Receiving Loop Antenna Question
 

On Jan 25, 9:52*am, Cecil Moore wrote:
wrote:
My 16 inch diameter circle loop for MW uses 12 turns.

I know multiple loop antennas are lossy for transmitting.
Are they adequate for receiving because of the AGC dynamic
range in the receiver?
--
73, Cecil *http://www.w5dxp.com

I'm not sure how the AGC comes into play here..
The 16 inch antenna provides plenty enough signal,
even with no preamp used. You could turn the AGC on
or off, wouldn't really matter. No different than any
other antenna you might connect in that regard.
They are lossy for transmitting, but on the MW bands
you have so much excess signal level it's not an
issue as far as receiving. Note the ferrite bar antenna,
which is even more lossy than the open loops I use.
It has no problem providing enough signal for a
cheap portable radio.
You might be surprised just how much level you can
get from a tuned small loop on the low bands.
As an example, that 16 inch loop provides more
signal than the whip on a car. I once tried it with a
delco radio in my truck. I hooked the loop up to it,
and it was as hot as a firecracker vs the standard
whip.
The catch is the system is very high Q, and requires
constant tuning of the cap as you change frequency.

Receiving Loop Antenna Question
 

On Jan 25, 11:11*am, Art Unwin wrote:


I would not be so quick to dismiss the ribbon wire on *the basis of
capacitance build up !

I would not be so quick to assume I dismissed ribbon wire
on the basis of capacitance buildup. Where do you read
any such thing in what I posted?
Has nothing to do with why I wouldn't use ribbon cable.
Using a ribbon cable would be a pain in the arse.
You would have to cut and jumper each turn to the
next turn. Makes more sense just to use a single
wire and thread it through the holes, row by row
if multiple turns are needed.

Receiving Loop Antenna Question
 

On Jan 25, 5:37*pm, wrote:
On Jan 25, 11:11*am, Art Unwin wrote:



I would not be so quick to dismiss the ribbon wire on *the basis of
capacitance build up !

I would not be so quick to assume I dismissed ribbon wire
on the basis of capacitance buildup. Where do you read
any such thing in what I posted?
Has nothing to do with why I wouldn't use ribbon cable.
Using a ribbon cable would be a pain in the arse.
You would have to cut and jumper each turn to the
next turn. Makes more sense just to use a single
wire and thread it through the holes, row by row
if multiple turns are needed.

I did this with ribbon cable once and it is actually pretty easy to
do. I couldnt have taken more than 15 minutes to fabticate an 8 turn
coil.

Jimmie

Receiving Loop Antenna Question
 

"Art Unwin" wrote in message
...
On Jan 25, 12:11 pm, "christofire" wrote:
"Art Unwin" wrote in message

8

I would not be so quick to dismiss the ribbon wire on the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

... but a multi-turn loop in which the self-inductance cancelled wouldn't
be
much of a receiving antenna! Production of EMF from the magnetic field
caused by current flowing in the adjacent turns and production of EMF from
the magnetic field component of an incident radio wave rely on the same
principle.

Chris

As an experimenter I am inclined to give things a try. If everything
can be solved by the brain while sitting on the sofa then it would be
a waste of time! As a recieving antenna all you would need is wire
that has distributed loads and ZERO lumped loads, so why not just get
rid of the lumped loads via cancellation?
The complications that you bring up, I suggest, would be applicable to
transmitting antennas only


That principle is Faraday's Law which is fully reciprocal, so no, this is
equally applicable to receiving and transmitting antennas.

I hope 'EMF' isn't being misread as anything other than its original meaning
in this context, that is, electro-motive force (the non-ambiguous form of
'voltage').

Chris

Receiving Loop Antenna Question
 

On Jan 26, 8:38*am, "christofire" wrote:
"Art Unwin" wrote in message

...
On Jan 25, 12:11 pm, "christofire" wrote: "Art Unwin" wrote in message

8



I would not be so quick to dismiss the ribbon wire on the basis of
capacitance build up ! If you start from the middle of one end by
joining
the two center wires together and from then on joining the end to end
wires
moving outwards what you have then done is to cancel not only the
capacitance build up but also the inductance build up.
You can then unfasten the first step on the center winding and feed it
from that point
i.e. center fed
Art

... but a multi-turn loop in which the self-inductance cancelled wouldn't
be
much of a receiving antenna! Production of EMF from the magnetic field
caused by current flowing in the adjacent turns and production of EMF from
the magnetic field component of an incident radio wave rely on the same
principle.

