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Re: Inverted L for 160 meters

Posted by Vic Rosenthal on Aug 26, 2020; 11:36am
URL: http://elecraft.85.s1.nabble.com/Inverted-L-for-160-meters-tp7664325p7664349.html

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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