St John Ambo?

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St John Ambo?

Postby Minus1 » Wed Oct 04, 2017 11:28 am

Anybody heard any transmissions from St John Ambulance recently?
There is some paging/signalling stuff on 166.75, but I don't seem to have heard any audio for months. Nothing digital on any of their freqs either.
Have they switched to an entirely new system?
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.
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Re: St John Ambo?

Postby Staffs Paul » Wed Oct 04, 2017 11:56 am

I hate to use the "swear word" but it could be they have gone onto the airwave system like a lot of mountain rescue teams. I live in hope that when the emergency services ditch airwave for 4g that most of the airwave systems will be taken down and the users will switch to more sensible equipment and modes such as dmr
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Re: St John Ambo?

Postby welshmonitor » Wed Oct 04, 2017 1:55 pm

My daughter is a member of St John here in Wales, was talking to her on Sunday and they have been told that they all have to do a new communications course, for the new radios that they are being issued with, no timescale for this happening was given to them. She didnt know what system will be used as this wasnt told to them, but there were told that the new radio handsets will cost approx £250 each.

Not much help I know but as and when she gets more information regarding this I will happily post that info to the forum.

Regards

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Re: St John Ambo?

Postby Staffs Paul » Wed Oct 04, 2017 2:17 pm

Thanks Welshmonitor :thumbup:
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Re: St John Ambo?

Postby bigboyblue » Wed Oct 04, 2017 8:30 pm

They are eventually moving to icom IDAS for their radios, so yes will be digital.

A fair few have already moved, but they haven't rolled out much training as it simply wasn't needed.

they must have one hell of a deal with Icom, as IDAS / NEXEDGE is the Betamax of digital - even Kenwood have started offering mototrbo compatible handsets now - its a dying breed.
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Re: St John Ambo?

Postby G4RMT » Wed Oct 04, 2017 10:26 pm

Absolutely NOT. Icom and kenwood have a big thing about it on their web sites, and FDMA systems have a number of positive advantages for users. dPMR has a narrower bandwidth, which gives a sensitivity benefit over 12.5KHz TDMA systems and as much St John work is direct radio to radio with minimal use of repeaters, this is an advantage. They also have the option to work with slightly lower power and get better battery life. With TDMA, there is always the prospect of timing issues, or non-compliant radios wrecking the system. Tier 1 DMR doesn't suffer this problem, but of course the capacity is the same as the old analogue systems, but with shorter back to back working distances. In Europe, but not so much here, dPMR is favoured because of the ITU and NATO links - with Kenwood/Icom being keen to take a lot of that business. They have confirmed they support both systems and while TDMA seems ideal for many users, it's over the top for others.

I've actually got both versions running and FM users can migrate to FDMA with no changes to how it works, which I suspect is why St John like it. While I can do the same things with TDMA, Tier 1 - I'm not using hardly any of the facilities, and price wise, FDMA kit is cheaper. There are some new DMR radios that are pretty cheap but they have far too many buttons and switches. I've got one system where I have two time slots as my plan, with a number of user groups and gizmos, and have discovered an alarming flaw in the DMR repeaters. One, they're very expensive, but worse, my experiments show that virtually all are wide open to abuse. If a client has say ten people with DMR radios, using a common group ID, and different ID radios, all works fine. However, if somebody programmes two extra radios but turns on encryption, the repeater passes the data and the two alien radios can communicate through the repeater, BUT, the other users are not aware of their presence (apart from a caller ID on the radios that would show something like GROUP 223 ID 127 if they happened to look at the radio. If they chose a different talk group, then the other radios show nothing at all. Somebody has a DMR repeater parked on one of the short term hire channels in my area, and as I too have a licence for this frequency, I tried programming up a couple of radios and I can happily work through their system, and they won't hear me. Unless they have a digital monitor package on their computers, they won't even know I'm using it! Scary.

So while it is a bit like Betamax and VHS from the compatibility side, the things do many different things. The thing at the moment is simply choice - customers can buy whatever system they like to do the job.
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Re: St John Ambo?

Postby bigboyblue » Wed Oct 04, 2017 10:58 pm

G4RMT wrote:Absolutely NOT. Icom and kenwood have a big thing about it on their web sites, and FDMA systems have a number of positive advantages for users. dPMR has a narrower bandwidth, which gives a sensitivity benefit over 12.5KHz TDMA systems and as much St John work is direct radio to radio with minimal use of repeaters, this is an advantage. They also have the option to work with slightly lower power and get better battery life. With TDMA, there is always the prospect of timing issues, or non-compliant radios wrecking the system. Tier 1 DMR doesn't suffer this problem, but of course the capacity is the same as the old analogue systems, but with shorter back to back working distances. In Europe, but not so much here, dPMR is favoured because of the ITU and NATO links - with Kenwood/Icom being keen to take a lot of that business. They have confirmed they support both systems and while TDMA seems ideal for many users, it's over the top for others.

I've actually got both versions running and FM users can migrate to FDMA with no changes to how it works, which I suspect is why St John like it. While I can do the same things with TDMA, Tier 1 - I'm not using hardly any of the facilities, and price wise, FDMA kit is cheaper. There are some new DMR radios that are pretty cheap but they have far too many buttons and switches. I've got one system where I have two time slots as my plan, with a number of user groups and gizmos, and have discovered an alarming flaw in the DMR repeaters. One, they're very expensive, but worse, my experiments show that virtually all are wide open to abuse. If a client has say ten people with DMR radios, using a common group ID, and different ID radios, all works fine. However, if somebody programmes two extra radios but turns on encryption, the repeater passes the data and the two alien radios can communicate through the repeater, BUT, the other users are not aware of their presence (apart from a caller ID on the radios that would show something like GROUP 223 ID 127 if they happened to look at the radio. If they chose a different talk group, then the other radios show nothing at all. Somebody has a DMR repeater parked on one of the short term hire channels in my area, and as I too have a licence for this frequency, I tried programming up a couple of radios and I can happily work through their system, and they won't hear me. Unless they have a digital monitor package on their computers, they won't even know I'm using it! Scary.

So while it is a bit like Betamax and VHS from the compatibility side, the things do many different things. The thing at the moment is simply choice - customers can buy whatever system they like to do the job.


The repeater issue was fixed in motorola repeaters many years ago - its called RAS (restricted access to system). This allows the repeaters to ignore any radio asking for a channel grant without giving the correct code to the repeater. This stops all hijacking of repeaters.

Hytera also has added their version to their repeater, again, about 2 years ago.

There are some lazy installers out there who simply plonk kit in, and don't programme it properly or correctly.

You've missed out the advantages of TDMA. One repeater gives 2 channels. No need for expensive antenna combiners, or one antenna per channel. When you have anything than a single channel need, this is a damn sight cheaper.

When the radios work in back to back mode, there is no timing issues, the unit reverts to a single channel per frequency, much like FDMA.


Red Cross are slowly changing over to mototrbo TDMA kit. And UHF handhelds for events based work. Seems although they aren't transfixed to ICOM kit, unlike the Johnnies.
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Re: St John Ambo?

Postby G4RMT » Fri Oct 06, 2017 10:52 am

Nice to buzz through these differences, and to be fair, quantity suggests TDMA will probably remain the system No. 1. I've been trying to source a repeater for a client (and this one will be DMR) but the price jump to secure systems like the Motorola's is severe, and the HYT entry level ones don't seem to do it, and plenty of the Chinese ones can't even do mixed mode.

On the two in one 12.5KHz channel subject, I note the TDMA people always trot out the antenna combiner, splitter, duplicate repeater line - which is of course true IF you want to do this. I suspect that most FDMA customers won't have the traffic levels that make it into a benefit, and with frequency space at a premium, it won't be long before OFCOM add bandwidth to their power and area pricing system. The price of a cheap dPMR system can be pretty cost effective for somebody upgrading to digital, and there's a cost penalty going DMR - it seems to be around 15%, which isn't a great amount. My guess is that if a customer lists their must haves, they'll point clearly to one or the other.

Keep it coming, it's useful info.
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Re: St John Ambo?

Postby G4RMT » Fri Oct 06, 2017 11:19 am

A few years ago I got asked to examine some St John people for one of their radio qualifications they take, and got sent to a very rural, country station. Compared to the well equipped ones I'd been to, who were very formal and official, this one was somewhat more of a social group who happened to stick a few plasters on at the local country shows from time to time. Lovely people. I'm not sure how the local accent will work in text, but it kind of went along these lines.

"Do you whatter see the am-bulance, boi? - Great, I said. They took me to the garage and started it up, it ran reluctantly. "be you hangin' on a mo, boi, I'll stick a brick on the accelerator-er-ator" which seemed to do the trick. "Better not press that button boi, it's sposed to go nee-nar, but we broke one last week so now it just goes nar-nar". We got to the test. This just required them to send some simple messages, and it went like this. ( I can't remember the number, so I made that bit up)

Them "Delta Golf 123, this is Delta Golf 124, uvver"
Me "release the PTT"
Them "Delta Golf 123, this is Delta Golf 124, uvver - release the PTT"
Me "No, you let go the button"
Them (into the radio, still holding the button) "Let go the button"
Me "no, you're still transmitting"
Them "bugger me, so I am - have I failed"

Then everyone went to the pub.

Doing a little job with the old Caister Lifeboat crew, somebody mentioned Percy, now in his 80s and forcibly retired from his Cox'n duties couldn't swim.

I asked him if it was true - "Percy, why didn't you ever learn to swim?" His answer - "I always had a boat!" They held most meetings in the pub - the 'Never Turn Back', and when the RNLI closed them down, Bernard Matthews bought them a big lifeboat, and Jim Davidson bought them an inshore one - and they still save lives.
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Re: St John Ambo?

Postby M0LFO » Sun Oct 08, 2017 1:30 am

Heh, nice anecdote :)

I work with SJA a lot with my Raynet group, I hadn't heard they were moving to digital. We have a PMR unit specifically for SJA in the MCU. Is this a nationwide change?

The SJA here have their own mobile comms unit but even with a lovely big pump-up mast, they seem to need us more often than not.
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