Gamma Matching Question
 

I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

My question is -- when I'm ready to test the antenna
do I adjust the gamma match at the lowest frequency I
plan to use, or the highest?

I have considered other forms of coupling the
rig to the transmitter but prefer to use the gamma
match.

Thanks in advance for any assistance or advice in this
matter.

Irv VE6BP

Gamma Matching Question
 

Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

The gamma match principle will work over a wide range of frequencies
but a given gamma match is rather narrow banded.

Unless your gamma match is really mechanically clever like perhaps the
SteppIR antennas, it isn't going to cover multiple bands.

Some references for study:

http://www.bcpink.com/KB3IFH/files/D...%20article.pdf

http://www.k1ttt.net/technote/gamma.html



--
Jim Pennino

Gamma Matching Question
 

On Sat, 21 Sep 2013 11:50:40 -0600, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match.

I understand
that a gamma match will work over a wide range of
frequencies.

Your understanding is in error.
At best a gamma match will "work well" over a 1-2% freq. range --
for selected definitions of "work well.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

Gamma Matching Question
 

Thanks to Jim and Jonesy -- I'm not very familiar with
all the ins and outs of Gamma matching, but in a number of
cases of Magnetic Loops where the loop covers a number
of bands e.g. 80-15m, 80-30M, the builders used a
Gamma match which when set needs no adjustment between
bands. Perhaps the Magnetic Loop has different properties,
although the authors of the articles claimed the matching
portion was a 'form of Gamma Match' and in one case
referred to the matching portion as a form of autotransformer
which I interpret to mean a non-circular feed loop of sorts.

In one loop design by Peter Parker VK3YE whose loop
covers 160-15 meters, the author advised me (when I
queried the Gamma question to him) that the
gamma when set as designed serves all bands well.
In other designs the gamma match or whatever it
might be, seems to work and did not seem to be a
problem or I think it might have been commented
on by the authors.

I will be investigating all these things soon -- I have just
recovered over a few years of some pretty heavy
abdominal surgeries and will be moving to a senior's
residence where I will have a balcony to work from.
It will be nice to get back on the air again after having
had to sell my house after the first surgery where I
had room for all different forms of antennas. Now I will
be back on the air again but will have to work under
certain restrictions such as no wires to nearby trees and
so forth. A magnetic loop or some form of windowsill
antenna will likely be my best bets. I'm looking forward to
the experience! I've always maintained to other old timers
who moved into condos where there restrictions that there
would always be some way to get on the air -- now I'm going
to have to walk the talk myself! One way or another I'm
not going to give up 55 years of hamming -- even if I can
only work across town! I'm shooting for multiband 80-10M
operation -- or bust! (Touch wood!)

Thanks,

Irv VE6BP
..
"Allodoxaphobia" wrote in message
t...
On Sat, 21 Sep 2013 11:50:40 -0600, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match.

I understand
that a gamma match will work over a wide range of
frequencies.

Your understanding is in error.
At best a gamma match will "work well" over a 1-2% freq. range --
for selected definitions of "work well.

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

Gamma Matching Question
 

Irv Finkleman wrote:
Thanks to Jim and Jonesy -- I'm not very familiar with
all the ins and outs of Gamma matching, but in a number of
cases of Magnetic Loops where the loop covers a number
of bands e.g. 80-15m, 80-30M, the builders used a
Gamma match which when set needs no adjustment between
bands. Perhaps the Magnetic Loop has different properties,
although the authors of the articles claimed the matching
portion was a 'form of Gamma Match' and in one case
referred to the matching portion as a form of autotransformer
which I interpret to mean a non-circular feed loop of sorts.

In one loop design by Peter Parker VK3YE whose loop
covers 160-15 meters, the author advised me (when I
queried the Gamma question to him) that the
gamma when set as designed serves all bands well.
In other designs the gamma match or whatever it
might be, seems to work and did not seem to be a
problem or I think it might have been commented
on by the authors.

I will be investigating all these things soon -- I have just
recovered over a few years of some pretty heavy
abdominal surgeries and will be moving to a senior's
residence where I will have a balcony to work from.
It will be nice to get back on the air again after having
had to sell my house after the first surgery where I
had room for all different forms of antennas. Now I will
be back on the air again but will have to work under
certain restrictions such as no wires to nearby trees and
so forth. A magnetic loop or some form of windowsill
antenna will likely be my best bets. I'm looking forward to
the experience! I've always maintained to other old timers
who moved into condos where there restrictions that there
would always be some way to get on the air -- now I'm going
to have to walk the talk myself! One way or another I'm
not going to give up 55 years of hamming -- even if I can
only work across town! I'm shooting for multiband 80-10M
operation -- or bust! (Touch wood!)

