## Some loop antenna ideas

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• Hello all, I think of the oddest things while walking the dog. To illustrate this, tonight I was thinking of antenna theory and loop antennas in particular.
Message 1 of 12 , Nov 3, 2005
Hello all,

I think of the oddest things while walking the dog. To illustrate this,
tonight I was thinking of antenna theory and loop antennas in
particular. I read somewhere that the production of electromagnetic waves
(radiation) is literally a function of the generation and combination of a
magnetic field and an electric field (the function of an antenna). It is
important to understand that the radiation is not a sum of the 2 fields, it
is the product. Thus a Mag. F. of 4 x Elec. F. of 1 = Radiation of 4 and
a situation where the Mag. F. of 1 x Elec. F. of 4 = Radiation of 4
!!! Exactly the same.

The EFFECTIVENESS of the antenna is a result of maximizing the EFFECTIVE
magnetic field and the EFFECTIVE electric field of the antenna either of
which will do the job equally well. What I mean by an EFFECTIVE field is
that it is arranged so it can contribute to radiation. A coil inserted in
series with a wire antenna creates an inductance allowing the antenna to be
shortened. The magnetic field within the coil creates an inductive
reactance but it does not add to the effective magnetic field of the
wire. In fact it subtracts from the effective magnetic field of the wire
(antenna) as the wire must be shortened to maintain the overall inductive
reactance (required for resonance). Conversely a capacitor can be added to
an antenna (as in a loop for example) in order to tune it to
resonance. The electric field (between the plates) does not contribute to
the effective electrical field of the loop and in fact allows the loop to
be reduced in size (while maintaining resonance) thus reducing the
effective electrical field.

Lets get back to practical loop configurations for both receiving and
transmitting. I'm thinking of small loops of approximately 1/10 of a
wavelength or less. Let's say a transmitting loop for 40M (7Mhz) that is
approximately 4 Ft. in dia. It will be necessary to tune the loop to
resonance by introducing a rather large external capacitor. The electrical
field created between the plates will be quite intense and the voltage
across the plates will rise to high values .... requiring substantial
spacing between them. The tuning capacitor will tune the loop to resonance
but it will not create an electric field that contributes to radiation.

So how are the effective electrical and magnetic fields created in this
loop? The effective magnetic field is a result of the electric current that
flows around the loop and the effective electric field is a result of the
differential voltage around the loop. The loop has self capacitance. This
differential voltage in combination with the self capacitance of the loop
creates the electric field. The combination of these highly interrelated

Having thought through this I ask myself how do I maximize the effective
magnetic and electrical fields of this 4' loop?

The magnetic field is a function of the current in the loop which in turn
is a function of the conductivity of the loop at 7 Mhz. I understand that
conductivity is a function of the material used (eg aluminium is good,
copper is better) and surface area (due to skin effect). Metal strap of 1"
width represents a surface of 1" x 2 = 2 (both sides) and a 1" pipe
represents a surface of 3.14 (pi) So the pipe has it in terms of
electrical conduction (and rigidity).

Now of what is the electrical field a function? Well certainly it is a
function of the self capacitance of the loop and the voltage
differential. The voltage differential is a function of the current flow
(interrelated to the magnetic field but out of phase, by what, 90 degrees
??). What is the self capacitance related to? I would think the surface
area of the inside of the loop. Am I right? If this is true how can we
increase the self capacitance of the loop (and maintain the required
conductivity). If we increase the electric field component by 10% we
increase the radiation by 10% as well since radiation is product of the
magnetic and electrical fields.

What if we constructed the loop of strap instead of tubular material would
that substantially increase the self capacitance of the loop? Fixed
capacitors use flat plates not curved plates. What about tacking a 3" or
4" wide strip of mesh around the inside of the loop? Would that
substantially increase the self capacitance of the loop?

If it is possible to substantially increase the self capacitance of the
loop what would be the effect on feed point impedance, radiation pattern,
near effect of metal objects, effect of aperture size or capture area (I'm
not sure of the correct terminology), etc..

Food for thought

Jim Dunstan
Thunder Bay, ON
• I don t think you are on the right track. If a radiating element is electrically short, it radiates either a predominantly electric or magnetic field,
Message 2 of 12 , Nov 3, 2005
I don't think you are on the right track. If a radiating element is
electrically short, it radiates either a predominantly electric or magnetic
field, depending on whether it is a whip or a loop. An electrically short
whip looks like a small capacitance that is a very high impedance. Adding
inductance in series with that capacitor decreases the high impedance
allowing more current to flow, hence better radiation efficiency. Likewise,
an electrically short loop used at HF and above is an inductive load that
will present a high impedance which can be decreased by a series capacitor,
again allowing more current to flow. You don't really need to have a deep
understanding of electromagnetics to get a feel for this, simply look at the
limiting cases. A short rod is close to an open circuit. Driving it from
50 or 75 Ohms places a potential on it but no current. That means no power
is flowing into the whip. If no power is flowing into the whip, then no
power can flow out in the form of a radiated field (conservation of energy).
The more current (power) you can get into the radiating element, the more
power in the field, and the better the transmitter.

