[Elecraft] K3 and noise

[Bill W5WVO]

Just want to reiterate and emphasize what Gary says here. Noise is ADDITIVE, 
and what you perceive as a universal presence of broadband noise is very 
likely coming from MANY different sources -- possibly a hundred or more --  
inside the shack, elsewhere inside the home, and external to the home. 
Common-mode noise emitted from the AC power cords of consumer electronics 
using cheap switching power supplies is a prime culprit, as it radiates 
through the house wiring and is easily picked up by your antenna, sometimes 
leading you to believe that is coming from some external source. Chasing down 
and suppressing each individual noise source is tedious work at best, but it 
will yield great dividends in the end. Start by turning off (and in many cases 
that means unplugging from the mains) EVERYTHING electrical/electronic in your 
home except your K3. Even the lights, appliances, etc. Then turn stuff back 
one at a time. Any time the noise floor increases perceptibly, rotate the 
antenna to find the worst-case bearing for that noise as verified by turning 
the offending item on and off so you can maximize the difference. Work on 
suppressing that one noise until it can no longer be detected in its 
worst-case antenna position. Then on to the next. You may be amazed at the 
things in your home that are generating horrendous noise! For example, some of 
the cheap low-voltage halogen light power supplies that are out there are so 
noisy they can take out the whole radio spectrum whenever that light system is 
switched on.

Once your broadband noise is under control, go after the single-frequency 
birdies that show up in your bands of interest. Computers and Wi-Fi modems are 
prime culprits here, but even these noises can be successfully suppressed in 
most cases.

Good luck on this!

Bill W5WVO


Gary NL7Y wrote:
> Hello Ron W3ZV. New owner of K3 2324 here. Noise at my QTH is local
> (lights, powerlines, electrical demand) that runs S5-9+ on SSB,
> depending upon time of day. It's more on AM, less on CW/Data modes.
> And that's on everything from my 160-L , 80 dipoles, to 3-El Steppir
> beam. Depending upon band, the K3 takes it at least 2-3 S units down
> via the dual NB's, and substantially improves the signal selectivity
> with the NR. I also use a Wellbrook loop for receive, which really
> helps with eliminating local stuff by 2-4 S units depending upon the
> source.
>
> I set my IF NB to 1-6, and the DSP NB to 1-6 or 2-6. Check for
> fidelity on SSB and CW. The NR works for me at 1-1/2 or 2-1/2. Narrow
> filters are better, and the NB's settings can vary by band.
>
> I would be concerned about your S2-3 w/o the antenna connected. If
> removing the antenna does not quell the noise to S0, then I suggest
> you have common-mode RF ingress from either your power supply, house
> wiring, or whatever else your K3 is connected to. See Jim K9AY's
> article on how to deal with this noise:
> http://audiosystemsgroup.com/RFI-Ham.pdf. I did and it worked for me.
> I used Fair-Rite Type 31 beads on every cable and coax in the shack.
> I also used a Tripp-Lite Ultra power conditioner on the 120V feeds,
> and ferrite beads on the 240V for the ACOM amp. Two to three S units
> of noise were lost via the common-mode suppression described.
>
> 73 and Merry Christmas from Santa Land