Thanks,

Irv VE6BP

The easiest way to achieve that is get yourself one of the autotunners
which will tune just about anything.

The high power ones tend to be expensive but if you are running the typical
rig barefoot in the 100 watt range they are not that expensive these days.

I have a vertical with an autotunner that covers all bands from 80 to 10,
including of course 30, 17, and 12.

I contemplated using a loop instead of a vertical but the vertical was
easier to put up where I live.


--
Jim Pennino

Gamma Matching Question
 

In article ,
"Irv Finkleman" wrote:

will be moving to a senior's
residence where I will have a balcony to work from.

Irv-

Go ahead and try the loop. At least you will be on the air, and you may
be surprised how well it works.

I once lived in an apartment where a previous resident had installed a
trucker's mirror antenna mount on the metal balcony rail. I used it
with mobile whips to get on HF. The metal rail worked as a ground
plane, and my TS-690S built-in tuner was able to match it.

You might also consider dipoles made from mobile whips. I have had good
luck, especially on higher bands. I currently have an "Octopus" antenna
made from four sets of mobile whips fed in parallel. It might not fit
on your balcony, but fits inside my attic. (The Octopus was published
in the December, 2007, issue of QST.)

73,
Fred
K4DII

Gamma Matching Question
 

OOps! I sent replies direct to Fred instead of the newsgroup!
Here's a repeat of one!
------------------

Thanks Fred. I am determined to experiment with the Magnetic Loop
only because I haven't worked with one before. I am also keeping
in mind a windowsill antenna as a backup, and also in case I run into
problems getting the Loop going.

I've previously worked the gamut of antennas from the old 'Gotham
Vertical' which was a classic back in the fifties, through all kinds
of dipoles, towers beams and rotors, random wires, folded Marconis,
and such but never a loop.

The Magnetic Loop is a fairly new concept that intrigues me, and
unlike a mobile whip or other compromise antenna, it is 'complete'
in itself and a lot of guys are giving it pretty good reports. As well,
it will serve on a balcony without being overrly obtrusive.

Time will tell but I'm going to have some fun!

I'll have to look for the Octopus in the QST Archives, not
to build one but to have a look at it.

Tks agn es 73

Irv VE6BP.

"Fred McKenzie" wrote in message
...
In article ,
"Irv Finkleman" wrote:

will be moving to a senior's
residence where I will have a balcony to work from.

Irv-

Go ahead and try the loop. At least you will be on the air, and you may
be surprised how well it works.

I once lived in an apartment where a previous resident had installed a
trucker's mirror antenna mount on the metal balcony rail. I used it
with mobile whips to get on HF. The metal rail worked as a ground
plane, and my TS-690S built-in tuner was able to match it.

You might also consider dipoles made from mobile whips. I have had good
luck, especially on higher bands. I currently have an "Octopus" antenna
made from four sets of mobile whips fed in parallel. It might not fit
on your balcony, but fits inside my attic. (The Octopus was published
in the December, 2007, issue of QST.)

73,
Fred
K4DII

Gamma Matching Question
 

On 9/21/2013 12:50 PM, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

My question is -- when I'm ready to test the antenna
do I adjust the gamma match at the lowest frequency I
plan to use, or the highest?

I have considered other forms of coupling the
rig to the transmitter but prefer to use the gamma
match.

Thanks in advance for any assistance or advice in this
matter.

Irv VE6BP




I gave up the idea of a magnetic antenna when I found how much the
tunable capacitor cost when using 1500 watts. Ouch

Gamma Matching Question
 

"Irv Finkleman" wrote in message
...
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

My question is -- when I'm ready to test the antenna
do I adjust the gamma match at the lowest frequency I
plan to use, or the highest?

I have considered other forms of coupling the
rig to the transmitter but prefer to use the gamma
match.

Thanks in advance for any assistance or advice in this
matter.

Irv VE6BP
The US Coast Guard has used circular loop antennas for transmitting. I
remember noting them when I did EMI inspections on several Coast Guard
cutters in the 1990's. Perhaps that knowledge will lead you in the
direction of existing documentation on the methods they used. All of my
data is long gone but I did see this guy's page on-line:

http://www.aa5tb.com/loop.html

Good luck.

Gamma Matching Question
 

On 9/21/2013 12:50 PM, Irv Finkleman wrote:
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

My question is -- when I'm ready to test the antenna
do I adjust the gamma match at the lowest frequency I
plan to use, or the highest?

I have considered other forms of coupling the
rig to the transmitter but prefer to use the gamma
match.

Thanks in advance for any assistance or advice in this
matter.

