One of my clients asked me to research really low-cost EMI antennas they could use for bench top troubleshooting radiated emissions. I wanted ones that included long coax cables and had common connectors attached. A quick search on Amazon revealed a couple affordable antennas that could be used. After ordering them, here are the results.
BingFu Dipole Antenna (Amazon: https://www.amazon.com/dp/B08HRPPRFM/) $10
This one has a fixed total length of 10.5 inches (half wave), so the resonant frequency would be 565 MHz. This would still work for most emissions, so long as it was positioned close enough to the EUT. If it could be placed at least 1m away and still observe the emissions, that would be fine. There is a sticky pad on the back where you could stick the antenna to a stick or wall for support. It includes a 2m long coax cable with BNC connector.
Garoua SDR Dipole Antenna (Amazon: https://www.amazon.com/dp/B0DLVC2DWM) $32
This one is much more versatile and the telescoping elements can adjust from 14 inches to 38 inches (half wave) and resonates from 77 to 422 MHz. This would be a much better choice, given that most emissions are in the range 90 to 300 MHz. For good measure, they also included a ferrite choke on the shorter cable. The included suction cup mount doesn’t appear to be a very reliable mounting solution, so I’d recommend a full-size or table top tripod to mount it. The antenna base includes a common 1/4-inch-24 threaded socket, so is designed to fit normal tripod screws. This one comes with a shorter coax cable and SMA connector, but with a longer 2m extension cable. I had to tighten the two hinge screws in order to keep the dipole elements in place. I’d probably use this one over the BingFu model.
Because neither of these antennas have calibrated antenna factors, they would only be useful for relative troubleshooting measurements. “Are the emissions getting higher or lower?”
