H FIELD ANTENNAS?
 

Is anyone aware of any sources of information/theory on H Field
antennas, such as the Chelton Loop for HF?

H FIELD ANTENNAS?
 

Any theory that predicts any antenna can produce an H field without an E
field, or that the H field is unusually large beyond a fraction of a
wavelength from an antenna(*), is flawed. So you're free to make up any
theory you like, and it'll be just as accurate.

(*) Or, from a receiving standpoint, that an antenna responds only to an
H field or it responds more strongly to an H field beyond a fraction of
a wavelength from the antenna.

Roy Lewallen, W7EL

wrote:
Is anyone aware of any sources of information/theory on H Field
antennas, such as the Chelton Loop for HF?

H FIELD ANTENNAS?
 

In article ,
Roy Lewallen wrote:

Any theory that predicts any antenna can produce an H field without an E
field, or that the H field is unusually large beyond a fraction of a
wavelength from an antenna(*), is flawed. So you're free to make up any
theory you like, and it'll be just as accurate.

(*) Or, from a receiving standpoint, that an antenna responds only to an
H field or it responds more strongly to an H field beyond a fraction of
a wavelength from the antenna.

Upon a cursory search, it appears to me that "H-field antenna" is
probably another (perhaps misleading) term for "small shielded
receiving loop".

Discussions about the latter do seem to have the requisite amount of
lore, mythology, and strenuous disagreements as to just what this sort
of antenna does respond to and how it works.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

H FIELD ANTENNAS?
 

Are you trying to pull our leg? A google search for "Chelton Loop"
antenna turns up only references to a street, Chelton Loop, in Colorado
Springs. If there's a "Chelton Loop" antenna, it must not have had
much written about it.

If you want to detect magnetic fields at HF, a small coil of wire
should work well. The size would depend on the size of the magnetic
field you're probing, and the spatial accuracy you want. If you want
to receive electromagnetic signals, as others have posted, be careful
about claims of sensing "only" the H field.

Cheers,
Tom

wrote:
Is anyone aware of any sources of information/theory on H Field
antennas, such as the Chelton Loop for HF?

H FIELD ANTENNAS?
 

K7ITM wrote:
Are you trying to pull our leg? A google search for "Chelton Loop"
antenna turns up only references to a street, Chelton Loop, in Colorado
Springs. If there's a "Chelton Loop" antenna, it must not have had
much written about it.

If you want to detect magnetic fields at HF, a small coil of wire
should work well. The size would depend on the size of the magnetic
field you're probing, and the spatial accuracy you want. If you want
to receive electromagnetic signals, as others have posted, be careful
about claims of sensing "only" the H field.

Cheers,
Tom

wrote:
Is anyone aware of any sources of information/theory on H Field
antennas, such as the Chelton Loop for HF?


FWIW, Tom, "chelton" was probably a typo. There is
indeed a Chilton Loop Antenna at a research
facility in the UK. I think the name refers to the
loop used at the Chilton facility, rather than to
a particular antenna design.

Chuck


http://www.ukssdc.ac.uk/ionosondes/chiltonpiccys.html
Pictures from the Chilton site

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H FIELD ANTENNAS?
 

chuck wrote:

FWIW, Tom, "chelton" was probably a typo. There is indeed a Chilton
Loop Antenna at a research facility in the UK. I think the name refers
to the loop used at the Chilton facility, rather than to a particular
antenna design.

There seem to be two possible kinds of "Chilton loop".

One is at www.chilton.com, which is a web-controlled SW radio receiver
located in the USA. This is just a loop of wire in some guy's attic.

The second kind may be related to the ionosondes located at the
Rutherford Appleton Lab, Chilton, UK; and at Port Stanley, Falkland
Islands. These do use crossed loop antennas (as the referenced picture
shows)... but in 25 years living just a few miles down the road,
including 12 years of working right next to RAL and regularly eating
lunch with the hams who work there, I never heard or saw the term
"Chilton loop" until yesterday, right here.

However, I will make some specific inquiries about those loops.