Irv VE6BP

Hi, Irv -

See if this link is of any help to you...

http://www.vk1od.net/antenna/GammaMatch/gbs.htm

John KD5YI

Gamma Matching Question
 

Thanks Sal -- I'm pretty sure I spotted a magloop on the Coast Guard ship,
but
the photo is a little too small and when enlarged the antenna blurs.

I have now decided from all my 'research' into the matter that what is
referred to as the 'gamma match' on these loops is more like a distorted
feed loop, and whatever the case, the persons who built the magloops
I looked at found that the feed when set, served the purpose across
all bands. That's good enough for me, and when I eventually build
a magloop (I've got most of the stuff already), I'll find out more about
the matching situation.

Next time I visit the coast (I go to Victoria B.C. periodically to visit
one of my daughters), I'll to a tour of the Navy dockyard and see if
I see anything new in antennas since my days on the ships there.

Irv VE6BP


"Sal" salmonella@food poisoning.org wrote in message
...

"Irv Finkleman" wrote in message
...
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

My question is -- when I'm ready to test the antenna
do I adjust the gamma match at the lowest frequency I
plan to use, or the highest?

I have considered other forms of coupling the
rig to the transmitter but prefer to use the gamma
match.

Thanks in advance for any assistance or advice in this
matter.

Irv VE6BP
The US Coast Guard has used circular loop antennas for transmitting. I
remember noting them when I did EMI inspections on several Coast Guard
cutters in the 1990's. Perhaps that knowledge will lead you in the
direction of existing documentation on the methods they used. All of my
data is long gone but I did see this guy's page on-line:

http://www.aa5tb.com/loop.html

Good luck.

Gamma Matching Question
 

"Irv Finkleman" wrote in message
...
Thanks Sal -- I'm pretty sure I spotted a magloop on the Coast Guard ship,
but
the photo is a little too small and when enlarged the antenna blurs.

I have now decided from all my 'research' into the matter that what is
referred to as the 'gamma match' on these loops is more like a distorted
feed loop, and whatever the case, the persons who built the magloops
I looked at found that the feed when set, served the purpose across
all bands. That's good enough for me, and when I eventually build
a magloop (I've got most of the stuff already), I'll find out more about
the matching situation.

Next time I visit the coast (I go to Victoria B.C. periodically to visit
one of my daughters), I'll to a tour of the Navy dockyard and see if
I see anything new in antennas since my days on the ships there.

Irv VE6BP


If it is not a magloop, it could be a DDRR (directional discontinuity ring
radiator).

Gamma Matching Question
 

On 10/17/2013 09:59 PM, Sal wrote:
"Irv Finkleman" wrote in message
...
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

Hello, and I would think by "magnetic" loop antenna there must also be a
"non-magnetic" loop antenna. Actually I'm just ranting a little bit -
we only have loop antennas (which can also be shielded or unshielded).
If we're talking about the use of such an antenna in the far field then,
like any other receiving/transmitting antenna it captures/radiates an
E-M field. The fact that the plane of the loop antenna aligns with the
magnetic component of the E-M field is due to the geometry of the
antenna. Adding the "loop" qualifier to the name is unnecessary and
invites confusion to those unfamiliar with basic electromagnetic theory
IMHO. Electric and magnetic fields in and of themselves don't radiate;
only E-M fields can do that. Sincerely, and 73s from N4GGO,


--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/21/2013 06:45 AM, J.B. Wood wrote:
Adding the "loop" qualifier to the name is unnecessary and
invites confusion to those unfamiliar with basic electromagnetic theory
IMHO. Electric and magnetic fields in and of themselves don't radiate;
only E-M fields can do that. Sincerely, and 73s from N4GGO,


Hello, and please substitute "magnetic" for "loop" in the above. (Got
caught in my own rant.) Sincerely,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Monday, October 21, 2013 5:45:48 AM UTC-5, J.B. Wood wrote:
I would think by "magnetic" loop antenna there must also be a
"non-magnetic" loop antenna.

The opposite would actually be an "electric loop antenna". According to Kraus, there exists a "small electric antenna", i.e. a physically short dipole.. The physically short loop and the physically short dipole are both standing wave antennas. The short loop operates close to a standing wave current maximum point, i.e. near a *magnetic loop* (electric node). The short dipole operates close to a standing wave voltage maximum point, i.e. near an *electric loop* (magnetic node). Full-size antennas have both magnetic loops/nodes and electric loops/nodes. Here's a quote from Kraus:

"The small horizontal loop antenna ... may be regarded as the *magnetic* counterpart of the short vertical (*electric*) dipole ... Booth loop and dipole have identical field patterns but *with the E and H interchanged*."

