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<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>EZNEC+ 5.0 calculates that a flat top 80M dipole
up 55 feet will have max gain at 90 deg elevation – straight up. At 75
feet up, the max gain will be at 55 deg elevation. An inverted vee with the apex
at 75 feet up (max gain at 75 deg) will be better than the 55-foot high flat
top, but not as good as a 75-foot high flat top. The gain of an inverted vee
is down slightly from a flat top with the apex of the vee at the same height as
the flat top. Given my choice of #1 or #2 below, I’d opt for #2.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>For max gain at a low take-off angle and a
deep overhead null on 80M, a vertical starts to look like a good way to go. A
full-length (approx 65 feet) vertical radiator is preferable over any loading method
used to resonate a shortened vertical radiator. On 80M #12 wire is so thin relative
to a wavelength, the Q of the antenna will be high, and the 2:1 SWR bandwidth
narrow. To cover the entire 80M band, the vertical radiator would need to be about
3 feet in diameter – not very practical. A wire “cage” with
multiple parallel wires separated by an insulator with all parallel wires
connected at each end could be used to make a “fat” conductor.
Bigger would be better.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>Radials – most Amateur Radio ops
just don’t have the real estate to install the ideal 120 radials each ¼ wavelength
long. To reduce the number required, an alternative of above-ground radials might
be a solution. The elevated radials can be shortened with inductive or linear
loading. I’d stay away from a ground rod and 1 long radial – the feed
point impedance might be good and the SWR low, but the ground losses will be
high and the antenna efficiency low.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>Two possibilities that may or may not be practical
in your situation:<o:p></o:p></span></font></p>
<ol style='margin-top:0in' start=1 type=A>
<li class=MsoNormal style='color:navy;mso-list:l0 level1 lfo1'><font size=3
color=navy face=Arial><span style='font-size:12.0pt;font-family:Arial'>A
dipole hung from a tall tower like a guy wire. At the center feedpoint, a
rope continues on to the ground, and the “second half” of the
antenna goes back to the tower - like an inverted vee hung vertically from
a tower with the apex pointing away from the tower. <o:p></o:p></span></font></li>
<li class=MsoNormal style='color:navy;mso-list:l0 level1 lfo1'><font size=3
color=navy face=Arial><span style='font-size:12.0pt;font-family:Arial'>A
lazy H (vertical dipole with end loading) hung between 2 supports (towers,
trees, masts, etc.) fed at the bottom. The vertical part of the antenna 40-feet
in length with 38.3-foot end loading wires could be starting dimensions. (The
vertical part attaches to the center point of each end loading conductor.)<o:p></o:p></span></font></li>
</ol>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>Sources: <i><span style='font-style:italic'>ARRL’s
Vertical Antenna Classics, The Antenna Handbook, Antenna Compendium Vol 1</span></i><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>In your case what would I go with? #2
with the apex as high as possible for NA, and # 3 with as many radials as
possible each as long as possible (or elevated radials) for DX.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>I’d be interested to know what you
decide to put up for 80M.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>73,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 color=navy face=Arial><span style='font-size:
12.0pt;font-family:Arial;color:navy'>Marsh, KA5M<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
lcc-bounces@louisianacontestclub.org
[mailto:lcc-bounces@louisianacontestclub.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Mark, K5ER<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, September 26,
2012 4:54 PM<br>
<b><span style='font-weight:bold'>To:</span></b> lcc@louisianacontestclub.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [LCC] 80 meter antenna
recommendations?</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Okay, now its my turn to ask the group. HFTA doesn't model these
combinations, and I'm not good enough with EZNEC to trust I get them built
right within that software. I plan to review info from the antenna book, as
well as Low Band DXing, but there is collectively A LOT of knowledge within
this club, so I'd like to tap into that, too. <br>
<br>
I need to replace my 80 meter antenna, and am considering three options:<br>
#1. go back up with a flat top dipole (actually, center always seems slightly
below ends) height abt 55 feet<br>
#2. replace with inverted vee - feedpoint can be about 75-80 feet<br>
#3. ground mounted vertical - feed point at 6" above ground, one #12 thhn
conductor running up in an oak tree, one ground rod and (maybe) only one
radial.*<br>
<br>
*The #3 antenna started out from the NCJ article last year "an easy
inverted-L for 160. They showed with only ONE radial, it should give close to a
50 ohm match, not needing a tuner or inductor/capacitor tuning at base. Since
there are FAR more contacts on 80, as compared to 160, I could convert this
inv-L to a vertical by simply cutting off the excess (leave it about 67' long).
My issue here is I buried hardline from shack to feedpoint (about 260 feet),
but did not realize I had used 75 ohm hardline for the last 120 feet of the
run. I may have a mis-match to deal with at the feedpoint, so I would need to
address that. On the radial issue, I only have abt 30 feet of yard in one
direction, and the septic field lines are in the other, so a complete set of
radials is out of the question. I might be able to get 4-8, MAX, but only if my
wife goes somewhere for a weekend this winter and I get them stapled in without
getting caught.<br>
<br>
Everything I have seen on other reflectors compares flat tops and inv-vee's at
the same height. I have read that a inv-vee is better for DX, but also read
that <i><u><span style='font-style:italic'>at the same height</span></u></i> an
inv-vee is 1/2 to 1 db <i><u><span style='font-style:italic'>down </span></u></i>from
a flat-top. Because of tree location, in my case, the inv-vee feedpoint would
be higher, (20-25') than I could get a flat-top.<br>
<br>
My standard reply when someone ask me about antenna is "who do you want to
talk to?" Although I enjoy SWEEPS, I haven't worked it from home is
several years. I do not regularly participate in 80 meter traffic nets, (though
it would be nice to be able to check in during emergency situation). I DO like
the NAQP contests in January and July. I have recently become more interested
in DX, and should have 4 band DXCC within a month or two, but I am only 1/2 way
there on 80, so I guess my primary focus will be DX, but without giving up
"some" domestic. There is a chance I could get away with EITHER #1 or
#2, and still do #3 as well.<br>
<br>
What would YOU put up, and why?<br>
<br>
Thanks and 73,<br>
Mark, K5ER<o:p></o:p></span></font></p>
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