Hi Ray,
The classic source for Fresnel zones as they apply to HF site selection
is NBS Technical Note 139:
https://nvlpubs.nist.gov/nistpubs/Legacy/TN/nbstechnicalnote139.pdf
While Technical Note 139 applies primarily to horizontally polarized
antennas mounted above the ground, its general conclusions apply to
1/4 wavelength 160 and 80 verticals mounted on the ground.
The outer edge of the Fresnel Zone is several kilometers for low angle
radiation from 1/4 wavelength 160 and 80 meter verticals, especially
when the verticals are installed on a highly conductive surface
( e.g., sea water, salt marsh or wet marshy soil ).
The outer edge of the Fresnel zone is much closer when 160 and 80 meter
1/4 wavelength verticals are installed over a low conductivity surface
(e.g., dry, chalky or sandy soil).
73
Frank
W3LPL
----- Original Message -----
From: "Ray Higgins" <ray.w2re@gmail.com>
To: topband@contesting.com
Sent: Thursday, April 18, 2019 2:48:57 PM
Subject: Topband: Fresnel Zone
I have two questions about fresnel zone.
I just purchased 22.5/ac near the ocean near Machiasport, ME. This is in the
Northeast corner of Maine about 30 miles south of Eastport and a Lubec. This is
going to be my personal Remote Contest station! I plan to be contesting from
this new qth starting in 2020 but will be QRV by mid 2019 for testing.
This qth is anywhere between 1-3 miles from the ocean or the bay, it sits on a
high plateau 150’ asl thats slopes in all directions to saltwater (peninsula)
except N/NW. The property has a saltwater river and marsh that runs the
perimeter from south to north favoring the NE direction, the marsh is only
50-100' wide and 1500-2000’ away from the property. The land has a gradual
slope to the marsh.
My questions:
1.) Is the saltwater river bed/marsh wide enough to be an effective field in
the Fresnal Zone?
2.) What is the wavelengths needed to be within the Fresnal zone of a
river/marsh compared to an ocean?
In this photo album (last pic) I have outlined the river saltwater marsh and
property boundry from a google earth shot.
https://photos.app.goo.gl/ui79t2jFo95b29et6
I’m only concerned about 80 and 160m in the Fresnal Zone.
Any input would be welcomed.
Thanks,
Ray W2RE
Sent from my iPhone
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