Hi Rik,
At some point it is simply easier to rise the POWER. Same here at the
moment on the new antenna :-)
73, Stefan
Am 05.09.2018 12:22, schrieb Rik Strobbe:
Hi Paul,
same here, losses are high in summer: up to 70 Ohm (475 kHz) or 180 Ohm (137
kHz). In winter it drops to 35 Ohm (475 kHz) and 120 Ohm (137kHz).
I always assumed it was not so much affected the soil but rather by all the trees
surrounding the antenna that loose their leaves and go to "sleep" in winter.
Last february I raised the antenna from 12m to 14m in my attempt to get some
extra ERP to cross the Atlantic and actually the losses increased slightly. I
thought this was caused by the topload coming closer to some branches. But
fortunately the overall effect was positive and we had our QSO ;-)
73, Rik ON7YD - OR7T
________________________________________
Van: [email protected]<[email protected]> namens
N1BUG<[email protected]>
Verzonden: woensdag 5 september 2018 11:06
Aan: [email protected]
Onderwerp: Re: R: LF: Antenna environment changes
Marco,
... a wingbeat of a butterfly... is very descriptive. I like it. :)
Maybe with a sensitive detector I can use the LF antenna to count
birds flying under it. :)
Stefan,
I have not seen any significant change in loss resistance during the
summer. Rain, dry... hot, less hot... grass mowed or not mowed seem
to have not much influence. My loss resistance in summer is very
high. I need that aluminum foil!
During the winter my loss resistance changed a lot with temperature.
Colder = lower resistance. I did not understand what was changing. I
do not think variations in temperature could affect the ground very
much with 1m of snow over it but maybe I am wrong. Perhaps it was
the snow itself changing with temperature, or maybe it was the
nearby trees.
73,
Paul
On 09/05/2018 04:23 AM, DK7FC wrote:
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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