interference sources
 

Hi folks, just in the last two weeks I've had some resets of a freeview box,
and decided to listen around the bands to see if it was being caused by
some odd mains borne stuff. It seems it is.
The offending signal is easily detected 24 hours as a kind of arcing noise
every 30 seconds or so. My thoughts are maybe..
Charger trying to see if it needs to charge, plug in air freshener, or
something else. I've tried to locate it with a portable radio as the signal
on medium wave is horrendously loud even on a portable.
Results are inconclusive. Not being on the best of terms with the property
implicated here, I am trying to find some way to approach them and knowing
if there is some device like this might be one of the ways. I'm thinking
along the lines of it might be going to catch fire or similar.
I'd have thought if it is affecting me, its affecting them.

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!

interference sources
 

On Mon, 27 Apr 2009 09:08:48 GMT, "Brian Gaff"
wrote:

Hi folks, just in the last two weeks I've had some resets of a freeview box,
and decided to listen around the bands to see if it was being caused by
some odd mains borne stuff. It seems it is.
The offending signal is easily detected 24 hours as a kind of arcing noise
every 30 seconds or so. My thoughts are maybe..
Charger trying to see if it needs to charge, plug in air freshener, or
something else. I've tried to locate it with a portable radio as the signal
on medium wave is horrendously loud even on a portable.
Results are inconclusive. Not being on the best of terms with the property
implicated here, I am trying to find some way to approach them and knowing
if there is some device like this might be one of the ways. I'm thinking
along the lines of it might be going to catch fire or similar.
I'd have thought if it is affecting me, its affecting them.

Brian

When you describe the sound, do you mean it is something you can hear
without using a radio? If so it should be easy enough to find.

If not, the medium wave radio can be used as a direction finder
(assuming it uses a ferrite rod antenna). Orient it until the
interference is at a minimum - the rod will then be pointing directly
at the source.

Sounds like the problem could be something like a thermostat, although
the size of the signal makes it sound like the load is inductive
rather than resistive. Whatever, it is quite likely that the problem
will go away soon because I am betting that switch is well on its way
to total failure.

d

interference sources
 

"Brian Gaff"

Hi folks, just in the last two weeks I've had some resets of a freeview
box, and decided to listen around the bands to see if it was being caused
by some odd mains borne stuff. It seems it is.
The offending signal is easily detected 24 hours as a kind of arcing noise
every 30 seconds or so. My thoughts are maybe..
Charger trying to see if it needs to charge, plug in air freshener, or
something else. I've tried to locate it with a portable radio as the
signal on medium wave is horrendously loud even on a portable.
Results are inconclusive. Not being on the best of terms with the property
implicated here, I am trying to find some way to approach them and
knowing if there is some device like this might be one of the ways. I'm
thinking along the lines of it might be going to catch fire or similar.
I'd have thought if it is affecting me, its affecting them.


** Might be a worn out fluoro tube trying to start itself up - that can
make one HELL of an RF burst in doing so.

The last time I tracked down such an evil RFI source, it turned out to be a
modest size, red neon sign in the window of a pharmacist shop almost 100
metres away.

The noise easily penetrated audio gear on my test bench as well as any sort
of AM radio - but luckily not broadcast FM or TV signals.



..... Phil

interference sources
 

That was what I meant, its audible on medium wave, but the direction nulling
only seems to locate it in our block not much else. I've had all my stuff
out, and the neighbour one way seems clear, but its just like you might
hear from an AC arc, but in a short say up to ten seconds burst, then thirty
seconds of nothing, then its back again, and its very loud on medium, even
worse on long wave and detectable on the fm band as well.
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Don Pearce" wrote in message
news:49f5768a.924662281@localhost...
On Mon, 27 Apr 2009 09:08:48 GMT, "Brian Gaff"
wrote:

Hi folks, just in the last two weeks I've had some resets of a freeview
box,
and decided to listen around the bands to see if it was being caused by
some odd mains borne stuff. It seems it is.
The offending signal is easily detected 24 hours as a kind of arcing noise
every 30 seconds or so. My thoughts are maybe..
Charger trying to see if it needs to charge, plug in air freshener, or
something else. I've tried to locate it with a portable radio as the
signal
on medium wave is horrendously loud even on a portable.
Results are inconclusive. Not being on the best of terms with the property
implicated here, I am trying to find some way to approach them and
knowing
if there is some device like this might be one of the ways. I'm thinking
along the lines of it might be going to catch fire or similar.
I'd have thought if it is affecting me, its affecting them.

Brian

When you describe the sound, do you mean it is something you can hear
without using a radio? If so it should be easy enough to find.

If not, the medium wave radio can be used as a direction finder
(assuming it uses a ferrite rod antenna). Orient it until the
interference is at a minimum - the rod will then be pointing directly
at the source.

