[BVARC] Slots, loops, and verticals. Oh, my!

Rick Hiller rickhiller73 at gmail.com
Sun Mar 14 18:52:28 CDT 2021


Hey, Jonathan,

Agreed that the different ways of feeding, but the way he is feeding his
loop is at the very bottom where series and shunt are the same.  And as I
point out on a greater than 1'/2 WL loop a current loop appears opposite of
the feed point..So it appears that it is shunt fed and the affect of such,
but is not.  IMHO.

Thanks for the reminder of the G8JNJ antenna.  I remembered seeing this in
Antennex years ago, but now I have the articles from RadCom.  Thanks!   He
gives an excellent introduction into broadbanding techniques and existing
art.

I did not get to participate in the Hamfest, but I did buy a ticket and I
want to see quite a few of the presentations.  Guess I have 30 days to take
advantage of that.

Sounds like you are on a fun trip toward a good low band antenna.   GL and
if you run into more good info on antennas, please send it my way.   Always
interested in learning something new (or old).  HI

73...Rick

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On Sat, Mar 13, 2021 at 9:41 PM Jonathan Guthrie via BVARC <bvarc at bvarc.org>
wrote:

> Hey, Rick
>
> I read the articles you pointed me to.  Here are some random thoughts
> about them, and the talk.  And antennas in general.  Oh, and one or two
> other things.
>
> It seems to me that the difference between a "slot" and a "loop" lies in
> how you feed it.  NBC basically says that if you connect one side of the
> feedline to one side of the loop and one to the other side of the loop,
> it's shunt fed and, therefore, a "skeleton slot".  Otherwise, they're the
> same wires in the same arrangement and I would expect them to perform
> similarly.  He even says as much during the talk, although he criticizes
> one delta loop he shows because it is fed at the bottom, and if there's a
> current antinode halfway around the loop from the feedpoint, then the
> feedpoint being close to the ground wouldn't make any difference from the
> radiation angle.  For me, the real value of the talk was finally
> understanding how a slot worked and, well, what "shunt fed" means.  (I'm a
> viscous aerodynamicist by training, and I find all these weird terms
> confusing.)  Well, that and pointing out that I should have bought the
> NanoVNA with the big screen instead of the small one.  I didn't even
> realize there were two.
>
> Of course, on HF, the polarization of the signal is not very important in
> most cases, and I don't think that the directionality of the antenna is
> worth talking about.  If you want a directional antenna, I like KL7AJ's
> idea of putting up two vertical antennas and driving them with a specified
> phase shift to send the signal where you want.  (I think I saw the idea in
> the "Receiving Antennas" book.)
>
> Since I prefer to work low-bands, horizontal dipoles are not generally a
> good choice for me.  I found out about a thing called a "Terminated Coaxial
> Cage Monopole" which the inventor (Martin Ehrenfried G8JNJ) says will give
> a basically flat impedance curve and decent efficiency from 1.8 to 70 MHz,
> and I've been considering building one of those, although it is both bigger
> than the loop (or the slot) antenna and requires radials.
>
> https://www.tc2m.info/
>
> I'm not going to build it any time soon, however because I have built, but
> haven't yet installed, a vertical monopole antenna which will be made
> broadband by the simple expedient of feeding it through a remote antenna
> tuner at the base.  It's made of a lot of wire turned around two-inch PVC
> pipe, so I expect that it will tune up on 160, but I have no idea how
> efficient it might be.  For a long time, I've toyed with the idea of
> vertical dipole antennas in order to avoid laying out radials, but
> eventually I concluded that creating a vertical support was the hard part
> of building a vertical antenna and a vertical dipole is twice as tall
> meaning that the construction of the antenna is at least twice as hard.
> Radials are easier simply because they lie upon the ground.  One advantage
> of the slot (or the loop) is that you can make the antenna wide in addition
> to tall, which means you don't have to go as tall.
>
>
> On 3/13/21 8:16 PM, Rick Hiller via BVARC wrote:
>
>
>
>
> Jonathan,
>
> Have  a read of this column
>
> *http://www.bvarc.org/Tech/October2020.pdf
> <http://www.bvarc.org/Tech/October2020.pdf>*
>
> NBC is kind of pushing the slot take on this antenna.  I disagree.
>
> What'cha think?
>
> Also see December 2020 The Radio Hotel in the Beacon
>   The paragraph on "Horizontally polarized vertically oriented multi-band
> antenna"
>
> .
>
> Regards...Rick  W5RH
>
>
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>
> On Sat, Mar 13, 2021 at 3:48 PM Jonathan Guthrie via BVARC <
> bvarc at bvarc.org> wrote:
>
>> 2 out of 4 now and the presentation on the skeleton slot antenna was
>> worth the cost of admission for me.
>>
>
>
> --
> Jonathan Guthrie
> ARS KA8KPN
>
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-- 
Rick Hiller
*e-mail:     rickhiller73 at gmail.com <rickhiller73 at gmail.com>*
*Cell:        832-474-3713*
*Physical: 9031 Troulon Drive*
*               Houston, TX 77036*
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