Re: Ideas for cheap and effective loop antennas

Leif Asbrink

I made a 30 cm diameter, two turn loop using RG8.

A 6.8 nF capacitor tunes it to 1.1 MHz. With one turn
on the primary and 18 turns on the secondary I see 50
ohms on 1.1 MHz.

The signal level is about 10 dB below what I see from
a 10 meter wire antenna - and that is enough with a margin
for a receiver with a low NF.

Suppression of conducted interference is poor however.
That is easy to fix - I will try to get the time to make
a video showing the nature of the problem and how to fix it.

The 30 cm loop when tuned to 1.1 MHz has a useful bandwidth
of about 500 kHz (with a low noise receiver.) Adding a very
simple amplifier would make the bandwidth MUCH larger.



A very good and cheap receiving loop antenna can be made from one turn
coaxial cable with diameter of about 1,5 meter and gap in the shield in
the middle of the antenna (at the top of the loop)
Why not rearrange the same one turn to achieve two turns with good shielding and balancing?
For the amplifier, I'm trying to keep things simple. I'll probably just rely on the low NF of the HF+ to exploit the small loop.

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