Chris

As an experimenter I am inclined to give things a try. If everything
can be solved by the brain while sitting on the sofa then it would be
a waste of time! As a recieving antenna all you would need is wire
that has distributed loads and ZERO lumped loads, so why not just get
rid of the lumped loads via cancellation?
The complications that you bring up, I suggest, would be applicable to
transmitting antennas only

That principle is Faraday's Law which is fully reciprocal, so no, this is
equally applicable to receiving and transmitting antennas.

I hope 'EMF' isn't being misread as anything other than its original meaning
in this context, that is, electro-motive force (the non-ambiguous form of
'voltage').

Chris

Hi Chris,
I need a bit more with respect to your response in more layman terms

When a multi turn helix is generated it can be used for both
transmitting and receiving.
When generating two helix antennas where one is contra wound and both
are connected at the top
you are saying that it will NOT be suitable for receiving !
We know by common use that the single helix is good for transmitt and
receive . So what exactly
does the addition of the contra winding do to prevent the combination
from receiving?
Looking forward to your take on the question.
Best regards
Art

Receiving Loop Antenna Question
 

"Art Unwin" wrote in message
...
On Jan 26, 8:38 am, "christofire" wrote:
"Art Unwin" wrote in message

8

Hi Chris,
I need a bit more with respect to your response in more layman terms

When a multi turn helix is generated it can be used for both
transmitting and receiving.
When generating two helix antennas where one is contra wound and both
are connected at the top
you are saying that it will NOT be suitable for receiving !
We know by common use that the single helix is good for transmitt and
receive . So what exactly
does the addition of the contra winding do to prevent the combination
from receiving?
Looking forward to your take on the question.
Best regards
Art


OK. The term 'helix' is most often applied to the travelling-wave antenna
invented by John Kraus, often used at VHF and above, which generates or
receives a circularly-polarised wave predominantly in the direction of its
axis. It is also used in 'normal-mode helix' for the type of monopole
element often found on walkie talkies, that generates and receives a
linearly-polarised wave. Both of these are connected to electronics at one
end only.

The discussion was about loop antennas having one or more turns, with both
ends of the winding connected to electronics. This construction can also be
called a solenoid, but it would provoke confusion to call it a 'helix'.

When an alternating current is passed through a solenoid it generates a
magnetic field, H, through its centre and around it - the transmitting case.
When a solenoid is placed in an alternating magnetic field, if any lines of
magnetic force pass through its winding it will generate an electro-motive
force (EMF) from which current can be drawn to operate a receiver - the
receiving case.

In the transmitting case the physical characteristics (described by the
intrinsic impedance) of 'space' - the air surrounding the solenoid - cause
an electric field, E, to be generated from the alternating magnetic field,
in phase with the H field that caused it (viz. the intrinsic impedance of
space is real not complex) and together these in-phase E and H components
give rise to an electromagnetic wave. A fraction of the input power will be
radiated away from the solenoid in that wave, in directions where their
vector cross-product ExH is not zero. The field strength of either the E or
H component of the radiated wave will decay linearly with increasing
distance.

You can find a good account of this process in books like 'Antennas' by the
late John Kraus but it isn't possible to get very far without use of
mathematics. Chapter 7 of 'Antennas for all applications' by Kraus and
Marhefka, the 2002 edition, covers all this in greater detail and would be
worth obtaining if you're interested.

The 'sense' (i.e. clockwise/anticlockwise with respect to some datum) of the
winding of a solenoid, and the direction of the current applied, affect the
polarity of the magnetic field it produces, and vice versa for the receiving
case. Consequently, the phase with respect to time of the alternating H
field (and the alternating E-field component of the radiated electromagnetic
wave) depend on the 'sense' of the winding, but the polarisation of the
radiated wave depends on the alignment of the axis of the solenoid. By
convention, 'polarisation' is the angular direction of the E field in the
outgoing wave, which is perpendicular to the H-field component, and both are
perpendicular to the direction of propagation, so solenoid with a horizontal
axis radiates a vertically-polarised (VP) radio wave - and receives best
from a VP wave; the ferrite-rod-in-a-broadcast-receiver case.

Back to my original point: if part of the winding of the solenoid is wound
in the opposite sense to the rest of the winding then its contribution to
the generated H field, or the EMF on receiving, will oppose the contribution
from the other part of the winding. If the winding has half in each
'sense', connected in series (like a non-inductive wire-wound resistor),
then it will not generate an H field or develop an EMF from an incident H
field, so it will not work as a transmitting or receiving antenna ... for
the reasons outlined above.

Enough?

