good match. The problem started during the NAQP
CW contest which is not a good time, what with jumping around the bands
snagging multipliers. Since then I have done a few tests on the gear.
First, I insured that "all" my SWR bridges were at least close to one
another. The 238 tuner provides a > 1.2 SWR on any of the antennas
tried. In addition, it makes the Hercules II very happy on any of the
antennas. Next I hooked up a dummy load and got the same results. I even
verified the SWR of the dummy load with the Autek RF analyst. Still the
problem persists. I have tried various length coax patch cables between
the boxes. The dummy load was connected direct to the OMNI VI
with an 18 inch piece of RG-213.
I use a TT 960 power supply that has been modified to a 961 by turning
the filter cap upside down per TT Service Dept. It has been around the
shack for 11 years and is still in good shape. The last thing that
happened to the OMNI before the problem presented itself was the Lock
Pulse alignment using TT's procedure and commercial grade scope and
counter (I have a friend who maintains all county radio/electronic
gear). That's about it. The rig performs as expected on all other bands
into a dummy load or antennas and/or antennas matched with the 238
tuner. 15 meters is the only place the problem exists.
Has anyone encountered this problem before? I would appreciate your
sharing any experiences you may have had. Perhaps the over-current
protection circuit is a bit on the stingy side and the OMNI VI needs a
bit more current to achieve full output on 15 meters? I dunno. I thought
I would first plumb the accumulated knowledge and wisdom of the
reflector before I once again call the wizards just down the road. Any
comments or suggestions will be much appreciated. Thanks in advance.
73/CUL,
Jim, N4IR
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