Sounds like the problem could be something like a thermostat, although
the size of the signal makes it sound like the load is inductive
rather than resistive. Whatever, it is quite likely that the problem
will go away soon because I am betting that switch is well on its way
to total failure.

d

interference sources
 

On Mon, 27 Apr 2009 18:42:15 GMT, "Brian Gaff"
wrote:

That was what I meant, its audible on medium wave, but the direction nulling
only seems to locate it in our block not much else. I've had all my stuff
out, and the neighbour one way seems clear, but its just like you might
hear from an AC arc, but in a short say up to ten seconds burst, then thirty
seconds of nothing, then its back again, and its very loud on medium, even
worse on long wave and detectable on the fm band as well.
Brian

Don't suppose you could record it and post it somewhere? Ten seconds
is a long time for a switch to be arcing - could it perhaps be a bad
DC motor brush?

d

interference sources
 

In message 49f7fe24.959375234@localhost, Don Pearce
writes
On Mon, 27 Apr 2009 18:42:15 GMT, "Brian Gaff"
wrote:

That was what I meant, its audible on medium wave, but the direction nulling
only seems to locate it in our block not much else. I've had all my stuff
out, and the neighbour one way seems clear, but its just like you might
hear from an AC arc, but in a short say up to ten seconds burst, then thirty
seconds of nothing, then its back again, and its very loud on medium, even
worse on long wave and detectable on the fm band as well.
Brian

Don't suppose you could record it and post it somewhere? Ten seconds
is a long time for a switch to be arcing - could it perhaps be a bad
DC motor brush?

10 seconds is typical of interference from an oil central heating
boiler.

In my first boiler, the ignitor was a hot wire coil, but my second and
third (present) boilers have both had sparkplug ignitors. These spark
away merrily until the oil vapour ignites - which usually takes about 10
seconds. Marconi (whose birthday it is today) would be envious of how
far these can radiate.

If the ignition fails, the sparking will continue for up to 30 seconds,
after which the system gives up (and probably locks up until a re-set is
performed).

I found that my previous boiler caused annoying interference to the
amateur 28MHz band (on which I was active at the time), and was also
distinctly audible over a wide range of frequencies. At one of the
annual services, I mentioned it to the service guy. He immediately
fitted a purpose-made 5k resistive suppressor (it seemed that he just
happened to have about his person), and that almost totally eliminated
any sign of the interference. My present boiler is 'liveable -with', and
I haven't had a suppresser fitted (yet).
--
Ian

interference sources
 

On Mon, 27 Apr 2009 20:20:54 +0100, Ian Jackson
wrote:

In message 49f7fe24.959375234@localhost, Don Pearce
writes
On Mon, 27 Apr 2009 18:42:15 GMT, "Brian Gaff"
wrote:

That was what I meant, its audible on medium wave, but the direction nulling
only seems to locate it in our block not much else. I've had all my stuff
out, and the neighbour one way seems clear, but its just like you might
hear from an AC arc, but in a short say up to ten seconds burst, then thirty
seconds of nothing, then its back again, and its very loud on medium, even
worse on long wave and detectable on the fm band as well.
Brian

Don't suppose you could record it and post it somewhere? Ten seconds
is a long time for a switch to be arcing - could it perhaps be a bad
DC motor brush?

10 seconds is typical of interference from an oil central heating
boiler.

In my first boiler, the ignitor was a hot wire coil, but my second and
third (present) boilers have both had sparkplug ignitors. These spark
away merrily until the oil vapour ignites - which usually takes about 10
seconds. Marconi (whose birthday it is today) would be envious of how
far these can radiate.

If the ignition fails, the sparking will continue for up to 30 seconds,
after which the system gives up (and probably locks up until a re-set is
performed).

I found that my previous boiler caused annoying interference to the
amateur 28MHz band (on which I was active at the time), and was also
distinctly audible over a wide range of frequencies. At one of the
annual services, I mentioned it to the service guy. He immediately
fitted a purpose-made 5k resistive suppressor (it seemed that he just
happened to have about his person), and that almost totally eliminated
any sign of the interference. My present boiler is 'liveable -with', and
I haven't had a suppresser fitted (yet).

But isn't that a series of splats, rather then a continuous arc? I
know how my boiler behaves when it is firing up, and it is "tick tick
tick, whoomph".

d

interference sources
 

Brian Gaff wrote:

Hi folks, just in the last two weeks I've had some resets of a freeview box,
and decided to listen around the bands to see if it was being caused by
some odd mains borne stuff. It seems it is.
The offending signal is easily detected 24 hours as a kind of arcing noise
every 30 seconds or so.

Aubible directly or through the amplification ? Does it come from the box or a
wall wart etc ?

Graham

interference sources
 

In message 49f90619.961412546@localhost, Don Pearce
writes


But isn't that a series of splats, rather then a continuous arc? I
know how my boiler behaves when it is firing up, and it is "tick tick
tick, whoomph".

No. Unless I'm completely mistaken, it's a continuous arc - well,
probably a 50 or 100Hz arc. I think the plug's driven by the mains
(stepped up). Both sparkplug boilers were like that.
--
Ian

interference sources
 

"Ian Jackson" wrote in message
...
In message 49f90619.961412546@localhost, Don Pearce
writes


But isn't that a series of splats, rather then a continuous arc? I
know how my boiler behaves when it is firing up, and it is "tick tick
tick, whoomph".

No. Unless I'm completely mistaken, it's a continuous arc - well,
probably a 50 or 100Hz arc. I think the plug's driven by the mains
(stepped up). Both sparkplug boilers were like that.
--

If it's anything like my boiler then the sparkplug is simply connected to
the high voltage (around 2kV) secondary of a mains transformer. This
transformer is energised as soon as the blower motor starts, though the oil
tap is not turned until around 15 seconds later. The transformer is switched
off as soon as light from the flame is detected by a light-dependant
resistor or, if no light is detected within 30 sec, the whole system trips
out until it is manually reset.

David.