Loop-On-Ground Receiving Antenna

Antenna Held in Hand

I live in an area with bad, broadband RFI. The constant S7 noise floor on the lower bands got a bit too annoying for me, so I decided to try a loop on the ground recieve only antenna. Users of this antenna say it often helps combat RFI, reducing the noise floor. Here are the most important facts about this antenna:

  • It is in the shape of a square loop, with the wire laying right on the ground (just as the name suggests). Its feedpoint is at one corner.

  • The total circumference is not critical, but should be no larger than 1/4 of the shortest wavelength (highest frequency) you plan to use it on. 15 feet long sides is a good size (that’s the size I used) for the 20 meter band and below.

  • This antenna is somewhat directional; it has two lobes. If we call the corner with the feedpoint home plate, the lobes are pointing away from first and third base, at right angles from the feedpoint.

  • The signal levels recieved by this antenna are low. After all it is on the ground. It requires a preamp.

The feedpoint requires a balun to isolate the antenna from coax and to match impedance. I used a BN-73-202 ferrite binocular core, with 5 turns on the antenna side and 2 turns on the coax side. I have designed an enclosure for it to house the balun and a BNC connector in FreeCAD; I have attached the STLs here: Brass M3 threaded inserts are melted into the holes to let 3 M3 screws secure the lid and 2 screws to attach to the antenna.

Transformer Assembly

The antenna gives me a noticable reduction in RFI. I put it on the side of my house away from the neighbor whom I think is causing the RFI. The preamp in my Kenwood-TS590SG was good enough to bring signal levels up (the Kenwood also has a dedicated RX antenna jack so I didn’t need an antenna switch). I started designing it in the morning; the 3D printing took a few hours, and I installed it in the afternoon. That evening, I used it to get my first ever CW contact!

KK5JY has a much more detailed descriptions of this antenna you can check out.