[clug] linux Digest, Vol 92, Issue 62

Bob Edwards bob at cs.anu.edu.au
Thu Sep 2 07:50:09 MDT 2010

On 02/09/10 23:32, Bob Edwards wrote:
> On 02/09/10 20:32, Conrad Canterford wrote:
>> On Thu, 2010-09-02 at 19:17 +1000, Mike Carden wrote:
>>> And I have no idea what any of this might have to do with Bob's radio
>>> reception. I've been waiting for one of this list's radio amateurs to
>>> chime in with advice for Bob.
>> Perhaps someone using Broadband-over-powerline in a nearby house? I
>> didn't think ACTEW-AGL were playing with that, but I'm not sure. Another
>> possibility could be a neighbour who has installed a powerline-LAN
>> system. The stuff I've read strongly suggests that both these (closely
>> related) technologies are prone to splattering RF all over the place. It
>> might also be possible if Bob is using a mains-connected radio that
>> these types of signals might be entering the radio via the power cables.
>> I will freely admit to just guessing, however. I have recently
>> re-acquired my amateur licence, but that was on the basis of having held
>> one 20 years ago, not on the basis of current knowledge. My knowledge is
>> therefore quite rusty, and we all know rust is not conducive to a good
>> signal-noise ratio.
>> Conrad
> So, thanks everyone for all the tips etc.
> The interference on my AM radio(s) (3 mains powered and one battery)
> continues on. I have turned off many mains devices but the interference
> remains. The interference appears to be localised to my house (drops
> off quite rapidly outside the house). There is a 0.4Hz (12 cycles in
> 30 seconds) "beat" (or maybe pulsing) to the interference.
> I have tried unplugging my Naked ADSL2+ link from the modem/router.
> No difference. I can't really isolate it any further - it goes
> directly to the incoming subscriber line point.
> I am currently wondering if I may have some sort of weird ground loop
> or similar (maybe my earth stake connection is faulty). The hunt
> continues. If anyone has a directional radio finder that works in
> the MW band, I would be interested in talking to you.
> Cheers,
> Bob Edwards (who is still tempted to install win32codecs... but hasn't
> succumbed - yet)

I wrote too soon. I have (finally) traced the source of the noise. I
still had a gigabit switch in my "hub room" (cupboard under the stairs)
but in these days of energy savings, I don't actually need to use it
and so hadn't noticed that it had stopped working.

(my ADSL2+ modem/router/VoIP/switch/WAP device connects directly to the
only machines I care about enough to keep on 24x7).

The switching supply plug-pack had died and was restarting (approx.
every 2.5 secs, going by the LEDs). The switch was almost powering up 
and then off again. Lots of cabling still connected to the switch and
radiating out all over the house (mostly unterminated) = lots of little
antenna for radiating out the noise.

So, I can now listen to ABC local radio again on my trusty clock radio

I still hope that ABC will either (or both) transmit local radio on FM
and/or use open-standards codecs for their Internet radio feed.

Thanks again everyone for all your help.

Bob Edwards (feeling somewhat silly).

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