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Cell phone causes interference to audio chain?

T

Turntable

About five minutes ago, watching fox news, I heard the all-too-familiar sound a cell phone makes (bippidy-biiiiip) when placed close to a badly shielded audio cable or amplifier circuit.

Someone should tell these people to keep thier phones either turned off, or away from the equipment.

<P ID="signature">______________
"...How can you be deaf, with ears like that??"</P>
 
PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

> ... cell phone makes (bippidy-biiiiip) when placed close to
> a badly shielded audio cable or amplifier circuit.

The shielding necessary to keep out 870/1800 MHz energy is
different than that necessary to keep out line noise and
any associated 60/120 Hz 'hum'.

Few customers would be willing to pay for chassis, the screening
and metal work (gaskets, tight-fitting metalwork) required to keep
out close-by RF fields, so, we end up with gear that is susceptable
to strong, nearby RF energy from radiators like a cellular or PCS
telephones.

Even today's Blackberries and 2-way pagers 'acknowldege' a transmission
or 'page' from the system, so there is no escaping some of these
'hazards'.

Regards, _Jim
 
Re: PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

Hi, Jim...

Just to make a few corrections...

My reference to bad shielding was not intended to fault the engineering of the affected system and equipment, perhaps I should have said "as occurs with cheap devices such as portable and clock radios with RF susceptible amplifier stages"

The point of my post was to remind people to restrict the use of cell/pcs/whatever you want to call them, mobile phones I guess, in a studio or production environment, especially live on air, to either shut them off or keep them at least a foot away from the equipment.

It is my belief that anyone who has a job that includes the operation of broadcast equipment should at least understand the basics of how the equipment works on a functional level, much like a person who drives a car should understand how to change a flat tire and know when the engine is overheating or when the brake pads need replacement.

I'm curious to know if the blips were recorded into "Hannity and Colmes" during the live broadcast or if it happened later. I'll know when they rebroadcast the show in a few minutes.

-A



> > ... cell phone makes (bippidy-biiiiip) when placed close
> to
> > a badly shielded audio cable or amplifier circuit.
>
> The shielding necessary to keep out 870/1800 MHz energy is
> different than that necessary to keep out line noise and
> any associated 60/120 Hz 'hum'.
>
> Few customers would be willing to pay for chassis, the
> screening
> and metal work (gaskets, tight-fitting metalwork) required
> to keep
> out close-by RF fields, so, we end up with gear that is
> susceptable
> to strong, nearby RF energy from radiators like a cellular
> or PCS
> telephones.
>
> Even today's Blackberries and 2-way pagers 'acknowldege' a
> transmission
> or 'page' from the system, so there is no escaping some of
> these
> 'hazards'.
>
> Regards, _Jim
>
<P ID="signature">______________
"...How can you be deaf, with ears like that??"</P>
 
You ought to hear what they do to a Neuman TLM-103 condensor mic from about a foot or two away. YIKES. I had to take a hosts phone away during a show once, for fear he'd destroy the mic...

fmnostatic


> About five minutes ago, watching fox news, I heard the
> all-too-familiar sound a cell phone makes (bippidy-biiiiip)
> when placed close to a badly shielded audio cable or
> amplifier circuit.
>
> Someone should tell these people to keep thier phones either
> turned off, or away from the equipment.
>
 
> You ought to hear what they do to a Neuman TLM-103 condensor
> mic from about a foot or two away. YIKES. I had to take a
> hosts phone away during a show once, for fear he'd destroy
> the mic...
>
> fmnostatic

Anyone who brings a cell phone into the studio during their show should be shot.
>
>
> > About five minutes ago, watching fox news, I heard the
> > all-too-familiar sound a cell phone makes
> (bippidy-biiiiip)
> > when placed close to a badly shielded audio cable or
> > amplifier circuit.
> >
> > Someone should tell these people to keep thier phones
> either
> > turned off, or away from the equipment.
> >
>
 
Re: PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

I have noticed Blackberries and Bluetooth devices are especially troublesome.

Much more then 800 MHz cell phones.<P ID="signature">______________
Never hold a cat and a dustbuster at the same time.</P>
 
This only happens with GSM and Nextel phones. Sprint and Verizon use CDMA which does not cause this...



> About five minutes ago, watching fox news, I heard the
> all-too-familiar sound a cell phone makes (bippidy-biiiiip)
> when placed close to a badly shielded audio cable or
> amplifier circuit.
>
> Someone should tell these people to keep thier phones either
> turned off, or away from the equipment.
>
 
Re: PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

> I have noticed Blackberries and Bluetooth devices are
> especially troublesome.
>
> Much more then 800 MHz cell phones.
>
When you hear that on your monitor feed, is it going out over the air too?
 
Re: PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

> > I have noticed Blackberries and Bluetooth devices are
> > especially troublesome.
> >
> > Much more then 800 MHz cell phones.
> >
> When you hear that on your monitor feed, is it going out
> over the air too?
>

Good question. I'm not longer around air studios, so I can't answer. I hear it on the car radio and on the PC.

<P ID="signature">______________
Never hold a cat and a dustbuster at the same time.</P>
 
Re: PN junctions and Schottky junctions rectify, causing a change in the quiescant (mid point bias) state

> I have noticed Blackberries and Bluetooth devices are
> especially troublesome.
>
> Much more then 800 MHz cell phones.

The extra-loud "ticking" sound you hear from the Nextel phones (in comparison with the even more annoying barely audible ticking of plain old TDMA/GSM) is the Direct Connect paging system. It uses it's own signal, connecting to it's own antennas on the towers.

If you have company phones with this feature, it is possable to have the service removed from the account on the phone which actually does turn off that part of the radio in the phone. :)

I have Direct Connect on my Blackberry 7520, since I dont come into physical contact with our production machines on a regular basis, and the NOC where our production machines are doesnt allow cellphones (and especially flash photography) anywhere near the floor (and we're all-digital audio anyways) so it's not a problem. Not like a cell would even work in a room with hundreds of racks of computers and network hardware in it. ;)
 
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