VK5HW - Hermes Loop

The Hermes Loop RX Antenna at VK1HW

I've had a bit of Aluminium bar lying around and so I've build a Hermes Loop with a 1m diameter. I've build a few single loops before, but only for indoor use.

Why a Hermes Loop, well to have the best possible signal transfer in to a FET LNA, the inductance of the loop should be as low as possible. As the inductance of a 1m loop is about 3µH, paralleling two loops should halve the inductance and as such give a better transfer into the FET LNA. A quick knock up and then a quick measurement of the test loop showed that the inductance has indeed halved. Measured inductance is about 1.4µH.

The LNA in use is the LZ1AQ amplifier. There is a plethora of information on Chavdar's website. Here are a couple of pictures of the final antenna before measuring and mounting on the shed.

Here are some spectrograms of the LF/MF spectrum (100-600 kHz) after the loop had been installed at its final resting place.

Low end spectrum using my LAZY-D

Low end spectrum using a ZS6BKW

Low end spectrum using the HERMES-LOOP

Here is a quick sketch of the antenna including my dimensions.

NOTE: If you plan to build one for yourself, make sure that you weld the interconnecting bars to the loop! If you only use rivets or screws, oxidation will form between the joins and then all hell on earth will hit your RX!