Chris

Receiving Loop Antenna Question
 

On Jan 26, 12:16*pm, "christofire" wrote:
"Art Unwin" wrote in message

...
On Jan 26, 8:38 am, "christofire" wrote:

"Art Unwin" wrote in message

8

Hi Chris,
I need a bit more with respect to your response in more layman terms

When a multi turn helix is generated *it can be used for both
transmitting and receiving.
When generating two helix antennas where one is contra wound and both
are connected at the top
you are saying that it will NOT be suitable for receiving !
We know by common use that the single helix is good for transmitt and
receive . So what exactly
does the addition of the contra winding do to prevent the combination
from receiving?
Looking forward to your take on the question.
Best regards
Art

OK. *The term 'helix' is most often applied to the travelling-wave antenna
invented by John Kraus, often used at VHF and above, which generates or
receives a circularly-polarised wave predominantly in the direction of its
axis. *It is also used in 'normal-mode helix' for the type of monopole
element often found on walkie talkies, that generates and receives a
linearly-polarised wave. *Both of these are connected to electronics at one
end only.

The discussion was about loop antennas having one or more turns, with both
ends of the winding connected to electronics. *This construction can also be
called a solenoid, but it would provoke confusion to call it a 'helix'.

When an alternating current is passed through a solenoid it generates a
magnetic field, H, through its centre and around it - the transmitting case.
When a solenoid is placed in an alternating magnetic field, if any lines of
magnetic force pass through its winding it will generate an electro-motive
force (EMF) from which current can be drawn to operate a receiver - the
receiving case.

In the transmitting case the physical characteristics (described by the
intrinsic impedance) of 'space' - the air surrounding the solenoid - cause
an electric field, E, to be generated from the alternating magnetic field,
in phase with the H field that caused it (viz. the intrinsic impedance of
space is real not complex) and together these in-phase E and H components
give rise to an electromagnetic wave. *A fraction of the input power will be
radiated away from the solenoid in that wave, in directions where their
vector cross-product ExH is not zero. *The field strength of either the E or
H component of the radiated wave will decay linearly with increasing
distance.

You can find a good account of this process in books like 'Antennas' by the
late John Kraus but it isn't possible to get very far without use of
mathematics. *Chapter 7 of 'Antennas for all applications' by Kraus and
Marhefka, the 2002 edition, covers all this in greater detail and would be
worth obtaining if you're interested.

The 'sense' (i.e. clockwise/anticlockwise with respect to some datum) of the
winding of a solenoid, and the direction of the current applied, affect the
polarity of the magnetic field it produces, and vice versa for the receiving
case. *Consequently, the phase with respect to time of the alternating H
field (and the alternating E-field component of the radiated electromagnetic
wave) depend on the 'sense' of the winding, but the polarisation of the
radiated wave depends on the alignment of the axis of the solenoid. *By
convention, 'polarisation' is the angular direction of the E field in the
outgoing wave, which is perpendicular to the H-field component, and both are
perpendicular to the direction of propagation, so solenoid with a horizontal
axis radiates a vertically-polarised (VP) radio wave - and receives best
from a VP wave; the ferrite-rod-in-a-broadcast-receiver case.

Back to my original point: if part of the winding of the solenoid is wound
in the opposite sense to the rest of the winding then its contribution to
the generated H field, or the EMF on receiving, will oppose the contribution
from the other part of the winding. *If the winding has half in each
'sense', connected in series (like a non-inductive wire-wound resistor),
then it will not generate an H field or develop an EMF from an incident H
field, so it will not work as a transmitting or receiving antenna ... for
the reasons outlined above.

Enough?

