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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