Re: Analog telephone - RF field susceptible

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

RE: Analog telephone - RF field susceptible

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.

RE: Analog telephone - RF field susceptible

[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

Re: Analog telephone - RF field susceptible

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

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 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