Atmospheric noise increases

[w7hd]

Has anyone else noticed the dramatic increase in atmospheric noise
lately?  On 20M, 30M, and 40M especially, I see a wide-band noise source
wandering back and forth across the bands.  At times it almost looks
like a sine wave on the waterfall display.  The noise will vary from an
S3 up to a 20/S9.   It is especially troublesome on the frequencies I
use most, namely, 10.1389, 14.045, 14.070, 7045, and 7070.   With the
antenna disconnected, the noise drops to S1 or less.

I use 3 different antennas, a Force-12 15 ft vertical about 50 feet from
the house, a homebrew 25 ft flagpole vertical about 30 feet away and an
inverted vee for 40M on the tower adjacent to the house fed with 450-ohm
ladderline to a 4:1 balun at 50 feet.  All three exhibit the same
patterns and are separated by at least 50 feet from each other.

I am using the Rocky utility connected to the I/Q output of my KX3 to a
48KHz USB sound card input to the laptop computer.

--  W7HD     KX3#6966
Licensed continuously since 1967
Now retired!
Tucson, AZ

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[k6dgw]

If it is wide band, but not "all over the entire band,", it's probably
not atmospheric noise, more likely created by humans [i.e. your
neighbors].  Especially if it drifts up and down slowly.

Odds generally are that it's correlated with the slowly increasing use
of LED and CFL lights ... and possibly increases in "indoor
agriculture."  The latter can generally be identified by a fairly strict
schedule of on and off.  I have one near me. :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org

On 7/23/2015 5:07 PM, [hidden email] wrote:
> Has anyone else noticed the dramatic increase in atmospheric noise
> lately?  On 20M, 30M, and 40M especially, I see a wide-band noise source
> wandering back and forth across the bands.  At times it almost looks
> like a sine wave on the waterfall display.  The noise will vary from an
> S3 up to a 20/S9.   It is especially troublesome on the frequencies I
> use most, namely, 10.1389, 14.045, 14.070, 7045, and 7070.   With the
> antenna disconnected, the noise drops to S1 or less.

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[RICHH]

I had a problem like that. I shut off all power to my house at the circuit
breakers. I ran my radio on batteries and noticed the noise went away.
By turning on the breakers one at a time the culprit was found. It was the
switching power supply for the cable TV.
Richard
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[Phil Anderson]

Hello W7HD,

I often see a noisy wave go across my P3 (with K3); however, I've never
seen it oscillator slowly but
I'll look more closely. The source of this noise is not in my
house.....but could be a neighbor's.

You noted that your noise level drops to S1 when that source is not
there? When I see a steady
but slowly moving "hump" on the P3 display my noise floor remains about
the same but
at S2.5 or so on 20 meters during the day. I'm two blocks from a
shopping center, population of Lawrence
is 100,000.

I've been able to drop that noise floor, thus increasing S/N by nearly 3
S units, using a 20-meter
beverage antenna (one wavelength due to short back yard) and attaching
it to the AUX BNC input
of my K3 for diversity reception. To that I've started using the K3's
built in APF filter during CW op to improve
listening too. If you'd like a copy of my Power Point presentation on
this setup (given to my local club), I'd
be happy to email it back to you.

Phil, W0XI, Lawrence, KS.
aldenmcduffie (at) sunflower.com


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