Getting rid of mobile phone galloping ghost from audio circuits.
 

On 22/11/2015 10:41, Dave Plowman (News) wrote:
In article ,
RJH wrote:
You seem to be very unlucky or live in an odd area or have odd
equipment if you're picking up interference on a pickup or mic?

My laptop reports some 20 Wi-Fi signals at usable level round here,
but no problems on the Hi-Fi here. Or with mobile phones which I'd
guess are as common as the above.

Obviously, roaming the radio waves for distant and obscure stuff might
be a different matter.


FWIW, my iPhone's 'polling' (not sure how, what or why) can be heard on
my hifi, FM radios, and work's PA systems in lecture halls. It's a sort
of chirping, and lasts about 10s.

Yes - that does happen, but moving the phone away a few feet should sort
it.

It used to happen frequently on live radio etc broadcasts despite those in
the studio being told to turn off any phones. Rather than go to silent.
It's far less common these days, so something has changed.


It was worse with analogue phones IIRC. Used to get it a lot on RTB
feeds on OBs

--
Graeme Wall
This account not read, substitute trains for rail.

Getting rid of mobile phone galloping ghost from audio circuits.
 

In article ,
Graeme Wall wrote:
Yes - that does happen, but moving the phone away a few feet should
sort it.

It used to happen frequently on live radio etc broadcasts despite
those in the studio being told to turn off any phones. Rather than go
to silent. It's far less common these days, so something has changed.


It was worse with analogue phones IIRC. Used to get it a lot on RTB
feeds on OBs

You've got me confused now. ;-) My first phone - 1992 - was a Technophone
analogue, and that didn't induce the chirping noise. It was replaced (when
the service stopped) with a Nokia, and that did. I still have it, and it
still works, so I assume was on the current digital system?

I do remember it causing a problem on a Calrec analogue sound desk while
clipped to my waistband. Moving it a few feet away sorted it.

--
*Seen it all, done it all, can't remember most of it*

Dave Plowman London SW
To e-mail, change noise into sound.

Getting rid of mobile phone galloping ghost from audio circuits.
 

Hmm well its mostly turntable and microphones into a mixer. It is being
domestic unballanced switchable impedence stuff, so probably not designed
for the problem as the unit was built in 1979 when we did not have mobile
phones. The stuff in throught the two speakers is coming in from next
door, who probably have the sofa up gainst the same wall as my speakers lie
against.
I also have a sub woofer which seems to alsopick it up with no leads
attached at all, so probably the leads inside the box on the amp are doing
the dirty.
I was interested in your comment about the cut of frequency of
capacitorrs, I am a bit out of touch, and most of the ones I fitted before
were of the simi transparent silver innards type.
Brian

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"Jim Lesurf" wrote in message
...
Top posted because it's Brian.

Looping speaker leads though ferrite clip-on block may fix that entry
route. You may find something similar plus more careful earthing or/and a
filtered mains block would help.

You'd need to say more about the details of your "Low level circuits" for
me to give more specific suggestions. e.g. a 100pF rf cap shunt may help,
but larger caps would be a problem for some inputs like "turntables"
(sic).
Maybe you've not tried caps that remain caps at UHF and above?

Diodes might simply make it worse by spraying the energy across into other
frequency bands and pulling more current.

Jim


In article , Brian-Gaff
wrote:
With the proliferisation of mobile devices running on the mobile phone
network its getting increasingly a annoying to listen to things on a
good old fashioned or even new fangled radio, without the noise
occurring at some point. Even from next door one can get it getting into
the audio chain. Anyone know if there is an easy way to stop it. In the
old days a few capacitors got rid of Radio China or Vatican City, but
due to the high frequencies of the phones and the spiky nature of the
handshaking noise, this seems not to work much. What is the mechanism.
they cannot be tuned to the r frequencies, so is it just straight diode
type detection due to the huge signal level?

Low level circuits like turntables, microphone inputs etc, seem to be
the worst, but I've also proved my Denon is picking it up from its
speaker cables.

Brian

--
Please use the address on the audiomisc page if you wish to email me.
Electronics
http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Getting rid of mobile phone galloping ghost from audio circuits.
 

Back in the heyday of hi fi, I had a very nice Tandberg amplifirer with a
torroidal transformer and lots of inputs and outputs, unfortunately, it was
based on din sockets and their parameters, but it seemed to work fine to
me, until that is during a quiet bit in a particualarly evocotive bit of
film music, I head Sk cs 1 to brown leader repeated sevveral times then a
one sided conversation about a problem on a boat.
Try as I might with capacitors ferrites mains filters on everything every
night in the summer this q guy would be there at some point with cryptic
conversations.
Eventually, I unplugeed every input and found that the only way to not get
it was to plug in the phones and remove the speaker plugs, bot of them.
As I say nothing worked. Asked Tandberg and they said basically their
systems all passed the radio interference specs so it has to be the
transmitter. I talked to at the time one of the gov deps that policed this,
they told me it was allocated to the local sea cadets and they would check
and get back to me. They of course said in about a month later that all the
installations passed to test.
So there you go, nobodys fault but it still happened, I lived with this
for about a year and then got a local shop to bring around a Pioneer
recever with more capapbilities than the tandberg to check at the allotted
wiching our and silence. No problems.
I gave him the tandberg and got a nice cheap price on th pioneer, That
thing lasterd for years. The only issue it had was short lived dial lights
in a pretty blue, but he gave me a handful of bulbs and though they were a
pain to get at we kept it going for years. A transistor went noisy in the
turntable circuit, a quick trip to get an equiv from tandy sorted that out.
Then a noisy electrolytic in the power amp. The next issue was the dil
string broke which was the staart of its demise many many years later I have
to say.
Now I've had a Denon receiver for many years and its only issue is that I
can no longer see the digital frequency and I had to clean the speaker relay
contacts a couple of times.
Its gothuge fets in it and sounds better as well. Sloight hum now but its
probably electrolytic dry out.
Brian