From: Jim Dunstan <jimdunstan@...>
Date: Thu, 03 Nov 2005 20:14:32 -0500
To: loopantennas@yahoogroups.com
Subject: [loopantennas] Some loop antenna ideas

Hello all,

I think of the oddest things while walking the dog. To illustrate this,
tonight I was thinking of antenna theory and loop antennas in
particular. I read somewhere that the production of electromagnetic waves
(radiation) is literally a function of the generation and combination of a
magnetic field and an electric field (the function of an antenna). It is
important to understand that the radiation is not a sum of the 2 fields, it
is the product. Thus a Mag. F. of 4 x Elec. F. of 1 = Radiation of 4 and
a situation where the Mag. F. of 1 x Elec. F. of 4 = Radiation of 4
!!! Exactly the same.

The EFFECTIVENESS of the antenna is a result of maximizing the EFFECTIVE
magnetic field and the EFFECTIVE electric field of the antenna either of
which will do the job equally well. What I mean by an EFFECTIVE field is
that it is arranged so it can contribute to radiation. A coil inserted in
series with a wire antenna creates an inductance allowing the antenna to be
shortened. The magnetic field within the coil creates an inductive
reactance but it does not add to the effective magnetic field of the
wire. In fact it subtracts from the effective magnetic field of the wire
(antenna) as the wire must be shortened to maintain the overall inductive
reactance (required for resonance). Conversely a capacitor can be added to
an antenna (as in a loop for example) in order to tune it to
resonance. The electric field (between the plates) does not contribute to
the effective electrical field of the loop and in fact allows the loop to
be reduced in size (while maintaining resonance) thus reducing the
effective electrical field.

Lets get back to practical loop configurations for both receiving and
transmitting. I'm thinking of small loops of approximately 1/10 of a
wavelength or less. Let's say a transmitting loop for 40M (7Mhz) that is
approximately 4 Ft. in dia. It will be necessary to tune the loop to
resonance by introducing a rather large external capacitor. The electrical
field created between the plates will be quite intense and the voltage
across the plates will rise to high values .... requiring substantial
spacing between them. The tuning capacitor will tune the loop to resonance
but it will not create an electric field that contributes to radiation.

So how are the effective electrical and magnetic fields created in this
loop? The effective magnetic field is a result of the electric current that
flows around the loop and the effective electric field is a result of the
differential voltage around the loop. The loop has self capacitance. This
differential voltage in combination with the self capacitance of the loop
creates the electric field. The combination of these highly interrelated

Having thought through this I ask myself how do I maximize the effective
magnetic and electrical fields of this 4' loop?

The magnetic field is a function of the current in the loop which in turn
is a function of the conductivity of the loop at 7 Mhz. I understand that
conductivity is a function of the material used (eg aluminium is good,
copper is better) and surface area (due to skin effect). Metal strap of 1"
width represents a surface of 1" x 2 = 2 (both sides) and a 1" pipe
represents a surface of 3.14 (pi) So the pipe has it in terms of
electrical conduction (and rigidity).

Now of what is the electrical field a function? Well certainly it is a
function of the self capacitance of the loop and the voltage
differential. The voltage differential is a function of the current flow
(interrelated to the magnetic field but out of phase, by what, 90 degrees
??). What is the self capacitance related to? I would think the surface
area of the inside of the loop. Am I right? If this is true how can we
increase the self capacitance of the loop (and maintain the required
conductivity). If we increase the electric field component by 10% we
increase the radiation by 10% as well since radiation is product of the
magnetic and electrical fields.

What if we constructed the loop of strap instead of tubular material would
that substantially increase the self capacitance of the loop? Fixed
capacitors use flat plates not curved plates. What about tacking a 3" or
4" wide strip of mesh around the inside of the loop? Would that
substantially increase the self capacitance of the loop?

If it is possible to substantially increase the self capacitance of the
loop what would be the effect on feed point impedance, radiation pattern,
near effect of metal objects, effect of aperture size or capture area (I'm
not sure of the correct terminology), etc..

Food for thought

Jim Dunstan
Thunder Bay, ON

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• ... I m not sure what my track was let alone if it was the right one hi. So let me see .... what you are saying above is that an electrically short whip
Message 3 of 12 , Nov 4, 2005
At 09:08 PM 11/3/2005 -0600, you wrote:
>I don't think you are on the right track. If a radiating element is
>electrically short, it radiates either a predominantly electric or magnetic
>field, depending on whether it is a whip or a loop.

I'm not sure what my track was let alone if it was the right one hi. So
let me see .... what you are saying above is that an electrically short
whip creates (radiates) an electromagnetic field that is predominantly
electric and an electrically short loop radiates an electromagnetic field
that is predominantly magnetic. Okay I'll buy that.

> An electrically short
>whip looks like a small capacitance that is a very high impedance. Adding
>inductance in series with that capacitor decreases the high impedance
>allowing more current to flow, hence better radiation efficiency. Likewise,
>an electrically short loop used at HF and above is an inductive load that
>will present a high impedance which can be decreased by a series capacitor,
>again allowing more current to flow. You don't really need to have a deep
>understanding of electromagnetics to get a feel for this, simply look at the
>limiting cases.

One thing for sure, I don't have a deep understanding of electromagnetics
hi. I'm getting a feel for what you are saying. You are saying a loop of
short electrical length say 4' diameter (12.5") represents an inductive
load (say at 7Mhz) and a high impedance. By placing a capacitor in the
loop it will it will decrease the impedance and allow more current to
flow. I assume this effect will maximize when the capacitive reactance
matches the inductive reactance (resonance).

