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Old April 22nd 06, 05:04 PM posted to rec.radio.shortwave,rec.radio.amateur.antenna
Irv Finkleman
 
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Default question about tunable capacitor: how to mount ??

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

--
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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)
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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
--
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Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada