On the picture, you'll see 7 connections for the cables, oe at the
bottom (7), 6 at the top of the C. How do I need to connect the cables
to have the maximum out of my AM/SW loop antenna ??

http://users.fulladsl.be/spb13810/amloop/tunablec.jpg


I would like to know what I can do with screws A, B, C and D, and of
course, where to connect the cable ends ...



I am making one loop with these tools:
these are the picts:
http://users.fulladsl.be/spb13810/amloop/loop83cm.jpg

the loop, diameter = 83 cm.

http://users.fulladsl.be/spb13810/amloop/loopbottom.jpg
The bottom, a plastic case 11 x 18 cm.

http://users.fulladsl.be/spb13810/am...oopbottom2.jpg
The plastic screws that fit the hulahoop.

I will mount the C inside the box, so I'll have no cables outside ...


Thanks,
Marc

--
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/

You have to very carefull when turning the slots,use a plastic
screwdriver.You might need to apply a little bit of heat first.Easy to
break something there.
cuhulin

Marc,

That's a fine picture of a variable capacitor, but how are we supposed
to know how the connections inside are made, or what the capacitance
values are? You may be able to tell if you inspect it carefully from
the outside. Even if I have one that _looks_ similar (which I may well
have) I would not rely on its having the same connections or
capacitance values as yours.

Have you done any analysis of the loop to see what capacitance you need
to tune it to the frequencies you care about? Reg Edwards has on his
website a program that's useful for analyzing loop antennas. I believe
it's only set up for square loops, but if you enter side lengths to
give the same loop area as you have, you should get quite close to the
same performance. You may find it's helpful to use a larger
cross-section wire in the hula-hoop, for lower resistance.

How will you tune the antenna to different frequencies if the capacitor
is sealed in the box? Will you provide a hole for adjustment? How
will you feed the antenna output to the receiver? What frequency range
do you hope to cover?

I fear there are more questions than answers...but questions are good
if they get you thinking about the whole situation before you put a lot
of work into something that may not do what you expect or what you
want.

Cheers,
Tom

On Fri, 21 Apr 2006 18:58:43 +0200, switcher
wrote:

Hi Marc,

Nice pictures by the way.

On the picture, you'll see 7 connections for the cables, oe at the
bottom (7), 6 at the top of the C. How do I need to connect the cables
to have the maximum out of my AM/SW loop antenna ??

http://users.fulladsl.be/spb13810/amloop/tunablec.jpg

You will need a VOM to check, but it appears that numbers 1, 3, 4, 6,
and 7 go to the frame (stator). Screws A, B, C, and D look like
trimmers, not wire attachments (that is, they are small variable caps
in parallel to the main caps).

Numbers 2 and 5 appear to be the main capacitor connections with
reference to the frame. This looks like an old AM tuning component
for which you would have two Caps. One for tuning the front end, the
other for the local oscillator, and the trim caps take care of both
matching the antenna, and keeping the IF tracking between the two
(usually adjusted at the high end of the band). The two main Caps
also have different maximums (because they tune over different ranges
of frequencies).

None of this is of any consequence to you for your project, however.
You need only confirm my guess of the frame connections. If that
bears out, tie them all together, or use just one and ignore the rest.
This is one half of your project's Cap. If 2 and 5 show no continuity
to anything else (except the screw heads, perhaps), then that confirms
their status as being the rotor half of the variable Cap. Tie them
together for the other half of your project Cap.

If there is any variation in testing with the VOM for continuity, you
may have a split frame. Visual inspection should reveal two
assemblies that would be very similar in construction. Take hints
from discussion above to reduce the complexity of all the leads.

73's
Richard Clark, KB7QHC

"switcher" wrote in message
...
On the picture, you'll see 7 connections for the cables, oe at the
bottom (7), 6 at the top of the C. How do I need to connect the cables
to have the maximum out of my AM/SW loop antenna ??

http://users.fulladsl.be/spb13810/amloop/tunablec.jpg


I would like to know what I can do with screws A, B, C and D, and of
course, where to connect the cable ends ...

I am not sure how to connect the wires to the loop, but they go to the tabs
that are numbered.
The screws go to 4 small trimmer capacitors for adjustments. Usually that
kind of capacitor comes out of an AM/FM radio and the capacitors are for
fine adjustments of the ranges. One for the frequency of the oscillator and
one for the tuning for each band. They mostly affect the high end of the
band as they are small in compairison to the main capacitor. The are hooked
internally to the main capacitors the shaft adjusts.
If you look close you will see the half round plate turn as you turn the
screw. A coil is usually adjust for the low end of the band. You go back
and forth from the low end , adjusting the coil and to the high end
adjusting the screw for the best tracking across the band. The oscillator
for the frequency readout and the tuning for maximum signal.

