WA Radio Scanner Users' Group

What causes noise or interference on HF or any other band?? and do you have a fix?


things that effect me pretty bad
Plasma screen tv - usually 40m gets hit hard by this
Laptop chargers - 40m and 80m
wireless modem power supply - 40m
fluro/ energy efficient globes - 80m (not yet confirmed)
Lightning - 40 and 80m really bad (and thats from 100+km away)
Tait 2020 uhf - 20m

This web page has some audio examples of noise and whats causing it.

http://www.arrl.org/tis/info/HTML/rfi-noise/

Jaycar 20A Switchmode power supply - noise on 80-20m. Have to operate on the battery

witch mode PSU + HF = world of hurt

I had a Jaycar unit for about 3 hours before upgrading to this
http://www.jaycar.com.au/productView.as ... BCATID=381

http://www.altronics.com.au/index.asp?a ... m&id=M8264

I bought one of these 45A Switchmode for work as a bench supply while it was on special. Turns out it has a variable frequency chopper so you can tune out noise on HF. I'm keen to test it out on an HF rig some time

VK6ZMS wrote: http://www.jaycar.com.au/productView.as ... BCATID=381

I got the 20 amp version of this one on your advice ZMS - the difference in background noise on the HF radio was quite noticeable!

Whilst sitting in my driveway and/or garage - when scan around to find some activity - i have noticed that i have been getting interesting interference on every step ... my rig is mounted in the car - running of the second battery - so no car noise/interference present

I noticed that is starts around 130MHz (at a minimum - could not be bothered going any lower) and cont right up until (i could not be bothered going any further again) at least 155MHz and i am picking up interference every 1MHz Step.

Eg 140, 141, 142, 143, 144, 145, 146, 147 etc

Could anyone have a possible reason as to why i am coping this interference in/around the home - however i dont seem to cop it when out and about driving ....

Very ironic as to how this is happening and very interested as to where this could be coming from...

Suggestions ..

orangepeel wrote: Very ironic as to how this is happening and very interested as to where this could be coming from...

What does the interference sound like?

generally - like an open mic - just a carrier wave - nothing else - no chopping etc

What sort of antenna are you using? Generally balanced (especially if you have a balun installed) or loop antenna produce much less electrical noise pick up. If you are using an Automatic Antenna tuner try a closed loop between the Ground and active antenna point.
From my experience an unbalanced antenna that is not properly grounded and doesnt have a low dc resistace to the ground from the active element (Via an RF choke or loading coil) will be very susceptable to electrical noise.

Regularly spaced quiet-carrier noise is usually caused by computers, TVs, set-top-boxes, network switches etc. If you can get away with it, kill the power to your house and see if the noise goes away...

The rig is mounted in my Prado - the current aerial i am using is SBB-5 but i have a SG-M507 on its way.

Thank you for your updates - yeh - it seems as soon as i move away from my house - the noise disappears ... just trying to figure out exactly what in my house might be the cause.

As for shutting down the power - the local authority will be doing that for around 1 hour whilst they upgrade the lines in the local area in the coming days - will try and get out of bed whilst that is happening and see if the noise goes away.

How far is the nearest cell antenna array? I get some very interesting noises from those things when mobile. One of them sounds like Captain Kirk is about to beam into my car.

edit: never mind. I should pay more attention

Also another finding.. Foxtel iq2 box and xbox 360 power supplies make a heck of noise on 40 and 80m.

Foxtel have always had problems with RFI. They bought out a modified wall socket that was grounded via a three pin plug to the mains earth (not Ideal but it worked). The way we used to get around the problem was to install the dish (indeed any TV antenna) to AS1417. Basically this means grounding the antenna properly.