[TowerTalk] Re: What was his name BUT HIS LEGACY LIVES ON!!!

[Ian White, G3SEK]

The "Muntz" thread is straying a bit far from towers, but TowerTalkians
do get involved in RFI issues, so...


K7GCO wrote:
> 
> This cutting of cost is exactly the reason that the public can't use their
> cell phones or other radio equipment in hospitals these days.  I was in a
> local hospital and keyed up a 440 HT on low power and set off the hospitals
> fire alarm, talk about poor quality!  

Sure, that's poor quality, but we find "Muntz" fire alarms everywhere.
It has nothing to do with the reasons for keeping RF away from
healthcare electronics.

>HP and the other major suppliers of
> critical care equipment have cut costs by taking out the very parts that
> would keep this equipment working in most environments.  Meaning bypass
> caps, ferrite beads and things to keep RF out of the device. 

Do you seriously believe that, just to save a few bucks, suppliers of
critical healthcare electronics would lay themselves open to massive
criminal negligence claims - in the USA, of all places? Sorry, that's
nonsense.

Part of the truth is that, no matter how hard they try, they can't make
them sufficiently RF-proof. Typical scenario: high-impedance sensor
inputs measuring millivolts or nanoamps, long leads with practical
limitations on shielding, no RF grounds available, no control over
correct installation by nurses - and above all, no control over external
RF fields. 

Far from skimping on components, modern healthcare equipment is
extensively RFI-protected (but note I didn't say "RFI-*proofed*" -
nothing ever is). Most computer-controlled equipment has extra routines
to carry out regular internal "health checks" on itself. But how can
they be absolutely sure that the control system isn't being interfered
with too? They can't.

An even larger part of the truth is that if hospitals fail to ban
transmitters wherever medical electronics are in use, they too lay
themselves open to negligence claims. Remember, it doesn't have to be
true... just claimed. That's the main reason why transmitter bans exist.
Also, the ban often extends to other areas in the hope of catching
transmitter users before they get into the vulnerable areas.

The main culprits for high RF field strengths in hospital environments
are the two-way VHF/UHF radios used by emergency services and the
hospital's own maintenance staff. If not controlled, these can appear
anywhere, at any time, and very close to the wired-up patients. Fixed
installations like base stations and RF diathermy equipment are much
easier to monitor. 

Many hospitals have now installed squawk-boxes which detect RF and play
a voice message telling people to switch their radios off. All part of
demonstrating that they've done their best to control the problem.

> I have had
> some hospitals say you can't carry a pager in their hospital because the 1st
> or 2nd oscillator may interfere with their critical care equipment!  You
> know how little RF is radiated from these oscillators, not much.
> 
In other words, you have the technical background to know that the pager
story is *not* part of the truth.


73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                          'In Practice' columnist for RadCom (RSGB)
                           http://www.ifwtech.com/g3sek

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