K3 and noise

[Ron Kenwood]

I have a continuous S7 to S8 noise level at normal SSB bandwidths. If I
had to describe the noise, I would say it sounds like amplified
background band noise. The source is outside my house. Removing the
antenna drops it to S2-3. It decreases slightly at 15 meters and higher.
I have been trying all possible combinations of IF and DSP noise
blanking. About the best I can do is to reduce an S7 with a blinking S8
bar to a steady S7. If I don't look at the S meter and try to discern a
difference in signal intelligibility, I can't really hear any.

I have read glowing reports on the effectiveness of the noise blanker,
here and elsewhere. I am wondering if the type of noise is part of the
equation, and I just have a type of noise where the noise blanker is
less effective, or am I doing something wrong, or do I just have
unreasonable expectations?

Any suggestions?

My next step will be one of the noise canceling gadgets, if I can't
improve the K3's noise performance.

Happy Holidays

Ron W3ZV
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[David Woolley (E.L)]

Ron Kenwood wrote:
> I have a continuous S7 to S8 noise level at normal SSB bandwidths. If
> I had to describe the noise, I would say it sounds like amplified
> background band noise. The source is outside my house. Removing the

If the noise is close to gaussian, there is nothing any receiver noise
reduction system can do with it, to actually remove it, although it can
do things like muting the receiver in gaps in the speech, if the speech
is above the noise, or generating a graphic equaliser that de-emphasises
frequency not also being used for the speech.

>
> I have read glowing reports on the effectiveness of the noise blanker,
> here and elsewhere. I am wondering if the type of noise is part of the

Noise blankers require that the noise be isolated spikes that can be cut
out without removing too much of the signal.

> equation, and I just have a type of noise where the noise blanker is
> less effective, or am I doing something wrong, or do I just have
> unreasonable expectations?

Knowing the source of the noise might help, as it might give a clue as
to its structure and therefore whether there is anything that can be
done to mitigate it.
>
> My next step will be one of the noise canceling gadgets, if I can't
> improve the K3's noise performance.

For gaussian noise, the best option is to eliminate it at source.
Failing that, put it in a null in the antenna pattern will help,
providing the noise has a well defined direction.  I assume you are
referring to the sort of noise cancelling device that works by
distorting the antenna pattern.

Note that such devices are not suitable when the antenna is already very
directional, or the sky noise is not significantly greater than the
receiver noise (the device is likely to contribute its own receiver noise).

--
David Woolley
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RFC1855 says there should be an address here, but, in a world of spam,
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[Gary NL7Y]

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 and sometimes 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 usually set my IF NB to NAR6 or MED 6, and the DSP NB to dsp t1-6 or 2-6. Check for fidelity on SSB and CW. The NR works for me at 1-1 or 2 or 2-1 or 2. Narrow filters are better, and the NB's settings can vary by band and time of day. The K3 is truly the best of many many radios that I've owned at this noisy QTH in Fairbanks, AK. for dealing with both common and differential-mode QRN. Thank you Elecrafters for the fine Christmas gift of hearing.

I would be concerned about your S2-3 w/o the antenna connected. Mine shows one bar only with the coax off the rig. If removing the antenna does not quell the noise to S1, then I suggest you may have common-mode RF ingress from either your power supply, house wiring, or whatever else your K3 is connected to. See Jim K9YC'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 Type 31 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

(edited a few times after original post as ideas surfaced)

[Bill VanAlstyne 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

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