TMC aerial connection

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

I've got a Garmin nuvi 670 with GTM21 TMC receiver. I have installed the nuvi into the lower part of the dash so that it looks neat but the TMC aerial is not good, have received a couple of traffic updates but not much so I've bought a Navilock Din antenna adaptor; http://www.cartft.com/catalog/il/671
which takes an aerial feed from the car aerial. It has a small stereo type plug on the lead to plug into a TMC receiver, however my TMC receiver only has a wire exiting from it to use as an aerial.

Am I correct in thinking that I can cut off the plug and solder the wire to the aerial wire? is it only a single core wire?

Any advice welcome. Smile

philpugh · Posted: Tue Aug 28, 2007 12:04 pm Post subject:

Yes,

the small black plastic end on the wire will pull off with gentle force (keep it in case you need to replace it to get the unit fixed under warranty!)

You can then strip the cable back as far as you need and away you go.

I have a similar set up (nuvi 660 + GTM21) and find that to get good reception you need to have the power lead plugged into the car power. This will be to get an earth/ground connection made I guess.
_________________
Phil

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

Thanks for the reply, I have fitted a plug to the Garmin lead - after reading some other posts I have connected to the tip of the connector (2.5mm stereo jack headphone style plug) but it doesn't seem to have made any difference to reception.

Do you know which connector(s) in the lead is used for the aerial signal, the base section of the plug goes to ground (the outer 'ring' of the din aerial plug) but not sure which goes to the centre core of aerial cable as it doesn't flash through with a meter (presumably only works when powered/connected)?

I suppose I could cut off the plug to see where it connects to and then replace it but was hoping for a quick fix.

I am using the car power.

Smile

mikealder · Posted: Wed Aug 29, 2007 7:29 am Post subject:

It won't give a reading with the meter as there will be a capacitor in line with the center aerial feed, this is fitted to block any DC voltage that might be sent up the aerial cable to a mast head amplifier.

If you are sure of the screen connection being correct I would try connecting the center aerial wire to both the remaining contacts - Mike

philpugh · Posted: Wed Aug 29, 2007 2:13 pm Post subject:

When I did mine I simply stripped about 2 inches from the end of the GARMIN aerial cable and wrapped this around the centre pin of the ISO Y cable splitter I had bought - it worked immediately and I haven't got around to replacing it with a plug/socket arrangement yet - perhaps when I get really bored!

Check the signal levels without any connection to the aerial and then with - you need to get to the 'hidden' pages on the nuvi to do this (see other threads for how to do this and what NOT to do when you get into them.)

Mike is correct about the capacitor - always catches you out the first time you try this sort of thing.

Does your car have an in-built aerial amplfier? Quite a few with the 'bee-sting' roof aerials do - this will give you good reception for TMC - otherwise you should see an improvement - but at the cost of slightly worse 'at the margins' FM radio reception.
_________________
Phil

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

Well I've now connected the aerial to both the centre and tip connector of the plug (shielding goes to base connector) and I can't say I've noticed any difference but how many traffic alerts are there to notice? (did get one today, about slow traffic ahead).

My car (Audi A3) has a rear window aerial, which I presume is amplified - there are 2 aerial connectors on the radio; 1 Din and 1 smaller, thinner squarish connector - the radio will work without the smaller one connected but not if the din plug is out? Radio reception appears unaffected.

In the nuvi settings menu there is a traffic section but it says that I am not yet subscribed and that it will automatically subscribe when the unit receives a traffic alert whilst receiving sattelite info - but I have had a few traffic alerts even when the GTM21 cable was behind the dash and not connected to the plug. is this something different?

How do I get into the hidden signal level page as that would be very useful?

Smile

mikealder · Posted: Thu Aug 30, 2007 7:27 am Post subject:

Check your e-mail as I have sent you the POI file that contains the transmitter locations and a user guide on how to use it - that also details how to get at the hidden menu - Mike

philpugh · Posted: Thu Aug 30, 2007 4:40 pm Post subject:

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

Vaneo · Posted: Thu Aug 30, 2007 8:18 pm Post subject:

Hi

Re the posts by DukeDesmo and philpugh

I presume the "small" connector was a FAKRA.
My daughters 2005 Peugeot 307cc radio/CD head unit only has one as the aerial connector.

Does anyone know the reasons for the change and the advantages over ISO and DIN.
Size and positive retention must be good on the production line.

FARKA users are ok with this :- http://www.cartft.com/catalog/il/540

Very Happy

philpugh · Posted: Tue Sep 04, 2007 12:15 pm Post subject:

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

Wiglet · Posted: Thu Sep 20, 2007 10:51 pm Post subject:

philpugh · Posted: Fri Sep 21, 2007 8:59 am Post subject:

At home (2 miles south of Jn 10 M56) I get about 27-30 in-car for channel 145 (Galaxy FM) and I am a little further away than you. I get a lock with the car parked in an old 'tin' barn. Before the connection to the aerial I was only getting 15-20 and failed to get any TMC data until I got to Jn 6 M56 or closer.

As you can get it working in your home it would suggest that there is something else going on here. It could be that you are getting electrical interference on the aerial lead. This would have adverse effects on the ability to decode the TMC info at low signal levels.

With the Volvo diversity aerial. Do the two aerials feed the radio separately (i.e. a 'special' Volvo unit) or do they go into a 'box', presenting one aerial feed to the radio? I was wondering if you can connect directly to one of the aerials and disconnect it from the diversity system entirely.
_________________
Phil

DukeDesmo · Occasional Visitor Joined: Jul 25, 2007 Posts: 14

So my radio has 2 aerial plugs (1 Din , 1 Fakra) is this because it uses 2 aerials? (I thought it was just the rear screen - there is no visible aerial).
I get no noticable improvement in TMC reception whilst connected to the din plug, would it be better on the fakra? I'd rather not buy another cable just to try but I don't mind if I know it will work. I suppose I could buy some Din-Fakra converters to try it that way but they would likely cost as much as the Fakra splitter cable.

Any ideas?

Smile

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