What is it in the construction of 220,221 and 222's that means GPS signals do not get through. I am on an ALR and like to have the GPS record where I have been and what speeds etc. Also how could the timekeeping is but whenever I get on one of these it does not work. It seems to be OK on everything else including Pendolinos.
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Classes 220,221,222 and GPS
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asylumxl
Established Member
Well in generic terms it could be many things, with the obvious one being line of sight.
But what I think is more likely is either roof mounted equipment reducing signal strength, or electromagnetic interference. I think they're both the cause, remembering that 22x have rheostatic brakes and resistor banks mounted on top of the carrriages.
As mobile phone reception seems to be affected too I think the latter is the cause.
Most GPS systems have a utility which allows you to view signal strength, so why not monitor strength from the platform, then onboard and at rest and under acceleration/braking? I reckon it will change most under the second.
Hope this helps.
But what I think is more likely is either roof mounted equipment reducing signal strength, or electromagnetic interference. I think they're both the cause, remembering that 22x have rheostatic brakes and resistor banks mounted on top of the carrriages.
As mobile phone reception seems to be affected too I think the latter is the cause.
Most GPS systems have a utility which allows you to view signal strength, so why not monitor strength from the platform, then onboard and at rest and under acceleration/braking? I reckon it will change most under the second.
Hope this helps.
. I get terrible (even worse than normal) signal on my phone as well when I'm on Voyagers
asylumxl
Established Member
If that were true reception would be poor while at a stand to. In 222s atleast I get perfect signal at a stand.
cyclebytrain
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Whilst reading the rest of this post, always remember that RF is basically black magic where anything can happen and often does.
The GPS issues may be to do with the traction/braking system, but I'd be quite surprised if that were the case. That sort of high current application is an obvious potential EMC issue and those tend to raise red flags during the design process and get designed out. Typically EMC issues arise from things you wouldn't think of (my personal favourite is the metal in a battery was acting as an aerial. Nobody predicted that, and it was downright tricky to track down).
But as regards examining the signal quality, I'd suggest the three measurements that your GPS is likely to show you that will be most useful would be number of satellites in view, HDOP and VDOP. Satellites in view is better as the number goes up, HDOP and VDOP as the number goes down. In general, you'd expect HDOP to be smaller than VDOP (with the proviso that I don't know every GPS system in the world and it's possible that some applications will display an inverse in the name of being "more user friendly")
The GPS issues may be to do with the traction/braking system, but I'd be quite surprised if that were the case. That sort of high current application is an obvious potential EMC issue and those tend to raise red flags during the design process and get designed out. Typically EMC issues arise from things you wouldn't think of (my personal favourite is the metal in a battery was acting as an aerial. Nobody predicted that, and it was downright tricky to track down).
But as regards examining the signal quality, I'd suggest the three measurements that your GPS is likely to show you that will be most useful would be number of satellites in view, HDOP and VDOP. Satellites in view is better as the number goes up, HDOP and VDOP as the number goes down. In general, you'd expect HDOP to be smaller than VDOP (with the proviso that I don't know every GPS system in the world and it's possible that some applications will display an inverse in the name of being "more user friendly")
asylumxl
Established Member
This is Bombardier we're talking about. The 377/5 door opening issues at STP were caused by RF interference from the OHLE. The fix was extra shielding, which can be seen where the side wall meets the floor.
starrymarkb
Established Member
It is the windows. ICEs have it as well and so certain coaches have Mobile Repeater Cells fitted, (obv not the quiet coach).
The silvering is designed to reflect heat, as heat is a form of electromagnetic radiation in a similar range to microwaves (used by GPS and Mobiles) then the signal will be affected. GPS signals are weak even under good conditions requiring extremely sensitive tuners to pick out signals 30db below the average background noise level!
