[RFI] FW: RF noise and ground
nlsa at nlsa.com
nlsa at nlsa.com
Thu Jan 23 07:30:00 EST 2025
Dear friends,
I have a question regarding self-generated RFI and its relation to ground.
Background: My 2m EME system uses a composite (i.e. mostly carbon fiber and fiberglass) mount that was built by my employer as a prototype for a US military contract. The mount has a stationary lower section and a rotating upper section. My QRZ.com page shows the setup The two sections are joined by a large ring gear that allows unlimited azimuth rotation. https://www.qrz.com/db/W9IP .
All RF equipment, including SDR, transverter, and SSPA reside in compartments in the upper section. AC power, “ground,” and a fiber optic line are supplied to the upper section through a large slip ring that is coaxial with the ring gear. There is no direct electrical connection between the upper section’s equipment and Earth ground.
All ground current flows through a dedicated (heavy) channel in the slip ring and then to Earth ground below the array. This path is undoubtedly inductive and probably not a very good RF connection to Earth. EME performance is good but I am always thinking about ways to improve it.
Question: I’ll bet that my noise floor could be improved by a better RF connection to Earth, but how can I do it? What mode does EMI take in this situation? What is “ground” in a non-metallic enclosure?
Suggestion welcome!
73,
W9IP
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