Steve,

Gotta agree with you on this one. I get people coming in to the store
almost every week wanting to know how they can get better reception
of AM stations on their radio. It's the same ol' thing every time.
They need an antenna but don't want to bother with the "hassle" of
hooking it up... even if it's just 25' of wire tucked between the
carpet and the wall.

Seems like no matter how long or hard we Priests of the Technocracy
preach the unwashed masses simply don't want to be redeemed!

73,

'Bear' NH7SR

--- In loopantennas@..., Steve Greenfield
<alienrelics@y...> wrote:

What most people want is just to buy a radio and have it pick up
the station they want.

It's only tyros like us who will go to the trouble of owning a
radio -and- an add-on antenna.

Had a gentleman come into a TV shop I was working in, looking for
an AM radio with really good reception, as his favorite station was
at the very edge and sometimes disappeared. I looked at what he had
and determined the only way he would get better reception was with
an add-on antenna of some kind, loop or wire. I spent time and
effort researching and buying parts for a tuned loop, specifically
made to look like one of the early wood-framed ones.

In the end he went out and bought some POS AM/FM table radio
because it looked like an old radio, and went with his furniture.
He couldn't pick up his radio station -at- -all- with it, but he
kept it because it looked good with his decor. And he didn't buy
the loop I was building for him, because he decided it wouldn't go
with his furniture.

People like us get satisfaction from hand-building something that
then pulls in stations from very far away. I'm betting there are
quite a few here who've even built their own radio from scratch.
I'm also on the CrystalRadio list, and there are people there who
even build their own tuning capacitors and galena crystals!

Most people just want to hit a button and hear music or their
favorite talk-radio station.

So in the end I think most people would rather pay $20 or $50 more
for a radio than have to buy and lug around even a $5 loop, no
matter how easy to transport it may be.

Steve

--- Bruce Carter <brucec@m...> wrote:
...

AM loops seem to be one of those products for which there would
be
demand if the AM band had less noise on it, better programming,
if
people were more educated about the product, and the product was
priced right. I think, for example, if you had a light weight,
portalbe / collapsible loop that was large enough to really make
a
difference, you could sell it if it was under $5 to people
relocated
from their "home team" city and they could DX their old 50 KW
sports
station. Much more $ than that, and people won't buy.

__________________________________
Do you Yahoo!?
Friends. Fun. Try the all-new Yahoo! Messenger.

Barry,

Yah... there doesn't seem to be a whole lot of "middle ground" in
loop theory. I had some calculus in high school 40 some odd years ago
but don't remember how to do any of it now. Simple algebra I can
handle.

I have thought about writing my own loop calculation program in VB6
but there are so many variables involved and the math is mostly
beyond my ken. I know what I would like to have the program do but
can't seem to pull up enough of the math in a form that I can
understand and code with.

Looks like we're riding in the same boat!

73,

'Bear' NH7SR

--- In loopantennas@..., "Barry Savage" <sofistic@s...>
wrote:

Hello All:
Over the last couple of years I have done extensive searching for
both theory and practice with regard to loop antennas, and here is
what I have found:
1. Most of the theory is way over my head, since the last calculus
class I took was over 30 years ago.
2. Most practice sites explain very well how to *make* things, but
not much time is spent on *how it works*.
3. There is not much in between, some exceptions are Ian Purdie's
Austrailian site and Rod Elliot's Elliot Sound Products (ESP)

site.

Both have excellent tutorials on them. A few ham sites have good
explanations of the connection between theory and practice.

So, what I see is a big blank area in between, and I find myself
going back and forth between the two without a lot of insight being
gained in the process.

For example, there are many sites with formulas for inductance of
solonoid, spiderweb, rook, conical, helical, etc coils, but very
little on distributed capacitance and how it varies with spacing

and

wire sizes (unless you want to flagellate yourself with a treatise
on Maxwell's equations).

I would love to use a spreadsheet that included the inductive,
capacitive and pure resistive components of everything from a long
straight wire to coils (as well as loops) as well as most of the
common shapes (circular, square, polygonal). If I had all the
formulas (in an algebraic form, not in differential calculus form)

I

would even be willing to put the spreadsheet together and post it

to

the group. I am using OpenOffice as my office suite, so I can

write

it out in Excel format.

A good starting place is the Dr. Coyle spreadsheet, which I use all
the time. It has formulas for both solonoid and spiderweb designs,
as well as input for capacitance and it will calculate the resonant
frequency for a given inductance, wire size and number of turns,

and

gives the physical size of the coil form and length of wire needed.