Okay I fully agree. Now lets say we feed some power into this loop (lets
leave coupling the power aside), there will be a radiated electromagnetic
field that you say (and I agree) will be predominately magnetic. Once we
have reached resonance the only way we can increase the magnetic field
(increase the current in the loop) is to improve the conductivity of the
loop (at 7MHZ) by selecting the best materials in the construction of the
loop. I am sure you will agree that such a loop constructed of #12 wire
would radiate a smaller field than one constructed of 1" copper pipe. The
loop constructed of copper pipe will conduct more current (input power and
resonance kept at a constant) than the wire and will have a stronger
magnetic field and thus create a stronger electromagnetic field (radiation).

Since the formula for radiation is magnetic F. x electrical field
increasing the magnetic field 10% (by careful construction) will increase
radiation 10%. Since the electric field is interrelated to the magnetic
field increasing the current flow will also increase the electric field
.... but the increase will be predominately magnetic. I ask is there a way
to increase the electric field in this loop .... that is in relation to the
magnetic field.

I am not talking about violating the law of conservation of energy .... I
am just asking is it possible to construct this loop in such a way that
significantly affects the ratio of magnetic field to electrical field ....
and if it is possible how will that affect the characteristics of the antenna?

Any ideas?

By the way, I asked my dog and all she does is wag her tail hi.
• As far as I know, you can t do anything to a loop of a given size to increase the electric field output in its immediate vicinity. As you move away from the
Message 4 of 12 , Nov 4, 2005
As far as I know, you can't do anything to a loop of a given size to
increase the electric field output in its immediate vicinity. As you move
away from the loop the field impedance (E/H) will increase from the loop
impedance itself to the impedance of free space, which is 377 Ohms.
However, I normally work with very small loops whose reactive impedance is a
few Ohms. That wouldn't be the case for a four foot loop at 7 MHz. The
rule is that in the quasi-static field (very close to the radiating element)
the field impedance mirrors the impedance of the radiating element, and the
farther away you are the closer the field impedance will be to 377 Ohms.
For a small loop the field starts out magnetic (lower than 377 Ohms) and
becomes more electric. For a short whip, the field starts out electric
(higher than 377 Ohms) and becomes more magnetic as you move away.

From: Jim Dunstan <jimdunstan@...>
Date: Fri, 04 Nov 2005 08:23:59 -0500
To: loopantennas@yahoogroups.com
Subject: Re: [loopantennas] Some loop antenna ideas

At 09:08 PM 11/3/2005 -0600, you wrote:
>I don't think you are on the right track. If a radiating element is
>electrically short, it radiates either a predominantly electric or magnetic
>field, depending on whether it is a whip or a loop.

I'm not sure what my track was let alone if it was the right one hi. So
let me see .... what you are saying above is that an electrically short
whip creates (radiates) an electromagnetic field that is predominantly
electric and an electrically short loop radiates an electromagnetic field
that is predominantly magnetic. Okay I'll buy that.

> An electrically short
>whip looks like a small capacitance that is a very high impedance. Adding
>inductance in series with that capacitor decreases the high impedance
>allowing more current to flow, hence better radiation efficiency. Likewise,
>an electrically short loop used at HF and above is an inductive load that
>will present a high impedance which can be decreased by a series capacitor,
>again allowing more current to flow. You don't really need to have a deep
>understanding of electromagnetics to get a feel for this, simply look at the
>limiting cases.

One thing for sure, I don't have a deep understanding of electromagnetics
hi. I'm getting a feel for what you are saying. You are saying a loop of
short electrical length say 4' diameter (12.5") represents an inductive
load (say at 7Mhz) and a high impedance. By placing a capacitor in the
loop it will it will decrease the impedance and allow more current to
flow. I assume this effect will maximize when the capacitive reactance
matches the inductive reactance (resonance).

Okay I fully agree. Now lets say we feed some power into this loop (lets
leave coupling the power aside), there will be a radiated electromagnetic
field that you say (and I agree) will be predominately magnetic. Once we
have reached resonance the only way we can increase the magnetic field
(increase the current in the loop) is to improve the conductivity of the
loop (at 7MHZ) by selecting the best materials in the construction of the
loop. I am sure you will agree that such a loop constructed of #12 wire
would radiate a smaller field than one constructed of 1" copper pipe. The
loop constructed of copper pipe will conduct more current (input power and
resonance kept at a constant) than the wire and will have a stronger
magnetic field and thus create a stronger electromagnetic field (radiation).

Since the formula for radiation is magnetic F. x electrical field
increasing the magnetic field 10% (by careful construction) will increase
radiation 10%. Since the electric field is interrelated to the magnetic
field increasing the current flow will also increase the electric field
.... but the increase will be predominately magnetic. I ask is there a way
to increase the electric field in this loop .... that is in relation to the
magnetic field.

I am not talking about violating the law of conservation of energy .... I
am just asking is it possible to construct this loop in such a way that
significantly affects the ratio of magnetic field to electrical field ....
and if it is possible how will that affect the characteristics of the
antenna?

Any ideas?

By the way, I asked my dog and all she does is wag her tail hi.

For uploading images, I prefer the Files section since Photos only allows
everyone (except the uploader and moderators) to see a max of 300x400.
http://groups.yahoo.com/group/loopantennas/files

Put them in the appropriate folder, or create one.

