AM Radio Signal Creates Noise on Medical Devices

Close down the transmitter.
Either the transmitter or the equiment in question doesn't meed the relevant EMI directive.
Del

Del the Cat is probably on the right track. What country are you in?

USA has the FCC. Other countrries may have similar regulatory bodies.

If no fruit from this pursuit, perhaps a Faraday Shield?

Try to lift the transmitter above 5 to 6 feet than the height of that hospital or from the present height(i.e from its actual position) Well this will be suitable if the concerned antenna produces waves that are less distorted in that particular direction..... this is just a suggestion but might work if planned over......

Make sure that the wire shields are earthed at one point only, grounding system resistance is normal and equipment frames are connected to ground bus with short path to ground.

The country is Turkey and when the stations was built there was no hospital. Then they built the hospital. The station works within legal power limits but not the devices in the hospital. So there is no solution such as shutting down the station or moving the hospital.

Making the Faraday cage to every device holding room with conventional copper is crazily costly while my idea was to use the conductive EM paintings together with ferrite beads to cut the high frequency components from mains together with reliable groundings. If necessary local isolation of devices could be another solution with silver fabrics is the last solution.

Once again you've hit the nail on the head AH. I've given both of your replies here a GA.

The difficulty here will be identifying the interference entry mode. Getting the assistance of a Ham operator is an exquisite suggestion. The one thing a Ham operator may notice at the AM station transmitter is that the broadcasting antenna may have a reflecting element missing, thus making the pattern of the energy distribution (EIRP) [Effective Isotropic Radiated Power] too high at the local ground level in the direction of the hospital.

It is also not unheard of that the RF sensitive diagnostic equipment of a hospital must be placed inside a Faraday cage to be useful.

For the hospital's sake I hope that the path is coming from the coupling into the power grid wires. Some strategically placed power line filters for the diagnostic equipment should block that path.

A good reply.

I like to draw your attention towards some more points:

1. All the power entree points must have In-Line Filters with earth as short as possible.

2. In one of hospitals [Children Hospital donated by Japan] in Islamabad the same roblem was seen & they installed all the sensitive Diagonostic appliances in Faraday Cages to rsolve the problem

what frequency does the station transmit on ??

as all AH has said you need to establish how am interference is entering system

if it were me i would fit suppresion to the mains supply coming into the building and tehn at all the fuse boards thus eliminating mains borne interference.

then filters on the mains outlet to the equipment.

it may even be possible to place a chicken wire type of mesh to the out side of the hosptial on the wall facing the transmitter then earth the mesh

by the way could you tell us what the AM transmitters frequency is this may help

if it has a set frequency it will be possible to build a filter that will stop selective frequencies

My point of it being an advantage if the path is the power main is that the power entering the instrument can be filtered. This will be the most cost effective since the instrument filter will not require anywhere near the power handling capability of a hospital filter.

the type of filter i have in mind does not have to handle the power, it just shorts out the radio content

and by providing a short to earth for radio then all systems connected to the mains will also short out radio energy

by the way has any one ever mentioned that the way you compose sentences makes it difficult to understand ?

also as i understand the problem perhaps better the reason being the wiring in the hospital is acting like an Ariel. so the best approach would be as i suggested ie to create as many radio short circuits in the wiring as possible thus terminating the spurious signals being induced in the wiring

http://www.google.co.uk/search?q=mains+filter+design&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=bTeZTMWmC8yNjAfj-tTlDw

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CR4 Admin: Modified Post

Copyright Violation: Reduced copied text according to copyright law. Please see Section 13 of the CR4 FAQ about posting copyrighted material.

http://www.google.co.uk/search?q=supresion+of+am+radio+signals&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=gCiZTKW1D9S5jAfImbgk

http://www.google.co.uk/search?q=radio+suppression&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=1yiZTKOuA5a8jAeHhaQ2

http://www.google.co.uk/search?q=how+does+am+radio+interference+affect+equipment&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=LimZTN6FDsK4jAeAwIAc

http://www.google.co.uk/search?q=how+do+ferrite+rings+work&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=WimZTPTHLY_KjAfKnrnuDw

http://www.google.co.uk/search?q=AM++suppression&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=sSmZTN3YPJKTjAeQuKjaCA

This is called RFI, (Radio Frequency Interference) There are two methods you can use. One is called RF bypass, and each wire that enters the piece of equipment would have a small high voltage capacitor to ground. This would be .001 Uf, 1000 volts (or higher if the circuits carries a higher voltage).

The other is called RF blocking. This uses what are called ferrite beads and they are placed so the signal wire passes through the opening in the bead.

You can use both, a bead and a capacitor.

These links will help

http://www.google.ca/#hl=en&safe=off&q=%22bypass+capacitor%22+%2BRFI&aq=f&aqi=&aql=&oq=%22bypass+capacitor%22+%2BRFI&gs_rfai=&fp=923260c4f0af2f7a

http://www.google.ca/#hl=en&source=hp&q=%22ferrite+bead%22+%2BRFI&btnG=Google+Search&aq=f&aqi=&aql=&oq=%22ferrite+bead%22+%2BRFI&gs_rfai=&fp=5d1036a107ea2675

I'm reaching here, but it's worth a reach. All medical equipment here in the US, must meet SADMERC qualifications for use, but they all come with a caveat re; RFI. I work with this equipment, notably, power wheelchairs and scooters, as well as the equipment you are probably using in your surroundings. The equipment is supposed to be shielded to meet standards, but of late, I have clients that call in from Walmart, and other stores that use tracking systems in-store to follow products and report back to their home base for inventory control and theft control. The signals they use are probably on an AM frequency as it caused havoc with some of the equipment in the stores. They won't divulge this info. My very simple "repair" was to wrap aluminum foil around the control modules and other sensitive electronic devices and it cleared it up. It worked, and it ain't too hi-tech to warrant a raise, unless you can come up with a better description of what you did to mitigate the problem so it looks good to your super.

I like your approach: "My very simple "repair" was to wrap aluminum foil around the control modules and other sensitive electronic devices and it cleared it up.". I solved a similar problem at a semiconductor facility a few years ago using a similar approach. I used copper foil tape, and wrapped it around the leads to the sensors that were feeding data to the instrument exhibiting the interference (these leads are feeding the most sensitive circuits in the system). I grounded only one end of the tape. This reduced the interference by 20 dB V.

Of course, this would be awkward for something like an EKG, because 14 leads have to be connected, and more weight would make it harder to keep them in place. However, if an experiemnt proves that this will solve the problem, maybe the EKG manufacturer could propose a solution.

copper foil wallpaper on the outside of the walls.

If you do end up going the Faraday cage route it's worth pointing out that you can get RF shielding for windows too.

This is just one example selected for no particular reason:- http://www.lessemf.com/plastic.html

http://news.thomasnet.com/fullstory/Copper-Foil-transforms-any-room-into-Faraday-cage-459490

if you can get access to the steel work in the building bonding or linking them together a nd earthing them will help to stop the structure radiating the signal

But AM is very difficult to suppress

http://www.google.co.uk/search?q=suppresion+of+unwanted+am+signals&sourceid=ie7&rls=com.microsoft:en-gb:IE-SearchBox&ie=&oe=&rlz=1I7GGLT_en&redir_esc=&ei=nVmaTIj8IoW6jAfc-qn4Dw