Robert,
I may not have seen all the postings, but one thing that isn't clear to
me is whether your shack is in the near field of your antenna, or what
specific antenna and feedline you're using. "80-10 meter dipole" - what
does that mean and how far from the shack is it? There have been good
suggestions made and you certainly can apply more than one to arrive at
a "shotgun" solution, but a physical description would help.
For example - if you're using a Windom or other off-center-fed dipole
fed directly with coax, you certainly could have substantial common-mode
currents on the feedline. Those can be choked off outside the shack by
various means - a stack of a dozen or more Mix 31 ferrite beads, a
"feedline isolator" or enough turns of a coil in the coax to form an
effective choke. (quite a few at 80M, not my favorite method)
OTOH, if your station if physically close to the antenna, choking off
feedline currents will only be part of the solution, and possibly best
done physically close to the rig or even in multiple places. You may
also need to choke the 1394 cable between the 5000A and the computer,
bypass the mic, speaker and PS leads, choke the PS leads etc.
As frustrating as it may be, RFI in the shack can be managed if not
conquered. I run OCF dipole antennas here (among others) for 6-80M, and
have stacks of Mix 31 ferrite on the feedlines where they first meet the
ground and just before they enter the shack. At 1500W I have zero RFI
problems in the shack, but the antenna itself is 200+ feet from the
house. OTOH I've had to put a few beads on the TV coax that runs all
around the house to prevent my full-power 160M AM & SSB signals from
overloading our satellite TV receivers - my 1/2 wave 160M sloper passes
within 75 feet of the house and near-field overload isn't a big surprise.
So - it can be conquered and many of us here are more than willing to
help, but a description of the antennas and their proximity to your
shack, feedline lengths etc. would help.
My .02 and 73,
Jim N7CXI
(Flex 5K user and QRO-capable 160-10M)
On 12/22/2012 2:15 PM, Robert Costa wrote:
All,
As you may have seen from previous posts, that I have RF ingress issues on my
Flex 5000a restricting my use of the flex to 40 meters and below. As I want to
start addressing these issues, I would like to know what products others have
used.
I need to eliminate common mode currents at the feedpoint of my 80-10 meter
dipole. I have seen Radio Works line isolators, but have been told that they
are not very effective. I have been told to use a W2DU current UNUN from a
company like the wireman.
I am open to suggestions as I do not want this to be an extended engineering
science fair.
As this RF ingress issue has been a complete irritating experience with my
Flex, I would like to hear who has used what and what the results and over all
costs have been.
Thank you,
Robert
KB6QXM
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