Note that the H field is directly proportional to the M field and that there are two distinctly different uses for the word "loop" above. One is physical, the other is electromagnetic. A "magnetic loop antenna" could just as easily be described as an "electric node antenna" and a small dipole could be called an "electric loop antenna" or a "magnetic node antenna".
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

On 10/21/2013 08:55 AM, W5DXP wrote:
On Monday, October 21, 2013 5:45:48 AM UTC-5, J.B. Wood wrote:
I would think by "magnetic" loop antenna there must also be a
"non-magnetic" loop antenna.

The opposite would actually be an "electric loop antenna". According to Kraus, there exists a "small electric antenna", i.e. a physically short dipole. The physically short loop and the physically short dipole are both standing wave antennas. The short loop operates close to a standing wave current maximum point, i.e. near a *magnetic loop* (electric node). The short dipole operates close to a standing wave voltage maximum point, i.e. near an *electric loop* (magnetic node). Full-size antennas have both magnetic loops/nodes and electric loops/nodes. Here's a quote from Kraus:

"The small horizontal loop antenna ... may be regarded as the *magnetic* counterpart of the short vertical (*electric*) dipole ... Booth loop and dipole have identical field patterns but *with the E and H interchanged*."

Note that the H field is directly proportional to the M field and that there are two distinctly different uses for the word "loop" above. One is physical, the other is electromagnetic. A "magnetic loop antenna" could just as easily be described as an "electric node antenna" and a small dipole could be called an "electric loop antenna" or a "magnetic node antenna".
--
73, Cecil, w5dxp.com

Hello, and no issues here. My OP was addressing practical ham antenna
(not usually electrically small) dimensions. I still contend though
that even if one shrinks a loop antenna to something approaching a
magnetic dipole, it still should be called a "loop antenna" vice
"magnetic loop antenna". Or you can call it a "magnetic dipole" if the
dimensions apply. None of my antenna textbooks, including Kraus, uses
the term "magnetic loop antenna". Frankly, I don't know how this
terminology ever got started, but it seems to be in somewhat common use
in the ham radio community. Perhaps it is the confusion between
operation of a coil of wire as an inductor immersed in a magnetic field
vs the operation of that same coil as an antenna). Sincerely, and 73s
from N4GGO,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Monday, October 21, 2013 8:57:01 AM UTC-5, J.B. Wood wrote:
Or you can call it a "magnetic dipole" if the dimensions apply.

I agree it should be called a "small loop" rather than a "magnetic loop". My above quote from Kraus seems to give us permission to call it a "magnetic loop" and here's what Balanis says:

"A comparison of (the small loop equations) with those of the infinitesimal magnetic dipole indicates that they have similar forms."
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

Magnetic, Shmagnetic! It works! A rose by any other
name would smell as sweet! :-)

de VE6BP Irv


"J.B. Wood" wrote in message
...
On 10/17/2013 09:59 PM, Sal wrote:
"Irv Finkleman" wrote in message
...
I am planning to build a magnetic loop antenna and
feed it by means of a gamma match. I understand
that a gamma match will work over a wide range of
frequencies. I hope to work a number of bands using
the same loop.

Hello, and I would think by "magnetic" loop antenna there must also be a
"non-magnetic" loop antenna. Actually I'm just ranting a little bit - we
only have loop antennas (which can also be shielded or unshielded). If
we're talking about the use of such an antenna in the far field then, like
any other receiving/transmitting antenna it captures/radiates an E-M
field. The fact that the plane of the loop antenna aligns with the
magnetic component of the E-M field is due to the geometry of the antenna.
Adding the "loop" qualifier to the name is unnecessary and invites
confusion to those unfamiliar with basic electromagnetic theory IMHO.
Electric and magnetic fields in and of themselves don't radiate; only E-M
fields can do that. Sincerely, and 73s from N4GGO,


--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/21/2013 9:41 AM, W5DXP wrote:
On Monday, October 21, 2013 8:57:01 AM UTC-5, J.B. Wood wrote:
Or you can call it a "magnetic dipole" if the dimensions apply.

I agree it should be called a "small loop" rather than a "magnetic
loop". My above quote from Kraus seems to give us permission to call
it a "magnetic loop"


Your interpretation of "permission" is only your interpretation. Please
do not infer for the rest of us.


and here's what Balanis says:

"A comparison of (the small loop equations) with those of the
infinitesimal magnetic dipole indicates that they have similar
forms." -- 73, Cecil, w5dxp.com

Rather than dancing now, please stay with Kraus.

