GTM21 traffic issues

JoshT · Posted: Wed Oct 18, 2006 7:37 pm Post subject:

I had more luck with TMC today!

This morning I travelled from Maidenhead to Milton Keynes - M4, M25, M1

All the way Led was yellow indicating not picking up TMC traffic data. Aerial was in vertical position.

At my destination I changed the aerial position to horizonal along the bottom of the windscreen - LED went green and TMC received :D

Travelled back to Maidenhead and had TMC most of the way down the M25, Lost signal there after from M1 juction all the way to Maidenhead.

JoshT · Posted: Sun Oct 22, 2006 7:03 pm Post subject:

I travelled to Reading on the M4 today from Maidenhead. No TMC reception along M4. Only got reception when I was off the motorway and half way from Junction 11 into Reading.

I don't think the GTM 21 is as good as the GTM 12 which has had issues on the Nuvi 310 D (resolved by latest cigarette charger)

Is anybody having similar problems with the GTM 21? If so have you reported it to Garmin? Garmin don't seem to be aware of any problems especially as the Nuvi 660 has just been released.

mwfox · Posted: Sun Oct 22, 2006 7:21 pm Post subject:

Has anyone connected their GTM 21 or 12 to the car aerial and managed to get better reception?

mikealder · Posted: Sun Oct 22, 2006 9:58 pm Post subject:

Flashyphotos · Posted: Mon Oct 23, 2006 10:12 am Post subject:

I have a GTM21 on a 660 and a GTM12 on a 360

Side by side in the same car the GTM12 provides a better reception

On the driveway, 12 gives Signal 11, 21 gives Signal 9

From home in NG17 to the M1 Junc 28 the 12 keeps signal
From home in NG17 to the M1 Junc 28 the 21 loses signal and hunts

Between J28 southbound and J27 the GTM12 keeps signal the GTM21 Hunts for a signal.

Also I have noted the GTM21 keeps a green light on the charger showing it has a signal for 2 to 3 minutes after it has actually started to hunt, so can lead to a false sense of security that it has a signal when it does not.

All in all the GTM21 seems a lot worse reception wise than the GTM12

Hope that helps

JoshT · Posted: Mon Oct 23, 2006 2:38 pm Post subject:

Flasyphotos - Thanks for your findings . Have you reported the issue to Garmin?

Hopefully if enough of us report it , Garmin will start to look at it seriously as they did with the GTM 12.

Flashyphotos · Posted: Wed Oct 25, 2006 1:29 pm Post subject:

Hi

Yes I reported it to Garmin, they really did not seem to have any real interest, and gave the normal response that traffic depends on the FM network and the levels are variable,

I tried explaining that if the units were next to each other then the signal should be similar, but they were having none of it!.

I have decided not to bother with Garmin FM TMC for now, as the reliability is not up to what I need,

Shame really, as so far I am more than satisfied with the actual performance of the New Nuvis compared to my old TT910.

For now I am not going to bother with integrated traffic and will rely on my external Trafficmaster and instinct!.

Cheers

len73 · Occasional Visitor Joined: Jun 03, 2006 Posts: 17

Can you display the TMC signal levels from a GTM21 on a StreetPilot c550 as you can on a Nuvi?

Thanks

Len

sparky8609 · Occasional Visitor Joined: Oct 30, 2006 Posts: 2

I have a c550 with a GTM21, I live in surrey and travel the M3 to work every day I only receive TMC after I have got off the motorway and am virtually at work, other than than zilch nothing nada, signal strength at home topped at 7 on channel 154, rest between 3-5.

JoshT · Posted: Fri Nov 03, 2006 10:51 am Post subject:

I'm having a problem getting Garmin to recognise their is a problem on the GTM 21.

I hope everyone is reporting their issues with the unit to Garmin (i've reported it both by phone and email)

Does anybody know anyone in Garmin Technical support who could champion this for us to get this resolved Question

Hopefully it's just a tweat of the GTM 21 software (As the GTM 21 is not as receptive as the GTM 12)

swing · Posted: Fri Nov 03, 2006 11:48 am Post subject:

Chances are it's not a problem with the GTM21 - it's simply the very weak signals that the radio station transmitters use (and before we blame Trafficmaster, it's actually not them that set the output limits on the transmitters either).

For example - even with a perfectly working setup, I've never seen traffic on the M4 between the M25 and Swindon, so no surprise you aren't getting it around Reading.

JoshT · Posted: Fri Nov 03, 2006 12:25 pm Post subject:

Swing,

I used to receive TMC information on the GTM12 (310D) between Junctions 8/9 and J11 all be it intermittantly before I took the unit back. One the 660 + GTM21 I get nothing at all

Flasyphotos did the following test:

swing · Posted: Fri Nov 03, 2006 1:07 pm Post subject:

Ah - that does seem to indicate that things could be better, although whether it's the best that the GTM21 can achieve I do not know.

Certainly I've never seen traffic on the M4, but I only use it very occasionally.

It does seem that with such a small difference between the two signal levels (remember the signal strength goes well above 100 - ie we're seeing 1 or 2% difference between the two) it might just be a small issue which is taking the GTM21 just over the edge, whereas the GTM12 can just cope.

Either way, it would be nice if Garmin could come up with an even better fix for the UK, but I doubt that's going to happen.

PhilGarmin · Posted: Sun Nov 12, 2006 11:49 pm Post subject:

I have just got the Nuvi 660 with a GTM21.

Tried GTM Aerial vertically on RHS of screen and got reasonable TMC coverage around M1 from A50 to A14 turn off. TMC then faded away.
Around St.Neots able to get TMC most of the time.

Donwloaded the first nuvi 660 update from Garmin (v2.6)and this has upgraded the GTM firmware to 3.70 from 2.3. Have not been down the same route as above yet . Will keep you all posted.

Is the aerial wire on the GTM21 just a single core and would it improve the reception if it was extended?

BTW, took back unit to Halfords and swapped it over as had two deadpixels (showing white on a dark screen). Anyone else had this?
_________________
Garmin DriveSmart 76 with Alexa

mwfox · Posted: Tue Nov 14, 2006 9:44 pm Post subject:

Yes the aerial cable is just single core - extending it seems to help - or connecting it to your car aerial with a splitter is another option to improve reception.

Inside the house I extend the aerial cable to get reception.

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