Don't know what kind of ferrite beads you are using, but many are
intended for VHF use and are not helpful at HF. Also, it is usually
ineffective to just put a bead on the coax -- you should wrap multiple
turns through a large toroid. Good ferrite materials for HF are #31 for
1.8-7 mHz and #43 for 14-30 mHz. Either one would probably work fine for
both antennas.
have been fighting what appears to be a common mode RFI problem which
causes the KAT500 to continuously power cycle as long as the K3 is
transmitting. Generally this only occurs when driving my KPA500 amp
beyond a certain output level which differs for a given band and
frequency. I am powering the KAT500 with its own AC adapter. The
problem can occur in both bypass and auto mode.
7-10 ferrite beads on the coax attached to the KAT500 solved the
power cycling problem for my hex beam antenna and I successfully
operate QRO in bypass mode on all bands and modes. However the beads
did not help with the wire vertical. I can drive 300w into my dummy
load with no ferrite beads on the coax and the KAT500 is fine.
The SWR is low enough I should be able to use these antennas to run
the KAT500 in bypass mode. If I put it in Auto mode the problem is
exacerbated. I can tune the wire vertical just fine with the KAT500
in Auto mode at a tuning level of 25w from the K3. However, if I try
to transmit at 5w or more (SSB for example), the KAT500 starts to
power cycle.
I have no problem using the wire vertical if it is connected directly
to the K3's internal ATU. I observed that in this configuration, I
could still trip the power on the KAT500 even though it's not even
connected to that antenna, so I do believe this may be a common mode
RF issue in the shack. Somehow noise is finding its way into the
KAT500. Several turns of the AC power adapter's cord around a few
ferrite beads hasn't helped either.
I will at some point remove the KAT500 from the equation and see how
things work by directly connecting the K3 to the KPA500. I would
like to keep it in service as I might need it at the extreme band
edges of the wire vertical.
The vertical wire is from W8AMZ. I don't believe there is any kind
of current Balun inside the feed point but I did place 10 ferrite
beads over the coax at the feed point. I'm running 100' of RG8X to
this antenna. The hex beam antenna is feed with LMR-400 and RG-213.
So I don't know if the problem is specific to my vertical wire
antenna and feedline or if I should suspect a defective KAT500.
Before I take the KAT500 offline, can anyone suggest some further
experiments to try?
73, Jeff W6UX
--
73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/
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