Gamma Matching Question
 

On 10/21/2013 9:45 AM, Irv Finkleman wrote:
Magnetic, Shmagnetic! It works! A rose by any other
name would smell as sweet! :-)

de VE6BP Irv

True, if you are opposed to learning.

Gamma Matching Question
 

On Monday, October 21, 2013 10:32:09 AM UTC-5, John S wrote:
Your interpretation of "permission" is only your interpretation. Please
do not infer for the rest of us.

Of course, everyone is free to infer whatever they please from Kraus' writings:

"The small horizontal loop antenna ... may be regarded as the *magnetic* counterpart of the short vertical dipole."

To me, the inference is clear. We may regard the small loop antenna as the magnetic counterpart to the short (implied electrical) dipole.
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

Always learning John, but like to throw in a little
humor now and again.

de VE6BP Irv

"John S" wrote in message
...
On 10/21/2013 9:45 AM, Irv Finkleman wrote:
Magnetic, Shmagnetic! It works! A rose by any other
name would smell as sweet! :-)

de VE6BP Irv

True, if you are opposed to learning.

Gamma Matching Question
 

On 10/22/2013 04:23 AM, Jeff wrote:

Small loop implies a magnetic loop, magnetic loop implies a small loop,
so pretty much 6 of one and half a dozen of the other; although magnetic
loop does give more information on the mode of operation, which is
probably why the name has stuck.

Jeff

This is exactly the faulty line of reasoning to which I previously
provided comment. W5DXP's recent comments are on the mark.

Perhaps a metaphor is appropriate: You just might expertly pilot an
airplane you built from a kit but you don't necessarily possess the
expertise in aerodynamics/fluid mechanics to design a viable aircraft.
And the lack of that knowledge can result in the formulation of invalid
"principles of operation". Now, if you act right now we'll double your
order and send you two revolutionary "Crossed Field Antennas" and
include the matching carrying cases. Just pay separate shipping and
processing. Enough said. Sincerely,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/21/2013 10:50 PM, Irv Finkleman wrote:
Always learning John, but like to throw in a little
humor now and again.

de VE6BP Irv

"John S" wrote in message
...
On 10/21/2013 9:45 AM, Irv Finkleman wrote:
Magnetic, Shmagnetic! It works! A rose by any other
name would smell as sweet! :-)

de VE6BP Irv

True, if you are opposed to learning.

Sorry, Irv. I failed to notice the smiley face. My fault.

Gamma Matching Question
 

No problem John, all's well!

de VE6BP Irv

"John S" wrote in message
...
On 10/21/2013 10:50 PM, Irv Finkleman wrote:
Always learning John, but like to throw in a little
humor now and again.

de VE6BP Irv

"John S" wrote in message
...
On 10/21/2013 9:45 AM, Irv Finkleman wrote:
Magnetic, Shmagnetic! It works! A rose by any other
name would smell as sweet! :-)

de VE6BP Irv

True, if you are opposed to learning.

Sorry, Irv. I failed to notice the smiley face. My fault.

Gamma Matching Question
 

On 10/23/2013 02:37 AM, Jeff wrote:

Krause (and W5DXP) state that the small loop may be considered as a
magnetic aerial.

Jeff,

Kraus never uses the term "magnetic aerial". Kraus shows the
equivalence of "a small loop" and a "short magnetic dipole". Yes, the
short magnetic dipole (a theoretical construct) acts as a
radiator/interceptor of E-M energy (or photons if you prefer). In that
regard it is certainly an antenna, albeit a fictitious one. But any
antenna, regardless of geometry deals with E-M energy. You can't
decouple the E and H fields (as the Maxwell equations under time-varying
conditions clearly show). The "designers" of the CFA tried to do that
but ignored the applicable physics and ended up with a complicated and
expensive electrically short antenna.

So I think using a term like "magnetic loop antenna" or "electric dipole
antenna" is misleading. At the very least these terms are redundant and
at worst they imply that there are other types of antennas such as
"electric loop antennas". The "magnetic" modifier might imply the loop
antenna has certain properties due to the H-field exclusive of the E-field.

Also, just because hams have adopted a terminology doesn't imply
widespread use in the electrical engineering community. Many hams, such
as myself, are EEs. So maybe it's folks in that category that get more
incensed by these things.

Perhaps a metaphor is appropriate: You just might expertly pilot an
airplane you built from a kit but you don't necessarily possess the
expertise in aerodynamics/fluid mechanics to design a viable aircraft.
And the lack of that knowledge can result in the formulation of invalid
"principles of operation". Now, if you act right now we'll double your
order and send you two revolutionary "Crossed Field Antennas" and
include the matching carrying cases. Just pay separate shipping and
processing. Enough said. Sincerely,


How is any of that relevant to what something is generically called and
has been for years.


