Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Wideband noise  (Read 2339 times)
M0ARM
Member

Posts: 18




Ignore
« on: August 27, 2008, 03:10:09 PM »

Hi all,

I'm getting wideband noise across 30M through 17M. The spectrum scope on my IC-756 shows large waveforms constantly moving from left-to-right (or-right-to-left) accompanied by pulsing white-noise. The noise gets faster and slower, changing the direction of the waveform when it slows right down. However, if I transmit with a bit of power the noise (and waveforms) disappear for a while but inevitably return randomly.

I've done the usual turn everything off in the house and I still have the problem. I'm concluding it's my 12-year old power supply causing the problem but I've no way of proving this (no other 12V supply to test (just sold my 2nd 15A PSU - doh!) but I get this problem on 3 HF rigs).

Am I thinking in the right direction or has anyone else had similar and managed to fix the problem?

I'd appreciate any help and comments.

73,
Les, M0ARM
Logged
N1UK
Member

Posts: 2203




Ignore
« Reply #1 on: August 28, 2008, 03:36:56 PM »

I would try running off a 12v car battery as a test. This should eleiminate your power supply or prove it's guilt. This way you will also be able to turn all the power off to your house at the main fuse box as well.

Mark N1UK G3ZZM
Logged
W7MAP
Member

Posts: 1




Ignore
« Reply #2 on: September 01, 2008, 06:03:01 AM »

You didn't describe your waveforms so I will have to guess. I am assuming that you are seeing large spikes in patterns moving at some rate higher in frequency. In my home this was sourced by a touch lamp in my wife's hutch. Other places to look are in small (typ) halogen lamps with high current low voltage sides connected to something called solid state transformers. These nasty devices pump out huge di/dt that can be heard for 100's of feet.These nasty things sometimes are active even if the lamp is dimmed by a dimmer. The best solution to be sure is investigation with a portable radio and an external receiving loop antenna.
Logged
M0ARM
Member

Posts: 18




Ignore
« Reply #3 on: September 01, 2008, 10:57:33 AM »

Hi,

It sounds like a steam train that continually speed up, slows down and then speeds up again. The visual waveform on the IC-756 scope is large, regular spikes in time with the increase of the white-noise volume travelling up-and-down the affected spectrum (30M thru 15M generally). The scope shows this as a wave-like action from either left-to-right or vice-versa, it then changes direction when it slows to a halt and speeds up again. I hope this better describes the interference.

I can replicate this on 2x IC-756's and audibly on an FT-897D which eliminates the transceivers. I've also ran a single transceiver from a battery and the noise remains, so it's not my DC power supply. I've also switched off and isolated everything in the house (but NOT touched the main consumer supply as yet) so I'm happy it's not the TV or other domestic electrical item. I'm more convinced it's from an external source, possibly a neighbour's house.

It still appears intermittently and I'm still looking for the source - my investigations continue.

73,
Les, M0ARM
Logged
ON4CCU
Member

Posts: 3




Ignore
« Reply #4 on: September 11, 2008, 07:43:35 AM »

Hi Les,

I've had similar symptoms, but on 17 meters and up. Turned out to be my laptop power supply... You didn't indicate if your station PSU is a switching one or not, if it's the "traditional" non-switching version, it's unlikely that it generates this kind of noise pattern.

Other sources that can cause this typical "steam train" noise are ADSL modems and related devices, such as Wifi hotspots and cable modems.

Good luck!

Bart - ON4CCU
Logged
M0ARM
Member

Posts: 18




Ignore
« Reply #5 on: September 11, 2008, 12:24:11 PM »

Hi Bart,

Thanks for replying, I've eliminated everything within my house now, having switched the power off to the house and running the rig from the battery. The source of the problem has to be external which makes it a bit harder to trace.

If I manage to find the source I'll post my findings. Thanks to everyone who've posted for helping.

73
Les, M0ARM
Logged
N1UK
Member

Posts: 2203




Ignore
« Reply #6 on: September 14, 2008, 07:09:21 AM »

Maybe it is time to get out there with a portable rx and directional antenna.

If the noise is local, coming in on ground wave and can be picked up on a smallish sense antenna as strongly as on your main antenna, then you could have good luck with something like the MFJ-1026. Something to take a look at


Mark N1UK G3ZZM
Logged
K9PU
Member

Posts: 67




Ignore
« Reply #7 on: September 25, 2008, 02:26:00 PM »

cell phone charger?
Logged
K9PU
Member

Posts: 67




Ignore
« Reply #8 on: September 25, 2008, 02:31:47 PM »

Load your p/s with a resistor, moderate size, suitable power.  Should change your p/s control loop, if it changes your noise pattern on your rig, likely it's your p/s making the noise.
Logged
M0ARM
Member

Posts: 18




Ignore
« Reply #9 on: September 25, 2008, 09:06:29 PM »

No joy yet, mainly because I haven't managed to source an old AM receiver and been busy with other matters; however, as mentioned previously the noise isn't emitted from within my house (see my last post), it has to be coming from a neighbours house and there are only 6 houses in my street and not another one for 2 miles! My next plan is to have a chat with my neighbours either side to see if they can help out which shouldn't be too bad as I'm not causing them any breakthrough when I transmit. So, when I do get the noise, I can just pop by and see if they've recently switched anything on, or have timer-based equipment that switches on about the same time as the noise starts.

Les.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!