Chris

Chris
First of all thank you very much for the effort that you placed in
your response.
It really what I expected from you after reading your profile ie the
anbsence of derision.
Now I am not fully convinced with your response as the rest of the
newsgroup already suspect
Coming from a different direction with respect to mathematics, when
adding a timevarying field
to a Gaussian field it equates in every way to the laws of Maxwell.
Both of these laws I consider
as an absolute truth. The above therefore states that the presence of
particles is undeniable in the generation of RF communication. Because
of the specificity of a state of equilibrium in a Gaussian field the
following can be stated. A radiator or array can be any size, shape or
varied elevation
...............AS LONG AS IT IS IN A STATE OF EQUILIBRIUM
From the above ground rules which is confirmed by Maxwells laws the
single winding of a wire
is NOT in equilibrium unless the lumped properties are cancelled which
leaves a structure that is in equilibrium ala wire that is conductive
and with no other properties other that he addition of distributed
loads that are common from a conductor.
Your response is based on the generation of fields without which the
radiator cannot receive by incoming waves from a transmitter, Where as
my response is based on the basis of particles impinging on a receive
antenna to create oscillation.
The biggest difference is the interpretation of a tank circuit( a
circuit in equilibrium) where in the perfect case of zero friction
your aproach would define this operation as a zero tx/rc element
My interpretation is that it cannot be zero friction even if the
distributed components were friction free because of the presence of
particles, which must be impelled by force to another radiator to
create oscillation.
So to sum up
Your aproach is from dissipating fields to provide communication and
mine is from non dissipating fields that dislodge particles as it
rotates to and from the distributed loads using both as energy
retainers..
As I have stated before, this is a presently a widely known method in
a macro re enactment of salvage processes that sorts materials by
directional magnetic field thrusts provided by eddy fields
I do need more time to study your response to see the difference
between the field aproach and the particle aproach tho with my present
circumstances I may not be able to determine.
Again, thankyou for your gentlemanly response, a rarity in this
particular newsgroup.
Regards
Art

Receiving Loop Antenna Question
 

"Art Unwin" wrote in message
...
On Jan 26, 12:16 pm, "christofire" wrote:
"Art Unwin" wrote in message

8


Chris
First of all thank you very much for the effort that you placed in
your response.
It really what I expected from you after reading your profile ie the
anbsence of derision.
Now I am not fully convinced with your response as the rest of the
newsgroup already suspect
Coming from a different direction with respect to mathematics, when
adding a timevarying field
to a Gaussian field it equates in every way to the laws of Maxwell.
Both of these laws I consider
as an absolute truth. The above therefore states that the presence of
particles is undeniable in the generation of RF communication. Because
of the specificity of a state of equilibrium in a Gaussian field the
following can be stated. A radiator or array can be any size, shape or
varied elevation
...............AS LONG AS IT IS IN A STATE OF EQUILIBRIUM
From the above ground rules which is confirmed by Maxwells laws the
single winding of a wire
is NOT in equilibrium unless the lumped properties are cancelled which
leaves a structure that is in equilibrium ala wire that is conductive
and with no other properties other that he addition of distributed
loads that are common from a conductor.
Your response is based on the generation of fields without which the
radiator cannot receive by incoming waves from a transmitter, Where as
my response is based on the basis of particles impinging on a receive
antenna to create oscillation.
The biggest difference is the interpretation of a tank circuit( a
circuit in equilibrium) where in the perfect case of zero friction
your aproach would define this operation as a zero tx/rc element
My interpretation is that it cannot be zero friction even if the
distributed components were friction free because of the presence of
particles, which must be impelled by force to another radiator to
create oscillation.
So to sum up
Your aproach is from dissipating fields to provide communication and
mine is from non dissipating fields that dislodge particles as it
rotates to and from the distributed loads using both as energy
retainers..
As I have stated before, this is a presently a widely known method in
a macro re enactment of salvage processes that sorts materials by
directional magnetic field thrusts provided by eddy fields
I do need more time to study your response to see the difference
between the field aproach and the particle aproach tho with my present
circumstances I may not be able to determine.
Again, thankyou for your gentlemanly response, a rarity in this
particular newsgroup.
Regards
Art


You're welcome.

I can't say I understand much of what you've written above but I'm sure
there are often many ways to visualise the same physical process; the
wave/particle duality of EM radiation being one often spoken about. For
this case, I wrote from the viewpoint of the work reported in a large number
of text books: the set of principles that's passed on at universities and
has been used to design the vast majority of antennas that have been used
since the discovery of radio. I'm not aware of any successful antenna
designs, operating lower than EHF, based on a particle theory of
electromagnetic radiation. However I am aware of a few unsuccessful designs
(e.g. the 'crossed-field antenna') for which the creators have purported to
re-write the known (wave) theory of radiation.

I know it's generally bad to generalise (!) but it seems clear to me, and
probably many others, that antennas based on well-documented,
well-understood, theory are always a safer bet! They certainly are in (most
lines of) business where cost matters - but perhaps not in amateur circles
where different motives apply.