It's relevant in that despite the performance of the device (antenna,
airplance, etc) the explanation of "why it works" the way it does can
rely on faulty science. When those flawed principles are used to design
a device, that device often doesn't measure up to expectations. And the
designers often claim that others "just don't understand these things".
The Wright brothers were successful when others failed because, while
Orville and Wilbur were not formally trained as mechanical engineers,
they understood flight aerodynamics (as best as could be understood at
the time), and painstakingly applied that science to their aircraft
designs. They definitely weren't tinkerers or dilettantes. Sincerely,
and 73s from N4GGO,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Wednesday, October 23, 2013 6:07:45 AM UTC-5, J.B. Wood wrote:
So I think using a term like "magnetic loop antenna" or "electric dipole
antenna" is misleading.

A short loop antenna responds more to the magnetic field than the electric field. A short dipole responds more to the electric field than the magnetic field. A full-sized dipole or loop responds equally to both fields - that's why they are the most efficient.

I'm also a EE and maybe my experience with receiving antennas will shed some light. I have, in the past, been involved with 75m mobile shootout measurements. At first, we tried to use a 75m hamstick but human bodies close to the antenna affected the receive signal strengths considerably because of the effect of human bodies on the electric field. We switched over to ferrite rod antennas which, because they respond primarily to the magnetic field, are more immune to the effects of human bodies. Although you are correct in stating that all radio waves in free space are ElectroMagnetic waves, some antennas are more sensitive to the magnetic portion of the EM wave and some are more sensitive to the electric portion of the EM wave. Since antennas are, in general, reciprocal for receiving/transmitting, I can understand why some antennas are associated with the magnetic field of an EM wave and some are associated with the electric field of an EM wave.
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

On 10/23/2013 03:26 PM, W5DXP wrote:
On Wednesday, October 23, 2013 6:07:45 AM UTC-5, J.B. Wood wrote:
So I think using a term like "magnetic loop antenna" or "electric dipole
antenna" is misleading.

A short loop antenna responds more to the magnetic field than the electric field. A short dipole responds more to the electric field than the magnetic field. A full-sized dipole or loop responds equally to both fields - that's why they are the most efficient.

I'm also a EE and maybe my experience with receiving antennas will shed some light. I have, in the past, been involved with 75m mobile shootout measurements. At first, we tried to use a 75m hamstick but human bodies close to the antenna affected the receive signal strengths considerably because of the effect of human bodies on the electric field. We switched over to ferrite rod antennas which, because they respond primarily to the magnetic field, are more immune to the effects of human bodies. Although you are correct in stating that all radio waves in free space are ElectroMagnetic waves, some antennas are more sensitive to the magnetic portion of the EM wave and some are more sensitive to the electric portion of the EM wave. Since antennas are, in general, reciprocal for receiving/transmitting, I can understand why some antennas are associated with the magnetic field of an EM wave and some are associated with the electric field of an EM wave.
--
73, Cecil, w5dxp.com

Sorry, Cecil, that while I usually agree with you I would take exception
to the "responds more" comment, if taken in the sense that it applies
everywhere. If the loop is being used as an inductive pickup, IOW in
the near field of a radiator or mutually coupled to another coil in
close proximity, then I can see that view. But not in the far field. In
the far field it would be just as correct to say that the loop responds
to the electric field. A better way of putting this IMO would be that
the loop (as a receiving antenna) in the far field (several wavelengths
removed from the transmitter) captures a portion of the E-M energy
incident upon it (what isn't captured is scattered). The amount of
energy captured is a function of the antenna's "effective area", which
depends upon antenna geometry and its orientation relative to the
incident energy (E/H field direction). Sincerely,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/23/2013 03:26 PM, W5DXP wrote:

We switched over to ferrite rod antennas which,
because they respond primarily to the magnetic field

Although you are correct in stating
that all radio waves in free space are ElectroMagnetic waves, some
antennas are more sensitive to the magnetic portion of the EM wave
and some are more sensitive to the electric portion of the EM wave.

If we're talking about radiant E-M energy, I can just as easily replace
anything attributed to the H-field component with the appropriate
E-field equivalent (using the Maxwell equations) and claim that field as
being the one to which the antenna is "sensitive". So the above
statements don't make sense. Again I'm assuming far-field, not close-in
coupling. Also, as I previously pointed out, I think this line of
thinking may have started from close-in coupling action but has been
incorrectly extended to everywhere. I've met some folks who think that
loop and dipole antennas, used as radiators, "transmit" the H and E
fields, respectively, without further elaboration. Sincerely,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Thursday, October 24, 2013 5:54:05 AM UTC-5, J.B. Wood wrote:
So the above statements don't make sense.