But I want more. The Qu would be nice, and so would the impedance
(since it does calculate the reactance). I added a table of wire
resistance to the spreadsheet, but at this point I am not clear on
which way to calculate the Q. (I mean, wouldn't the Q tend to
infinity as the resistance went to zero?)

And then there is the distributed capacitance.
I mean, how many Coulombs (sp) does a wire of a given diameter (at
least of copper) have per unit length, given a specific voltage?
And how much of a charge is induced into an adjacent wire a given
length away? And (while I'm on a roll) how fast does the
electrostatic charge collapse at a specific frequency and voltage?
It seems to me that this information could be used to calculate the
capacitive reactance, and therefore the self-resonant frequency of
the coil (or loop). And couldn't one simply multiply the turns by
some constant instead of integrating a complex function from one

end

of the coil to the other?

And (Oh, my god!), none of this has taken into account

permeability,

reluctance, admittance, etc. for non-air-core devices.

Woe is me and Oy Vey! Where do I go from here?
Any help would be most appreciated.
Barry

Just received the invitation to join this list. Pleasure to be here;
thankyouverymuch.

One of the loop antennas I have built was about 4 feet on a side,
about 4 turns; built for listening to atmospherics, or 'spherics as I
understand they are called. Worked great; had to take it well out of
town, which at that time turned out to be to Coal Oil Point, CA.

Did it near sunset, and heard lots of chirping and whistling. It was
the third most amazing science project I have done.

The instructions for construction of the antenna were from an
excellent book called, "Listen to Radio Energy, Light and Sound", by
Calvin R. Graf (now out of print).

The other loop I built, I didn't really have to build. It was one of
those VHF loops from a portable TV. All I did was add a Germanium
diode and plug it into an audio amp. This one was great for picking up
all sorts of transmissions at the local airport. Mostly radar and
flight path beacons (what are those called)?

-Brian Wesley Rich

I read that as "get you back in, enough said."
-Brian

Man, where do you find the time? I mean, HAM, propmaking, electronics,
weird antennas, mad scientisting, moderating...

I need a tutorial from you!

-Brian Wesley Rich



--- In loopantennas@..., Steve Greenfield
<alienrelics@y...> wrote:

I'm also on the CrystalRadio list, and there are people there who
even build their own tuning capacitors and galena crystals!

Let's just let this drop, and talk about loops.

Steve

--- In loopantennas@..., "Brian Wesley Rich"
<science@w...> wrote:

Man, where do you find the time? I mean, HAM, propmaking, electronics,
weird antennas, mad scientisting, moderating...

I need a tutorial from you!

My brain won't stop buzzing. It's hard to wind down and sleep at
night. When I was young and my body could take it, I might stay up for
a couple of days or 3 days (rarely!) in a row. If you only knew how
many projects I have going... I used to read Sci Fi and science
constantly, now it's datasheets and technical lit.

I'm not a Ham, though. Never learned morse code.

Way above AM BCB, but is anyone here making DDRR antennas? Those
horizontal loop, omnidirectional antennas? Direct driven ring radiator?



Found a site for one that does not require a ground plane. It is to
the DDRR above what a vertical 1/2 wave is to a 1/4 whip with ground.



How about microwave patch antennas? How do you feel about allowing the
related topics of radio direction finding and low profile antennas as
on topic subjects?

Steve

--- In loopantennas@..., "Brian Wesley Rich"
<science@w...> wrote:

Just received the invitation to join this list. Pleasure to be here;
thankyouverymuch.

Welcome!

I found a free online book on antennas, still being written. From
Rutger's University, called Electromagnetic Waves and Antennas.



Sad to say, I didn't take enough math so much of it is beyond me.

See Chapter 15 for Loop Antennas.

Steve

Steve,

DDRR stands for Directional Discontinuity Ring Radiator. I thought
about building one for 30 meters (and still may) but rejected it at
the time since horizontal space is more of a premium item for me than
vertical space. They have basically the same physical requirements as
MagLoops. Fat conductors, low loss connections, high voltage
capacitors if you're gonna transmit through them. Since they are more
akin to a 1/4 wavelength transmission lines they are probably not as
size tolerant as MagLoops. Haven't tried it, though, so can't really
say.

I'm in favor of discussing just about any kind of compact antenna
here. There's lots of controversy over whether EH, CFA and Capacitive
Disc Antennas work or not. Most of that has to do with inventor's
claims that seem to contradict Maxwell's equations. I don't think
that is very important. Some of the designs look like they may be
very viable solutions for SWLs or folks who are limited to using
indoor antennas.

