Soft
copper Tube Loops
Air
conditioning soft copper tubes are perfect for loop construction.
If you want to try a loop you must have an air variable
capacitor or a vacuum variable capacitor.
The
vacuum types are hard to find and expensive, but they
have high isolation figures (ideal for high power operation)
and can range from some Pico farads to hundreds of Pico
farads indicated to design a small magnetic loop that
can cover 10 meters to 80 meters.
For
high power operation you will need big spacing between
the plates of the air capacitor.
The
most common variable capacitors present high losses due
to the mechanical electric contact on the metal surfaces.
The
most recommended are the butterfly or the split stator
air variable capacitors.
Do
not be disappointed with you have only the standard metal
air capacitors. I still use them on some projects despite
knowing all the performance compromise they can represent.
On
the “Magnetic Loop Links”, you can have all
the theoretical information to design your loop. My personal
proposal is give to the reader practical ideas for the
loop construction.
On the following photos
can be seen two soft copper small magnetic loops, both
of them are made on 3/4 inches soft copper tubes.
The
bigger has 91 CMS in diameter and measures 2.89 CMS from
each extreme.
The excited loop is made on coaxial cable and measures
2.89 CMS divided by 5.
The capacitor is 10 Pico farads to 80 Pico farads split
stator.
The
smaller one has 66 CMS in diameter and measures 2.08 CMS
from each extreme, and is closed with a standard 12 to
100 Pico farads capacitor.
The excited loop follows the 1/5 of the main loop measures.
Soft copper magnetic
loop
66 CMS diameter
1.9 CMS soft tube |
Standard 12/100 capacitor
Coupling made with two
glued plastic knobs |
Tuning
knob. |
Velcro
over de cable. |
91
CMS Diameter. |
Split
stator 10 / 80 Pico farads. |
Tuning
knob and excited loop. |
Soldering
the loop to the capacitor. |
PY1
AHD ALEX (Alexandre Grimberg).
