Wimpie wrote:
. . .
There is an "however". When you make a single turn loop from flat
strip that has the same width as the length of your two-turn loop, you
will notice: 1. reduced AC resistance (because of the significantly
larger circumference of the flat strip with respect to a thin round
tube, 2. inductance will decrease (H field lines have to take a longer
path around the wide strip), 3. radiation resistance will not change
with respect to a single turn loop from wire/tube.
This results in higher efficiency and increased bandwidth. The
overall result will be better then for your two-turn loop. I think
that is the reason why most programs are for single turn loops.

So for the transmit case, given fixed diameter of your loop, the
larger the copper surface (=length*circumference), the better the
efficiency. Best thing to enhance conductor surface is to use very
wide flat strip (high wind load), or multiple wires (with some spacing
in between) in parallel (limited wind load).
. . .

Flat conductors aren't as attractive as they look at first glance. The
problem is the same proximity effect mentioned earlier in the posting.
Current is distributed evenly around a round conductor (assuming the
perimeter is a very small fraction of a wavelength), but not along a
flat strip. Because of proximity effect, the current is much more
concentrated near the edges than at the middle. The result is that the
resistance is considerably higher than for a wire with the same surface
area. In figuring an "equivalent diameter" of a thin flat strip in order
to get the same L and C properties, the rule is that a strip is
equivalent to a wire whose diameter is half the strip width. This means
that a strip of width w or total "circumference" 2 * w is equivalent to
a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C
go. Since the same phenomenon affects the inductance and resistance,
this would also be a good working rule for estimating the relative R of
a strip or wire.

Roy Lewallen, W7EL

On Nov 21, 5:18*pm, Wimpie wrote:
On 21 nov, 16:44, Art Unwin wrote:



On Nov 21, 5:38*am, Wimpie wrote:

On 21 nov, 04:47, Steve wrote:

I've seen several programs that will help you calculate the precise
dimensions of a single-turn loop, given the composition of the
radiating element, its thickness, and so on. However, none of these
programs are written to cover the case of a two or more-turn loop.

Does anyone know of a program that will offer guidance in the
construction of a two or more-turn loop?

Thanks,

Steve

Hello Steve,

You probably did some loop calculations and found that in a transmit
case the voltage across the tuning capacitor is very high (and
bandwidth is limited). Also for small loops, most input power is lost
as heat due to copper resistance.

When you make a two turn loop, the radiation resistance will increase
with factor 4. So with half the current through the loop, the radiated
power is same (as for a single turn loop). *When the 2 turns of the
loop are relative close together, the inductance increases with factor
4, hence the reactance.

The current has been halved, but because of the reactance, the voltage
across the tuning capacitance will be 2 times the value for the single
turn loop with higher probability on corona effects. *An advantage can
be an almost 4 times smaller tuning capacitor.

One may expect that the loss resistance due to heat of a two-turn
inductor will be twice as high (w.r.t. single turn case). This is not
true; the loss resistance will be more then twice as high because of
proximity effect. The current will not equally distribute along the
circumference of the tube/wire. *So the efficiency of the loop will be
less then twice as high (w.r.t. single turn case).

When the turns are far apart (with respect to wire/tube diameter),
inductance will not be 4 times higher and proximity effect will be
less. You will get better performance than the single turn loop made
of same diameter tube/wire. The result will be the same as when you
place the two turns in parallel. Inductance will decrease somewhat
(hence lower voltage across capacitor), AC resistance also, hence
radiation efficiency).

There is an "however". When you make a single turn loop from flat
strip that has the same width as the length of your two-turn loop, you
will notice: *1. reduced AC resistance (because of the significantly
larger circumference of the flat strip with respect to a thin round
tube, 2. inductance will decrease (H field lines have to take a longer
path around the wide strip), 3. radiation resistance will not change
with respect to a single turn loop from wire/tube.
This results in higher efficiency and increased bandwidth. * The
overall result will be better then for your two-turn loop. I think
that is the reason why most programs are for single turn loops.

So for the transmit case, given fixed diameter of your loop, the
larger the copper surface (=length*circumference), the better the
efficiency. *Best thing to enhance conductor surface is to use very
wide flat strip (high wind load), or multiple wires (with some spacing
in between) in parallel (limited wind load).

Off course for the receive-only case, a multi turn loop can be helpful
as you can use a smaller tuning capacitor.

Best regards,

Wim
PA3DJSwww.tetech.nl
In case of PM, don't forget to remove abc.

Seems to me you are recommending the "?slinky" !
Is that correct?
Art

Sorry Art, I am not talking about a slinky.

I am just talking about a multi turn (2 turns) loop where overall wire
length is 0.25 lambda so you can assume that current in wire is
constant along the length. It must be tuned by external capacitance.

Regarding the strip. When you take a 3.14m long 20cm wide thin copper
strip and make a loop of it (1m diameter), it will have a better
efficiency then when you take 6.28m *copper tubing with Dtube=2cm and
make a two-turn loop (Dloop=1m, turns 18 cm apart).

In the strip case, the current has more circumference to flow (40cm)
instead of 6.28cm for the copper tubing. *AC resistance of copper
tubing will be about 10 times higher. Off course, current in two-turn
loop will be half (for same radiated power), but still heat losses
will be 10*0.5^2=2.5 times higher (for the two-turn loop).

When both loops have good efficiency (so radiation resistance
dominates), the strip loop will have better bandwidth as flux path is
longer and therefore results in less inductance.

I hope this clarifies my posting.

Best regards,

Wim
PA3DJS
Please remove abc in case of PM.

I think I am missing something Wim. A slinky has a strip winding that
is edge wound which provides the largest disparity
between the inside radius and the outside radius. On one of the top
transmitters the inductance winding is such that the inner radius
is close to the outside radius. Naturally the different pitch of the
windings is very different as is the inter coil capacitance.
As Roy stated charges accumulate on sharp edges which I see as correct
but I cannot see how that alteres the diference all that much as the
same clearance is required So in the final analysis for less
inductance which form is which., the longer inductance or the shorter
inductance on the assumption that the number of turns are similara nd
I can acceptt your word for it? I referred to a slinky purely to
emphasize the importance of reverse windings so that lumped loadings
applied are cancelled. Actually the modern slinky is not contra wound
for some reason but I assume that is for the novelty movement reasons
for children and not because of radiation reasons. The slinky patent
is now defunct if that matters and iI am assuming that the fed would
be centre fed.
Thank you so much for responding
Best regards
Art

Steve wrote in news:cde8dec9-5103-41c0-896b-
:

I've seen several programs that will help you calculate the precise
dimensions of a single-turn loop, given the composition of the
radiating element, its thickness, and so on. However, none of these
programs are written to cover the case of a two or more-turn loop.

Does anyone know of a program that will offer guidance in the
construction of a two or more-turn loop?

Dunno about a program. I made a 2-turn transmitting loop for 160 one time,
using a variation of Ted Hart's matching scheme. I did it by cutting it a
bit long, then trimming it with an analyzer to see where it resonated.
Eventually got it to 1:1 at about 1890khz where I wanted it and it received
as well as could be expected. Transmit efficiency was on a par with a
hamstick.


--
Dave Oldridge+
ICQ 454777283
VA7CZ

On Fri, 21 Nov 2008 18:24:20 -0800, Roy Lewallen
wrote:

Flat conductors aren't as attractive as they look at first glance. The
problem is the same proximity effect mentioned earlier in the posting.
Current is distributed evenly around a round conductor (assuming the
perimeter is a very small fraction of a wavelength), but not along a
flat strip. Because of proximity effect, the current is much more
concentrated near the edges than at the middle. The result is that the
resistance is considerably higher than for a wire with the same surface
area. In figuring an "equivalent diameter" of a thin flat strip in order
to get the same L and C properties, the rule is that a strip is
equivalent to a wire whose diameter is half the strip width. This means
that a strip of width w or total "circumference" 2 * w is equivalent to
a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C
go. Since the same phenomenon affects the inductance and resistance,
this would also be a good working rule for estimating the relative R of
a strip or wire.

