[RFI] FW: RF noise and ground

[nlsa at nlsa.com]

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