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GTM21 traffic issues
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PhilGarmin
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Joined: Nov 07, 2006
Posts: 52
Location: Kidsgrove, Staffordshire, UK

PostPosted: Tue Nov 14, 2006 10:56 pm    Post subject: Reply with quote

Used some two-core doorbell wire, wrapped (coiled) approx 20cm tightly around the end of the GTM21 wire. Routed the bellwire across top of front windscreen down left pillar and across bottom of windscreen.
Twisted the end of the cable together.

Nuvi is on rhs of windscreen

Got some TMC sat in front of house last night which is an improvement as I have never had TMC in this area. (Stoke-on-Trent).

Doesn't look too messy either as the cable is tucked in the front of the headlining and behind the trim around the windscreen.

Also found the Diagnostic menu on the Nuvi 660. Press and hold the time for approx 6 seconds.
It seems to start some diagnostics tests as soon as you enter the screen.
Only way to get out of the screen is to reset (behind the GPS aerial).

Could not find a 'Signal' meter for the GTM (which is referred to as GTM10 btw). However there is a value in volts which showed 0.89 whilst receiving TMC (LED Green). Lower value when LED Orange).

There is a section which mentions the FM transmitter, however it does not allow you to adjust the FM frequency. (I reckon there is a hardware link missing for UK models)

Hope this helps the nuvi newbies. Wink
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Joeee
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Joined: Nov 09, 2006
Posts: 1

PostPosted: Wed Nov 15, 2006 9:06 pm    Post subject: GTM 21 traffic reception Reply with quote

Just bought nuvi 660 with GTM 21.

Spend most of my time adjusting the FM ariel to get tms reception. I live in South Lincolnshire. This morning I drove for 1 hour up the A17 to the A1 - No Signal.

Also M56 Warrington to Chester - No Signal.

BUT I have got a better signal by;

cutting off the end of the suppiled ariel, and connecting a connector to a 1m length of FM single core wire. This is mounted in a L shape veryically down the center of the windscreen and horozontally to the drivers side. The unit is mounted in the centre.

Its not pretty, using blue tac, but its better than it was.

I have passed this onto Garmin, and suggested an accessory of this sorts.

It is still not good, or even reliable.

Has anyone any experience of connecting to the Car ariel, by whatever means.

Regardless of the causes, either low signal strength, or a crap receiver, its not working and, as I said to Garmin, damaging what is otherwise a good unit.

Can people let me know if getting BMW to fit to the ariel is a worthwhile expense.

Thanks
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swing
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Joined: Nov 04, 2003
Posts: 2225
Location: Bedfordshire, UK

PostPosted: Fri Nov 17, 2006 10:55 am    Post subject: Reply with quote

I think one person has successfully connected a GTM12 / GTM21 to a proper aerial, and found improvement.
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mwfox
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Joined: Jun 18, 2006
Posts: 149
Location: Buckingham. UK

PostPosted: Fri Nov 17, 2006 12:32 pm    Post subject: Reply with quote

I have connected the end of my GTM 21 aerial to a GNS car aerial splitter and used a Velleman aerial amplifier to boost the signal. I am picking up traffic information at my house where I wasn't before.

This would work with the GTM 12 as well I am sure.
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mwfox
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Joined: Jun 18, 2006
Posts: 149
Location: Buckingham. UK

PostPosted: Fri Nov 17, 2006 10:11 pm    Post subject: Reply with quote

I have since found the GNS splitter doesn't work well in this set up with the GTM21 - I am going to try and straight aerial splitter if I can find one.
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JoshT
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Joined: Aug 05, 2006
Posts: 93
Location: Berks, England

PostPosted: Thu Nov 23, 2006 10:46 am    Post subject: Reply with quote

Due to GTM21 reception problems reported, Garmin Tech support advised me to go and change the Nuvi 660 unit . I've done this.

