Receiving loop antenna for indoor or portable use.
Updated: Jan 11
Height and width of the loop are 1 meter.
This means that one turn = 2.80 meters.
In this case i have used two turns = 5.60 meters.
I used 1 turn of 1.60 meters visible on the left side to achieve a good coupling with an acceptable SWR.
Measured minimum C value = 35 pf. This results in a resonance frequency of 7.560 KHz (see below). Calculated coil value of the loop is 12.6 uH.
Measured maximum C value = 150 pf. This results in a resonance frequency of 3.660 KHz (see below). Calculated coil value of the loop is 12.6 uH.
The 80 meter band is not covered completely. I need to add at least 15pf to reach 3.500 KHz. C max becoms 165 pf and C min becoms then 50 pf. With 5o pf the highest frequency is 6.344 KHz. 40 meter band is not covered anymore.
Changes made to increase the frequency range.
- Switch in middle position:
no extra capacity in parallel.
- Switch to the left:
39 pf in parallel.
- Switch to the right:
550 pf in parallel.
With 39 pf in parallel, f minimum becomes 3.220 KHz, f maximum 5.000 KHz. SWR = 1.1. Whole 80 meter band is covered now.
With 550 pf in parallel, f minimum becomes 1.720 KHz, f maximum 1.890 KHz. SWR = 3.8. High SWR can be improved by experimenting with the size and the coupling of the loop.