" on the web.

To unsubscribe from this group, send an email to:
loopantennas-unsubscribe@yahoogroups.com
<mailto:loopantennas-unsubscribe@yahoogroups.com?subject=Unsubscribe>

<http://docs.yahoo.com/info/terms/> .

[Non-text portions of this message have been removed]
• ... You can t increase the electric field of a loop antenna. What your saying is that no matter how you construct a loop the electric field will be exactly
Message 5 of 12 , Nov 4, 2005
At 08:34 AM 11/4/2005 -0600, you wrote:
>As far as I know, you can't do anything to a loop of a given size to
>increase the electric field output in its immediate vicinity.

You can't increase the electric field of a loop antenna. What your saying
is that no matter how you construct a loop the electric field will be
exactly the same ... eg whether it is #12 wire or 3'" diameter pipe. Hmmm.

> As you move
>away from the loop the field impedance (E/H) will increase from the loop
>impedance itself to the impedance of free space, which is 377 Ohms.

Lets leave impedance aside for the moment and not confuse the issue. I
assume E means electric field and H means magnetic field .... if not, what
do they mean? As far as I know every antenna that radiates by definition
has an E and H field. These fields by definition do no by themselves
radiate beyond the antenna. however when they come into contact with each
other they create a new field, an electromagnetic field that leaves the
does not radiate, but an electromagnetic field does.

The radiated electromagnetic field is a product of the two
fields. Therefore it is legitimate to ponder how each of the 2 fields is
created and controlled as any design feature that can increase either of
the 2 fields will have a direct effect on the radiated electromagnetic field.

I don't mean to be contrary but I'm looking for some ideas that might
contribute to increasing the electric field of a loop as well as the
magnetic field of a loop. The same question could be asked of a vertical
or dipole antenna .... but since this is a loop group I am limiting to loop
antennas.

>However, I normally work with very small loops whose reactive impedance is a
>few Ohms. That wouldn't be the case for a four foot loop at 7 MHz. The
>rule is that in the quasi-static field (very close to the radiating element)
>the field impedance mirrors the impedance of the radiating element, and the
>farther away you are the closer the field impedance will be to 377 Ohms.
>For a small loop the field starts out magnetic (lower than 377 Ohms) and
>becomes more electric. For a short whip, the field starts out electric
>(higher than 377 Ohms) and becomes more magnetic as you move away.

Here I am confused, I am not sure about "quasi-static field" let alone it's
impedance? Does this mean a field that doesn't radiate? eg not an
electromagnetic field? It is very interesting what you say (leaving
impedance out of the discussion); that a radiated field (electromagnetic)
from a small loop starts out as a predominately magnetic and becomes
predominately (at least more) electric .... while a short whip radiates an
electromagnetic field that is primarily electric and becomes more magnetic
as it moves away from the antenna.

I think what you are saying in the examples above is that the ratio of
magnetic to electric component in the electromagnetic field radiated from
the antenna changes as it moves away from the antenna. However the ratio
may change as the electromagnetic field moves away from the antenna the
total field stays the same as it is a product of these components .... or
am I wrong?

Here we are talking about compromised antennae ... eg short ones hi hi ...

Lets go back to that 4' dia. 7Mhz loop example. We place a capacitor in
series and adjust (tune) it to resonance. We couple a 1W transmitter to it
(lets leave how aside). The current in the loop creates both electric and
magnetic fields which combine (as a product) in proportion to their values
to form an electromagnetic field that radiates. Now the proportions of
magnetic and electric may change as the field leaves the loop (antenna) but
is a value of this electromagnetic field is (X).

The literal value of (X) will depend on the quality of construction of the
loop. We all know that to maximize the current in the loop will contribute
to increased magnetic field and to a lesser extent electric field. If we
double the current the radiation may become (2X) or (1.5X). We are not
creating power from nothing ... all we are doing is increasing radiation by
reducing the amount of power that is consumed (as heat?) by the loop.

In tuning the loop with a series capacitor we are creating an electric
field between the plates of the capacitor. This will dramatically increase
the currents in the loop and ultimately the radiation. However, the
electric field contained between the plates of the tuning capacitor is
wasted as it is not a part of the electromagnetic mix that radiates. Am I
wrong?

Is there a way to transfer some of that wasted electric field in the tuning
capacitor to the loop where it can contribute to radiation. If the design
of a 4' loop for 7Mhz should require half the tuning capacitor value to
tune it to resonance then the electric field of the antenna should increase
with a resultant increase in electromagnetic radiation.

I can't believe that the amount of electric field possible in a loop is
fixed .... depending on its diameter. A 4' loop is a 4' loop and if you
want more electric field build a 5' loop. Perhaps a well designed 4' loop
can create as much electric field as a poorly designed 6' loop. I don't
remember ever seeing a chart of loop size vs electric field capability hi hi ..

