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!

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

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

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

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.

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@...> 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.

Does anyone here personally know Adam?

I looked up his profile and stumbled onto his web site. He is 26
years old, and seems to be a normal guy. I think he wants to
develop intellectual property regarding loop design, and possible go
into business selling loops. I am sure not going to do any more
speculation than that as to the events surrounding the groups. And
I wish him luck selling the things - Terk and Radio Shack sure
didn't have very good luck.

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.

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

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

I just left it inside... after a week or so it gets nice and stiff.
Makes for good re-inforcement of the box.

73,

'Bear' NH7SR

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

I find it helps if you finish off the pizza first.

The Q is increased quite a bit.

;')

Steve

--- qrpbear <qrpbear@y...> wrote:

Scott,

Oh.. ya gotta space 'em otherwise you'll have nowhere to wind the

colored yarns to make it pretty <G>

Spacing at least one wire diameter will improve efficiency and Q.
For
a Pizza Box Loop it probably doesn't matter all that much and the
difference may be un-noticeable.

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

Scott,

I live on the ground floor. The Pizza Box Loop sits about 3' off the
ground and seems to do quite well there. I have tried it on the floor
and also on top of a bookshelf but didn't notice any difference. It
should be noted that I have only received stations within the State
of Hawaii with it (all of them including the 100 watters). I don't
know how well it will perform for DXing since I don't have a good
receiver for MW at present. The nearest MW stations other than Hawaii
would be in Los Angeles some 2500 miles away.

73,

'Bear' NH7SR

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

Thanks for the info bear, one more question though does the loop

work best closer to the

ground or not ? I am on the second story of the house and it seem

to work best on the floor.

Scott



----- Original Message -----
From: qrpbear
To: loopantennas@...
Sent: Tuesday, June 08, 2004 6:33 PM
Subject: [loopantennas] Re: More strangeness


Scott,

Oh.. ya gotta space 'em otherwise you'll have nowhere to wind the
colored yarns to make it pretty <G>

Spacing at least one wire diameter will improve efficiency and Q.

For

a Pizza Box Loop it probably doesn't matter all that much and the
difference may be un-noticeable.

73,

'Bear' NH7SR

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

ofcourse this is my opinion and ill leave it at that i shouldnt

have sent the email.... ok so on to another subject should i close
space my pizza box loop turns or space them a wires distance apart ?

Scott


----- Original Message -----
From: Scott Savage KC7WDG
To: loopantennas@...
Sent: Tuesday, June 08, 2004 5:59 PM
Subject: Re: [loopantennas] More strangeness


Not I but for some reason he seems to act like a 14yr old with a

new toy and its annoying........

Scott
----- Original Message -----
From: Steve
To: loopantennas@...
Sent: Tuesday, June 08, 2004 3:33 PM
Subject: [loopantennas] More strangeness


Got a strange IM from electronicdx:

alienrelics: Why did you kick me off your lists? What do you mean,
"put down by your members"? I don't control anyone, and I can't

see

anything for you to be mad about.
alienrelics: What have I ever said to make you angry?
electronicdx: What I mean is that they are against me in a way,

but

this talk is over. I will get you back in enough said. ok. :-<


This is a little disturbing. "get you back"?

Does anyone here personally know Adam?

Steve



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Service.

I find it helps if you finish off the pizza first.

The Q is increased quite a bit.

;')

Steve

--- qrpbear <qrpbear@...> wrote:

Scott,

Oh.. ya gotta space 'em otherwise you'll have nowhere to wind the

colored yarns to make it pretty <G>

Spacing at least one wire diameter will improve efficiency and Q.
For
a Pizza Box Loop it probably doesn't matter all that much and the
difference may be un-noticeable.

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

开云体育

Scott,

Oh.. ya gotta space 'em otherwise you'll have nowhere to wind the
colored yarns to make it pretty <G>

Spacing at least one wire diameter will improve efficiency and Q. For
a Pizza Box Loop it probably doesn't matter all that much and the
difference may be un-noticeable.

73,

'Bear' NH7SR

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

ofcourse this is my opinion and ill leave it at that i shouldnt

have sent the email.... ok so on to another subject should i close
space my pizza box loop turns or space them a wires distance apart ?

Scott


----- Original Message -----
From: Scott Savage KC7WDG
To: loopantennas@...
Sent: Tuesday, June 08, 2004 5:59 PM
Subject: Re: [loopantennas] More strangeness


Not I but for some reason he seems to act like a 14yr old with a

new toy and its annoying........

Scott
----- Original Message -----
From: Steve
To: loopantennas@...
Sent: Tuesday, June 08, 2004 3:33 PM
Subject: [loopantennas] More strangeness


Got a strange IM from electronicdx:

alienrelics: Why did you kick me off your lists? What do you mean,
"put down by your members"? I don't control anyone, and I can't see
anything for you to be mad about.
alienrelics: What have I ever said to make you angry?
electronicdx: What I mean is that they are against me in a way, but
this talk is over. I will get you back in enough said. ok. :-<


This is a little disturbing. "get you back"?

Does anyone here personally know Adam?