I agree that the E/M ratio for far field signals in space is a constant. That doesn't prohibit a receiving antenna from creating its own unique near-field conditions and altering that ratio just as there is nothing prohibiting a load from altering the E/M ratio that exists in a transmission line. In fact, the E/M ratio must necessarily be altered at impedance discontinuities.

Example: Two different antennas are receiving the same signal and indicating the same signal level. As a human walks close to the two antennas, the received signal strength of one antenna changes radically while the received signal strength of the other is affected by only a small amount. If both antennas were *accepting* the same fixed far-field E/M ratio, a human body should have the same effect on both antennas but we can demonstrate that it doesn't.
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

On 10/24/2013 08:10 AM, W5DXP wrote:
On Thursday, October 24, 2013 5:54:05 AM UTC-5, J.B. Wood wrote:
So the above statements don't make sense.

I agree that the E/M ratio for far field signals in space is a constant. That doesn't prohibit a receiving antenna from creating its own unique near-field conditions and altering that ratio just as there is nothing prohibiting a load from altering the E/M ratio that exists in a transmission line. In fact, the E/M ratio must necessarily be altered at impedance discontinuities.

Example: Two different antennas are receiving the same signal and indicating the same signal level. As a human walks close to the two antennas, the received signal strength of one antenna changes radically while the received signal strength of the other is affected by only a small amount. If both antennas were *accepting* the same fixed far-field E/M ratio, a human body should have the same effect on both antennas but we can demonstrate that it doesn't.
--
73, Cecil, w5dxp.com


No

--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/24/2013 08:10 AM, W5DXP wrote:
On Thursday, October 24, 2013 5:54:05 AM UTC-5, J.B. Wood wrote:
So the above statements don't make sense.

I agree that the E/M ratio for far field signals in space is a
constant. That doesn't prohibit a receiving antenna from creating its
own unique near-field conditions and altering that ratio just as
there is nothing prohibiting a load from altering the E/M ratio that
exists in a transmission line. In fact, the E/M ratio must
necessarily be altered at impedance discontinuities.

Example: Two different antennas are receiving the same signal and
indicating the same signal level. As a human walks close to the two
antennas, the received signal strength of one antenna changes
radically while the received signal strength of the other is affected
by only a small amount. If both antennas were *accepting* the same
fixed far-field E/M ratio, a human body should have the same effect
on both antennas but we can demonstrate that it doesn't. -- 73,
Cecil, w5dxp.com


Don't have argument with the above, Cecil, but these phenomena appear to
be in addition to what I think was being discussed. Sincerely,
--
J. B. Wood e-mail:

Gamma Matching Question
 

On 10/24/2013 8:02 AM, J.B. Wood wrote:
On 10/24/2013 08:10 AM, W5DXP wrote:
On Thursday, October 24, 2013 5:54:05 AM UTC-5, J.B. Wood wrote:
So the above statements don't make sense.

I agree that the E/M ratio for far field signals in space is a
constant. That doesn't prohibit a receiving antenna from creating its
own unique near-field conditions and altering that ratio just as
there is nothing prohibiting a load from altering the E/M ratio that
exists in a transmission line. In fact, the E/M ratio must
necessarily be altered at impedance discontinuities.

Example: Two different antennas are receiving the same signal and
indicating the same signal level. As a human walks close to the two
antennas, the received signal strength of one antenna changes
radically while the received signal strength of the other is affected
by only a small amount. If both antennas were *accepting* the same
fixed far-field E/M ratio, a human body should have the same effect
on both antennas but we can demonstrate that it doesn't. -- 73,
Cecil, w5dxp.com


Don't have argument with the above, Cecil, but these phenomena appear to
be in addition to what I think was being discussed. Sincerely,

J.B. -

I have always understood EMF to be exactly as you have explained. I did
not know how to refute the misunderstanding by others on this topic.
Thanks for handling this discussion.

Gamma Matching Question
 

On Thursday, October 24, 2013 7:57:52 AM UTC-5, J.B. Wood wrote:
On 10/24/2013 08:10 AM, W5DXP wrote:
... a human body should have the same effect on both antennas but we can demonstrate that it doesn't.

No

I'm sorry, but that is a non-answer. Please explain, within what you have been asserting, how a human body can have a completely different effect on two antennas that receive identical EM waves.
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

On 10/24/2013 02:15 PM, W5DXP wrote:
On Thursday, October 24, 2013 7:57:52 AM UTC-5, J.B. Wood wrote:
On 10/24/2013 08:10 AM, W5DXP wrote:
... a human body should have the same effect on both antennas but
we can demonstrate that it doesn't.