73,

'Bear' NH7SR

--- In loopantennas@..., "Steve" <alienrelics@y...> wrote:

--- In loopantennas@..., "Brian Wesley Rich"
<science@w...> wrote:

Man, where do you find the time? I mean, HAM, propmaking,

electronics,

weird antennas, mad scientisting, moderating...

I need a tutorial from you!

My brain won't stop buzzing. It's hard to wind down and sleep at
night. When I was young and my body could take it, I might stay up

for

a couple of days or 3 days (rarely!) in a row. If you only knew how
many projects I have going... I used to read Sci Fi and science
constantly, now it's datasheets and technical lit.

I'm not a Ham, though. Never learned morse code.

Way above AM BCB, but is anyone here making DDRR antennas? Those
horizontal loop, omnidirectional antennas? Direct driven ring

radiator?

Found a site for one that does not require a ground plane. It is to
the DDRR above what a vertical 1/2 wave is to a 1/4 whip with

ground.

How about microwave patch antennas? How do you feel about allowing

the

related topics of radio direction finding and low profile antennas

as

on topic subjects?

Steve

Gents,

Here's the link to a compact antenna that I think deserves more in
the way of exploration and exploitation.

<>

There's a bunch of other stuff in the Antennex site archives but you
have to be a member to access it. Wish I could port some of it over
here. Hmmm... maybe some non-infringing synopses as I have the time.

This is the kind of thing I think would be an appropriate topic for
this group in addition to our loopy stuff.

73,

'Bear' NH7SR

Here is another link to a site dealing with compact antennas
including the coffee can antenna, cone disk, bicone and eh antennas.
There are a number of useful Javascript calculators here as well.

<>

Check out the "What Can Small Antennas Do?" and "Per request - Pages
from old Web Site" links on this site.

The emphasis here is on ham radio and antennas that can be used for
transmitting as well as receiving. The instructions for tuning with
an impedance bridge can probably be ignored if the antenna is only to
be used for receiving. Tuning "by ear" will probably work just as
well.

Much of the criticism regarding compact antennas such as these stems
from the fact that they exhibit a loss compared to a full-size dipole
or vertical. That is true... so do MagLoops. OTOH, they also have a
reputation for lower noise in receiving applications.

73,

'Bear' NH7SR (On the prowl for more goodies)

Following up on a post in the VLF group this morning I visited
Renato's VLF site at...

<>

where he posted details of a new antenna he is using for VLF/ELF
reception.

<>

Although the antenna is designed for VLF/ELF it is quite possible
that the same approach will work well for LF/MW and maybe even HF.

As we say here in Hawaii... Try look!

73,

'Bear' NH7SR

Hello !
Question in the title...
Can anybody give me some info about these antenas ?
73's
Gilles FM5AD

开云体育

Gilles,

HF horizontal loops are usually fairly large antennas. Typically cut
to 1005/f(MHz) for circumference in feet. They are often fed with
open wire transmission line using balanced antenna tuners. This makes
them capable of operation over a range of up to 3 octaves. Their
radiation pattern depends on whether they are operating on their
fundamental frequency, a harmonic or somewhere in between. Take off
angle (and best reception angle) is dependent upon height above
ground. They do have a reputation for being relatively low noise. I
say relatively because when they are mounted at a height less than
1/4 wavelength above ground they have a predominantly "straight up"
radiation pattern which makes them very efficient at picking up
atmospheric noise.

Hope this helps you.

73,

'Bear' NH7SR

Ah, shucks, Scott! ('Bear' sheepishly grins and scuffs his foot)
Thanks!

Sounds like you've got a pretty high Q loop. I have noticed a small
degree of sideband cutting on mine at the low end of the band. The
polyvaricon cap I'm using is probably cutting down on the overall
circuit Q.

Not surprised that you got better directionality at ground level.
From about 3 MHz on down rf seems to like "falling down" and
traveling along the ground. Same thing happens with acoustic waves.
The lower the frequency, the more they hug the ground.

73,

'Bear' NH7SR

--- In loopantennas@..., "Scott Savage KC7WDG"
<kc7wdg@c...> wrote:

well tried an experiment tonight took the yaesu frg-7700 and look

outside and the pizza box loop and from what I see the loop is more
directional closer to ground and seems to work better on some
stations. Also the tuning cap needs to be very finely tweaked to peak
the station its amazing how just adjusting it can change the sound of
the audio and or remove adjacent interference. also the loops works
just about as well as my big dipole only quieter most of the time the
bonus is the size of it the loop is much much smaller and works just
as well if not better on some station because of its directionality.
I am very impressed with this MacGyver antenna or MPBL for MacGyver
Pizza Box Loop hehe. I also took and used some hot glue to secure the
turns in 4 spots on each side also on the corners I may take some
pics later for you guys its ugly but works great. Also thanks to
everyone who suggested ideas and what not and a big thanks to bear
for the description.