Steve



Yahoo! Groups Sponsor
ADVERTISEMENT





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------------

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a.. To visit your group on the web, go to:


b.. To unsubscribe from this group, send an email to:
loopantennas-unsubscribe@...

c.. Your use of Yahoo! Groups is subject to the Yahoo! Terms of

Service.

开云体育

开云体育

Agreed.

Steve

--- qrpbear <qrpbear@...> wrote:

Steve,

Personally I don't think we should get involved with this kind of
discussion here. ... snip....

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

Steve,

I got the motors out this morning. Two 7.5 degree steppers and one
conventional motor (rpm??). I was thinking more along the lines of
coupling through two 6:1 epicyclic ball drives to the capacitor. That
should give me about 0.21 degrees per step. Might be fine enough for
government work. I'll still have to build a controller of course.

I'll check out the Electronics 101 group.

73,

'Bear' NH7SR

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

--- qrpbear <qrpbear@y...> wrote:

While walking home from the bus stop yesterday I encountered an
HP
printer that someone had thrown away. Naturally I snagged that
puppy!
I've been thinking about using the stepper motors out of it for
remote tuning drive for loop capacitors.

Have any of you folks tried steppers from old printers? Anything
special I should look out for?

There is a stepper motor driver list, but it's rather dead and
starting to get taken over by spammers.

You might also try the Electronics_101 list, it is very active.



I don't think you will be happy with the stepper connected directly
to the tuning cap. It's probably 200 steps per rev, or 1.8 degrees
per step. Half stepping won't do you any good unless you intend on
leaving the stepper powered up all the time.

So you'll want to try and use the gears. Scanners and dot matrix
printers are another source of already geared-down steppers. In
fact, some scanners use a stiff string to move the scanning head,
so you could perhaps use it with a tuning cap taken from an old
dial radio.

=====
Steve Greenfield // Digital photography, scanning,
Polymorph Digital Photography // retouching, and photomorphing
253-318-2473 voice // to your specs.
polymorph@p... //
// Based in Tacoma, WA, USA




__________________________________
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Steve,

Personally I don't think we should get involved with this kind of
discussion here. It can't lead to anything constructive. Best to just
let this play itself out somewhere else.

Some things are simply best left ignored.

73,

'Bear' NH7SR

Bruce,

Curious... that goes contrary to my intuition also. It has always
been one of the "laws" of coil winding that best Q is obtained in
solenoid coils when the diameter to length ratio is square (1:1).

Ah... I just remembered best Q is with the diameter to length ratio
at 1:1 or greater! It still seems, though, that a solenoid type
multiturn loop with very wide spacing between turns should exhibit a
larger capture area due to its 3D form factor. Possibly it does but
it may be a case of diminishing returns once one has passed the one-
wire-diameter spacing rule.

I think I'll add that to my "build this someday" list. Mebbe a 3-turn
2' diameter with 1' between turns. I could always tell people it's a
new kind of Dreamcatcher... especially after I hang some feathers on
it.

My take on the capacitors is that they seem to be related to the eras
in which radios were built. Prior to the introduction of the All
American Five most radios used external antennas. The RF/Mixer stages
commonly used values as high as 500 pF. With the All American Five
the use of an oval spiral wound loop on the back of the radio became
common as did the 365 pF capacitor. With the introduction of ferrite
bars we began to see 220 pF capacitors being used for tuning. I think
the shift had more to do with the available inductance in a given
space than any other factor. Higher inductance requiring less
capacitance and exhibiting better Q (more signal voltage) resulting
in the ability to simplify design and reduce parts count.

73,

'Bear' NH7SR

--- In loopantennas@..., "Bruce Carter" <brucec@m...>
wrote:

Contrary to my intuition, closely spaced windings seem to vastly
increase the Q of the antenna. I, too thought about the capture
volume, but then the capture volume of a spiral loop would be

zero.

Aperature size appears to be everything in determining the
sensitivity of a loop. I made three identical 27 MHz loops, out of
10 guage, 20 guage, and 30 guage wire. All had the same
sensitivity, but the Q varied.

I have not researched the inter-winding capacitance question, but I
am beginning to suspect it doesn't have the effect I first

assumed.

It seems to be much easier to encompass the whole band with a 9 to
250 pF tuning capacitor than a 9 to 365 or 9 to 500 pF capacitor.
Again - counter intuitive, but why did radio manufacturers make the
change? Wire is cheap compared to tuning capacitors. Especially
when the first 9 to 250 pF capacitors were probably special order.
I will get to the bottom of it when I have time. For now, loops
made of 24 guage hookup wire, turns wound flush, on large styrofoam
forms are light weight, easy to make, have fantastic Q's, and span
the whole band. I may get around to posting articles soon, plus
updating a lot of my old ones.

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

Another thing that keeps floating up from the depths of my
subconscious...

How would a multi-turn loop having space between turns a

significant

percentage of the loop diameter work relative to one that has

closer

spacing? For instance, a 2-turn 36" diameter loop with 12"

between

turns. My instincts tell me that there would be an increase in

the

physical capture area of the loop due to its taking on a more 3-D
profile. This would lead to higher performance than a close-

spaced

loop winding. How much increase in performance? Would there be an
optimal spacing? What about spacing equal to loop diameter?

Hmmm... obviously I need more copper... a LOT more! Uhh... got

any

spare capacitors?

73,

'Bear' NH7SR