No

I'm sorry, but that is a non-answer. Please explain, within what you
have been asserting, how a human body can have a completely different
effect on two antennas that receive identical EM waves. -- 73, Cecil,
w5dxp.com

I would like to think this is an easy one: Say we have a receiving
antenna such as a loop that isn't operating in the presence of nearby
(close in coupling) objects such as metal, ferromagnetic cores, or human
skin. If we introduce these objects, we see that compared to operation
in their absence we have in general altered the antenna's gain, pattern
and feedpoint impedance. IOW, the nearby structures are now part of the
antenna.

Suppose we setup a dipole antenna and a loop antenna of appropriate
dimensions such that both are responding to the same E-M wave and
produce the same available receive power at their feedpoints. Just to
keep things simple, assume both antennas are low in resistive losses and
they are operating free of nearby objects of the type I mentioned.
Either antenna could produce the same power dissipated in an conjugately
matched load at its feedpoint.

If we now place objects near either antenna, anything goes, depending on
the objects and how they're oriented with respect to either the loop or
dipole.

None of this, however, can be used to assert that the E field is
favored/more responsive than the H field or vice-versa for a particular
antenna structure. Sincerely,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Thursday, October 24, 2013 2:15:11 PM UTC-5, J.B. Wood wrote:
None of this, however, can be used to assert that the E field is
favored/more responsive than the H field or vice-versa for a particular
antenna structure.

Next time you have an MRI, please try to convince the doctors that an ERI would work just as well.:)
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

On 10/24/2013 10:07 PM, W5DXP wrote:
On Thursday, October 24, 2013 2:15:11 PM UTC-5, J.B. Wood wrote:
None of this, however, can be used to assert that the E field is
favored/more responsive than the H field or vice-versa for a particular
antenna structure.

Next time you have an MRI, please try to convince the doctors that an ERI would work just as well.:)
--
73, Cecil, w5dxp.com


I wouldn't view the huge MRI coil as a transmitting antenna insofar as
its intended usage. It's more akin to the primary of transformer with
the human body serving as the "secondary".

Cecil, I've done my best to point out the difference between a close-in
coupling (capacitive and/or inductive) situation and that involving two
(decoupled electrically but in the same medium) antennas separated by
many wavelengths. I can't think of anything else to say at this point.
Sincerely, and 73s from N4GGO,

--
J. B. Wood e-mail:

Gamma Matching Question
 

On Friday, October 25, 2013 5:32:34 AM UTC-5, J.B. Wood wrote:
I can't think of anything else to say at this point.

I don't know what the disagreement is. A small loop operates with a high magnetic field (high current) and a low electric field (low voltage) on both transmit and receive as required by the laws of physics. It seems reasonable to me to call it a "magnetic" loop. A small dipole operates with a high electric field (high voltage) and a low magnetic field (low current) on both transmit and receive as required by the laws of physics. It seems reasonable to me to call it an "electric" dipole.

I also cannot think of anything else to say. There was never any disagreement that all coherent far-field ExB photons are identical. The remaining question is: Given identical capture areas, why does a human body have such a large effect on an electric dipole and such a small effect on a magnetic loop?

I see the same thing with my indoor TV antenna. The VHF section is an electric dipole and I can affect VHF signal strength by walking between the transmitting station and the TV antenna. The UHF section is a magnetic loop and walking between the transmitting station and the TV antenna has very little effect on signal strength. My converter box has both an audible and visual signal strength indicator.
--
73, Cecil, w5dxp.com

Gamma Matching Question
 

In article W5DXP writes:
On Thursday, October 24, 2013 5:54:05 AM UTC-5, J.B. Wood wrote:
So the above statements don't make sense.

I agree that the E/M ratio for far field signals in space is a constant. Th=
at doesn't prohibit a receiving antenna from creating its own unique near-f=
ield conditions and altering that ratio just as there is nothing prohibitin=
g a load from altering the E/M ratio that exists in a transmission line. In=
fact, the E/M ratio must necessarily be altered at impedance discontinuiti=
es.


Example: Two different antennas are receiving the same signal and indicatin=
g the same signal level. As a human walks close to the two antennas, the re=
ceived signal strength of one antenna changes radically while the received =
signal strength of the other is affected by only a small amount. If both an=
tennas were *accepting* the same fixed far-field E/M ratio, a human body sh=
ould have the same effect on both antennas but we can demonstrate that it d=
oesn't.

Of course, if the antennas are accepting the signal from different directions,
they will be affected differently by people walking around them. My point is
that other factors could cause the antennas to have different results when
a person moves near them.

Alan
wa6azp