Loop antenna question
 

I just got through picking up a ton of discontinued wire from my local Home
Depot, and was planning on building a "broomstick" antenna like some I found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.

Thanks,

Dave

"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have
a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They
are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't
I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.


Inductance isn't all there is to an antenna.. you need capture area, too.
Broomstick antennas are not all that good, and are not very efficient. Yes,
they look good on paper, as the 'electrical length' is much longer than that
much straight wire, but without capture area, the efficeincy drops way off.
You're better with a longwire, even just a few meters (yards) run along the
eaves of your house.

I won't go into detail but the broomstick (or any helicaly wound antenna)
gives up performance for size. The straiter the wire, the better off you
are. If you have the space, just stretch it out strait.


"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have
a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They
are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't
I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.

Thanks,

Dave

CW wrote:

I won't go into detail but the broomstick (or any helicaly wound antenna)
gives up performance for size. The straiter the wire, the better off you
are. If you have the space, just stretch it out strait.


Experimentation and experience have taught me that this is
basically correct. "Broomstick" antennas give pretty good performance
in a very compact space - they are even (marginally) "portable". But
for signal-pulling ability, they'll never beat a well-thought-out
longwire or randomwire. If you can tuck a one-meter broomstick into
your car somewhere for traveling, you've got the world
by the butt for shortwave listening away from home. But at home - your
"permanent space" - go with a random or longwire, if you possibly can.

Tony





"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have
a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They
are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't
I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.

Thanks,

Dave





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Hmm. Okay. Only I don't have much outside space available. I *might* be
able to manage 20-30 feet of random wire, but that is about it. And I have
more than a mile of small-guage wire on these two spools. I was planning on
wrapping it around a five-foot long piece of 4 inch PVC and standing it
behind a closet door. Since my last last message I tried a very crude
"hook-up" with one of the spools of wire and got absolutely no improvement
in reception. Now I understand why, thanks to you good people.

Back to the 20-30' piece of random wi my only option is to run it out the
window and along the top rail of the fence in the back yard. Would this
really outdo a massive broomstick antenna?

Thanks for the input. You've all got me thinking.

Dave


"Tony Meloche" wrote in message
...


CW wrote:

I won't go into detail but the broomstick (or any helicaly wound
antenna)
gives up performance for size. The straiter the wire, the better off you
are. If you have the space, just stretch it out strait.


Experimentation and experience have taught me that this is
basically correct. "Broomstick" antennas give pretty good performance
in a very compact space - they are even (marginally) "portable". But
for signal-pulling ability, they'll never beat a well-thought-out
longwire or randomwire. If you can tuck a one-meter broomstick into
your car somewhere for traveling, you've got the world
by the butt for shortwave listening away from home. But at home - your
"permanent space" - go with a random or longwire, if you possibly can.

Tony





"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out"
the
coil to a meter or more reduce the inductance of the resulting coil?
Why
wouldn't it work better to just leave it on the spool? I was under
the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of
the
coil width to length. Wouldn't this mean that a "longer" coil would
have
a
lower inductance than a "shorter" coil, given the same length of wire
and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I
have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi
Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar,
and
then looked at the two spools of wire that I was about to unwrap.
They
are
already coils, so shouldn't I be able to just hook them up to an
aligator
clip and stick this to my whip antenna? (I am now thinking about
taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't
that
work?) And if I leave the wire on the spools (which are plastic)
couldn't
I
turn them toward or away from the station of interest to further
improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would
greaty
value the opinions of those who have actually done something like one
of
these two options.

Thanks,

Dave





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News==----
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Newsgroups
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The currrent in the wire produces an electromagnetic field which has a
defined radius.


The field coil of a motor is used to turn it into a magnet so the motor will
work...stretch out the windings, no emf imposed upon the core..no
magnet-action-no work


Stretch it out, you exceed the radius of the electromagnetic field, no
interaction, no function.

The whole purpose of the antenna in coil-structure is to use the induced emf
to create a load on the antenna so it "thinks" it is longer

Yodar


"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have
a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They
are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't
I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.

Thanks,

Dave

Brenda et al:

This statement facinates me:

related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states.

1.2 kM of wire; Heck of a lot of capture area !

Is there some ratio of loop diameter and spacing between the wire loops that
results in the most capture area?

There is a nice ratio of mirror diameter to magnification limits in telescopes
This is the analogy I was thinking of.

Dan


Inductance isn't all there is to an antenna.. you need capture area, too.
Broomstick antennas are not all that good, and are not very efficient. Yes,
they look good on paper, as the 'electrical length' is much longer than that
much straight wire, but without capture area, the efficeincy drops way off.
You're better with a longwire, even just a few meters (yards) run along the
eaves of your house.

Tony Meloche wrote:

CW wrote:

I won't go into detail but the broomstick (or any helicaly wound antenna)
gives up performance for size. The straiter the wire, the better off you
are. If you have the space, just stretch it out strait.

snip If you can tuck a one-meter broomstick into
your car somewhere for traveling, you've got the world
by the butt for shortwave listening away from home. But at home - your
"permanent space" - go with a random or longwire, if you possibly can.

Tony


For portable use, I've found the AT-271/A antenna designed for the PRC-25 or PRC-77 works quite well. It's about 10' long, and it's set up like the supports used for dome tents - to take it down - you pull the sections apart (they have a chain/shock cord
running through them) and fold them for storage.

I got it he http://www.american-milspec.com/c765.html

Unfortunately, it's just a hair too long to fit inside the aluminum attaché case I transport my 7030 in.

Personally, I think I'd use a slinky over a broom stick. More compact for travel, and if you have more room, you can spread it out.




"Dave" wrote in message
...
I just got through picking up a ton of discontinued wire from my local
Home
Depot, and was planning on building a "broomstick" antenna like some I
found
described on the net. Got a question though: doesn't "stretching out" the
coil to a meter or more reduce the inductance of the resulting coil? Why
wouldn't it work better to just leave it on the spool? I was under the
impression that the formula for calculating the inductance for a given
coil
involved multiplying the square of the number of coils by the ratio of the
coil width to length. Wouldn't this mean that a "longer" coil would have
a
lower inductance than a "shorter" coil, given the same length of wire and
approximate diameter of coils?

Forgive me if I'm being stupid here, it has been twenty years since I have
attempted anything like this, but that was what I thought.

The main account I am thinking of was related by someone in Saudi Arabia
who
wrapped 1.2 kM of wire around a piece of PVC and vastly improved their
reception of WWV in the states. I was going to do something similar, and
then looked at the two spools of wire that I was about to unwrap. They
are
already coils, so shouldn't I be able to just hook them up to an aligator
clip and stick this to my whip antenna? (I am now thinking about taking
the
wire off of the smaller spool and adding it to the larger. Shouldn't that
work?) And if I leave the wire on the spools (which are plastic) couldn't
I
turn them toward or away from the station of interest to further improve
reception? (I could even put this in my attic, gaining a few feet of
elevation and hiding it from my unappreciative wife.)

Any input on any part of this idea is more than welcome. I would greaty
value the opinions of those who have actually done something like one of
these two options.

Thanks,

Dave




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---= 19 East/West-Coast Specialized Servers - Total Privacy via Encryption =---

"Brenda Ann" wrote in message
...

"Dave" wrote in message
...
Hmm. Okay. Only I don't have much outside space available. I *might*
be
able to manage 20-30 feet of random wire, but that is about it. And I
have
more than a mile of small-guage wire on these two spools. I was
planning
on
wrapping it around a five-foot long piece of 4 inch PVC and standing it
behind a closet door. Since my last last message I tried a very crude
"hook-up" with one of the spools of wire and got absolutely no
improvement
in reception. Now I understand why, thanks to you good people.

Back to the 20-30' piece of random wi my only option is to run it out
the
window and along the top rail of the fence in the back yard. Would this
really outdo a massive broomstick antenna?


Almost anything will outdo a broomstick antenna. 30' of longwire along
your
fence (presuming it is wood, and not steel) would do a great job. Even
better still would be to run it around your rafters (presuming again that
they are not concrete or aluminum siding or such). Either way, I would use
some kind of standoffs (you can find them at hardware stores, or make your
own from old thread spools).




Okay, so here's the problem. The fence is metal, and the house is covered
with steel siding. My DX-402 does pick up BBC on 5975 pretty well with just
the whip (next to a window), but VOK is extremely weak to vanishing. (This
last one is what I want the broomstick antenna for.) If I do go with the
broomstick, should I stick with the five-foot piece that I already have cut,
or go with a longer eight-foot piece which will still fit nicely in the
corner I have in mind. Or should I go all out with a ten-foot piece (or
even multiples maybe) and put it in the attic? Also, what type of ground
should I use? I could run a ground wire out the window to a ground rod that
is as old as the house, but that's about my only option (the house predates
three-prong plugs with a real ground.)

I really appreciate your thoughts on these things. You obviously know a lot
more about this stuff than I do.

Thanks,

Dave

In article , "Dave"
writes:

Or should I go all out with a ten-foot piece of 4 inch PVC (or
even multiples maybe) and put it in the attic?

If the attic is non-metal, I'd try this solution ..