Hi Robert, You've used the term 'receiver noise', but specifically mentioned heterodynes and harmonics as being of concern. All receivers, Elecraft not excluded, have internal spurious signals generated in the VFO and BFO circuits as well as clocks for digital circuits in the radio. The best way to identify internal spurious signals is to remove the antenna(s) from the radio, terminate the antenna ports in 50 ohm dummy loads, and then carefully sweep the bands of concern to see if anything is audible. Internal spurs will typically be insensitive to front-end gain/attenuation settings, but may vary in strength with IF gain controls (e.g., the K2 has IF gain control even though labeled as RF gain). If you have a second, different radio, try the same experiment and see if the spurious carriers are replicated on it.
Switch-mode power converters are ubiquitous these days and generate buzzy, drifting harmonics of the switching frequency. Turn off power to your entire house, power your radio from a battery source, and see if you still hear such signals. Finding these sources is easy, if a bit time consuming, once you've determined they're on your local AC circuits. Ethernet signaling is long understood to generate clock/data signals that are audible in the ham bands. These signals can be identified once found on the receiver by turning off (including any UPS-powered) routers/switches that use Ethernet cabling. Dave, NK7Z, has a nice tutorial on methods to identify RFI sources generally: https://www.nk7z.net/category/info/rfi-mitigation/i-have-rfi-series/ It sounds like you've done the good work of grounding and bonding, which can help with self-induced RFI (ask me how I know!), but it won't address RFI sources such as internal spurs in the radio or the other predominant sources cited above. 73, Mike, K8CN ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