Roy Lewallen, W7EL

Thanks. I think you just explained the cause of a problem I fought in
about 1980. I had "designed" a 930MHz yagi antenna for a utility
telemetry system. In order to cut system costs, I decided to build
the antenna from stamped 0.062" aluminum. My initial dimensions were
stolen from a Scala yagi which used approximately 0.500" diameter
round rods for elements. I reasoned that to obtain the same
bandwidth, I would need to use the same circumference as the rod. That
made the initial prototypes elements 0.8" wide. After some tweaking,
the antenna tuned to the correct center frequency, but the 2:1 VSWR
bandwidth was much less than the original Scala antenna.

So, I increased the width of the stamped elements (with aluminum duct
tape) until the bandwidth improved. I landed at 1.25" or 2.5 times
the width of the rod elements, somewhat larger than the recommended
2.0 times the rod diameter.

However, when I added a coined stiffener groove to the stamped "boom"
and elements, the bandwidth increased again, to much more than
necessary. After the usual all night cut-n-try session, I landed on
2.0 times the width of the rod elements, with the coined stiffeners,
which apparently increased the effective diameter of the elements.

Coining the "boom" also wrecked all the element tuning since it
increases their effective end to end length by the depth of the
coining. I had a hell of a time dealing with the sheet metal vendor,
trying to control the stiffener dimensions. It seems that aluminum
stretches when coined, often in a rather unpredictable manner. I
eventually gave up and went to 0.125" sheet aluminum and no
stiffeners. Unfortunately, only a handful of prototypes were made and
shipped, so I have no clue as to how well (or badly) they worked in
the field.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 22 nov, 03:24, Roy Lewallen wrote:
Wimpie wrote:
. . .
There is an "however". When you make a single turn loop from flat
strip that has the same width as the length of your two-turn loop, you
will notice: *1. reduced AC resistance (because of the significantly
larger circumference of the flat strip with respect to a thin round
tube, 2. inductance will decrease (H field lines have to take a longer
path around the wide strip), 3. radiation resistance will not change
with respect to a single turn loop from wire/tube.
This results in higher efficiency and increased bandwidth. * The
overall result will be better then for your two-turn loop. I think
that is the reason why most programs are for single turn loops.

So for the transmit case, given fixed diameter of your loop, the
larger the copper surface (=length*circumference), the better the
efficiency. *Best thing to enhance conductor surface is to use very
wide flat strip (high wind load), or multiple wires (with some spacing
in between) in parallel (limited wind load).
. . .

Flat conductors aren't as attractive as they look at first glance. The
problem is the same proximity effect mentioned earlier in the posting.
Current is distributed evenly around a round conductor (assuming the
perimeter is a very small fraction of a wavelength), but not along a
flat strip. Because of proximity effect, the current is much more
concentrated near the edges than at the middle. The result is that the
resistance is considerably higher than for a wire with the same surface
area. In figuring an "equivalent diameter" of a thin flat strip in order
to get the same L and C properties, the rule is that a strip is
equivalent to a wire whose diameter is half the strip width. This means
that a strip of width w or total "circumference" 2 * w is equivalent to
a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C
go. Since the same phenomenon affects the inductance and resistance,
this would also be a good working rule for estimating the relative R of
a strip or wire.

Roy Lewallen, W7EL

Hello Roy,

You are right regarding non-uniformity, losses in the flat strip are
higher then based on the uniform current distribution (because of non-
uniformity). But this does not declassify loop antennas out of strip
material.