In article ,
switcher wrote:

On the picture, you'll see 7 connections for the cables, oe at the
bottom (7), 6 at the top of the C. How do I need to connect the cables
to have the maximum out of my AM/SW loop antenna ??

http://users.fulladsl.be/spb13810/amloop/tunablec.jpg


I would like to know what I can do with screws A, B, C and D, and of
course, where to connect the cable ends ...



I am making one loop with these tools:
these are the picts:
http://users.fulladsl.be/spb13810/amloop/loop83cm.jpg

the loop, diameter = 83 cm.

http://users.fulladsl.be/spb13810/amloop/loopbottom.jpg
The bottom, a plastic case 11 x 18 cm.

http://users.fulladsl.be/spb13810/am...oopbottom2.jpg
The plastic screws that fit the hulahoop.

I will mount the C inside the box, so I'll have no cables outside ...

The capacitor will go across the coil or in other words connect to the
ends of the coil.

The capacitor is made of two opposing conducting plates with an
insulator between them. For most tunable capacitors the insulator is
air. One plate will stay in place and the other will rotate by turning
the shaft. When the plates are meshed together you have maximum
capacitance and lowest frequency of operation. You will have to look
through the case to find the connections to the opposing plates for each
section.

I can't tell from the picture but it looks like this box has two or more
sections. You can parallel the sections together if one section does not
have enough capacitance.

Also hard to tell is what the "screws" are in the picture but I expect
that they are trimmers (additional small adjustable capacitors) that are
arrayed across the main capacitor sections for alignment purposes.

--
Telamon
Ventura, California

switcher wrote:

On the picture, you'll see 7 connections for the cables, oe at the
bottom (7), 6 at the top of the C. How do I need to connect the cables
to have the maximum out of my AM/SW loop antenna ??

http://users.fulladsl.be/spb13810/amloop/tunablec.jpg

I would like to know what I can do with screws A, B, C and D, and of
course, where to connect the cable ends ...

I am making one loop with these tools:
these are the picts:
http://users.fulladsl.be/spb13810/amloop/loop83cm.jpg

the loop, diameter = 83 cm.

http://users.fulladsl.be/spb13810/amloop/loopbottom.jpg
The bottom, a plastic case 11 x 18 cm.

http://users.fulladsl.be/spb13810/am...oopbottom2.jpg
The plastic screws that fit the hulahoop.

I will mount the C inside the box, so I'll have no cables outside ...

Thanks,
Marc

--
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/

The capacitor device is very common in most portable radios. It has two sections
for AM tuning, and two for FM tuning. The 'screws' adjust trimmer capacitors which
are in parallel with the four main capacitors.

You do not specify what frequency you intend to tune the loop to. If you want it
for a band of frequencies what range to you plan to cover. I suggest that you
take some alligator clip leads and temporarily hook up the loop to one end of
each lead. Then try connecting the other ends to different terminals on the
capacitor and tune the cap through its range and listen for an increase in
noise at the receiver. You will have to tune very slowly as the high Q of
the loop will make the selectivity very sharp and you can miss the noise point
easily.

You would be much better off to get some ham to give you a small variable
from his junk box. It will work better and will be much easier
to mount in the case. With a one meter loop, a capacitor with a value of 100 pf
or less should beable to tune between about 7 and 30 mhz.

Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/index.html
Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm
Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

You take care,Irv.Stay with that diet and exercize,,,, Beat that
diabetes.
My old buddy retired from the U.S.Navy.He was on the USS Ticonderoga.
www.google.com USS Ticonderoga
cuhulin

switcher wrote:

In article , Irv Finkleman
wrote:

With a one meter loop, a capacitor with a value of 100 pf
or less should beable to tune between about 7 and 30 mhz.

A 80 cm loop gives me reception between about 5 and 12 Mhz, this is with
a cap from a FM/AM radio kit ...
http://users.fulladsl.be/spb13810/oc/IMAG0018.JPG

So, to have higher freq, the loop should be made smaller ... (or higher
cap ?..)


Make the cap smaller. You can if you put a similar cap in series with
the first you will reduce the total capacity and raise the resonant frequency.
Changing loop length is too much trouble, changing a cap is easy.

Irv VE6BP
--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/index.html
Visit my Baby Sofia website at http://members.shaw.ca/finkirv4/index.htm
Visit my OLDTIMERS website at http://members.shaw.ca/finkirv5/index.htm
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada