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. For max. performance be sure that the 'hot' side of the antenna points to the window. 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 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|