External Antenna for Navman TMC Module?

[lesmals]

Hi Mike.
Thanks for the advice.
Perhaps the best thing to do is to hold back and see if Navman or w.h.y bring out some sort of dedicated add on aerial. Hopefully if they get enough complaints about the T1 they will.

The other thing as there are only a couple of frequencies for Classic FM, if the T1 looses one will it automatically re tune it's self for the other frequency or does it have to be done manually, which if driving alone would be impossible on a motorway or clearway.
I shall be doing a 350 mile round trip to Newcastle next week-end so I should have a better idea of how it performs.

I love the simplicity of the Navman ICN 530 compared with the Navman PIN 570 which i've been using for the last year, but for what the T1 Traffic module costs, with hindsight, perhaps I should have waited a little longer.
Cheers Les.

[mcogman]

Hi Lesmals,

I can confirm that it does appear to retune itself, not only to Classic FM but also to any other TMC transmitting station. I haven't been able to prove this conclusively over a long period as all I saw today was the T1 recognise Galaxy as a TMC station as I did the other day with Leicester Sound.

The stations were showing together and for a minute or two Galaxy had a better signal than Classic FM and the T1 locked to that. As there was little happening on my route I couldn't say if the lock was successful enough to receive any TMC data.

In practical terms my T1 just works! I think you have to learn to "trust" it though even though sometimes the data lags behind and the problem clears just after you've turned off - but then that's always going to be the twist in the tail!

[Mav281]

Have a quick read of my post here and see if this helps at all,

http://www.pocketgpsworld.com/modules.php?name=Forums&file=viewtopic&t=43369

[peecee]

Well, having had my unit for almost 1 month for the first time ever I picked up a TMC broadcast.

Now I know the systemis actually working as I was having my doubts I will persue the antenna problem again with renewed motivation.


Mike, I'll find your number again and possibly give you a call so we can have that quick meet-up and see if the hybrid you devised has any benefit on my device.

Then following that I will source a better solution, something which is centered around the Classic FM frequency band.

Various ariels have varying degrees of gain, so I think it would be imperitive to find one that has the maximum gain structure but at the same time keeping it compact and practical.

I picked up my first signal ever in Cheshir eon the A49 last week, and yes I sat in a 1 Hour traffic Jam of which was never reported to me.. so it worked in a sense but did me no good whatsoever.

I'm back off into Cheshire tonight (other side of Cheshire though) so I'll see what I pick up later.

I'll be in the A34 at some point so let's hope I am informed of any problems prior me finding them.

[Unhban]

[peecee]

Not sure how the data is collated, however on Friday night I was again back in Cheshire and on the A34 this time. The system worked again, but no details received. Got held up for 3 minutes at some roadworks with temp traffic lights at Mottram St. Andrew just off the A34. Next morning on my way back (3am) I was notified of the roadworks.

Ironically the lights hit green as I approached and didn;t cost me a second in wasted time.

So for now I have lost over an hour in not being told of problems and not saved a single second when I have been informed of problems enroute.

Whenever a company or contractors need to dig up a road they have to submit a request to the local authorities. This is no doubt put into a database for their own use so it would be very helpful if this info was then transferred over to the TMC system.

That is of course if it's not done this way already.

At least we'd know about fixed roadworks.

I think Classic FM would do better if they fitted a repeater on Blackpool Tower.

Next week I'm going northwards so hope to pick up the other good signal that way.. typical of my luck to live in a dead zone for TM broadcasts.

[peecee]

Here is some info I just found.


The private company ITIS Holding is providing a commercial TMC service iTMC in the United Kingdom. It is broadcast on Classic FM The price of the service can be included in the price of the car or of the navigation system.

Next to that, there is a service RAC Live operated by RAC Trafficmaster Telematics (RTT) a 50-50 joint venture between RAC Motoring Services and Trafficmaster. It uses 3 commercial radio broadcasters, GWR, Capital radio and Chrysalis who together ensure reception across mainland Britain.

Both providers are responsible for their own location tables. The current location table version of ITIS is 4.5, which will be followed by 5.0. The current location table version of Trafficmaster is 1.4. A new version 2.0 has been certified.

[peecee]

Each traffic incident is sent as a TMC message. One message consists of an event code and a location code in addition to time details.

The message is coded according to the Alert C standard. It contains a list of about 1460 events which can be translated by a TMC receiver into the language of the user.

Location code tables are maintained on a national level and assign numbers to locations on the road network. Those location tables are integrated in the maps provided by Tele Atlas and NAVTEQ.

The source of traffic information is typically police, traffic cameras, loops, Floating Car Data and others.


Floating Car Data or FCD is a method to determine the traffic speed on the road network. It is based on the collection of localisation data, speed, direction of travel and time information from driving vehicles. This data can be used as a source for traffic information. This means that every appropriately equipped vehicle acts as a sensor for the road network. Based on this data, traffic jams can be identified, travel times can be calculated, and traffic reports can be instantly generated.

In contrast to traffic cameras, number plate recognition systems, and sensor loops embedded in the roadway, no additional hardware on the road network is necessary.

