Re: Off-Topic: Your advice/suggestion about antenna

Posted by David Gilbert on Mar 13, 2020; 11:08pm
URL: http://elecraft.85.s1.nabble.com/Off-Topic-Your-advice-suggestion-about-antenna-tp7658892p7658904.html


Lyn,

A dipole over ground has considerably more than 2.14 dbi maximum gain,
and since you said you had a tree in the middle I assumed (probably
incorrectly) that it was enough in the middle to allow a 40m dipole to
fit crossways your lot to other trees.  If that isn't the case, OK.

You didn't say whether your model that gave you 4.7 dbi for the EDZ was
a free space figure (and I'm too lazy to model it myself now to check),
but if so yes ... there would be at least a 2.5 db benefit to the EDZ. 
I've done my own tests to demonstrate the clear advantage that even 2 db
can provide (see http://www.ab7e.com/weak_signal/mdd.html), but I still
wouldn't call that "far outperforming".

And who said anything about putting up a rotating yagi??  Your EDZ is
not rotatable so why eliminate a wire yagi from consideration because it
isn't.  As I said, you do have to settle for unidirectionality but your
original comment was that other wire options would beat the yagi for
gain ... they don't.

I've read your reply three times now and still don't understand what
20KW into a ten curtain array has anything to do with this discussion.

Dave,
AB7E



On 3/13/2020 12:49 PM, Lyn Norstad wrote:

>
> Dave -
>
> I actually /do/ consider 4.7 dbi as "far outperforming" 2.14 dbi
> (ordinary dipole).
>
> And since cost is an issue for some of us (along with HOA
> restrictions), I rejected the idea of getting a couple extra dbi at
> the cost of many thousands of dollars.  And adding a N-S 40m dipole
> fed at the same point would have required either traversing my
> neighbor’s yard, or erecting a 2 towers … neither of which is feasible.
>
> And forget the logistics of erecting a 2 element beam for 80 meters
> (see OptiBeam OB2-80+ with 74 foot elements on a 36 foot boom), tower
> and rotor for that monster.
>
> We have a commercial (HST) shortwave station a few miles away that
> runs a 20kw transmitter on various 7 - 10 MHz frequencies into an 18
> dbi gain "curtain" antenna aimed over the pole to Europe.  Their beam
> width is 38º.  Ten curtains could be hung using relatively inexpensive
> towers or masts spaced at 36º in a circle.  The 20kw input results in
> an ERP of 808 KW, according to their FCC license, at an extremely low
> angle of radiation, and very low maintenance.
>
> That would actually be my first choice.
>
> 73
>
> Lyn, W0LEN
>
> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of David Gilbert
> Sent: Friday, March 13, 2020 1:39 PM
> To: [hidden email]
> Subject: Re: [Elecraft] Off-Topic: Your advice/suggestion about antenna
>
> That is certainly a perfectly viable antenna and probably a fine choice
>
> for your needs ... but it does not "far outperform" either a dipole or
>
> especially a 2 element yagi at the same height. (although the yagi would
>
> of course be unidirectional).  4.7 dbi is dipole territory.  You could
>
> have gotten pretty much the same result with an E-W 80m dipole and a N-S
>
> 40m dipole fed at the same point (orthogonal fan dipole).  And assuming
>
> you used capacitors for the EDZ, dipoles are easier to build.
>
> 73,
>
> Dave   AB7E
>
> On 3/13/2020 11:19 AM, Lyn Norstad wrote:
>
> > Duane -
>
> >
>
> >
>
> >
>
> > I am of the mind that the antenna is the most crucial part of any
> station,
>
> > and probably the most often maligned.  I have made a number of
> presentations
>
> > to ham groups on the design and construction  process involved in
> getting
>
> > the most bang for the buck, depending on your wants and needs
> (everybody's
>
> > are different).
>
> >
>
> >
>
> >
>
> > In my own situation (2 acre semi-rural lot approx.150 feet x 600 feet
>
> > running E-W feet, and active HOA) the goal was to have a single
> antenna that
>
> > would provide the best primary signal on 80 meters in a North-South
>
> > direction, while providing the best possible signal on 40 meters in an
>
> > East-West direction, consistent with the 80 meter performance and
> without
>
> > unduly provoking the HOA (or my XYL).
>
> >
>
> >
>
> >
>
> > I decided on an Extended Double Zepp, cut for 3.5 MHz.  That
> resulted in a
>
> > length of 360 feet, which worked nicely since I have 400 feet clear
> from the
>
> > house (West end) to a perfect tree for the far East end.  And
> another tree
>
> > in the center for support of both the antenna and the feedline.
>
> >
>
> >
>
> >
>
> > I am feeding it with a 160 foot length of 600 ohm "true ladder
> line."  I can
>
> > go into more detail if this sounds like something that would work. 
> Modeling
>
> > this antenna with EZ NEC shows a maximum theoretical gain of 4.7 dbi
> in both
>
> > North and South directions.  With the ladder line, a dual hybrid
> balun and
>
> > short length of coax into the shack, my KAT500 tunes it very nicely
> on all
>
> > bands 160 m thru 6m.
>
> >
>
> >
>
> >
>
> > I don't have your call so can't see where you are, but would be happy to
>
> > make other suggestions based on the coverage you seek.
>
> >
>
> >
>
> >
>
> > 73
>
> >
>
> > Lyn, W0LEN
>
> >
>
> >
>
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