Table-top LF / HF receiving loop made using 3D printed parts

HF loop series

This is a table top receiving antenna that covers much of the LF and HF spectrum. If you live in a flat so don't have much room, or just need a small antenna to monitor the bands this works surprisingly well. There is a nice sharp null in the pattern so you can rotate it to reduce noise. It is basically a six turn square loop (ca. 45 x 45 cm) brought into resonance by a tuning capacitor. A small single turn triangular coupling coil takes the signal to the receiver via standard coax. Using 6 turns and a small tuning capacitor the loop covers both Top Band and 80m. The main receiving / tuning coils are shown in red wire while the coupling coil is shown in black wire.

spreaders spreaders

This 3D printed version consists of an octagonal base and center piece and four spreaders to hold and space the turns of wire. The bottom left hand side spreader also includes a flat section to hold the tuning capacitor. Each spreader goes to a dowel (I used 30cm) that slots into the center piece. Self tap screws can be used to secure the dowles into the center piece and then spreaders (I have built in screw holes for this purpose). The long side of the triangular coupling coil is close to one side of the main coil the other two sides meet close to the middle (see the connector block in the photo). I have made holes in the spreaders to take the coupling coil.

loop cap

The table below shows the frequency the loop covers verses number of turns of wire for two different tuning capacitors: a 500 + 500pf Jackson type and also a small 'Japanese' type tuning capacitor found in transistor radios etc. In both cases the two sets of vanes are connected together in parallel and are connected to the two ends of the loop. It is difficult to find knobs to go on the small capacitors (they don't have the usual 6mm shaft) so I 3D printed a knob to fit (secured by a 20mm 2.5M bolt through the top of the knob).

Number of
500 + 500pf cap
min f
max f small Japanese cap (both vanes)
min f
max f (all MHz)
6 0.9 4.6 1.7 4.8
5 1.1 5.4 1.9 5.6
4 1.2 6.5 6.8 2.3
3 1.6 8.3 2.9 8.9
2 2.2 12 4.0 13
1 3.6 21 6.7 23

cap knob files
".stl" file
".g" file
".scad" file
spreader files
".stl" file
".g" file
".scad" file
center and base files
".stl" file
".g" file
".scad" file
my antenna page

my radio page
Non 3D
printed loop
back to
3D page

radio and loop


Dr Jonathan Hare University of Sussex, Brighton.

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