Different types are possible:

GPS based: Here a small number of cars (typically cars driving in a fleet, such as courier services and taxi drivers) are equipped with a box that contains a GPS receiver. The data is then communicated with the service provider using the regular on-board radio unit or, more expensive, via GSM or GPRS.
GSM based: In this case, no special devices are necessary: every switched-on GSM device is a source of information. The location of the GSM device is determined using triangulation. As the localisation is less accurate than GPS based systems, lots of devices have to be tracked and complex algorithms need to be used to extract high quality data.
FCD is also an effective surveillance method, although most companies deploying FCD systems give assurances that all data is anonymized in their systems, or kept sufficiently secure to prevent abuses.


Inductive loops can be placed in a roadbed to detect vehicles as they pass over the loop by measuring the vehicle's magnetic field. The simplest detectors simply count the number of vehicles during a unit of time (typically 60 seconds in the United States) that pass over the loop, while more sophisticated sensors estimate the speed, length and weight of vehicles and the distance between them. Loops can be placed in a single lane or across multiple lanes, and they work with very slow or stopped vehicles as well as vehicles moving at high-speed.


Traffic flow measurement using video cameras is another form of vehicle detection. Since video detection systems do not involve installing any components directly into the road surface or roadbed, this type of system is known as a "non-intrusive" method of traffic detection. Video from black-and-white or color cameras is fed into processors that analyze the changing characteristics of the video image as vehicles pass. The cameras are typically mounted on poles or structures above or adjacent to the roadway. Most video detection systems require some initial configuration to "teach" the processor the baseline background image. This usually involves inputting known measurements such as the distance between lane lines or the height of the camera above the roadway. A single video detection processor can detect traffic simultaneously from four to eight cameras, depending on the brand and model. The typical output from a video detection system is lane-by-lane vehicle speeds, counts and lane occupancy readings. Some systems provide additional outputs including gap, headway, stopped-vehicle detection and wrong-way vehicle alarms.


A bit more info on the RDS-TMC canbe found here.

Sorry for the mutliple posts, couldn't find an Edit button

[peecee]

Ok, last one I promise :D


Here's a link to a PDF, that hopefully will add a few more answers to the whole TMC episode.


ftp://ftp.rds.org.uk/pub/acrobat/tti_article_spring99_e-2.pdf

[Unhban]

Top marks, peecee! That answers it all! So it seems the TMC service, whether by ITIS Holding or RAC Live, is using all methods available.

Also, it looks like that when you're on roads where there are none of the electronic forms of capture you're down to the Police giving information, and perhaps they were a bit slow with that for the A34 roadworks?

Or perhaps they just didn't bother at all and it needed a device-equipped vehicle to get held up before the roadworks got noticed? 8O

[Unhban]

[peecee]

Well based on the Classic FM Frequency range of 101.1 to 101.8 Mhz respectively, I calculated the optimum length of an antenna should be:

2.4272323630981747 Feet

So basically 2.43 ft should do it.

That's for a Quater Wave, for a Five Eights Wave:

5.772076961026148 Feet.

For Half Wave:

4.6176615688209175 Feet.



If you wish to experiment with a FULL WAVE, which would be the best solution, this would be:

9.916132215096201 Feet.


With a Full wave you could effectively run it around the edge of the screen.

I wonder how effective a 90' dipole would be, so you use two 1/4 wave lengths one running vertically and one horizontally.

Depending on the height of your vehicle a 1/4 wave whip would be best with no base loading at all.

Being at just under 2.5ft, wouldn't be that large and you could use fine wire, just enough to resist bending in the wind at motorway speeds.

Oh, just for referenc eI used a Frequency of 101.350 as the basis to these calculations.

[Unhban]

[peecee]

It should perform ok.

Though I suppose a great deal will depend on the vehicle body and the windscreen type also.

Some windscreens are heated or have other elements embedded which can cause weak reception internally.

Most wire whip FM antennas for Cars, much like the one fitted to my roof at present should be approx 2.51 ft in length if 1/4 wave, they might be 1/8th wave however if they seem to be about half that length.

Since the optimum length for the Northwest region is 2.47 ft, you can see you need to snip a very small length off the end to match it more accurately.

Whether or not this actually will have any gain is debateable, but worth trying in such a weak reception area.

From what I can work out a std FM antenna for a car would need 11mm snipping off the end.

What you must remember within the car the windscreen surround and door pillars etc all make an effective screened box, with reception only being passable through the screen itself and possible side windows but to a lesser degree of effectiveness.

I have seen antennas in the past for window placement where they have been a clear tape, like sellotape but with a hair-fine wire in the centre.

When affixed correctly makes for an almost invisible antenna.

Also very easy to cut to the correct length.

[sadcrab]

I've just bought the miniscan magnetic aerial from Maplin at £15 and also managed to get a suitable connection BNC female to MCX Plug from http://www.coax-connectors.com/introduction.htm at less than £6.00. I can now connect the T1 module to an external aerial for improved reception, further more I spoke to Moonraker the manufacturer of the aerial and I've been told that by extending the aerial by 3 inches I could pick up transmissions below 100mhz. Hope this helps anyone wanting better reception for the T1 module

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