Depending on where you live, and how dense the housing is, the noise
could easily be coming from your neighbor's gear.

The usual culprits for 50 to 100Khz noise are switching power supplies.
They live in TVs, Fax machines, telephone answering machines, battery
chargers, computers, monitors, printers, LED and vacuum fluorescent
clocks, and the biggest supplier of this noise of all, so far, the
compact fluorescent lamp.

If you want to check your house for sources of this noise, the easiest
way is to kill all the breakers except for one, and unplug everything
in that circuit except for your receiver. If you still have the noise,
it is being conducted into your house from elsewhere.

-Chuck, WA3UQV

No Spam (ckh) wrote:


I have an S9+ noise level on all the HF bands. I've suspected my
computers, fluorescent lamps, BPL, but I'm not certain. It
sounds/looks like this.


XxxxXxxxXxxxXxxxxXxxxXxxxXxxxxXxxxxX
0----v----1----v----2----v----3----v----4

The scale is, oh, 40 meters from 7.0 to 7.4, each lowercase x is
S7-8 pink noise. Each uppercase X is a roughly 10 kHz wide cluster
of shot-noise, S9+.

The uppercase X's are about 55 kHz apart. It's all approximate and
seems to be different at different times.

I've turned off all the computers and other appliances, alarm
clocks, etc. There is no change in the noise.

I hear it on all my receivers which include 3 SB-303's and a
Signal/One.

any ideas?

de ah6gi/4

On Mon, 3 Nov 2003 03:07:24 UTC, Chuck Harris
wrote:

Depending on where you live, and how dense the housing is, the noise
could easily be coming from your neighbor's gear.

The usual culprits for 50 to 100Khz noise are switching power supplies.
They live in TVs, Fax machines, telephone answering machines, battery
chargers, computers, monitors, printers, LED and vacuum fluorescent
clocks, and the biggest supplier of this noise of all, so far, the
compact fluorescent lamp.

If you want to check your house for sources of this noise, the easiest
way is to kill all the breakers except for one, and unplug everything
in that circuit except for your receiver. If you still have the noise,
it is being conducted into your house from elsewhere.

-Chuck, WA3UQV

Thanks for the tip, I made another pass around the house, turning
stuff off. It's my problem. It seems to be my laptop, a small IBM
Thinkpad, the LCD display seems to be the problem and not so much
the small powersupply.

Might be the "inverter" that produces the high voltage that runs the
fluorescent backlight for the LCD panel. I took one apart and IBM
has an RF bead on the ribbon cable that powers the LCD light so it
seems to be a known problem.

I'm guessing that all the stuff in my place adds to the din. I have
a half dozen compact fluorescent lamps, a dozen wall warts,
computers that stay on all the time.

Might be time to put the Ham Shack in an RF screen room and RF
supress the AC power going into the shack. Then run the antenna
away from the house.

I'm not using coax. My antenna is just 50 feet of speaker wire that
runs from the back of the Signal/One and the SB-303, across the
floor, out the window and down across the awning to a bush.

With the Thinkpad powered off, I tuned across 75 and yep, 20-30
Geezernets going full-bore.

40 meters was the usual deafening din of foreign broadcasters
playing that weird foreign music.

Still nothing on 20, 15, 10 though.

de ah6gi/4



No Spam (ckh) wrote:


I have an S9+ noise level on all the HF bands. I've suspected my
computers, fluorescent lamps, BPL, but I'm not certain. It
sounds/looks like this.


XxxxXxxxXxxxXxxxxXxxxXxxxXxxxxXxxxxX
0----v----1----v----2----v----3----v----4

The scale is, oh, 40 meters from 7.0 to 7.4, each lowercase x is
S7-8 pink noise. Each uppercase X is a roughly 10 kHz wide cluster
of shot-noise, S9+.

The uppercase X's are about 55 kHz apart. It's all approximate and
seems to be different at different times.

I've turned off all the computers and other appliances, alarm
clocks, etc. There is no change in the noise.

I hear it on all my receivers which include 3 SB-303's and a
Signal/One.

any ideas?

de ah6gi/4





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