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

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

On Nov 20, 7:47*pm, 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

Search for Reg Edwards programs. RJELOOP3 is probably what you want.
I'm assuming here that you're talking about loops that are very small
compared with a wavelength, which may offer advantages as receiving
antennas for low frequencies.

Cheers,
Tom

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
PA3DJS
www.tetech.nl
In case of PM, don't forget to remove abc.

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.

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

Art Unwin wrote:

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

I believe, he is speaking of rotating the flat surfaces of the
conductor(s) 90 degrees to what a "slinkys'" orientation places them at.

In which case, "mondo-capacitive loading to the 'environment'" is also
introduced ... while minimizing capacitive loading between turns.

Regards,
JS

On Nov 21, 9:52*am, John Smith wrote:
Art Unwin wrote:
...
Seems to me you are recommending the "?slinky" !
Is that correct?
Art

I believe, he is speaking of rotating the flat surfaces of the
conductor(s) 90 degrees to what a "slinkys'" orientation places them at.

In which case, "mondo-capacitive loading to the 'environment'" is also
introduced ... while minimizing capacitive loading between turns.

Regards,
JS

Wouldn't that take more room than a slinky per turn?
His attic is very small!.I think he would be much better placing the
turns as close together as possible
to obtain axial directivity. The only mod required to the slinky is to
ensure the number of right hand turn loop
are equal to the number of left hand turned loops. Feed could still
be at the center and depending on the amount
of wire used it would radiate like a dipole or axially. What this does
is cancel the lumped loads created in manufacture which
Wim suggests is a problem ie the two supposedly lumped loads will
cancel
such that you have several wavelengths of wire helix style and no or
repetitive points of none reactive impedances. He could ofcourse
place
the windings in a vertical direction to obtain an omnidirectional
pattern and utilise the available room to a maximum.
A lot depends on what frequencies he wishes to use as to what form the
radiator becomes.
Best regards
Art

On Fri, 21 Nov 2008 04:55:35 -0800 (PST), Steve
wrote:

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.

Hi Steve,

As offered by another corespondent here, the work of Reg Edwards
revealed that a multiturn transmit loop, designed for "efficiency's
sake" is never as efficient as a single turn loop. There are, of
course, any number of alternative designs if you don't want
efficiency. Many of those designs are touted here in this group -
usually appended with hitherto unrealized advances the masters were
never aware of. Usually, the longer the thread, the poorer the
design.

You have already recognized the significant variables you would have
to attend to to go lower in frequency - it is not for the faint of
heart and the Q keeps climbing.

73's
Richard Clark, KB7QHC

On Nov 21, 10:51*am, Art Unwin wrote:
On Nov 21, 9:52*am, John Smith wrote:

Art Unwin wrote:
...
Seems to me you are recommending the "?slinky" !
Is that correct?
Art

I believe, he is speaking of rotating the flat surfaces of the
conductor(s) 90 degrees to what a "slinkys'" orientation places them at..

In which case, "mondo-capacitive loading to the 'environment'" is also
introduced ... while minimizing capacitive loading between turns.

Regards,
JS

Wouldn't that take more room than a slinky per turn?
His attic is very small!.I think he would be much better placing the
turns as close together as possible
to obtain axial directivity. The only mod required to the slinky is to
ensure the number of right hand turn loop
are equal to the number of left *hand turned loops. Feed could still
be at the center and depending on the amount
of wire used it would radiate like a dipole or axially. What this does
is cancel the lumped loads created in manufacture which
Wim suggests is a problem ie the two supposedly lumped loads will
cancel
*such that you have several wavelengths of wire helix style and no or
repetitive points of none *reactive impedances. He could ofcourse
place
the windings in a vertical direction to obtain an omnidirectional
pattern and utilise the available room to a maximum.
A lot depends on what frequencies he wishes to use as to what form the
radiator becomes.
Best regards
Art

I forgot to mention that a similar type radiator is shown in Antenna
Applications
Reference Guide by Johnson and Jasik with slight modification. This
design was succeeded by the helix antenna
to obtain circular polarization which is now universal with respect to
space communications.
The beauty of this design is the multiplicity of resonant points and
the use of different frequencies.
The economy of space is some what altered by the need of multi
wavelength of wire because
of slow wave.but then it enables axial directivity. There are many
hams who are delighted by the slinky performance
and they are still sold in huge numbers to the ham community, so it
must be performing!
Art Unwin