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Starting-Off Today with Only
Heinz 57 to go +1 ) ~ RHF
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The Number "57" has Mystical Significance
http://www.straightdope.com/classics/a1_195

"Richard Clark" wrote in message
...
On Sat, 06 May 2006 08:35:28 +0200, switcher
wrote:

Yes, I would buy fixed, of course, they have them in eu at www.conrad.fr

Make sure they exhibit low ESR (Equivalent Series Resistance). Not
all capacitors are especially suitable for tuning.

73's
Richard Clark, KB7QHC

Don't use the cheap ceramic capacitors that are meant to be used for
bypassing. A friend of mine used some in a tuned circuit, and he got a
distorted sine wave output. In addition to possibly high ESR, the value of
these capacitors changes with the instantaneous applied voltage. To be safe,
use caps with mica or plastic dielectric.

Tam

switcher wrote:

The loop is 2 x 3 meter of PVC tube, bended in a circle.
There are now 3 turns. Guess ... how many turns to have the LW
153-279khz ???

If 3 turns resonated with about 11000 pF (your 10 nF plus about 1 nF
from the tuning capacitor) produces a resonance within that band, then
raising the turns to about 9 (3 times as much for about 3^2 times as
much inductance) would resonate at the same frequency with about 1/9th
as much capacitance (same L*C product). Of course, those extra turns
will also add quite a bit of stray capacitance between turns, so you
may not be able to reach the top of the band at minimum tuning
capacitance.

What kind of insulation is on the wire in the big loop? Its thickness
and dielectric constant have a big effect on the total stray
capacitance each turn will add.

In article ,
John Popelish wrote:

switcher wrote:

The loop is 2 x 3 meter of PVC tube, bended in a circle.
There are now 3 turns. Guess ... how many turns to have the LW
153-279khz ???

If 3 turns resonated with about 11000 pF (your 10 nF plus about 1 nF
from the tuning capacitor) produces a resonance within that band, then
raising the turns to about 9 (3 times as much for about 3^2 times as
much inductance) would resonate at the same frequency with about 1/9th
as much capacitance (same L*C product). Of course, those extra turns
will also add quite a bit of stray capacitance between turns, so you
may not be able to reach the top of the band at minimum tuning
capacitance.

What kind of insulation is on the wire in the big loop? Its thickness
and dielectric constant have a big effect on the total stray
capacitance each turn will add.

I guess copper 0.7 mm, insulation soft plastic .25 mm

--
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switcher wrote:
In article ,
John Popelish wrote:
(snip)
What kind of insulation is on the wire in the big loop? Its thickness
and dielectric constant have a big effect on the total stray
capacitance each turn will add.


I guess copper 0.7 mm, insulation soft plastic .25 mm

Sounds like ordinary PVC insulated hook up wire. The PVC is a little
lossy, but not too bad at this low frequency. You would have a lot
more trouble with high capacitance if you were using enameled (magnet)
wire. My favorite for such things is Teflon or Tefzel insulated wire
(low loss and low dielectric constant), but it is expensive and hard
to find. Another good, but hard to find insulation is polyethylene.
It is sometimes used in low capacitance, data grade cables, but
stripping out enough for this project would be a career.

Do you think it is practical to pull 6 more turns through your pipe?

In article ,
John Popelish wrote:

switcher wrote:
In article ,
John Popelish wrote:
(snip)
What kind of insulation is on the wire in the big loop? Its thickness
and dielectric constant have a big effect on the total stray
capacitance each turn will add.


I guess copper 0.7 mm, insulation soft plastic .25 mm

Sounds like ordinary PVC insulated hook up wire. The PVC is a little
lossy, but not too bad at this low frequency. You would have a lot
more trouble with high capacitance if you were using enameled (magnet)
wire. My favorite for such things is Teflon or Tefzel insulated wire
(low loss and low dielectric constant), but it is expensive and hard
to find. Another good, but hard to find insulation is polyethylene.
It is sometimes used in low capacitance, data grade cables, but
stripping out enough for this project would be a career.

Do you think it is practical to pull 6 more turns through your pipe?

It is possible .... I'll look for some time ...
I have the right tools ..

--
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http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/

If you search the archives of this group (for example with Google), you
wil find some good info about loops for low frequency reception. One
way to keep the loop's effective self capacitance down is to wind it
with the wires spaces apart some. It is common to use at least one
wire diameter spacing between wires, so it would be at least two times
the wire diameter, center to center. You can also put, say, 11 pieces
of wooden dowel or PVC pipe in a circle. Number them in sequence.
Then wind the wire outside 1, inside 2, outside 3, ... outside 11,
inside 1, outside 2, ... so that each successive turn is on the
opposite side of each particular pipe. (The axis of each pipe is
perpendicular to the plane of the circle.) As you can see, you must
use an odd number of posts in this construction.

There is benefit to making the loop very symmetrical about a vertical
plane, because local sources of noise are likely to be electric field
which is perpendicular to the earth, and will be rejected by such a
symmetrical antenna.

Cheers,
Tom

NIce.

Three grey boxes stacked like this one

http://users.fulladsl.be/spb13810/am...oopbottom2.jpg

would allow to make a spiral with 8 turns ... etc ...
should be the best solution ...

I bought 2 of these at a sell out for 4 euro/$/piece, now they are at 17
;-( .. !




In article . com,
"K7ITM" wrote:

If you search the archives of this group (for example with Google), you
wil find some good info about loops for low frequency reception. One
way to keep the loop's effective self capacitance down is to wind it
with the wires spaces apart some. It is common to use at least one
wire diameter spacing between wires, so it would be at least two times
the wire diameter, center to center. You can also put, say, 11 pieces
of wooden dowel or PVC pipe in a circle. Number them in sequence.
Then wind the wire outside 1, inside 2, outside 3, ... outside 11,
inside 1, outside 2, ... so that each successive turn is on the
opposite side of each particular pipe. (The axis of each pipe is
perpendicular to the plane of the circle.) As you can see, you must
use an odd number of posts in this construction.

There is benefit to making the loop very symmetrical about a vertical
plane, because local sources of noise are likely to be electric field
which is perpendicular to the earth, and will be rejected by such a
symmetrical antenna.

Cheers,
Tom


--
een appeltje te schillen met http://applefaulty.be
http://users.fulladsl.be/spb13810/bwnl.htm
Breng je iMac G5 terug (ik wil binnen 2 jaar geen defecte 2de hands Apple kopen)
http://www.apple.com/nl/support/imac...ensionprogram/