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.