John:
I have a set up similar to your dimensions with the middle half of the ant
passing over the roof.
I use Radio Works classic North Carolinia 80 M - 10M Windom Ant about 133'
long, 67% offset. There are 2 baluns in it which can help the RFI problem (If
caused by the antenna).
The shack is 12 feet directly below the stub feed point, 30 feet below the top
balun feed of the 133 length. The ant top is 50' above ground. With 600 watts
PEP there is no RFI in a shack full of transceivers, lots of quality test
equipment
and many antennas. The house has 4 laptops, 2 high speed servers fancy hi fi
and wireless TV/Web. No RFI from this antenna.
It routinely gets 59+ in N., S. America and Europe. The first time I joined a
national net I was requested to do a call for NCS to find more stations. For
the far east on 20M I go to the beam. The home is at the lower part of hills
where the brook flows.
On your property I would turn the short leg of the above 7 feet down at your
tree or compromise to the keep the center as high as possible. My ant is turned
down 10 feet at each end but the feed point is sitting pretty at 50 feet. The
ant is fed through a tuner which is switched out since the SWR varies from
roughly 1.1 to 2.5 on band extremes.
Talk to me directly if you 4Mhz. is critical to you.
Good luck,
John, K2SFS, caraj@cox.net
_____________________________________________________
---- Jim Miller Waco Texas WB5OXQ <wb5oxq_1@grandecom.net> wrote:
> I must move my 40 and 75 dipoles due to rfi in the house that I cannot
> resolve. I am thinking about 1 dipole fed with ladder line or window line. I
> have 2 possable support points.
> 1 pair is 126' from end to end and 50' high at one end and 30' at the other.
> Second pair 139' apart but 25' at one end and 30' at the other. The longer
> but lower is farther from the house by about 10' and runs over level yard
> with no obstructions. What is up with the 130' dipole fed with balanced line?
> Is this better for a multiband antenna than using 1/2 wave at the lowest
> desired freq? I have a MT-3000A Dentron tuner which is supposed to work with
> ballanced line. The maximum power I run is 800 watts rms not pep.
> Suggestions please. I have never used a dipole fed with balanced line. Will
> the window line take 800 watts or should I get the open wire feeder? I really
> only need this antenna to work on 75 and 40. I use my triband beam for 20+.
> How do you bring this line into the shack? Obviously it cannot touch anything
> metal along its run. Is the length of the feeder critical?
> Should the wire be long as possable or 1/2 wave at the lowest desired
> frequency? (3.9mhz)
> wb5oxq
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