The silvering is designed to reflect heat, as heat is a form of electromagnetic radiation in a similar range to microwaves (used by GPS and Mobiles) then the signal will be affected. GPS signals are weak even under good conditions requiring extremely sensitive tuners to pick out signals 30db below the average background noise level!
asylumxl
Established Member
If so then how do I get signal when at a station no problem?
cyclebytrain
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I think this discussion proves my point that EMI issues are complex!
starrymarkb
Established Member
Doppler effect? Given that my in car GPS locks on much quicker when stationary that may be a factor
asylumxl
Established Member
But if that were true then I would lose signal in another type of stock at the same speed?
cyclebytrain
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No, no train in this country is fast enough for a Doppler effect to make a serious difference. Changes in terrain will have a much bigger effect.
The GPS works fine on the platform and on all other trains no matter how fast they are going, Javelins, Pendolinos but on the 22's it just stopss as soon as I get on the satellite display show no satellites available. I just tried an experiment as I am currently on a 221 and it is something to do with the actual carriage as it works fine if i stand in the bendy bit between coaches.
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Peter Mugridge
Veteran Member
On a 222 I can get a GPS signal easily in the vestibules ( and there are tip up seats in there so you don't have to stand ). Haven't tested on a 220 / 221 yet...
Phil6219
Member
I may be wrong here but didn't a TOC coat the windows of it's quiet coaches with a film which reduced the signal strength on mobile phones to prevent people from flouting the rule? I believe it was an experimental thing that happened a good 3 or so years back.
Perhaps that would cause the signal to be weak inside the passenger cabin and not in the vestibule area, although it wouldn't make sense for the whole train to be treated and not just the quiet coach.
Perhaps that would cause the signal to be weak inside the passenger cabin and not in the vestibule area, although it wouldn't make sense for the whole train to be treated and not just the quiet coach.
junglejames
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It came out ages ago that it was the film they have coated the windows with which has caused the poor mobile and GPS signals inside the coaches. Didnt Virgin even admit this at one point?
--- old post above --- --- new post below ---
Nope, not the case.
Doppler effect may or may not be the reason you pick a signal up better whilst at a stand, but the fact other passenger stock doesnt have the anti glare film covering the windows, means mobile signals are still ok.
It may be reduced when underway, but signal will be infinitely better than on a voyager due to no window covering.
--- old post above --- --- new post below ---
Nope, not the case.
Doppler effect may or may not be the reason you pick a signal up better whilst at a stand, but the fact other passenger stock doesnt have the anti glare film covering the windows, means mobile signals are still ok.
It may be reduced when underway, but signal will be infinitely better than on a voyager due to no window covering.
Tomonthetrain
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Pretty sure that was c2c on their 357s. I seem to recall it didn't work so was abandoned shortly afterwards.
route:oxford
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OK but having paid for a 1st Class ALR, I do not want to sit in the vestibule.
Well, you could do the traditional thing and sit in first class with a stop watch and look for the mile posts.
If you're really good. You should be able to count time in your head, watch for mile posts and do the speed calculation in your head too.
If there is no challenge, what is the point?
Minilad
Established Member
Or you could just sit and enjoy the journey and not worry about how fast you are going !
asylumxl
Established Member
Minilad
Established Member
asylumxl
Established Member
Is it ? whoops, now I know where I am going wrong
I know right? That would explain the people shaking their fist at you as you fly through their station
Minilad
Established Member
I know right? That would explain the people shaking their fist at you as you fly through their station
Managed to avoid doing that so far. Although I did stop at Wolverhampton when I wasn't supposed to once
Managed to avoid doing that so far. Although I did stop at Wolverhampton when I wasn't supposed to once
Why would you WANT to do that?! Get through there as fast as you can! (very difficult admittedly to move faster than a snail through Wolves station, but still!)
Minilad
Established Member
I know, of all the places. It wasn't to admire the architectural splendour I can tell you. Maybe to listen to that lovely accent for a few minutes !!
Soooo XCDriver, when did you realize your mistake? Was it when the people on the platform were giving you funny looks or was it when the guard rang you up and said "mate, we're not stopping at Wolverhampton" or did you actually manage to avoid anyone noticing...
Minilad
Established Member
Answer B..when the guard buzzed me and said "this isn't Stafford !
strange6
Established Member
Bet you got your blood tested when arriving back at the depot
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