This max. size magnetic loop antenna for 14 MHz with a totall circumference of 6m. ( 19.68 feet ) is designed to attach to a wall . Not sutable for reenforced concrete walls . It has a no tune bandwidth of more than 300 KHz with a centre swr of 1 : 1.1. A capacitor was put over the feedpoint to shunt up the feedpoint impedance. The 150 pF parallel capacitor was the best value in my situation ( brick wall ) but can be replaced by a 500 pF tuning capacitor in order to find the lowest SWR at resonance in any setup. First contacts gave good reports in Europe. Although a lot of the hf power is absorbed by the wall, the results are surprisingly good. A test was made with 100 Watts without arcing however 5 Watts are more than enough for indoor use...
The top capacitor is made of twisted pvc coated antenna wire or a piece of 25cm RG-213 coax and is cut for tuning to the frequency . This antenna can also be build on a fibreglass or wooden frame in a diamond shape for field or attic use. Loop circumference for other bands:
30m : 7m
20m. : 6m
17m. : 4.8m
15m. : 4.2m
12m. : 3.5m
10m. : 3m
Tuning steps : Change the length or the turns of the top capacitor to tune the loop to the desired frequency then put a 500 pF tuning capacitor over the feedpoint and look for the lowest swr.
You can replace this capacitor by a fixed type.
Follow the thread on QRZ.com :https://forums.qrz.com/index.php?threads/wall-loop-20m.511714/
|The capacitor . A piece of RG-213 coax can also be used|
|Verry good SWR|
|Feedpoint with 100pF and 47pF in parallel. Notice the line choke.|
|The loop made by SP3BGD|
|SP3BGD feedpoint capacitor for wide range use|
|The loop at DB9MAT|