Chris

Receiving Loop Antenna Question
 

On Jan 26, 1:59*pm, "christofire" wrote:
"Art Unwin" wrote in message

...
On Jan 26, 12:16 pm, "christofire" wrote:

"Art Unwin" wrote in message

8



Chris
First of all thank you very much for the effort that you placed in
your response.
It really what I expected from you after reading your profile ie the
anbsence of derision.
Now I am not fully convinced with your response as the rest of the
newsgroup already suspect
Coming from a different direction with respect to mathematics, when
adding a timevarying field
to a Gaussian field it equates in every way to the laws of Maxwell.
Both of these laws I consider
as an absolute truth. The above therefore states that the presence of
particles is undeniable in the generation of RF communication. Because
of the specificity of a state of equilibrium in a Gaussian field the
following can be stated. A radiator or array can be any size, shape or
varied elevation
..............AS LONG AS IT IS IN A STATE OF EQUILIBRIUM
From the above ground rules which is confirmed by Maxwells laws the
single winding of a wire
is NOT in equilibrium unless the lumped properties are cancelled which
leaves a structure that is in equilibrium ala wire that is conductive
and with no other properties other that he addition of distributed
loads that are common from a conductor.
Your response is based on the generation of fields without which the
radiator cannot receive by incoming waves from a transmitter, Where as
my response is based on the basis of particles impinging on a receive
antenna to create oscillation.
The biggest difference is the interpretation of a tank circuit( a
circuit in equilibrium) where in *the perfect case of zero friction
your aproach would define this operation as a zero tx/rc element
My interpretation is that it cannot be zero friction even if the
distributed components were friction free because of the presence of
particles, which must be impelled by force to another radiator to
create oscillation.
So to sum up
*Your aproach is from dissipating fields to provide communication and
mine is from non dissipating fields that dislodge particles as it
rotates to and from the distributed loads using both as energy
retainers..
As I have stated before, this is a presently a widely known method in
a macro *re enactment of salvage processes *that sorts materials by
directional magnetic field thrusts provided by eddy fields
I do need more time to study your response to see the difference
between the field aproach and the particle aproach tho with my present
circumstances I may not be able to determine.
Again, thankyou for your gentlemanly response, a rarity in this
particular newsgroup.
Regards
Art

You're welcome.

I can't say I understand much of what you've written above but I'm sure
there are often many ways to visualise the same physical process; the
wave/particle duality of EM radiation being one often spoken about. *For
this case, I wrote from the viewpoint of the work reported in a large number
of text books: the set of principles that's passed on at universities and
has been used to design the vast majority of antennas that have been used
since the discovery of radio. *I'm not aware of any successful antenna
designs, operating lower than EHF, based on a particle theory of
electromagnetic radiation. *However I am aware of a few unsuccessful designs
(e.g. the 'crossed-field antenna') for which the creators have purported to
re-write the known (wave) theory of radiation.

I know it's generally bad to generalise (!) but it seems clear to me, and
probably many others, that antennas based on well-documented,
well-understood, theory are always a safer bet! *They certainly are in (most
lines of) business where cost matters - but perhaps not in amateur circles
where different motives apply.

Chris

Understood
I have an applied patent that is on the net somewhere that goes thru
these same motions to obtain an array inequilibrim whbich are then
displayed via the AO pro program whiuch confirms the
equilibrium theoryn that is obtained by the Gaussian field aproach on
Maxwells laws.
On the same patent request I provided an analysis of a verticle dipole
which for maximum gain is tipped with reference to earth. The tipping
force is the weak force or the eddy field I spoke of which is not
included in programs associated with planar forms that are based on
intercoupling coupling.
The same aproach can also be applied using the equilibrium requirement
as I proposed earlier.
The only problem I can see in using MOM programs is the validity of
close spaced conduntors where it is possible to conceive of
interfering eddy currents not impinging upon particles, but it terms
of receiving there is nothing to prevent the impact of particles on
the radiator. At present my tower antenna is made of circularly wound
wires in both the cw and ccw direction, again based on the equilibrium
finding, where the antenna is a travelling wave form that is end fed
which allows for smaller volume antennas to those presently known.
Everything revolves around the extended Gaussion theorem which equates
to Maxwell's laws with the addition of particles within a boundary in
equilibrium. Break that association down then all of mine falls apart.
I will place a dual wound helix on my page in the next couple of days
that is produced via
the AOP Minninec program for antennas by Beasely so that you can see
it for your self. It will not be completely accurate as such an
arrangement requires many more point calculations than I have
available to me. Will be at hospital all day tomorrow so please be
patient on my page issue.
Best regards
Art

Receiving Loop Antenna Question
 

"christofire" wrote in message
...

I can't say I understand much of what you've written above but I'm sure
there are often many ways to visualise the same physical process;

and be glad that you don't understand it! its pure bafflegab, unless you
really like magical levitating diamagnetic neutrinos that hop off the
antenna to make em waves.