Receive Active Loop Antenna

I operate 2 multi-band receivers, both capable of receive from 0 to 30 MHz and I wanted to find a receive antenna that would perform well on HF and LF. Dipoles, long wires or EFHW are fine up to a point, but without some matching, they will not work over a wide frequency range.

HL2 5w Transceiver

The Hermes Lite 2 is currently configured as a 10 band FT8 and FT4 receiver, simultaneously decoding and spotting from 1.9 MHz to 28 MHz

KiWi SDR 4 slice receiver 0 to 30 MHz

The Kiwi SDR is currently spotting WSPR on 137, 472 and 1.9 MHz and can also provide receive access to 0 to 30 MHz via the internet. They are both fed from the active loop, via a RX splitter.

Active loops can work extremely well from a very small circular loop, but they do also come with some disadvantages. They require to be powered, typically using a Bias Tee providing power up the coax. You cant transmit into them, if you do by accident then it will be the last time you operate with that antenna.

Active Loop

I purchased a Wellbrook loop second hand, and found the low band performance amazing compared to my small doublet antenna. The loops directivity could help null out SMPS noise from a neighbour, and on mediums wave broadcast I could use it to selectively pick broadcast stations on the same frequency.

I had tried other active antennas, mostly based around the mini whip design with varying success.

The PA0RDT mini whip and design notes can be found in this article.

I’m currently running a Wellgood loop after George M1GEO decided to attempt a repair on his loop. This works in a similar way to the Wellbrook and requires a circular section of aluminium.

Reception on 1.9 MHz seemed really good, allowing me to decode several stations over 4,000 km

NDB stations are also easy to pick out, the low band performance seems very good.

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