Alas no better Crying or Very sad In fact I'd go on to say the replacement is worse than the old unit.
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mwfox
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Joined: Jun 18, 2006
Posts: 149
Location: Buckingham. UK

PostPosted: Thu Nov 23, 2006 11:21 am    Post subject: Reply with quote

I had a GTM 12 with a Nuvi 360 - and it did seem to have better reception than the GTM 21 - but I didn't do any scientific tests. I got traffic info on my drive with it and don't with the GTM 21.

I have had some success with connecting the GTM 21 to my car aerial - but last night I changed the coax cables with better quality ones - and this morning - traffic info wasn't received well - until I got near to the transmitter in Milton Keynes. Not sure what is going on.
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swing
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Location: Bedfordshire, UK

PostPosted: Thu Nov 23, 2006 12:18 pm    Post subject: Reply with quote

JoshT wrote:
Due to GTM21 reception problems reported, Garmin Tech support advised me to go and change the Nuvi 660 unit . I've done this.
I think you meant GTM12, as the 660 uses a GTM21 ;)

I would have thought the GTM12 and the GTM21 should provide identical abilities, but speaking to many users I get the impression the GTM12 is very slightly better, which may be due to the overall design of where the receiver is located, and the options available for positioning the antenna.

If you still had the Nuvi 3x0 and the GTM12, one option is to purchase a GTM10 or GTM11 (discontinued, but they still pop up for sale here and there) and connect it to your car aerial. Of course, with the 660 this is not an option...
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inspiredron
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Joined: Dec 17, 2006
Posts: 302
Location: Ellesmere UK

PostPosted: Wed Dec 20, 2006 2:02 am    Post subject: Reply with quote

My complete C510D was replaced after I asked awkward questions of TrafficMaster. However, no improvement. Garmin sales manager says that unit swork fine (in Romsey) and that they have had no other complaints!

Garmin sales manager is deaf or does he speak with forked tongue?
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inspiredron
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Joined: Dec 17, 2006
Posts: 302
Location: Ellesmere UK

PostPosted: Wed Dec 20, 2006 2:03 am    Post subject: Reply with quote

PS Have just updated to latest unit software including updated TMC software. Will try out at weekend.
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swing
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PostPosted: Wed Dec 20, 2006 8:24 am    Post subject: Reply with quote

That's a poor response from Garmin - the Garmin Europe office is not very far away from the local Trafficmaster broadcasting radio mast, so a good signal would be expected.

However, he would only have to drive a few miles East or North and he should find the signal soons drops off ;)
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emmanueld
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Joined: Aug 30, 2006
Posts: 5

PostPosted: Wed Dec 20, 2006 9:05 pm    Post subject: Reply with quote

Well, unfortunately, I can report that I have the same problems with a brand new Nuvi 660. I bought it less than a week ago. From the first time I used it, I noticed that the Traffic info was extremely unpredictable. Went from London to Bristol, I had only info for 5 minutes. I came back from Bristol to London and it worked fine most of the time.
I've just noticed that it seems to be working fine at the begining of each trip (i.e. the first 5 or 10 minutes.) Then, it is completely unpredictable. (i.e. no information for a while, then an update for 5 minutes, then maybe nothing for hours).
If I am correct, it is a GTM21, i.e. one shared cable for the GPS and the GTM. The light is either green or yellow / orange. Yellow meaning no traffic update, Green being all okay.
It is very frustating, and I can't find any "official" information from Garmin. I reported the problem online on their website, but no feedback so far. To me, this is completely unacceptable!!!
I am thinking about briging it back to the shop, but I don't like the TT910 as it is too bulky.
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paul3
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Joined: Dec 08, 2006
Posts: 24

PostPosted: Thu Dec 21, 2006 12:30 pm    Post subject: GTM21 Traffic issues Reply with quote

Dear emmanueld,
Just read your post and have just been talking to Garmin support. I am also in the same postion regarding traffic information. My green LED light is constantly on. The orange/yellow light flashed on twice on a 30 mile journey yesterday around a major city with no info. On the menu bar, the two car symbol appeared, greyed out, and I couldn't get any more info. This morning as stated above, I rang Garmin support and was sent an email of how they recommend the aerial to be fitted to the windscreen, with the cable running horizontally and for the last 4 or 5 inches running vertically up the windscreen.

