[Elecraft] (ot) noise reduction resources

[Michael Carter]

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