Scott
KC7WDG


----- Original Message -----
From: Bruce Carter
To: loopantennas@...
Sent: Wednesday, June 09, 2004 12:27 PM
Subject: [loopantennas] Re: Pizza box loop


Or better yet get a clean one from the pizza restaurant so it
doesn't STINK or attract ants.


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Now available at:



Then click on the "design calculator utilities", and the loop
antenna calculator is at the bottom. The choice for "wire" is the
one you want. Remember this is for wire with no spacing between
turns, I will post a more general version on my site later ----

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the loopantennas
group.

File : /SpiderWeaveCoils.txt
Uploaded by : alienrelics <alienrelics@...>
Description : The Basket Weave (Spider Weave) Loop Antenna Coils by RHF. With links for other parts necessary for loop ant. and crystal radio construction.

You can access this file at the URL



To learn more about file sharing for your group, please visit



Regards,

alienrelics <alienrelics@...>

Bear,

I tried to answer you on the GCC Loop Group. For some reason the
post didn't appear. So:

Bear,

My shoggoth upchucked allowing me to provide the following example:

An impedance analyzer gives an impedance of 3 + j215 ohms at 1.6 MHz
for a certain Pioneer AM loop. Let's make the proximal capacitor
(Cp) 7900 pF and the distal capacitor (Cd) 490 pF. That gives
capacitive reactances –j12.6 ohms and –j203 ohms respectively at 1.6
MHz.

The loop in series with Cd gives

3 + j215 – j203 = 3 + j12

Using the parallel impedance formula gives

(0 – j12.6)(3 + j12)/[ (0 – j12.6)+(3 + j12)] = 50.9 – j2.4 ohms

That's not too bad for the shoggoth and me making some wild guesses.

Cp could be a 5100 pF cap with a dip switch to add 200, 400, 800,
1600, and 3300 pF in parallel. Cd could be a 360 pF variable with
200 pF in parallel.

Actually the shoggoth used



and transformed the negative inductor in the upper right network
into a capacitor.

Regards,

Steven

Steve,

Ahh... thanks for that. I'm still puzzling over the math but perhaps
they point to a possibility of success.

For those who may not be aware of the "Street Sweepings Loop" it is
based on the idea of feeding the loop directly from 50 ohm coax using
the loop inductance itself as part of a Pi-Network. The most
important remaining questions are... what would be the output
impedance of the Pi-net? 377 Ohms (the impedance of free space) or
some other value? Would a resistive output termination be required?
All this preliminary to building such an animal of course. The real
answer would be to build it and compare it against a conventional
loop of the same size but Summer is coming on and 'Bear' is more
concerned with eating berries and catching salmon to fatten up on for
the coming Winter's sleep.... and mebbe finding Lady Bears, too <G>.

73,

'Bear' NH7SR (Yo! Shoggoth!! Fetch me a beer!!! No... not St. Pauli
Girl you dumb beast!!!!)

--- In loopantennas@..., "Steven S. Coles"
<steven_coles@y...> wrote:

Bear,

I tried to answer you on the GCC Loop Group. For some reason the
post didn't appear. So:

Bear,

My shoggoth upchucked allowing me to provide the following example:

An impedance analyzer gives an impedance of 3 + j215 ohms at 1.6

MHz

for a certain Pioneer AM loop. Let's make the proximal capacitor
(Cp) 7900 pF and the distal capacitor (Cd) 490 pF. That gives
capacitive reactances –j12.6 ohms and –j203 ohms respectively at

1.6

MHz.

The loop in series with Cd gives

3 + j215 – j203 = 3 + j12

Using the parallel impedance formula gives

(0 – j12.6)(3 + j12)/[ (0 – j12.6)+(3 + j12)] = 50.9 – j2.4 ohms

That's not too bad for the shoggoth and me making some wild guesses.

Cp could be a 5100 pF cap with a dip switch to add 200, 400, 800,
1600, and 3300 pF in parallel. Cd could be a 360 pF variable with
200 pF in parallel.

Actually the shoggoth used



and transformed the negative inductor in the upper right network
into a capacitor.

Regards,

Steven