On 11/5/2015 8:40 PM, Jeff Liebermann wrote:
On Wed, 4 Nov 2015 00:17:11 -0500, rickman wrote:

On 11/2/2015 7:39 PM, Jeff Liebermann wrote:
On Mon, 2 Nov 2015 09:13:38 -0600, amdx wrote:

Below some pressure level, it will probably flop over if mounted
vertically. That's why I mumbled that I wasn't sure if it should be
mounted vertically with a support pole, or horizontally on a flat
sheet of plywood. Both will work, but I'm not sure which is better.

Hang it upside down.
Mikek

But, all the photons will fall out of the loop that way.

Actually, there's a problem. It doesn't work as well upside down.
The magnetic loop has a rather directional field and takeoff angle and
does NOT have a constant current around the loop:
http://www.nonstopsystems.com/radio/vids-ant/antenna-Mag-Loop-Demo1.wmv

I don't get this video. I can't really hear what he is saying so when
he says at the end, "this is not what you would expect" I don't get it.

I had the same problem. I would guess(tm) that what he's mumbling is
that one would expect the current to be constant around all parts of
the loop, yet it displays obvious maxima and minima.

He isn't saying anything about the current since he isn't measuring
current. I think the "isn't what you would expect" maybe be about
polarization.


https://www.youtube.com/watch?v=SUYI81dkEMA

This video is about the voltage and current around a loop, but he says
it is a 1/10 wave loop, but I can't tell that. He has another video
showing the directionality of a 1/4 wave delta antenna. I'm wondering
if this is also a 1/4 wave antenna.

At 6:30 in the above video, he proclaims that it's a 1/4 wave loop.
At 6:42, the MFJ-259B shows 29.555 MHz on the display. I couldn't
find where he said it was a 1/10 wave loop. 1/10 wave is the
defacto definition of a "small" loop.

The start says the purpose is to settle the dispute about current
distribution in a 1/10 wave loop. Doesn't make sense he would be
doing that with 1/4 wave antenna. At 2:45 it says this loop is 1/10
wave on 10.5 meters 28.26 MHz.

The comment at 6:30 is about the impedance in a 1/4 wave loop, but he
isn't saying this *is* a 1/4 wave loop. I believe the 1/4 wave loop is
the one he uses in the next clip, but this is a bit confusing.


I suspect that an inverted loop will send most of the RF into the
ground. I should probably test this.
http://www.nonstopsystems.com/radio/img-ant/antenna-magloop-rad-angle.gif

Which type of loop antenna are you talking about, 1/4 wave, or 1/10
wave (small, magnetic)? I can't tell anything about this antenna and it
seems to contradict the other video.

I'm not saying anything about the drawing except that it shows that
the loop might be somewhat directional, which might be a problem.
Where's the contradiction?
http://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm

If you take this drawing literally it shows a maximum at 30-45 degrees
from horizontal while all the others show a max at the capacitor. I
don't know that this diagram is intended to show field strength, rather
just that it may vary and the angle is what you should measure.

There will be interaction with the ground unless the antenna is spaced
well above it. Once that is done the remaining radiation pattern will
be far field which is very different from near field. So I think the
"radiating into the ground" thing may be overstated. Place the loop
horizontal and it will radiate 360° with a null at the ground. No
rotator needed.

--

Rick