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).