back to article Ambulance radios don't like the rain

A Health and Safety report into the London Ambulance Service has raised concerns about its radio comms network and vehicle panic buttons. But a spokesman for LAS said all the problems had been fixed since the report came out. The investigation in March found ambulance crews often working without radios - especially in heavy …

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Silver badge

The Nature of Radio

Lots of radio kit doesn't work too well in buildings, and generally the higher the frequency, the worse it gets. It shouldn't be too surprising that a UHF radio suffers a bit with a few walls between it and the base station, especially if there are also other buildings in the vicinity to add their walls to the attentuating circumstances.

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Joke

Have they considered?

That they may just be holding it wrong?

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Jobs Horns

Simple solution :

Just don't use it when it's raining !

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Go

Who sold you that then?

The Airwave network operates at 380-400MHz and this should have much more 'punch' when it comes to in-building coverage than the commercial networks at 900, 1800 or 2200MHz however the network is planned and implemented at a specified minimum field strength that is part of the network SLA.

The baseline level for the network coverages is approximately 20dB above absolute minimum needed to make a call and provides good coverage to fixed installations in vehicles and a reasonable level to hand-portable radios but does not guarantee in-building coverage or operation in underground car parks and the like...

Users such as the police, fire or ambulance can request an uplift in coverage by paying for 'enhanced service' but they have to pay for the additional equipment to do this.

The emergency button comment is most likely a non-issue since the button, when correctly programmed, results in a message delivered to the control centre where it is presented to the customer's Command & Control system. It is most likely that this was a configuration and/or system integration issue and has been resolved.

Mike

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Anonymous Coward

Shadows

Bedfordshire police always joke with me and my friend when they see our CB aerials on our cars: "I'll bet they work better than our radios?!" they say. They have also complained that the panic buttons do not work as the digital signal cannot always be heard by the base station, so the information is not relayed out to other officers. Analogue radio did not suffer from this as the S/N ratio was usually sufficient for a trained ear to pick out the voice from the noise.

A secondary problem highlighted this past Saturday was one officer from the "Rave Busters" trying to find a charged battery. Seems no-one thought to include a vehicle charger. I have one for my hand-held CB!

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Not sure about the rain thing

I've never heard of problems with Tetra and the rain - seems ludicrous. We've used it in Hill search and rescue for years. Torrential rain is the norm and I've never noticed a problem. Buildings, cliffs, dense forests, yes (though we have vehicle mounted relays to get around this). But rain? Rarely heard anything so daft.

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Rainfall

If there are reception problems caused by heavy rain then that would be down to the frequency of the RF radiation and claims they've fixed the issues would be BS. Short of changing the wavelength they can't sort that.

However, I haven't checked what frequency Tetra is running off, I'd be surprised if the RF energy is absorbed by rain, certain frequencies are, and from what I recall, tend to be in the Gigahertz range.

In fact an experiment conducted by the Met.Office years ago was investigating the use of point to point microwave links for making measurements estimations of rainfall rates, the signal being attenuated in heavy rain.

It is almost certain that the effects of rainfall absorbtion on the wavelengths used by Tetra would have been assessed, determined in the early stages of the project, and I'd be very surprised if there was shown to be absorbtion issues and the decision still made to go ahead with those frequencies.

More than likely, the wavelength of Tetra was chosen because there wouldn't be any rainfall absorbtion issues.

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Silver badge

Its not (just) the rain absorbing the signal

but the damp walls its creates. Signals are both absorbed and bounced around to generally fuck up the system.

Funnily enough its just the sort of thing that doesn't get tested properly - we engineers chose desk jobs to avoid standing around outside in hurricane conditions when these things might become apparent.

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Happy

Estimations of rainfall rates? old news ;)

"In fact an experiment conducted by the Met.Office years ago was investigating the use of point to point microwave links for making measurements estimations of rainfall rates, the signal being attenuated in heavy rain."

They are late, very late, that has been on-going project at least in Helsinki since 2005. ;)

http://testbed.fmi.fi/About_Testbed.en.html

With help of Vaisala, of course, The Company in weather instrumentation bussiness. But Somehow I have feeling that Met. Office tries to invent their own devices to do everything, basically re-inventing the wheel. That's the way every bureucreacy with enough resources would do that, even here.

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Megaphone

Never heard of......

If there are reception problems caused by heavy rain then that would be down to the frequency of the RF radiation and claims they've fixed the issues would be BS. Short of changing the wavelength they can't sort that.

......................network optimisation?

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"We have no evidence of..."

Translation: We've made damn sure we don't ask the question - so even if it is a load of old cock, there's no evidence which can be used against us when we get done for incompetence.

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Pint

And...

"our technical team carries out regular checks to ensure that all vehicles are equipped with the appropriate number of radios."

We don't check that they work, just that they're there.

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Anonymous Coward

Not That Bad

I know Airwave has copped a lot of criticism since it was first implemented, and a lot of it was deserved. I'm not a telecomms engineer but have used Airwave, and I can say that while it does dip towards dodgy on occasion, it really isn't as bad as some dedicated critics still insist. It's not the all-conquering solution that was promised, and it does have weaknesses, but no more than the UHF/VHF systems that were in use, and when it works, which is more often than not, it is much better.

Granted the telephony option isn't hugely reliable, but then neither are mobile phones in my experience, certainly in comparison to landlines. Airwave's certainly no worse than that - even in the rain.

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Anonymous Coward

Consultants sell, PHBs buy

"We have fully investigated the points raised about our Airwave radio systems in this report and followed the recommendations made. "

In plain English: CEO's nephew made a 10-page powerpoint slide show (="fullu investigated) about this and recommended a hefty fee for himself (="followed the recommendations made").

Tetra isn't working properly here in Finland either (rain or snowstorm and no radio) and authorities are frantically looking for alternatives to it. It's also so expensive to use that voluntary fire brigades (common here) can't afford to use it at all. Nobody (at diciding level) has bothered to think about that before buying the system.

Yet another example of consultants selling shit to government and them idiots buying because consultants have always enough money to bribe a couple of deciding people, who have no idea about cost nor technical issues.

These people don't listen their subordinates either, real PHBs.

"... and it (Airwave) does have weaknesses, but no more than the UHF/VHF systems that were in use, and when it works, which is more often than not, it is much better."

Except VHF/UHF systems were basically free, very old technology, while Airwave is expensive, very expensive. Both to buy and to use.

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