Loop efficiency, was multi-turn magnetic loops
 

Steve wrote:

Yes, I know there's nothing to gain in terms of performance. However,
I have very little space to work with. I have a 1 meter diameter loop
installed in my (tiny) attic that works very respectably on 10-30
meters. It won't get me onto 40 meters, though, and getting onto 40 is
either going to require a much larger diameter single-turn loop, a two-
turn loop, or a much more robust capacitor. Trying out a two-turn loop
seems like it would be the easiest and least expensive alternative,
and I already have the copper tubing I would need.



I separated this out from the noise floor......


When I was dealing with a loop, I wanted to extend the frequency
downwards - it's a pretty big loop, but trying to hit 75 meters was a
goal, I had some exchanges with Reg, and he pretty much told me to put a
extra capacitor across the terminals so I could tune it to the lower
frequency. That was a smack the forehead moment for me.

And Oh yes, tuning will be sooooooo tight. But the cap will probably be
better than an extra loop. You'll just have to figure out how to switch
it in and out of the circuit.

- 73 de Mike N3LI -

Loop efficiency, was multi-turn magnetic loops
 

On Mon, 24 Nov 2008 16:56:45 -0500, Michael Coslo
wrote:

But the cap will probably be
better than an extra loop. You'll just have to figure out how to switch
it in and out of the circuit.

Hi Mike,

More the achievement would be finding the capacitor that could carry
the current.

Did you follow through with this frequency extension of your loop?

73's
Richard Clark, KB7QHC

coils?multi-turn magnetic loops
 

In article ,
Roy Lewallen wrote:

Wimpie wrote:
. . .
There is an "however". When you make a single turn loop from flat
strip that has the same width as the length of your two-turn loop, you
will notice: 1. reduced AC resistance (because of the significantly
larger circumference of the flat strip with respect to a thin round
tube, 2. inductance will decrease (H field lines have to take a longer
path around the wide strip), 3. radiation resistance will not change
with respect to a single turn loop from wire/tube.
This results in higher efficiency and increased bandwidth. The
overall result will be better then for your two-turn loop. I think
that is the reason why most programs are for single turn loops.

So for the transmit case, given fixed diameter of your loop, the
larger the copper surface (=length*circumference), the better the
efficiency. Best thing to enhance conductor surface is to use very
wide flat strip (high wind load), or multiple wires (with some spacing
in between) in parallel (limited wind load).
. . .

Flat conductors aren't as attractive as they look at first glance. The
problem is the same proximity effect mentioned earlier in the posting.
Current is distributed evenly around a round conductor (assuming the
perimeter is a very small fraction of a wavelength), but not along a
flat strip. Because of proximity effect, the current is much more
concentrated near the edges than at the middle. The result is that the
resistance is considerably higher than for a wire with the same surface
area. In figuring an "equivalent diameter" of a thin flat strip in order
to get the same L and C properties, the rule is that a strip is
equivalent to a wire whose diameter is half the strip width. This means
that a strip of width w or total "circumference" 2 * w is equivalent to
a wire with a circumference of pi * w / 2 ~ 1.6 w, in so far as L and C
go. Since the same phenomenon affects the inductance and resistance,
this would also be a good working rule for estimating the relative R of
a strip or wire.

Roy Lewallen, W7EL

does this rule also hold true for example i've opened some tuners
and linear amps, often, i see straps instead of wire going to the
larger coils and switches, even some switch box's have straps from
relays to connectors etc would wire have been 'better' and or
avoid the proximity effect??

coils?multi-turn magnetic loops
 

ml wrote:
does this rule also hold true for example i've opened some tuners
and linear amps, often, i see straps instead of wire going to the
larger coils and switches, even some switch box's have straps from
relays to connectors etc would wire have been 'better' and or
avoid the proximity effect??

Proximity effect isn't a factor unless conductors are very close
together -- I suggest you review the previous postings which explain it.
As far as "better", the answer is that it probably doesn't matter, since
either a wire or strap can usually be pretty easily made large enough to
make loss negligible in those applications.

Roy Lewallen, W7EL

coils?multi-turn magnetic loops
 

Roy Lewallen wrote:
ml wrote:
does this rule also hold true for example i've opened some tuners
and linear amps, often, i see straps instead of wire going to the
larger coils and switches, even some switch box's have straps
from relays to connectors etc would wire have been 'better'
and or avoid the proximity effect??

Proximity effect isn't a factor unless conductors are very close
together -- I suggest you review the previous postings which explain it.
As far as "better", the answer is that it probably doesn't matter, since
either a wire or strap can usually be pretty easily made large enough to
make loss negligible in those applications.

Roy Lewallen, W7EL

Proximity effect is when you are too close to a directional microphone
and the bass is accentuated. I think you mean mutual coupling.

coils?multi-turn magnetic loops
 

On Nov 25, 5:53*am, Dave wrote:
Roy Lewallen wrote:
ml wrote:
does this *rule also hold true * for example i've opened some *tuners
and linear amps, *often, i see *straps *instead of wire going to the *
larger coils and switches, *even some switch box's * *have *straps *
from relays *to connectors *etc * *would wire *have been 'better' *
and *or *avoid * the *proximity *effect??

Proximity effect isn't a factor unless conductors are very close
together -- I suggest you review the previous postings which explain it..
As far as "better", the answer is that it probably doesn't matter, since
either a wire or strap can usually be pretty easily made large enough to
make loss negligible in those applications.

Roy Lewallen, W7EL

Proximity effect is when you are too close to a directional microphone
and the bass is accentuated. *I think you mean mutual coupling.

Wrong one of the several meanings, Dave. See fourth entry under
http://en.wikipedia.org/wiki/Proximity_effect.

;-)

coils?multi-turn magnetic loops
 

K7ITM wrote:
On Nov 25, 5:53 am, Dave wrote:
Roy Lewallen wrote:
ml wrote:
does this rule also hold true for example i've opened some tuners
and linear amps, often, i see straps instead of wire going to the
larger coils and switches, even some switch box's have straps
from relays to connectors etc would wire have been 'better'
and or avoid the proximity effect??
Proximity effect isn't a factor unless conductors are very close
together -- I suggest you review the previous postings which explain it.
As far as "better", the answer is that it probably doesn't matter, since
either a wire or strap can usually be pretty easily made large enough to
make loss negligible in those applications.
Roy Lewallen, W7EL
Proximity effect is when you are too close to a directional microphone
and the bass is accentuated. I think you mean mutual coupling.

Wrong one of the several meanings, Dave. See fourth entry under
http://en.wikipedia.org/wiki/Proximity_effect.

;-)

Thanks. Seems to be the realm of the esoteric however.

coils?multi-turn magnetic loops
 

On Wed, 26 Nov 2008 13:52:08 +0000, Dave wrote:

Proximity effect isn't a factor unless conductors are very close

Thanks. Seems to be the realm of the esoteric however.

Esoteric? As an issue of loss, it is probably more common than
conductor shape, and is (unlike most of the scribblings here to this
group) decidedly on-topic and focused.

73's
Richard Clark, KB7QHC