Paul,
did the LF loss resistance drop after mowing the grass?
Someone should try to roll out household aluminium foil completely
within a radius of the height of the antenna to see how it loweres the
losses :-) Not so expensive actually.
73, Stefan
Am 05.09.2018 09:56, schrieb [email protected]:
.. a wingbeat of a butterfly..
be careful to move around the antenna and touch metal parts while
transmitting Paul it is a very "reactive" area not only for the field
strenght concept :-))
I guess that the pipe laying on the ground it is part of the ground
itself (maybe improving it ) when you rise it from ground level and
eventually connect to other existing metal parts you really make
change in the environment of the antenna (it is like to tophat wires
moving in the space when wind blows)
73, Marco IK1HSS
----Messaggio originale----
Da: [email protected]
Data: 5-set-2018 1.09
A: "[email protected]"<[email protected]>,
"[email protected]"<[email protected]>,
"Discussion of the Lowfer (US, European, & UK) and MedFer
bands"<[email protected]>
Ogg: LF: Antenna environment changes
Subtitle: Be careful what you do in the vicinity of your LF antennas...
I had a 14m length of aluminum tube (proposed 30 meter rotatable
dipole) laying on the ground just under one end of the top hat of
the LF antenna. Today I picked it up and moved it about 20 meters
away. To get it off the ground for mowing, I ran it through the
lattice of a short tower (9m) that is not at all under the LF top
hat. I placed it about 2m above ground. This caused the LF antenna
resonance to change so much I could not retune with the variometer!
It was quite a large shift in resonant frequency.
I then experimented with moving the piece of aluminum tube around.
It seems I can lay it on the ground anywhere I want with no affect
to the LF antenna. But put it one or two meters above ground
connected to another tower or mast and the LF antenna is drastically
changed.
I must remember not to move any pieces of metal around while the
beacon is active! :-)
Paul
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