On 10/20/2015 3:03 AM, rickman wrote:
On 10/19/2015 7:55 PM, amdx wrote:
On 10/19/2015 2:14 PM, rickman wrote:

To be a bit simplistic, the amount of signal captured is proportional
to the loop area; the number of turns has little to no effect on that.

I'm pretty sure that is not correct. The signal strength is
proportional to the number of turns *and* the loop area. I will have to
dig out my notes on this, but some factors (like Q) even out with
various changes in antenna parameters such as number of turns, loop
size, etc. But signal strength is proportional to the area of the loop
and the number of turns.

From
http://www.lz1aq.signacor.com/docs/f..._loop_engl.htm

E = 2pi w S µR e / λ
λ is the wavelength in meters
w - the number of ML turns;
S – is the area of the windings in m2;
μR is the effective magnetic permeability of the ferrite rod SML. μR is
always less than the permeability of the material used and depends from
the size, geometry and the way the windings are constructed. μR = 1 for
aerial loops.

The product:
� = w μR S (3)
is called effective area of the SML.


Correct me if I'm wrong,
A 1 meter square loop with 5 turns would equal 5 square meters.
A = 5 sq. meters.

A 2.23 meter x 2.23 meter 1 turn loop would equal 5 square meters.
A = 5 sq. meters.

A 5 meter x 5 meter 1 turn loop with a series inductor would equal 25
sq. meters.
A = 25 Sq. meters.

A 5 times increase in A (S) means about a 7db increase in signal
strength. (minus losses caused by series inductor)

Does that all seem right?

I forgot to include the following definitions.
Е – is the voltage between antenna terminals in uV;
е – is the intensity of electromagnetic wave in uV/m.

Not sure where you are going with this. For the purpose of calculating
the received signal strength of an antenna without factoring in
resonance, the area is just the area of one loop (S = pi r^2), not the
loop area times the number of turns. The number of turns (w) is
multiplied by the loop area in the formula along with the relative
permeability of the core material to get the effective area. Is that
what you mean?

Yes. I was getting at the point, a loop single turn loop of 2.23
meters square will have the same E as a 1 meter square loop with 5 turns.
Just some idea to consider when it comes to construction.


The post that Jim made explicitly stated, "the number of
turns has little to no effect on that", with "that" meaning "the amount
of signal captured", or E in the above formula. That is the point I was
correcting.

For equal capture area, a single turn loop uses less than 1/2 the wire
of a 5 turn loop. However you do lose inductance.



So why do you feel the need to include a series inductor with the 25 m^2
1 turn loop?


My thoughts are for a AMBCB loop, generally a 240uH loop and a 365pf
cap. So I need the extra inductance to resonate it in the AM broadcast Band.

If you want to exercise some of the math for this, try the page here and
tell me if the example about half way down the page was done correctly.
I get a different value for the radiation resistance and I'm pretty
sure the skin effect was not done correctly for the AC resistance.

http://sidstation.loudet.org/antenna-theory-en.xhtml

I'm a good constructor, but as much as I'd like to, I can't help you
with the math.
Mikek