On Dec 7, 8:57 pm, "Dale Parfitt" wrote:


I would not be quoting some ham¹s web site as an authority on
electromagnetic theory or folklore.

You might want to Google Tom W8JI and find out who he is. To describe one of
the U.S.'s brighter engineers and designers as "some ham" is a real
disservice. The fact that he happens to have a ham license is purely a
coincidence. His explaination of how the shielded loop functions is embraced
by the IEEE group on Electromagnetics and Propagation, Roy Lewellen (writer
of EZNEC software) et al.
W4OP

W8JI's view, as I understand it, is that small shielded loops are no
less susceptible to local noise in virtue of their shielding, since
the shield, in his view, is part of the antenna. It's probably worth
pointing out that, even if this is true, it is still consistent with
the view that small loops pick up less noise than other types of
antennas in virtue of their directional characteristics. I guess W8JI
would then maintain that a shielded loop would be no less susceptible
to local noise than an unshielded loop, since in this case both
antennas enjoy the benefits of directionality; but he isn't commited
to denying that loops are quieter than, say whips when all things are
considered. Is this correct or am I missing something here?

W8JI's view, as I understand it, is that small shielded loops are no
less susceptible to local noise in virtue of their shielding, since
the shield, in his view, is part of the antenna. It's probably worth
pointing out that, even if this is true, it is still consistent with
the view that small loops pick up less noise than other types of
antennas in virtue of their directional characteristics. I guess W8JI
would then maintain that a shielded loop would be no less susceptible
to local noise than an unshielded loop, since in this case both
antennas enjoy the benefits of directionality; but he isn't commited
to denying that loops are quieter than, say whips when all things are
considered. Is this correct or am I missing something here?

Correct. Here it is from VE7SL perhaps more concisely:

Please note that a 'shielded loop' will not do anything to improve local
noise problems that any other type of loop (such as a multi-turn air core
loop) might do. Don't confuse the 'shielded' nomenclature with 'noise
shielding' as this is not the case. Like any other type of loop, it can be
used to null nearby noise sources or signals or turned to enhance desired
directions.
The shielded loop might more properly be called a 'two-turn' loop or a
'close coupled' loop as this more accurately describes it's behaviour. In
actual operation, it is the shield itself that is the active antenna
element. Signals picked up by the shield are coupled into the inner
conductor, which in turn are coupled back to the receiver via the preamp.
The loop is capable of good nulls on both groundwave and skywave signals.
The more 'balanced' the loop is (gap placed at exact center), the more
balanced the nulls will be.

In article CoC6j.3689$581.3625@trnddc04,
"Dale Parfitt" wrote:

W8JI's view, as I understand it, is that small shielded loops are no
less susceptible to local noise in virtue of their shielding, since
the shield, in his view, is part of the antenna. It's probably worth
pointing out that, even if this is true, it is still consistent with
the view that small loops pick up less noise than other types of
antennas in virtue of their directional characteristics. I guess W8JI
would then maintain that a shielded loop would be no less susceptible
to local noise than an unshielded loop, since in this case both
antennas enjoy the benefits of directionality; but he isn't commited
to denying that loops are quieter than, say whips when all things are
considered. Is this correct or am I missing something here?

Correct. Here it is from VE7SL perhaps more concisely:

Please note that a 'shielded loop' will not do anything to improve local
noise problems that any other type of loop (such as a multi-turn air core
loop) might do. Don't confuse the 'shielded' nomenclature with 'noise
shielding' as this is not the case. Like any other type of loop, it can be
used to null nearby noise sources or signals or turned to enhance desired
directions.
The shielded loop might more properly be called a 'two-turn' loop or a
'close coupled' loop as this more accurately describes it's behaviour. In
actual operation, it is the shield itself that is the active antenna
element. Signals picked up by the shield are coupled into the inner
conductor, which in turn are coupled back to the receiver via the preamp.
The loop is capable of good nulls on both groundwave and skywave signals.
The more 'balanced' the loop is (gap placed at exact center), the more
balanced the nulls will be.

This is wrong. I already explained why. Go back and read the part of my
post you cut out of the thread. You are being to general in the
description of shielded.

--
Telamon
Ventura, California

In article
,
Steve wrote:

On Dec 7, 8:57 pm, "Dale Parfitt" wrote:


I would not be quoting some ham¹s web site as an authority on
electromagnetic theory or folklore.

You might want to Google Tom W8JI and find out who he is. To describe one of
the U.S.'s brighter engineers and designers as "some ham" is a real
disservice. The fact that he happens to have a ham license is purely a
coincidence. His explaination of how the shielded loop functions is embraced
by the IEEE group on Electromagnetics and Propagation, Roy Lewellen (writer
of EZNEC software) et al.
W4OP

W8JI's view, as I understand it, is that small shielded loops are no
less susceptible to local noise in virtue of their shielding, since
the shield, in his view, is part of the antenna. It's probably worth
pointing out that, even if this is true, it is still consistent with
the view that small loops pick up less noise than other types of
antennas in virtue of their directional characteristics. I guess W8JI
would then maintain that a shielded loop would be no less susceptible
to local noise than an unshielded loop, since in this case both
antennas enjoy the benefits of directionality; but he isn't commited
to denying that loops are quieter than, say whips when all things are
considered. Is this correct or am I missing something here?


This is wrong. I already explained why. Go back and read the part of my
post Dale cut out of the thread.

--
Telamon
Ventura, California

This is wrong. I already explained why. Go back and read the part of my
post Dale cut out of the thread.

--
Telamon
Ventura, California

It was not my intent to cut censor your comments Telamon- I was attepmting
to clean up the thread and address Stece's question explicitely.
I respect your comments and we can agree to disagree as gentlemen.
73,
Dale