Based on a uniform current distribution (20cm wide strip versus two-
turn loop from tube with D=2cm) one would expect heat loss reduction
of 3.2. In my posting on Art's comment a mentioned heat loss reduction
w.r.t. the 2-turn loop of factor 2.5 (to account for non-uniformity).

A strip (not near to other constructions) has effective diameter of
half the width to have same characteristic impedance (as you
mentioned). So a strip with physical circumference of 40cm (width =
20cm) has an effective circumference of 40*0.785=31.4cm. You need to
have tube with D=10cm to have same effective circumference. I agree
with you that this effective circumference is also a good starting
point for calculation of AC loss resistance.

When Dloop is no longer large with respect to Dtube, current in the
tube tends to take the shortest path, hence reducing effective
diameter (and loop area) of the loop. In case of the strip, effective
diameter (hence area) does not reduce. Radiation resistance is
proportional to A^2 (for electrically small loops), hence Dloop^4.
10% reduction on loop diameter, gives 34% reduction of radiation
resistance.

In my opinion, advantage of a strip is still significant with respect
to a tube as long as you use a strip with width 2*(tube diameter).

Best regards,

Wim
PA3DJS
www.tetech.nl
you can use PM, but please remove abc.

"Art Unwin" wrote in message
...
On Nov 21, 4:07 pm, "Dave" wrote:
"Art Unwin" wrote in message

...

the law that I continually state from the
extension of the Gaussian law of statics which I derived.

you haven't presented anything that you derived... state the equation.

Oh come on David I do not work for you, do it for yourself as you have
superior background than I do.

finally he got something right!

If you are proficient in mathematics check out the addition of
displacement current of Maxwell and review it as just that.

it works fine for me as is... no weak force, no magic levitating neutrinos,
just a displacement current.

a current in circular foirm that DOES generate a displacement
magnetic field such that it displaces a charged particle
from the surface of the radiator.

bull!

This eddy current has the units of
current which somehow would match the
description of the "weak force:".

eddy currents don't require weak force, nor displacement currents, they are
perfectly well described by existing magnetic field and conduction
equations.

You stated previously that you wanted to know
where the weak current equation is so, now you can start on a series

not me, i know where the weak 'force' is, and it has nothing to do with
electrical currents even though it is sometimes refered to as the
electro-weak force. that is a throwback to a VERY short time after the big
bang when the forces were merged, right now, unless you are experimenting
with a supercollider you can ignore the weak force as far as electric fields
are concerned.

Stae equation you ask?
handwaving bs snipped

yes, state your equation that you 'derived'.

Ofcourse you can declare antenna computer programs are in error and
salvage your credability or place such a statement in the practicable
book that you are writing! After all if it is printed in a book it
must be right.......right?

but the computer programs that exist today, and DON'T use the weak force in
anyway are perfectly in tune with maxwell's equations. and my book doesn't
mention them at all, so don't hold your breath for that.

On Nov 22, 9:32*am, "Dave" wrote:
"Art Unwin" wrote in message

...
On Nov 21, 4:07 pm, "Dave" wrote:

"Art Unwin" wrote in message

....

the law that I continually state from the
extension of the Gaussian law of statics which I derived.

you haven't presented anything that you derived... state the equation.
Oh come on David I do not work for you, do it for yourself as you have
superior background than I do.

finally he got something right!

If you are proficient in mathematics check out the addition of
displacement current of Maxwell and review it as just that.

it works fine for me as is... no weak force, no magic levitating neutrinos,
just a displacement current.

a current in circular foirm that DOES generate a displacement
magnetic field such that it displaces a charged particle
from the surface of the radiator.

bull!

This eddy current has the units of
current which somehow would match the
description of the "weak force:".

eddy currents don't require weak force, nor displacement currents, they are
perfectly well described by existing magnetic field and conduction
equations.

You stated previously that you wanted to know
where the weak current equation is so, now you can start on a series

not me, i know where the weak 'force' is, and it has nothing to do with
electrical currents even though it is sometimes refered to as the
electro-weak force. *that is a throwback to a VERY short time after the big
bang when the forces were merged, right now, unless you are experimenting
with a supercollider you can ignore the weak force as far as electric fields
are concerned.

