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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.





Results:

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.

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