Topband: Square "loop" antenna for 160

[James V Redding PE]

A low tuned horizontal split loop with a single point of vertical grounding
(the DDRR "Hula Hoop")  was once popular and is on page 150 of Electronics
Engineering Manual (Vol XI).  Or you could look at U.S. Patent USR26196E
and the third image using a single conductor which is grounded on one end.
That is the Boyer patent and is assigned to Northrup. It might be the first
DDRR patent.

Figure 11 of the patent offers another variation, balanced, but with no
ground.

If you are thinking QRO, then please verify the exposure limits. . .
"Critters" in the walls are no issue, but no one wants to be accused
of cooking the family dog.

Jim/vez
USRE26196E USR26196

On Thu, Feb 3, 2022 at 2:31 PM Richard (Rick) Karlquist <
richard at karlquist.com> wrote:

> On 1/31/2022 6:22 PM, Radio KH6O wrote>
> > I have to live with CC&R homeowner restrictions. I plan to erect a
> disguise
> > wire antenna around the perimeter of my roof; total length will be about
> > 190 feet. Elevation will be about 20 feet above ground and will be fed
> with
> > 150 ohm twin lead.*
> >
> > My question is: Should this be a continuous loop or should the point
> > opposed the feedline be terminated with an insulator, thus giving two
> >
> > Jeff KH6O
> > Naval Air Staiton Point Mugu, CA
>
> Warning, long posting.  Sorry for the BW.
>
> It just so happens that I have a horizontal square loop antenna made of
> #18 insulated wire, that has a perimeter (AKA length) of 200 feet, and
> an adjustable height of zero to 30 feet, and is in the clear, away from
> buildings, etc.  It has a drive impedance of about 5 ohms + j600, IOW a
> Q of about 100, and therefore a bandwidth of a dozen or two kHz.  At 30
> feet, it consistently has a gain of -30 dB vs my 90 foot top loaded
> vertical over a massive ground screen on high conductivity ground.
> Except for certain stations within a few hundred miles where the loop
> might be "only" 20 dB down from the vertical, due to NVIS or short skip,
> or something.  Reducing the height to 20 feet only affects the gain by a
> few dB.
>
> IMPORTANT!  The size of this loop is too large for it to be "magnetic"
> with constant current.  However, I use a trick to make the current
> constant.  Without that, the loop would be even worse.
>
> Now to your questions:
>
> Not closing the loop creates a bent dipole.  It is approaching a half
> wave, but will still need loading coils.  I don't know how loading coils
> are going to qualify as "stealth".  I live on 20 acres so I don't think
> about stealth.  I will say that I have also erected full size 160 meter
> dipoles at a height of 30 feet.  Your bent dipole at 20 feet would be
> worse than this of course.  My dipoles had a fairly narrow bandwidth,
> maybe a few dozen kHz.  I don't remember for sure, but the gain was
> perhaps 6 dB higher than the loop, but don't quite me.  Running the
> legal limit power, you will be lucky to get a watt or two EIRP.  The
> digital modes like FT8 will be your only viable option.
>
> If you don't have an amplifier, you need to get a cheap used tube type
> one.  They don't command much money these days.
>
> Puh-leeze! don't feed it with twin lead.  You need a remote matching
> network at the feed point.  Hopefully with some frequency switching so
> you can cover more than a sliver of the band.  The question about
> stealth is again raised.
>
> BTW, I only use my loop for receiving.  I worked a JA while using it for
> receive when it was lowered to 10 feet.  It generally receives as well
> as the vertical in terms of signal to noise ratio, with the loop at its
> usual 30 foot height.
>
> 73
> Rick N6RK
>
>
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