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From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
"Phil Allison" wrote in message
...
Jim Lesurf wrote:



The Armstrong 626 I had refurbished recently was an early version. These
were prone to clicks, etc. The first impression might be that they were
getting in via the mains.



** Nearly everyone imagines that pops and clicks heard through stereo
systems as appliances are switched on or off MUST arrive conducted via mains
wiring.
But this is only rarely the case, iron transformers and other PSU components
do a thorough job of blocking RF energy arriving that way.

The source of the energy is the arc that briefly forms when a mains switch
opens - or closes and then bounces. Much like a spark transmitter, RF energy
from the arc is then radiated by the active and neutral wiring carrying
current to and from the switch.

There can be a fair bit of power involved too, particularly when the load is
inductive - like a fridge compressor or washing machine motor. The arc's
energy's spectrum spreads from audio frequencies right up to the top of the
VHF band interfering with radio and TV reception too.

So the actual path is through the air and into audio signal cables (ie RCA,
microphone, DIN and speaker leads) where the RF energy can then enter
directly into sensitive audio circuitry. In the case of speaker leads, it
enters via the NFB loops in output stages.

With well screened cables, the bursts of RF energy are picked up and travel
on the shields, dissipating harmlessly IF these are grounded to each chassis
right where they enter and leave equipment. Most makers know this while some
appear not to and so allow RF to come right in the door.

Many domestic appliances have RF suppression components across their
switches and this IS the best solution - but some do not plus the components
can fail due to age.

IME adding EXTERNAL (ie plug in) suppression devices to offending appliances
rarely helps and adding one to your stereo system never does.


.... Phil

Getting rid of mobile phone galloping ghost from audio circuits.
 

The clue was what you found re speakers. Chances are ferrite blocks on the
speaker leads would have helped.

Jim

In article , Brian-Gaff
wrote:
Try as I might with capacitors ferrites mains filters on everything
every night in the summer this q guy would be there at some point with
cryptic conversations. Eventually, I unplugeed every input and found
that the only way to not get it was to plug in the phones and remove
the speaker plugs, bot of them.

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Getting rid of mobile phone galloping ghost from audio circuits.
 

No I remember having some from Tandy at that time and no difference. I could
vary it a bit by routing the cables of course, but also if I then placed a
hand on any connected item even if earthed to the mains, I could change the
level of it.

I suspect that the transmitter in question had harmonics oll over the place
and as I'm not far from the Thames as the rf flies, the whole wiring and
house was an aerial, and it just happened to be a coincidence that thee amp
had poor rejection at one of these.
The fact that the pioneer was fine seems to suggest there is better
screening less earth currents and possible better filtering.

It had little coils in the output stages, well quite big ones actually.
Nothing like that in the Tandberg just lots of heatsink.
Brian

--
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
"Jim Lesurf" wrote in message
...
The clue was what you found re speakers. Chances are ferrite blocks on the
speaker leads would have helped.

Jim

In article , Brian-Gaff
wrote:
Try as I might with capacitors ferrites mains filters on everything
every night in the summer this q guy would be there at some point with
cryptic conversations. Eventually, I unplugeed every input and found
that the only way to not get it was to plug in the phones and remove
the speaker plugs, bot of them.

--
Please use the address on the audiomisc page if you wish to email me.
Electronics
http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

Getting rid of mobile phone galloping ghost from audio circuits.
 

The clue is still the fact that the problem evaporated when you
disconnected the speaker cables.

That implies that the injection was either

1) common mode on the speaker leads. If so using a suitably ferrite block
in common mode near the amp sockets should reduce it.

2) Differential mode - probably because the speaker coils were picking it
up. In which case you might need to apply a shut cap near the speakers.
(potentially more problematic for the amp, of course.) And/Or a
differential ferrite near the speakers.

Jim

In article , Brian-Gaff
wrote:
No I remember having some from Tandy at that time and no difference. I
could vary it a bit by routing the cables of course, but also if I then
placed a hand on any connected item even if earthed to the mains, I
could change the level of it.

I suspect that the transmitter in question had harmonics oll over the
place and as I'm not far from the Thames as the rf flies, the whole
wiring and house was an aerial, and it just happened to be a coincidence
that thee amp had poor rejection at one of these. The fact that the
pioneer was fine seems to suggest there is better screening less earth
currents and possible better filtering.

It had little coils in the output stages, well quite big ones actually.
Nothing like that in the Tandberg just lots of heatsink. Brian

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html