Use twisted pairs and DO NOT UNBALLANCE the grounds. Make
everything as symmetrical as possible.
Close ALL loop areas.
- Robert -
On Mon, 29 Aug 2005 06:45:06 +0200
"Amund Westin" wrote:
> Many analog telephones are susceptible to radiated
> fields. It's easy to
> observe audibl
Amund
The common solution to this problem is to wind about seven turns of the
telephone cable on to a large ferrite ring of about 75mm diameter. Not very
elegant, but it works over wide frequency range and down to at least 27 MHz.
Keep the ferrite close to the phone and do not overlap the turns.
[mailto:neve...@comcast.net]
Sent: Tuesday, August 30, 2005 11:59 PM
To: emc-p...@ieee.org
Subject: Re: Analog telephone - RF field susceptible
A couple of pointers:
Automatic Gain Control circuis (typuically in the phone chip) can be very
susceptible - essentially they change gain with
neve...@comcast.net wrote (in
<083120050359.15859.43152B06000C80073DF32206999735CECE020A900A02@comc
ast.net>) about 'Analog telephone - RF field susceptible', on Wed, 31
Aug 2005:
>Electret microphones, actually a transistor in the mic, can also be
>susceptible. The handset cable picks up t
A couple of pointers:
Automatic Gain Control circuis (typuically in the phone chip) can be very
susceptible - essentially they change gain with the 1 kHz rythm from the
applied RF field. Decouple/filter them and as Robert pointed out - keep small
loop areas on the PCB.
Electret microphones, act
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