Stae equation you ask?

handwaving bs snipped

yes, state your equation that you 'derived'.

Ofcourse you can declare antenna computer programs are in error and
salvage your credability or place such a statement in the practicable
book that you are writing! After all if it is printed in a book it
must be right.......right?

but the computer programs that exist today, and DON'T use the weak force in
anyway are perfectly in tune with maxwell's equations. *and my book doesn't
mention them at all, so don't hold your breath for that.

You must be older than I thought, you never are going to change.
Before you fade away
this last bit that you are now supporting regarding the weak force.
Can you account for every action
that reside in Maxwells laws including his addition? Can you state
that without doubt that eddy currents do not exist
during radiation? Or more importantly, that Maxwell's laws also omit
the presence of the eddy current?
Are you still of the opinion that radiation is a wave which implies a
string of connected energies instead of individual particle ejection?
Then pray tell me how exactly does the transmition of communication
eminate from a radiator and do a reverse action
in the transportation of intelligence? And then comes the biggy, How
does the Universe exist without being in equilibrium
a term you resist with abandon. Your knee jerk reactions to me are
starting to be absurd but as you are unemployed
you do not need now to answer to anybody regarding the thoughts of an
old man or concern yourself of the possibility of being fired.
Art

"Art Unwin" wrote in message
...
this last bit that you are now supporting regarding the weak force.
Can you account for every action
that reside in Maxwells laws including his addition?

yes

Can you state
that without doubt that eddy currents do not exist
during radiation? Or more importantly, that Maxwell's laws also omit
the presence of the eddy current?

where did you ever get this idea. eddy current are currents in a conductor
caused by exposure to an electromagnetic field. of course they are covered
by maxwell's equations. you just have to use the proper boundry conditions
and permeability/conductivity of the conductor to account for them. i have
written software that modeled eddy currents from fields set up by power
transformers, every equation was out of a standard text book.

Are you still of the opinion that radiation is a wave which implies a
string of connected energies instead of individual particle ejection?

yes, particle ejection, your magical levitating diamagnetic neutrino theory,
is not necessary for electromagnetic propagation.

Then pray tell me how exactly does the transmition of communication
eminate from a radiator and do a reverse action
in the transportation of intelligence?

energy my dear man, energy is conveyed by the electromagnetic waves and
hence can carry intelligence... as opposed to what goes on between your
ears, which must be quite a vaccuum.

And then comes the biggy, How
does the Universe exist without being in equilibrium
a term you resist with abandon.

i abandoned equilibrium long ago. it is neither necessary nor desirable for
any possible use of electromagnetic propagation that i want to make use of.
if everything were in equilibrium the universe would be dead, it takes
energy moving from here to there to make everything work. without flowing
energy, hence non-equilibrium, nothing would exist... much like the space
between your ears, maybe that is the problem, you brain has reached
equilibrium with the outside world, hence nothing can flow in... though that
doesn't explain the outpouring of bafflegab.


Your knee jerk reactions to me are
starting to be absurd but as you are unemployed
you do not need now to answer to anybody regarding the thoughts of an
old man or concern yourself of the possibility of being fired.

my reactions to your are pure humor. i love the pure illogic of your
writings, reminds me of some old science fiction stuff by writers who didn't
care if their proposals made any physical sense in this universe. perhaps
that would be a good line of work for you art, you could write science
fiction in the 'alternate universe' genre. maybe there you could come up
with a story line that would make use of your distorted physics. and no, i
am gainfully employed, someone has to contribute to the welfare system so
you can collect your checks.

