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Date: Tue, 18 Jan 2000 10:58:55
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: Re: Transatlantic
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At 11:54 17/01/00 -0800, G3KEV wrote:
>There is a big difference in the radiation pattern and angle of take off 
>between a high vertical antenna and a very low antenna given the same rf
power 
>to the antenna. 1 Watt erp from a dummy load or low horizontal wire is
hardly 
>the same as 1 Watt erp from a vertical antenna at 120 ft. There is also
the RX
>consideration especially on long haul signals. At LF the delivery system ie
>ANTENNA is the most important factor. Even with large towers, and high 
>elaborate antennas, which are still physically small relative to 137 khz
and a 
>limit of 1W erp, one has to realize the limitations, but at least there
might 
>be a chance.

Indeed the radiation angle is important. But on longwave we have a very
strong groundwave, so radiation at 0 degrees (or close to that) might be
'bound to the earth' and not participate in the skywave. I am not sure that
a vertical is better for long distance propagation than a long horizontal
wire. Recently DJ9IE is using a horizontal wire (200m long at 15m hight)
and despite the fact that he is at only 200km from me I can notice up to
10dB 'QSB' on his signal at night. Other stations in the 200km range, using
more conventional Marconi antennas do not have this QSB.

73, Rik  ON7YD