View Full Version : Re: radio interference

Edmund Cramp
06-05-1997, 09:29 PM
Hi there Haroldo,

I haven't spoken to you for a while - how is everything in Brasil?

I've just been sent a copy of your email that you posted (attached below).
What is the nature of the problem and what tests have you done? I've
never had any reports of interference before and we conducted extensive
tests when the system was designed to prevent strong RF fields from causing

Are you seeing interference problems with any other equipment?

How far is the radio transmitter from the lab and what is the output power?

Do you only see the interference when the electrodes are connected to the
back-pack or is the interference present when the system is powered up
without any electrodes connected? I'm wondering if the problem is that the
signal is getting into the system through the subject/electrode interface
or is actually getting in through the MA-100 unit. We need to find out
where the signal is entering the system so that we can stop it.

Do you see any interference problems on the force plates? Do you see any
interference on the EMG channels when the MA-100 is not switched on? Yes
to either of these questions would suggest that the interfering signal is
entering the system through the Etherbox analog interface.

Edmund Cramp support@emgsrus.com
Motion Lab Systems http://www.emgsrus.com

> From: Jose Haroldo de A. Cavalcante - SARAH Hospital

> Subject: radio interference
> Date: Thursday, June 05, 1997 2:18 PM
> Dear all,
> We are facing a strong problem of radio-interference in our EMG
> equipment (Motion Systems MA-100), that is being caused by a
> FM commercial station which had the transmitter recently installed in a
> just a few hundred meters from our own building. The audio from this
> is mixed with the EMG signal, resulting in totally unusable data.
> We are looking for solutions, both from technical and legal points
> of view. Thank you in advance for your help,
> Jose Haroldo de A. Cavalcante
> Biomedical Engineer
> SARAH Hospital
> SMHS 501-cj. A
> 70.330-150
> Brasilia-DF
> e-mail: haroldo@lab01.sarah.br
> phone: 55-61-319-1440
> fax: 55-61-319-1448