Jim Dunstan,
Thunder Bay, ON
• Hi Jim, I don t think the ratio of electric and magnetic fields in an antenna has anything to do with how it works or well it works. As far as I can
Message 6 of 12 , Nov 4, 2005
Hi Jim,

I don't think the ratio of electric and magnetic fields in an
antenna has anything to do with how it works or well it works. As far
as I can determine, the only requirement for an antenna is a
conductor/wire of some sort along which electrons flow back and forth
in a time varing fashion, creating a magnetic field around the
conductor/wire. Whether the antenna has balanced electric and
magnetic fields, or creates mainly a magnetic field as in a loop is
not relevant.

impedance of 377 ohms is the magic that occurs where a field becomes
an electromagnetic wave. The fields are finite and will expand out to
1 wavelength from the antenna. The electromagnetic wave travels
infinitely and is the process that Maxwell conceived and modeled with
mathematics. This process occurs at or beyond one wavelenth from the
antenna. The electromagnetic wave is viewed as a magnetic field which
collapses as an electric field is formed. The fields are at right
angles to each other. This process of one field morphing into the
other continues infinitely.

Note that this electromagnetic wave is not dependent on the relative
abundance of electric and magnetic fields near the antenna. It does
seem to require a time varying magnetic field. I don't believe the
concept of a pure capacitor antenna holds much water.

Somewhere on the internet, I think on the Grimes website (Penn State
University) is a cartoon of the process of an electromagnetic wave
travelling. I believe it is generated with Maxwell's equations. I
will try to find the url and post it later.

Regarding the "effectiveness" of a loop antenna. By effectiveness do
you mean gain? If so, the gain of a loop is related to the area it
surrounds.

Dave WA6YSO

--- In loopantennas@yahoogroups.com, Jim Dunstan <jimdunstan@r...> wrote:
>
> At 08:34 AM 11/4/2005 -0600, you wrote:
> >As far as I know, you can't do anything to a loop of a given size to
> >increase the electric field output in its immediate vicinity.
>
> You can't increase the electric field of a loop antenna. What your
saying
> is that no matter how you construct a loop the electric field will be
> exactly the same ... eg whether it is #12 wire or 3'" diameter pipe.
Hmmm.
>
>
> > As you move
> >away from the loop the field impedance (E/H) will increase from the
loop
> >impedance itself to the impedance of free space, which is 377 Ohms.
>
> Lets leave impedance aside for the moment and not confuse the issue. I
> assume E means electric field and H means magnetic field .... if
not, what
> do they mean? As far as I know every antenna that radiates by
definition
> has an E and H field. These fields by definition do no by themselves
> radiate beyond the antenna. however when they come into contact
with each
> other they create a new field, an electromagnetic field that leaves the
field
> does not radiate, but an electromagnetic field does.
>
> The radiated electromagnetic field is a product of the two
> fields. Therefore it is legitimate to ponder how each of the 2
fields is
> created and controlled as any design feature that can increase
either of
> the 2 fields will have a direct effect on the radiated
electromagnetic field.
>
> I don't mean to be contrary but I'm looking for some ideas that might
> contribute to increasing the electric field of a loop as well as the
> magnetic field of a loop. The same question could be asked of a
vertical
> or dipole antenna .... but since this is a loop group I am limiting
to loop
> antennas.
>
>
> >However, I normally work with very small loops whose reactive
impedance is a
> >few Ohms. That wouldn't be the case for a four foot loop at 7 MHz.
The
> >rule is that in the quasi-static field (very close to the radiating
element)
> >the field impedance mirrors the impedance of the radiating
element, and the
> >farther away you are the closer the field impedance will be to 377
Ohms.
> >For a small loop the field starts out magnetic (lower than 377
Ohms) and
> >becomes more electric. For a short whip, the field starts out electric
> >(higher than 377 Ohms) and becomes more magnetic as you move away.
>
>
> Here I am confused, I am not sure about "quasi-static field" let
alone it's
> impedance? Does this mean a field that doesn't radiate? eg not an
> electromagnetic field? It is very interesting what you say (leaving
> impedance out of the discussion); that a radiated field
(electromagnetic)
> from a small loop starts out as a predominately magnetic and becomes
> predominately (at least more) electric .... while a short whip
> electromagnetic field that is primarily electric and becomes more
magnetic
> as it moves away from the antenna.
>
> I think what you are saying in the examples above is that the ratio of
> magnetic to electric component in the electromagnetic field radiated
from
> the antenna changes as it moves away from the antenna. However the
ratio
> may change as the electromagnetic field moves away from the antenna the
> total field stays the same as it is a product of these components
.... or
> am I wrong?
>
> Here we are talking about compromised antennae ... eg short ones hi
hi ...
>
> Lets go back to that 4' dia. 7Mhz loop example. We place a
capacitor in
> series and adjust (tune) it to resonance. We couple a 1W
transmitter to it
> (lets leave how aside). The current in the loop creates both
electric and
> magnetic fields which combine (as a product) in proportion to their
values
> to form an electromagnetic field that radiates. Now the proportions of
> magnetic and electric may change as the field leaves the loop
(antenna) but
> is a value of this electromagnetic field is (X).
>
> The literal value of (X) will depend on the quality of construction
of the
> loop. We all know that to maximize the current in the loop will
contribute
> to increased magnetic field and to a lesser extent electric field.
If we
> double the current the radiation may become (2X) or (1.5X). We are not
> creating power from nothing ... all we are doing is increasing
> reducing the amount of power that is consumed (as heat?) by the loop.
>
> In tuning the loop with a series capacitor we are creating an electric
> field between the plates of the capacitor. This will dramatically
increase
> the currents in the loop and ultimately the radiation. However, the
> electric field contained between the plates of the tuning capacitor is
> wasted as it is not a part of the electromagnetic mix that radiates.
Am I
> wrong?
>
> Is there a way to transfer some of that wasted electric field in the
tuning
> capacitor to the loop where it can contribute to radiation. If the
design
> of a 4' loop for 7Mhz should require half the tuning capacitor value to
> tune it to resonance then the electric field of the antenna should
increase
> with a resultant increase in electromagnetic radiation.
>
>
> I can't believe that the amount of electric field possible in a loop is
> fixed .... depending on its diameter. A 4' loop is a 4' loop and if
you
> want more electric field build a 5' loop. Perhaps a well designed
4' loop
> can create as much electric field as a poorly designed 6' loop. I
don't
> remember ever seeing a chart of loop size vs electric field
capability hi hi ..
>
> Jim Dunstan,
> Thunder Bay, ON
>
• ... Is this the URL? http://www.ee.psu.edu/grimes/antennas/ I wish these eggheads would produce a website for people like me. Call it EH Fields for Dummies.
Message 7 of 12 , Nov 5, 2005
> Somewhere on the internet, I think on the Grimes website (Penn State
> University) is a cartoon of the process of an electromagnetic wave
> travelling. I believe it is generated with Maxwell's equations. I
> will try to find the url and post it later.

