Just as a basic experament, I tried building a loop antenna out of a hoola
hoop.

I wrapped 4 turns of 24 gauge (cheap speaker wire) around a hoola-hoop.

While the antenna "worked" it didn't have the directional properties I had
expected. It basically seemed as though it was just a plain wire antenna.

Rotating it or placing magnetic materials inside of the loop seemed to have
little or no effect.

Could it be that I used electrical tape to hold the wires in place? Could it be
the curve of the tubing? (Unlike a very large diameter cardboard tube or spool,
with a flat surface, the wires aren't flat they're on a curved surface (plastic
tubing) making a circle. I hope I'm explaining this right.

How does one determine the number of twists to use?

Anyone else try this with success?


Jamie
--
http://www.geniegate.com Custom web programming
(rot13) User Management Solutions

Do you have some sort of amplifier to go along with the loop? Some
antenna wire in a hoola hoop will work with a wellbrook ALA 100. One
loop is enough.. My preference is to use an "X" frame and build a
square loop because the hoola hoop isn't very rigid. However, for
something quick and dirty to set up, the hoop will work.

There are all sorts of tune loops you can build using circuits from the
ARRL handbook. The basic idea is to make a LC series circuit, then you
inductively couple the signal to a Jfet amp. I just find the notion of
having to tune the loop to be a PITA. I just wish there was a more cost
effective version of the Wellbrook.

NOS,

There are all sorts of tune loops you can build using circuits from the
ARRL handbook. The basic idea is to make a LC series circuit, then you
inductively couple the signal to a Jfet amp. I just find the notion of
having to tune the loop to be a PITA. I just wish there was a more cost
effective version of the Wellbrook.

************************************************** *************************

RHF, will be along with some great info.
i have the RS MW loop/ the TorusTuner loop, and the Wellbrook 330S here.
loops are fun to play with. last year someone posted the "Pizzabox
loop",
here. really fun to build; check the google groups for info. the yahoo
groups has 2 or 3 groups devoted to loops. and, my favorite- Joe Carr's-
"Loop antenna handbook". about $20 from Universal Radio. this is the-
everything you wanted to know about loops- ref. Joe's book is great.
loops are easy and fun...
Drifter...

In article ,
wrote:

Just as a basic experament, I tried building a loop antenna out of a
hoola hoop.

I wrapped 4 turns of 24 gauge (cheap speaker wire) around a
hoola-hoop.

While the antenna "worked" it didn't have the directional properties
I had expected. It basically seemed as though it was just a plain
wire antenna.

Rotating it or placing magnetic materials inside of the loop seemed
to have little or no effect.

Could it be that I used electrical tape to hold the wires in place?
Could it be the curve of the tubing? (Unlike a very large diameter
cardboard tube or spool, with a flat surface, the wires aren't flat
they're on a curved surface (plastic tubing) making a circle. I hope
I'm explaining this right.

How does one determine the number of twists to use?

Anyone else try this with success?

The twisting the wire around the hoop will make the coil look less flat
than a one turn electrically similar to physically and this will make a
null less defined but that may not be the main problem.

The main problem may be the frequency you are trying to operate it at. A
loop null will work best when you have a transmitted source that looks
like a point source like daytime BCB or a ground wave signal. If you are
trying to use this hoop on short wave with reflected or refracted waves
off the ionosphere then the source is spread out and you won't get a
good null on a signal with the hoop. On the short wave band you can get
a null on a one turn loop at the low end. I've done it for 5 MHz WWV but
the higher you go in frequency the harder it gets. A small amplified
loop can probably do it at higher frequencies.

Another problem might be the way you terminated it as any antenna needs
to be terminated properly.

--
Telamon
Ventura, California

All small (compared to a wavelength) loops have the same pattern
and an infinite-depth null.

Alas, they have separate patterns for electrical and magnetic
fields. A tall loop tends to act as a vertical antenna and pick
up plenty of electric field. So where you have your nice automatic
magnetic field infinite null, it's filled in by electric field
which can't be cancelled by a magnetic field since it's 90 degrees
out of phase (otherwise it would just shift the null).

Shortwave tends to give you electric field responses faster than
MW, just owing to the relative size of the loop and the wave getting
larger as the wave gets smaller.

In addition, as said, multiple or moving apparent sources owing to
ionospheric bounce may make a permanent null difficult to find.

Careful construction is said to reduce the electric field response
to something very small, so you get deep unfilled-in nulls.

An amplifier on the loop amplifies the magnetic field response mostly,
and so gives the same effect as good construction without having to
have good construction.

--
Ron Hardin


On the internet, nobody knows you're a jerk.

Just an FYI, you can make "clean" loops using ribbon cable. [It's that
flat cable with many parallel wire of different colors. I'm sure you've
seen it before.] What you do is put on insulation displacement
connectors that mate on either end and connect them in a manner where
there is a one pin shift between the connectors. The free pin and free
socket are the locations where you connect to the loop.

The problem with running many wires in parallel is there is capacitance
between the wires, so the loop is really a distributed inductor and
capacitor.

It seems to me what you are not getting in a loop of many turns is a
large aperture. That is, does one big loop act the same as many turns
in a smaller loop? My gut feeling is you would get a better null with
one big loop. The null is quite important in many situations.

I've planned on doing single turn versus multiturn comparisons, but
haven't got around to it. I can tell you that bigger sure is better
than small.
This is a loop 4ft on the diagonal:
http://www.lazygranch.com/images/radio/loop1.jpg
This version is 11ft on the diagonal, and is probably at the practical
limits of this style of support:
http://www.lazygranch.com/images/radio/bigassant.jpg

In: .com, wrote:
Do you have some sort of amplifier to go along with the loop? Some
antenna wire in a hoola hoop will work with a wellbrook ALA 100. One
loop is enough.. My preference is to use an "X" frame and build a
square loop because the hoola hoop isn't very rigid. However, for
something quick and dirty to set up, the hoop will work.

Really I just wanted to see one in operation. It's cool, maybe I'll build
another some day (I got 2 hoops, one slightly smaller, figured I'd "play"
with the idea of placing one inside the other and rotating it)

There are all sorts of tune loops you can build using circuits from the
ARRL handbook. The basic idea is to make a LC series circuit, then you
inductively couple the signal to a Jfet amp. I just find the notion of
having to tune the loop to be a PITA. I just wish there was a more cost
effective version of the Wellbrook.

Yea, tuning it is a pain. (I tried it with the variable cap. as well) turns
out the problem was in the long leads. Shorter leads made it work very well!
(Was actually able to get stations from other states during daytime hours!)

One problem though... the station I really want to get.. nothing comes in
on that freq. w/out the loop, but when I put the loop in, there are several
stations. Apparently, there are 3 or 4 of them, so, rotating it pulls in the
one on the OTHER side. :-/

Aside from that, it is a very fun toy, can't believe I could hear NPR on the
AM band. :-)

As far as the amplifier, some years ago... I built a regenerative receiver
(tube based) it was kind of a fun toy, I was thinking of doing something like
that for the amp, but based on this circuit:

http://www.tricountyi.net/~randerse/regen.htm

(resonant in the broadcast band instead of 40m as that circuit is designed)

One would imagine that "holding" the loop would make tuning nearly impossible, but...
wouldn't such an amp be really powerful? (Not such a good idea in places
like apartments though, lest one annoy the neighbors with RF pollution..)

Wonder if that circuit presented by Mr. Andersen could be powered via some
exotic means. :-)

Jamie
--
http://www.geniegate.com Custom web programming
(rot13) User Management Solutions