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Pocket GPS World :: View topic - External Antenna for Navman TMC Module?
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External Antenna for Navman TMC Module?
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Mr_Womby
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PostPosted: Wed May 10, 2006 1:53 pm    Post subject: External Antenna for Navman TMC Module? Reply with quote

Has anyone succeeded in adding an external antenna for the Navman TMC module? I have an iCN550 with TMC and I find the reception using the "wet string" antenna supplied is very poor. I live near the M25/M3 junction and, driving anticlockwise on the M25, I don't get anything until I get near Godstone (J6).

I've tried mounting the antenna at different locations in the windscreen (and even in the side windows) but can't get any improvement.

Does anyone know of a manufacturer that sells an add-on - alternatively, what's the pin-out of the antenna connector? Then at least I could try a standard car antenna, provided I can wire it to a suitable connector.

I e-mailed Navman's support address a couple of weeks ago but got no response (apart form the automated "You're message has been received and is being dealt with" bull).
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Tim Buxton
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PostPosted: Wed May 10, 2006 2:10 pm    Post subject: Reply with quote

I too have an iCN550 with TMC and I, too, have reception problems in the areas you describe. Apparently it's due to poor Classic FM coverage i the area concerned.

I had tried splicing the TMC antenna into my radio aerial coax, but while this did nothing for the TMC reception it did attenuate my radio signal quite a bit.

I have now purchased a magmount aerial with a BNC plug. Unfortunately, the only magmout aerial I could find was a 100-300MHz one, and Classic FM transmits at about 100MHz so it is right at the bottom of the spectrum.

I then got very technical and cut the end off the 'wet string' antenna supplied with the TMC and soldered it to a BNC socket, which I attached to the magmount.

TMC reception is still very poor between the A3 and Clacketts Lane but it is much better than before. I'm off to France in August where I've been told that the TMC transmission is not so weak as it is here in the UK, and my results should be much better.
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Mr_Womby
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PostPosted: Wed May 10, 2006 6:09 pm    Post subject: Reply with quote

Hi Tim,

Thanks for the suggestions. I can listen to Classic quite clearly on three different frequencies in the 'problem' area - I realise the manual states that TMC reception is more critical than audio reception but then you have to wonder why Navman didn't design a module with better performance in the first place. As it is, I'm almost at the end of my journey before I get any traffic info - I might have to go back to my Trafficmaster Q2!

Incidentally, have you ever experienced a lock-up with the TMC/550 where the unit just alternates between "Scanning" and "Receiving" but never gets to "Receiving TMC", even in good reception areas? I eventually realised that this was a software fault and cured it by resetting the 550.

Off to place an order with Maplin!
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Tim Buxton
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PostPosted: Wed May 10, 2006 7:20 pm    Post subject: Reply with quote

I got mine from Maplin, too. I'd like one in the 88-108MHz range ideally, though.

No, never had your scanning/Receiving scenario.
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Mr_Womby
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PostPosted: Fri May 26, 2006 10:12 am    Post subject: Reply with quote

Just to update this topic, I now have excellent TMC reception using a Miniscan antenna from Maplin (their part ref QT30H). Although this only has a small magmount footprint (about 1" diameter) and the aerial itself looks quite thin and whippy, it sticks to the roof of the car very well and because the profile is thin it doesn't bend too much as you drive along (tested to 80mph!).

Rather than try to solder it onto the "wet string" Navman aerial I managed to find a couple of adaptors from CPC that allow me to plug it straight into the TMC module. One adaptor (part CN04192) goes from BNC socket to 3.5mm plug and the second (part AR70703) accepts the 3.5mm plug and converts to a 2.5mm plug. (I couldn't find an adaptor that went from BNC to 2.5mm in one step.)

As I said, the reception is now greatly improved and I get Classic FM for the entire journey to work now instead of only during the last 15 miles. There are a couple of grey reception areas where the signal isn't quite good enough to decode the TMC signal, but this only lasts for a couple of minutes at a time.

All in all, a great result for an outlay of around 16. I'm driving around the continent in August (mostly Germany) so I'll be interested to see how good the TMC coverage is there.
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Tim Buxton
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PostPosted: Fri May 26, 2006 5:57 pm    Post subject: Reply with quote

That is exactly the same one I bought! Now, what is CPC so that I might buy the extras that you have in order to do away with the string?

Also, when you go to Germany, can you experiment with the string as well as your new aerial? I will be doing so in France in August; I'm told that France and Germany transmit TMC at a stronger power level, so the original antenna might suffice.
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Mr_Womby
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PostPosted: Tue May 30, 2006 4:39 pm    Post subject: Reply with quote

You can find CPC at www.cpc.co.uk. They are really for trade customers but you may be able to buy as a retail customer. As well as electronic bits (like Maplin) they also do domestic appliance spares, general car bits, etc. (Their catalogue is over 2700 pages.) The two adaptors work out at just over 1 combined (plus VAT) but there is a hefty delivery charge (about 6 plus VAT I think) if your order is less than 40.

Alternatively, it might be less hassle to get the bits from Waters & Stanton www.waters-and-stanton.co.uk. Their part references are NC-1958 & ADP-P005. Although their prices are higher (2.95 & 2.99) their postage is only 2.55. Even if it works out much the same, it may be easier than having to set up an account with CPC (assuming CPC are happy to do a one-off order for a retail customer).

I will certainly try the standard antenna while I'm in Germany and let you know the results.
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peecee
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PostPosted: Thu Aug 03, 2006 11:43 pm    Post subject: Reply with quote

Right having been led to this thread by "mikealder" (thanks), I can shed some light on this antenna/plug fiasco.