Is this the URL?

http://www.ee.psu.edu/grimes/antennas/

I wish these eggheads would produce a website for people like me. Call it
EH Fields for Dummies.
My eyes glaze over every time I see the Greek alphabet, squiggly lines and
mathematical voodoo.

Tom Curtola
• ... Call it ... lines and ... Yes, that s the site. Problem is I have not yet found the graphic which I was describing in my previous post. Tom, I share your
Message 8 of 12 , Nov 5, 2005
--- In loopantennas@yahoogroups.com, "Tom Curtola" <tcurtola@r...> wrote:
>
>
> > Somewhere on the internet, I think on the Grimes website (Penn State
> > University) is a cartoon of the process of an electromagnetic wave
> > travelling. I believe it is generated with Maxwell's equations. I
> > will try to find the url and post it later.
>
> Is this the URL?
>
> http://www.ee.psu.edu/grimes/antennas/
>
> I wish these eggheads would produce a website for people like me.
Call it
> EH Fields for Dummies.
> My eyes glaze over every time I see the Greek alphabet, squiggly
lines and
> mathematical voodoo.
>
> Tom Curtola
>

Yes, that's the site. Problem is I have not yet found the graphic
which I was describing in my previous post. Tom, I share your
"problem" with the math. My level of understanding of this stuff is
on a concept level. Never was very good at math!

Dave WA6YSO
• ... Heh !! who are you calling an egghead hi hi .... hello Tom. I get the same dizziness with the formulas ... I was going to say formulae but thought
Message 9 of 12 , Nov 5, 2005
At 08:23 AM 11/5/2005 -0500, you wrote:

> > Somewhere on the internet, I think on the Grimes website (Penn State
> > University) is a cartoon of the process of an electromagnetic wave
> > travelling. I believe it is generated with Maxwell's equations. I
> > will try to find the url and post it later.
>
>Is this the URL?
>
>http://www.ee.psu.edu/grimes/antennas/
>
>I wish these eggheads would produce a website for people like me. Call it
>EH Fields for Dummies.
>My eyes glaze over every time I see the Greek alphabet, squiggly lines and
>mathematical voodoo.
>
>Tom Curtola

Heh !! who are you calling an egghead hi hi .... hello Tom. I get the
same dizziness with the formulas ... I was going to say formulae but
thought better of it hi.

How are things back in Toronto?

I have been looking at this proposition of increasing the capacitive aspect
of antennae .... especially the vertical variety. You know I have been
doing a few experiments and have been finding some truth in the
pudding. However I find it easier to put my mind around the concept with
vertical and dipole types. As they say an antenna is an antenna .... so
how does it apply to the loop antenna? How does one go about increasing
displacement current (in phase) with the electric current etc.

Well to make you more dizzy one of my favorite websites discussing these
antenna fundamentals (be cautious there are formulas {ae}) is

I get back to Toronto from time to time ... next time I'll give you a call
and maybe we can go for a coffee.

73

Jim Dunstan
Thunder Bay, ON
• Hi Jim, Thanks for the link. Very interesting site. He even has a nice pictorial, which for people like me, really appreciate. Things are going well in
Message 10 of 12 , Nov 5, 2005
Hi Jim,

Thanks for the link. Very interesting site. He even has a nice pictorial,
which for people like me, really appreciate.

Things are going well in Toronto. Still operating in the ham shack at the
Science Centre on Mondays. Recently slapped together a coaxial receiving
loop and was quite astounded that they really do work well at attenuating
local noise.

Also been playing with an MFJ 1026 Noise Canceller / Antenna Phaser.
Interesting little box. Does the job quite well at nulling local RFI. Also
can use it to 'sort of' steer the verticals and null out local AM BCB
stations to hear DX beneath. That quite impressed me.

Next month, at our meeting at the Science Centre, one of the club members is
going to bring in his transmitting loop he just built. He's really good
with construction projects and I can't wait to see it and learn some of his
techniques. I'll snap some pictures and post them to this group.