Now if you want something really serious to talk about, those
RAL/Stanley ionosondes are being closed down! The scientists who work
there are horrified, because it would pull the plug on a major
international source of daily data, and terminate the world's
longest-running continuous sequence of ionospheric observations:
http://www.wdc.rl.ac.uk/wdcc1/news/closure_notice.html

(This actually looks like a clumsy political move to shift the running
costs away from the UK science budget and find some other source of
funding, using the threat of closure as a way to get attention. But
suicide bids of this kind can occasionally go wrong...)


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

H FIELD ANTENNAS?
 

"Ian White GM3SEK" wrote in message
...
chuck wrote:

FWIW, Tom, "chelton" was probably a typo. There is indeed a Chilton Loop
Antenna at a research facility in the UK. I think the name refers to the
loop used at the Chilton facility, rather than to a particular antenna
design.

There seem to be two possible kinds of "Chilton loop".

One is at www.chilton.com, which is a web-controlled SW radio receiver
located in the USA. This is just a loop of wire in some guy's attic.

The second kind may be related to the ionosondes located at the Rutherford
Appleton Lab, Chilton, UK; and at Port Stanley, Falkland Islands. These do
use crossed loop antennas (as the referenced picture shows)... but in 25
years living just a few miles down the road, including 12 years of working
right next to RAL and regularly eating lunch with the hams who work there,
I never heard or saw the term "Chilton loop" until yesterday, right here.

However, I will make some specific inquiries about those loops.


Now if you want something really serious to talk about, those RAL/Stanley
ionosondes are being closed down! The scientists who work there are
horrified, because it would pull the plug on a major international source
of daily data, and terminate the world's longest-running continuous
sequence of ionospheric observations:
http://www.wdc.rl.ac.uk/wdcc1/news/closure_notice.html

(This actually looks like a clumsy political move to shift the running
costs away from the UK science budget and find some other source of
funding, using the threat of closure as a way to get attention. But
suicide bids of this kind can occasionally go wrong...)


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

There is a company named Chelton that makes antennas listed on the web.
Shows reference to a lot of military stuff. If they are claiming they have
an H antenna then...............

H FIELD ANTENNAS?
 

yes

H FIELD ANTENNAS?
 

OK, let me display my ignorance once again.

There are many construction articles about ferrite-core antennas for the low
bands. (Not to mention all the ferrite-core antennas in AM receivers.) Are
these not H-field antennas, to a large extent?

Bill
W2WO

H FIELD ANTENNAS?
 

Bill Ogden wrote:
OK, let me display my ignorance once again.

There are many construction articles about ferrite-core antennas for the low
bands. (Not to mention all the ferrite-core antennas in AM receivers.) Are
these not H-field antennas, to a large extent?

Only very locally, and only to a limited extent.

When a signal originates far from an antenna, the response to E and H
fields is in the ratio of about 377 ohms, the impedance of free space.
This is true for *all antennas*. In other words, all antennas have the
same relative E and H response to signals originating far away.

Very close to a small loop antenna, response is greater to an H field
than E field. It does respond to both, however, as all antennas must. As
you get farther away from the antenna, the response to the H field
decreases in relation to the E field response. At around an eighth
wavelength distance from the antenna, the response to E and H fields are
about the same as for a distant source. Beyond about an eighth
wavelength, the response to the H field is actually *less* than the
response to an E field compared to a source at a great distance. The
ratio of E to H field responses then decreases to the distant value as
you get farther from the antenna.

In summary, the antenna responds more strongly to the H field if the
source is within about an eighth of a wavelength from the antenna.
Beyond that, it actually responds more strongly to the E field relative
to the H field than a short dipole or many other antennas -- you could
more properly call it an "E-field antenna" in its response to signals
beyond about an eighth wavelength. The difference in relative E and H
field response among all antennas becomes negligible at great distances;
for antennas which are small in terms of wavelength, the difference
becomes negligible beyond about a wavelength.

Now, suppose you could make a magic antenna which would respond only to
the H field of a signal originating at any distance from the antenna
(which is impossible). What advantage would it have over a real antenna?
Remember that the E/H ratio of any signal originating very far away is
377 ohms, regardless of what kind of antenna or source it came from.

Roy Lewallen, W7EL