On Nov 22, 11:59*am, "Dave" wrote:
"Art Unwin" wrote in message

...

this last bit that you are now supporting regarding the weak force.
Can you account for every action
that reside in Maxwells laws including his addition?

yes

Can you state
that without doubt that eddy currents do not exist
during radiation? Or more importantly, that Maxwell's laws also omit
the presence of the eddy current?

where did you ever get this idea. *eddy current are currents in a conductor
caused by exposure to an electromagnetic field. *of course they are covered
by maxwell's equations. *you just have to use the proper boundry conditions
and permeability/conductivity of the conductor to account for them. *i have
written software that modeled eddy currents from fields set up by power
transformers, every equation was out of a standard text book.

Are you still of the opinion that radiation is a wave which implies a
string of connected energies instead of individual particle ejection?

yes, particle ejection, your magical levitating diamagnetic neutrino theory,
is not necessary for electromagnetic propagation.

Then pray tell me how exactly does the transmition of communication
eminate from a radiator and do a reverse action

*in the transportation of intelligence?

energy my dear man, energy is conveyed by the electromagnetic waves and
hence can carry intelligence... as opposed to what goes on between your
ears, which must be quite a vaccuum.

And then comes the biggy, How
does the Universe exist without being in equilibrium
a term you resist with abandon.

i abandoned equilibrium long ago. *it is neither necessary nor desirable for
any possible use of electromagnetic propagation that i want to make use of.
if everything were in equilibrium the universe would be dead, it takes
energy moving from here to there to make everything work. *without flowing
energy, hence non-equilibrium, nothing would exist... much like the space
between your ears, maybe that is the problem, you brain has reached
equilibrium with the outside world, hence nothing can flow in... though that
doesn't explain the outpouring of bafflegab.

Your knee jerk reactions to me are
starting to be absurd but as you are unemployed
you do not need now to answer to anybody regarding the thoughts of an
old man or concern yourself of the possibility of being fired.

my reactions to your are pure humor. *i love the pure illogic of your
writings, reminds me of some old science fiction stuff by writers who didn't
care if their proposals made any physical sense in this universe. *perhaps
that would be a good line of work for you art, you could write science
fiction in the 'alternate universe' genre. *maybe there you could come up
with a story line that would make use of your distorted physics. *and no, i
am gainfully employed, someone has to contribute to the welfare system so
you can collect your checks.

Well your background on this subject is far superior to mine so you
have the last word
and I must wander off to ponder my silly ideas. It was several years
ago that I brought up the subject
of pulses with respect to the tank circuit and the propersition that
current flows thru the center
of a radiator that was not in equilibrium. When you banish the idea of
equilibrium
I have nothing left to support what I say such that I have now reached
the Rubicon which
requires me to succumb to the teachings of books and abolishion of all
personal thought and reasoning.
Fortinately I am retired and thus cannot be fired or put to death on
account of my personal thoughts
so in my own little world I can still continue in what I am doing
except with regard to sharing or suggesting change
which on this group is a impenatrational barrier.
It was fun for a while but as I stated you have the last word.
Now await my next posting on a different subject!
Regards
Art

"Steve" wrote in message
...
On Nov 21, 12:32 am, Richard Clark wrote:
On Thu, 20 Nov 2008 19:47:24 -0800 (PST), Steve

wrote:
However, none of these
programs are written to cover the case of a two or more-turn loop.

Hi Steve,

For transmit, there's nothing to "gain" by it.

Success generally floods the marketplace and few complain about not
finding resources to make a knock-off.

73's
Richard Clark, KB7QHC

Yes, I know there's nothing to gain in terms of performance. However,
I have very little space to work with. I have a 1 meter diameter loop
installed in my (tiny) attic that works very respectably on 10-30
meters. It won't get me onto 40 meters, though, and getting onto 40 is
either going to require a much larger diameter single-turn loop, a two-
turn loop, or a much more robust capacitor. Trying out a two-turn loop
seems like it would be the easiest and least expensive alternative,
and I already have the copper tubing I would need.

Two 1m dia turns will cover 40 with the same variable capacitor, I think
that is all you wanted to know!!! Experiment ...

Lee ... G6ZSG ...