73,

Tom Curtola
VA3TY

----- Original Message -----
From: "Jim Dunstan" <jdunstan@...>
To: <loopantennas@yahoogroups.com>
Sent: Saturday, November 05, 2005 5:44 PM
Subject: Re: [loopantennas] Re: Some loop antenna ideas

> At 08:23 AM 11/5/2005 -0500, you wrote:
>
>> > Somewhere on the internet, I think on the Grimes website (Penn State
>> > University) is a cartoon of the process of an electromagnetic wave
>> > travelling. I believe it is generated with Maxwell's equations. I
>> > will try to find the url and post it later.
>>
>>Is this the URL?
>>
>>http://www.ee.psu.edu/grimes/antennas/
>>
>>I wish these eggheads would produce a website for people like me. Call it
>>EH Fields for Dummies.
>>My eyes glaze over every time I see the Greek alphabet, squiggly lines and
>>mathematical voodoo.
>>
>>Tom Curtola
>
>
> Heh !! who are you calling an egghead hi hi .... hello Tom. I get the
> same dizziness with the formulas ... I was going to say formulae but
> thought better of it hi.
>
> How are things back in Toronto?
>
> I have been looking at this proposition of increasing the capacitive
> aspect
> of antennae .... especially the vertical variety. You know I have been
> doing a few experiments and have been finding some truth in the
> pudding. However I find it easier to put my mind around the concept with
> vertical and dipole types. As they say an antenna is an antenna .... so
> how does it apply to the loop antenna? How does one go about increasing
> displacement current (in phase) with the electric current etc.
>
> Well to make you more dizzy one of my favorite websites discussing these
> antenna fundamentals (be cautious there are formulas {ae}) is
>
> I get back to Toronto from time to time ... next time I'll give you a call
> and maybe we can go for a coffee.
>
> 73
>
>
> Jim Dunstan
> Thunder Bay, ON
>
>
>
>
>
>
> For uploading images, I prefer the Files section since Photos only allows
> everyone (except the uploader and moderators) to see a max of 300x400.
> http://groups.yahoo.com/group/loopantennas/files
>
> Put them in the appropriate folder, or create one.
>
>
>
>
>
>
>
• At 07:15 AM 11/5/2005 +0000, you wrote: Hi Dave I appreciate your thoughtful response; it has driven me back to my reading (I do most ... or a lot of it on
Message 11 of 12 , Nov 5, 2005
At 07:15 AM 11/5/2005 +0000, you wrote:

Hi Dave

I appreciate your thoughtful response; it has driven me back to my reading
(I do most ... or a lot of it on the internet). My favorite site is
http://hawkins.pair.com/eRadiation.html . The formulae are a little
difficult to follow (especially for me) but I find the way he has broken it
down, and the way he presents summary conclusions in text format to be very
useful. I have read his web site many times and find new things every time

I find that there is a problem in looking at an antenna in terms of its EXH
characteristics because there are a number of pretty goofy experiments out
there that blur the basic concepts. I have examined a number of them and
the only one I found that made sense in the reading and in practice was the
one made by GAP antennas. They call it the "SuperC" antenna and are
selling it commercially. I have two home QTH's, this one in Thunder Bay
where I have lots of room for traditional antennas and the other in
downtown Toronto on the 9th floor of an apartment block.

In Toronto my antenna farm was the balcony 5"x12" where I started out with
a 20M wire dipole bent and held out with plastic fishing rods in creative
ways. It worked fine and I made lots of contacts. However because of the
space restriction I kept looking for an alternative. I tried a tuned loop
as well but found some difficulty with all the close metal objects in the
immediate location .... like the iron railing of the balcony. I came
across the GAP SuperC experiment and basically I copied the idea.

The result was an eye opener for me. The 20M antenna became a vertical 4'
5'x10'. The vertical element was a copper pipe surrounded by a galvanized
metal garbage can! You make do with what you have around hi hi. As I
said, I basically followed the same design concept of the GAP SuperC antenna.

To be clear the antenna was not better than the dipole but it certainly was
different. It appeared to be reasonably efficient (compared to the
dipole). Where it differed was the size !! 4' tall with no loading
coil. My antenna tuner had no difficulty matching it (it appeared to be a
rather low impedance). However what was most fascinating was how immune it
was to nearby metal objects. I could bring a metal object next to the
vertical element and the SWR would change very little if at all!!

I mentioned that I experimented with a tuned loop in the same location. It
radiated well but was very narrow in bandwidth and if I did the same
experiment of bringing a metal object close to it the swr would jump way
out of site!!

I am back in Thunder Bay now... with lots of room .... and I plan to build
a similar vertical antenna (on the roof of the carport ... what will the
neighbors think) but for 80M. The Gap SuperC is not a better antenna it a
very DIFFERENT antenna. It looks different and it behaves differently, but
works about the same as a traditional antenna of the type. Different but
not better ... in certain situations the difference might be an advantage

While thinking about the new project I started to think about loop
antennas. I always liked the loop antenna .... maybe something about a
complete circle hi hi. In any event I thought that if changing the design
of a vertical antenna can have such dramatic effects on behavior how could
the design of a loop be modified to create some of the same differences
.... which drove me back to the basics again and venturing on this
loopgroup hi hi.

>I don't think the ratio of electric and magnetic fields in an
>antenna has anything to do with how it works or well it works. As far
>as I can determine, the only requirement for an antenna is a
>conductor/wire of some sort along which electrons flow back and forth
>in a time varing fashion, creating a magnetic field around the
>conductor/wire. Whether the antenna has balanced electric and
>magnetic fields, or creates mainly a magnetic field as in a loop is
>not relevant.

