Kevin,
My advice is to get Moxon's book, "Wire Antennas for All Locations."
Follow his advice, which is (roughly): use four elevated radials at a
level higher than an Elk's antlers. Make the radials equal in length,
about 0.15 wavelength long, connect them together, and add an inductance
in this common ground lead to resonate them. This helps equalize the
currents in the radials, which keeps your radiation angle low.
Do not use buried radials unless you have room for at least 16 of them.
In that case they can also be about 0.15 wl long.
73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
On 26/08/2020 3:31, kevinr wrote:
I have to be very careful of raised wires on my property. If they are
not above the height of an elk's antlers I am in trouble. I plan to
bury them. This is something I've never done before which has its own
merit. I have plenty of wire scrap from broken antennas so the
non-resonant, buried radials work better for my circumstances. I need
to calculate the feed point impedance to see if I need to design a balun
for the system to work. Once my main project is done I'll have more
time for modeling each method.
Thanks for all the ideas guys,
73, Kevin. KD5ONS
On 8/25/20 5:23 PM, Wes wrote:
You probably should get acquainted with Rudy Severns, N6LF.
(https://www.antennasbyn6lf.com/) He has written more than you ever
want to know about vertical antennas,
More specifically to your case, are you planning the radials to be
elevated? If so, they need to be the same length, in fact some effort
should be made to get all of the currents the same. The last thing
you want is a fifty ohm feedpoint impedance with a shortened vertical
(which is what an L is). There is evidence that elevated radials are
an improvement over on-the-ground or buried radials. Mine are on the
ground, mainly because 1) I didn't want to give up radiator height to
raise the radials, 2) all of the big guns bury theirs and I don't have
room for full length radials anyway in my cactus patch. See my QRZ
page for evidence.
My modeling shows a little bit of directivity away from the horizontal
wire, but it's negligible.
Wes N7WS
On 8/25/2020 4:23 PM, kevinr wrote:
From what I can find, and what I can calculate, five wires, each ~130
feet long, could make a nice inverted L for 160 meters. One leg for
the vertical and horizontal portion of the antenna. Four legs for
the counterpoise (ground plane). There are many broken wire antennas
stored in my shed which are fodder for the radials. Do all of the
legs for the counterpoise need to be 1/4 wavelength or can I
substitute some shorter lengths? The feedpoint should somewhere
above 50 ohms impedance. As I add more radials that number will
reach 50 ohms asymptotically.
I can get the vertical part up to 70 or 80 feet above ground with the
rest of it horizontal. Most of the radiation should take place from
the vertical part since it is closer to the feed point. But there
should be some effect from the direction of the horizontal portion.
How strongly does the direction of the horizontal portion effect the
radiation pattern of the antenna system? My property allows me to
point it from 300 degrees around to 200 degrees so I have plenty of
options. Between 200 and 300 degrees there is a road used by
loggers, and the folks maintaining the towers at the top of this
mountain. They can break any antenna lower than 80 feet above
ground. Spar poles and cranes clear out any dead limbs across the road.
Inquiring minds...
Kevin. KD5ONS
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