I also mentioned after being told that the conversation was being recorded for training purposes, that the level of info in the manual was very poor indeed. Ie. Aerial positioning and LED light info.

Also regarding taking your unit back to the shop, I did this with mine at Halfords and was told that because I had registered the software with Garmin, they couldn't exchange the unit! So it looks like we've got a battle on our hands! I will check the position with Trading Standards, because like you, I am not happy with a) halford's response and b) Garmin's info in the manual.

Hope this helps in some way (?)
Paul.
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emmanueld
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Posts: 5

PostPosted: Thu Dec 21, 2006 9:02 pm    Post subject: Reply with quote

Paul, Thank you for sharing your experience. Garmin's behaviour is absolutely unacceptable: Paul, thank you for sharing your experience.
Garmin's behaviour is totally unacceptable: They very well know that there is a problem with their GTM21 (as well as they knew that there was a similar problem with the GTM12). This has been reported by many users since June. They seem to be unable to solve the problem. Rather than admitting it and telling us that they are working on a fix, they deny any issues and give us BS as an answer. (as if running the aerial first horizontally then vertically was going to change something!! What about waving with the right hand and swinging the left foot while driving!!)
As far as Halfords is concerned, they are also guilty (like any other shop that sells or any High-Tech magazine that reviews the product) of selling the product while advertising the Traffic capability. Basically, everyone who has tried this unit knows that the Traffic is not working but nobody says anything in order to sell as much as possible.
My only hope is that they are going to sell thousands of these faulty units over Christmas. Because there will be more and more unsatisfied customer.This will eventually create a very bad publicity for Garmin, maybe some of us will have the courage and the motivation to let Watchdog know, and with more pressure on their back, Garmin will eventually do something to solve the problem.
I read somewhere that it is actually a UK problem, and that the traffic signal is not strong enough or clean enough to be received by the GPS. What about other brands / models? Does anyone know whether the TT910 is receiving Traffic Info with their new aerial? I have the feeling that this is not specific to Garmin.
Today, I went from Newbury to Swindon on the M4. There was an accident between junction 14 and 15. It was not reported by my Nuvi 660 and I went straight into it. It took me 90 minutes to do 17 miles. Thank you Garmin!!!
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swing
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Location: Bedfordshire, UK

PostPosted: Fri Dec 22, 2006 10:28 am    Post subject: Reply with quote

To be fair to Garmin, the main problem with the Nuvi 3x0 and the GTM12 was the car charger, and had nothing to do with the GTM12 at all. Having said that, even with the new car charger, the GTM12 does not perform as well as many would expect it to (including me).

Garmin are right to provide suggestions on how to improve reception though - there are things that will make it worse.

Both Halfords and Garmin should at least state "Traffic reception varies across the country" - I'll note Garmin do provide such a warning on their website. Having said that, it's not that "traffic doesn't work" it simply doesn't work everywhere.

There are certainly similar threads in the TMC and TomTom forums relating to both Navman's TMC unit and TomTom TMC unit (of which I expect a lot more complaints once all the £299 Go 510 with free RDS-TMC units that Dixons / Currys / whoever are advertising on TV get opened in a few days time). Both have similar issues (and both use the "other" RDS-TMC service in the UK - which shows it isn't even limited to one UK service!).

Yes, this is limited to the UK - the radio transmissions are strictly controlled in the UK, and each radio mast is only allowed to put out a fairly weak radio signal - in both the US and across mainland Europe the radio masts are allowed much higher transmissions, which means the problem doesn't occur.

The last point I will add - I believe the Navman unit has its simple 1 wire antenna (like the GTM12 / GTM21) attached via a connector - some people have used this connector to connect it up to their car aerial (like the GTM10 / GTM11 allows) and found a great improvement. 1 or 2 PGPSW members have done the same with their GTM12 / GTM21 units (obviously invalidating any warranty) and found much improved reception.
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