I am convinced the difference in behavior between the SuperC vertical
antenna and a traditional vertical antenna (as they claim and I experienced
in my knock-off version) is due to the change in ratio between the magnetic
and electric fields generated in the antennae. The ratio in a traditional
antenna is predominately magnetic (easily affected by local metal objects)
while the SuperC antenna has a ratio that is predominately electric (little
affect from local metal objects).

Indeed electric current flows on the conductor as you say .... however
there are two kinds of current flowing on the element; there is the
current that flows that is generally referred to as electric and there is
the additional DISPLACEMENT current that is associated with the creation of
the electric field .... eg like charging a capacitor. According to Maxwell
and Poynting the actual power converted to radiation is a product of the
mixing of these fields and is expressed as the formula ExH=P .... the power
radiated expressed as watts per square meter. (I am paraphrasing Jim
Hawkins from his web site http://hawkins.pair.com/eRadiation.html ).

>impedance of 377 ohms is the magic that occurs where a field becomes
>an electromagnetic wave. The fields are finite and will expand out to
>1 wavelength from the antenna. The electromagnetic wave travels
>infinitely and is the process that Maxwell conceived and modeled with
>mathematics. This process occurs at or beyond one wavelenth from the
>antenna. The electromagnetic wave is viewed as a magnetic field which
>collapses as an electric field is formed. The fields are at right
>angles to each other. This process of one field morphing into the
>other continues infinitely.
>
>Note that this electromagnetic wave is not dependent on the relative
>abundance of electric and magnetic fields near the antenna. It does
>seem to require a time varying magnetic field. I don't believe the
>concept of a pure capacitor antenna holds much water.

Well according to Maxwell and Poynting .... and quotes from Jim Hawkins
that the power in the electromagnetic wave is directly related to the value
of the magnetic and electric fields that result from the combined electric
and displacement currents (by the way the currents must be in phase [called
the Poynting vector] for lift off to take place) and as I mentioned above
is expressed as P(power)=ExH

I don't think we are talking about a 'pure' capacitor antenna. According
to the formula above that wouldn't radiate .... it needs a magnetic field
as well .... and not just any magnetic field ... but one created in phase
with the electric field. There is no such thing as a purely magnetic or
purely capacitive antenna.

>Somewhere on the internet, I think on the Grimes website (Penn State
>University) is a cartoon of the process of an electromagnetic wave
>travelling. I believe it is generated with Maxwell's equations. I
>will try to find the url and post it later.
>
>Regarding the "effectiveness" of a loop antenna. By effectiveness do
>you mean gain? If so, the gain of a loop is related to the area it
>surrounds.

I was too loose with my words .... all antennae can be measured in terms of
their efficiency .... that is for 1 watt in and 1 watt of radiation would
be 100% , a miracle antenna hi. Gain is really a misnomer and relates to
antenna patterns and measurements like front to back ratios and increased
signals compared to standard antennas etc.

The ratio of power in and power out is always less than 1:1.

I guess what I should have said is how can we alter the design of a loop so
it can display some of the same characteristics (I outlined above for a
vertical antenna). Is it possible to increase the displacement current on
the loop?

By the way Dave ... my friend Tom is listening in ... he's the one calling
me an egg head hi hi.

Jim Dunstan VE3CI
• ... Hi Tom, We had a demo of a transmitting loop at our local QRP group meeting. One of the members brought it .... he had a small motor tuning the loop and
Message 12 of 12 , Nov 5, 2005
At 06:30 PM 11/5/2005 -0500, you wrote:
>Hi Jim,
>
>Thanks for the link. Very interesting site. He even has a nice pictorial,
>which for people like me, really appreciate.
>
>Things are going well in Toronto. Still operating in the ham shack at the
>Science Centre on Mondays. Recently slapped together a coaxial receiving
>loop and was quite astounded that they really do work well at attenuating
>local noise.
>
>Also been playing with an MFJ 1026 Noise Canceller / Antenna Phaser.
>Interesting little box. Does the job quite well at nulling local RFI. Also
>can use it to 'sort of' steer the verticals and null out local AM BCB
>stations to hear DX beneath. That quite impressed me.
>
>Next month, at our meeting at the Science Centre, one of the club members is
>going to bring in his transmitting loop he just built. He's really good
>with construction projects and I can't wait to see it and learn some of his
>techniques. I'll snap some pictures and post them to this group.
>
>73,
>
>Tom Curtola
>VA3TY

Hi Tom,

We had a demo of a transmitting loop at our local QRP group meeting. One
of the members brought it .... he had a small motor tuning the loop and was
using a small picki up loop to couple it to an elecraft K1
transceiver. It was amazing to watch ... as he tuned the loop with the
motor the K1's internal antenna tuner would clunk away following it and
producing a 1:1 SWR. When I made a transmitting loop I used a manual
system to tune the loop and a manual antenna tuner to match the pickup loop
to the transceiver.

I also used a tuned receiving loop on the balcony and I had thought about
using that MFJ 1026 to see what a pair of crossed receiving loops would do
if they could be phased .... just like the old direction finders on the
ships. Did you actually buy the 1026 or are you borrowing it hi hi..