The latest AutoEZ update includes the ability to create EZNEC models having 2
separate ground media. One typical use is to model a vertical located on a
sandy beach next to salt water.
Using AutoEZ you can assign a variable to the media 2 linear boundary and then
run a series of test cases
This is somewhat related to the vertical on a beach thread but I figured if I
put that in the subject line I might get lynched.
In the past there have been questions about the accuracy of NEC far field
calculations at low take-off angles for vertical antennas since the far field
does not
Nermin wrote:
There was an article in recent issue of ARRL QST, A 20 and 40 meter
Vertical on Autopilot, ...
That article by K6MHE is available here:
http://k6mhe.com/files/DualBandVert.pdf
And here's a blog entry and a corresponding YouTube video by AB8XX for a
similar 80m/40m antenna:
W0BTU was kind enough to include a link to his inverted-L EZNEC model so I
added that to a thread over on eHam which discusses using a dual-band
autopilot matching network, in this case using the inverted-L on 160 and 80
with no tweaking or switching of the matching network needed:
Tom wrote:
A resonant 160 meter loop around 20-30 feet above the ground has a
feedpoint impedance of around 50 ohms on 160, and about 80 ohms on 80
meters. The antenna impedance isn't really high until 40 meters, where it
would be resonant far outside the band and have a terrible mismatch
The recent thread on 8 circle arrays prompted me to create a few different
AutoEZ models, mostly because I was curious about the relationship between
array size, element phasing, and number of active elements (4 with W8JI, 8 with
Hi-Z).
First thing I did was educate myself. For W8JI type
Based on some user feedback, the 8-circle models mentioned earlier have been
modified with an additional variable to control the azimuth direction of the
main lobe. That lets you change the direction just by changing (or doing a
sweep on) a single variable. So you can easily: 1) see how the
AutoEZ can display near field data on polar, rectangular, and 3D plots. For
several illustrated examples see section Electric or Magnetic Field Strength -
Near Field here:
http://ac6la.com/aepatterns.html
AutoEZ home page: http://ac6la.com/autoez.html
Dan, AC6LA
_
Topband
IV3PRK has several interesting papers available as links from this page
http://www.iv3prk.it/TX3A-DHDL.htm
including one which compares both a single DHDL and a dual DHDL with a Waller
Flag.
Dan, AC6LA
_
Topband Reflector Archives - http://www.contesting.com/_topband
Marsh Stewart wrote:
I found a website with detailed info on the ZS6BKW antenna.
Another nice analysis of the ZS6BKW was done a while ago by K4SAV over on
qrz.com:
http://forums.qrz.com/showthread.php?442166-Which-is-better-G5RV-or-ZS6BKW
Jerry showed pattern comparisons but did not include
Frank wrote:
A 160 meter receiving 4-square can be built with verticals as short as 20
feet and can be built with 80 foot sides, or even smaller.
Azimuth and elevation patterns for a few typical arrays can be found in the
last section on this page:
http://ac6la.com/aecollection6.html
At the
Mike Waters wrote:
If anyone has patterns for those, that would be interesting.
I haven't yet written a typical AC6LA more words than any human should be
forced to read at one time example, but this post to the Shared Apex Loop
Array Yahoo group shows some pattern comparisons:
Rick Karlquist wrote:
>>> Models well on EZNEC.
There are some fairly detailed 8-circle modeling studies in the last section on
this page:
http://ac6la.com/aecollection6.html
Lots of illustrations and several url links for more info.
Dan, AC6LA
http://ac6la.com
_
Topband
K8BHZ wrote:
>>> The length to avoid is nothing more than a half wavelength, which
>>> translates the same impedance from end to end
>>> i.e., the high Z open end translates to a high Z antenna base end. This
>>> results in minimum radial current.
I'm not so sure I buy that and I don't think
This page, and the links to a couple of N6LF documents that are included there,
might help:
http://ac6la.com/aecollection3.html
Not covered on that page are a) how the efficiency changes as the radials are
placed closer to the ground, and b) whether there is any difference in best
radial
For AutoEZ users: A model similar to the parasitic array that Tim described is
available on this page:
http://ac6la.com/aecollection8.html
In the first section of that page, scroll down to topic "Parasitic Elements"
and then look for the text "For a vertical parasitic example I chose a model
N8PR wrote:
>>> You might consider four half wave sloping dipoles with the upper end hung
>>> out about 3 – 4 feet from the top of the tower.
For those who enjoy antenna modeling there are a few specialized AutoEZ models
available to do just that. Everything is controlled via variables so it
Oops, dupe of part of Frank's reply. My apologies.
Dan, AC6LA
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Also see this 2004 NCJ article by Al Christman, K3LC.
http://ncjweb.com/bonus-content/k3lcmaxgainradials.pdf
Dan, AC6LA
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Grant wrote:
>>> Or the inverse as I did, cut my T for the low end of the band. Then three
>>> series capacitors with PCB relays to short each individually (none, 1, 2,
>>> or 3) yielded nearly full band coverage <1.5:1 swr. My T is 85' to top and
>>> a 50:25 ohm TLT is a close match, then the
Marcel De Canck, ON5AU, has recently revised his website: http://on5au.be
This site is a gold mine of information related to antenna modeling and radio
propagation. Much of it free, the remainder very low cost. A few examples:
* Just so you'll know who he is: http://on5au.be/biography.html
As others have said, a good *RF* ground is a requirement. Here's a comparison
of modeled elevation patterns for a K9AY loop with a very good (low impedance)
RF ground vs one with a very poor (high impedance) RF ground.
https://i.postimg.cc/N0MqJg0x/image.png
The trick to modeling a good
Bob wrote:
>>> The problem I’m having is I can’t figure out how to separate the radials
>>> from the vertical and put the source at the base of the vertical and the
>>> radials. All five wires are connected and I can’t separate them.
That has to be the #1 point of confusion for folks just
Grant wrote:
>>> If you really want to know the parameters, see antennasbyn6lf.com as Rudy
>>> describes techniques for ground RF properties measuring.
Turns out that very subject was being kicked around on a recent qrz.com thread:
For the answer to that question see this tribute post by ON5AU:
http://on5au.be/Homage_to_ON4UN.html
Dan, AC6LA
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Stan Stockton wrote:
>>> Specifically what I want to find out is how much louder I would likely be
>>> in Europe from 25 degrees to 50 degrees if the vertical was on that line
>>> you drew as compared to being 70 feet below the line.
>>> Can AutoEZ be used to model this?
Yes, but only
Stan Stockton wrote:
Maybe someone has some idea of just how much better my signal would be if I had
a 160m vertical 65 feet closer to the water?
Stan, I have it on good authority that you have a modeling wizard in your back
pocket. :-) So for anyone who might be interested in modeling a
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