Being a time served electronics engineer and now in self employment, and also living very close to both Maplin and CPC I can call in and get stuff whenever I need to, also I have other sources for parts as and when it suits me.

So what I will do is find a better solution to this, even if it means using the Maplin antenna and fitting a 2.5mm jack directly to it.

Very simple mod, and if enough interest is shown I could buy a few in at once and mod them all thus saving on the postage from CPC for individuals etc.

Not sure what the end costings will be until I source the parts etc...

Depending on the thickness of the Maplins antenna cable I might be able to fit some better/thinner cables to make routing easier.

When I get the time I'll see about opening my TMC module up and seeing what the circuit is made up of.

Probably has a current limiting component in there which could possibly be tweaked with a replacement to give the receiver some extra gain.

Also since classic FM is on a narrow frequency band, making an antenna specifically for that wavelength would be pretty easy, having an antenna which is a prime number of the full wavelength will increase gain on it's own.

So the antenna needs to be a full fraction of the wavelength such as 1/8th, 1/4qtr, 1/2th of a wavelength etc..

The good thing is the higher the frequency the shorter the wavelength, so a 1/4 wavelength dipole should be managable.

I'll need to go scrub some figures together, but what I am saying is the Maplins antenna could be cut shorter to a more specific lenght suited to Classic FMs frequencies.
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mikealder
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PostPosted: Fri Aug 04, 2006 8:10 am    Post subject: Reply with quote

Peecee, I have the bits for doing this in my spares box (I bought three sets last time I went to CPC as they only cost around 1.30), so if you want to try the basic antenna coupled to your system give me a shout, I am sure we could meet up somewhere as you are in the local area - Mike
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Davegthomas
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PostPosted: Fri Aug 04, 2006 9:12 pm    Post subject: Reply with quote

Hi Guys

As a Navigon user, which has apparently changed to Trafficmaster, please don't forget us. I believe they use Capital, GWR and Chrysalis radio stations to transmit - so that might alter the calculations or perhaps spawn another model!

Dave T
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swing
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PostPosted: Sat Aug 05, 2006 10:18 am    Post subject: Reply with quote

Indeed - the frequencies that Trafficmaster use vary throughout the whole range of FM.
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mikealder
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PostPosted: Sat Aug 05, 2006 10:25 am    Post subject: Reply with quote

swing wrote:
Indeed - the frequencies that Trafficmaster use vary throughout the whole range of FM.
I that case a standard FM car aerial will do the trick 88 to 108MHz, or use the existing car aerial, not the best of solutions - I hate splitting aerial feeds into two devices. The extra aerial is the way to go - Mike
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lesmals
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PostPosted: Thu Aug 10, 2006 1:33 am    Post subject: Reply with quote

Hi all.
Having bought the Navman 530 about 6 weeks ago I have been trying to get hold of the T1 traffic module.
I finally got hold of one this week but was disappointed at not being able to tune in the unit. I rang Navman support and after waiting for half an hour was connected to someone who only spoke broken english and after getting advice from some one else at the call centre told me it needs tuning in and the only station it would tune was Classic FM.
I tried for hours and in the end did finally get it to lock on to Classic FM by wrapping the coax lead round the car aerial, hardly the right thing to have to do.

Anyway I wish I had read all your comments before ringing Navman as I didn't realise the aerial was so critical.
I have been looking on Ebay and found this car windscreen radio aerial and wondered if this would work and if the plug on it would also fit the T1 Traffic module aerial connection.

http://cgi.ebay.co.uk/Blaupunkt-on-glass-DAB-digital-car-radio-aerial-antenna_W0QQitemZ170016584326QQihZ007QQcategoryZ14932QQrdZ1QQcmdZViewItem

Although a bit pricey it would be a neat and tidy way round the problem.
Any advice would be appreciated.
Thanks Les.
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mikealder
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PostPosted: Thu Aug 10, 2006 7:55 am    Post subject: Reply with quote

Les, As the aerial you have found is for DAB radio reception I wouldn't have thought it will be of much use. The reason being the frequency, this aerial is NOT optomised for the normal FM transmision band of 88 to 108 MHz (Clasic FM works on various frequencys from 99.9 to 101.9MHz).
Even the advert recomends you to keep your existing FM aerial, although they do offer a combined DAB/ FM variant of this product (Jack of all trades Master of none springs to mind though) And the connector will not fit, the TMC unit will accept a 2,5MM mono jack plug - Mike
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mcogman
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PostPosted: Thu Aug 10, 2006 8:29 pm    Post subject: Reply with quote

Reading the above conversations, it has left me wondering exactly what to expect when I travel to Italy later in the year and try to use my T1.

If what the chap from Navman said is true, then, as Classic FM is the only station the T1 will receive (I assume in the UK here), what are the stations I am to expect on the continent?

Has Navman struck an agreement with radio owners in Germany and France similar to Classic FM? If so who are they as there is nothing to tell me in the T1 documentation.

Will the T1 receive more than specific carriers? In the UK I have noticed that I was offered Leicester Sound once so perhaps it isn't just Classic FM. Has anyone else found a station other than Classic FM?

Will the T1 receive a carrier in Italy even though Navman say only Germany and France? In fact, will I lose the T1 signal if I travel via Belgium and Holland, and then Switzerland and Austria?

So many questions - so little time!

None of this is "mission critical" but it would be a nice to know and may be helpful for someone considering divesting themselves of in excess of 100.
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