Thread: Using TMC in Garmin nuvi for free

AH! The penny has dropped. Thanks Giomen. Yes i knew that the vehicle charger cable was used as an antenna for on-board traffic receivers [much as a mobile phone earpiece cable is used as an aerial for radio reception], but didn't make that connection until now [Bl**dy translations!]. So, is that 'version' of 2497 only available in RU region or are there other on-board regional versions in EU as well?

Also, can you add a JM sub the same as with an external GTMxx?

PS: I've bought bits and pieces from Russia. 2nd hand screens, GTM21 recently [it had a US 3 month sub on-board strangely], but never a new unit. One of the few types of units i don't own is an on-board traffic model [someone was going to go to Germany last year to buy me a nuvi 150 for Christmas but spent the money on Vodka instead i think ].
Best you send me one of those Ruskki 2497s this year or i'll sic my 'roo onto your bear's sorry saggy brown a*se!

I do not know Russian market. In Russia is not office of Garmin and so buying device is dangerous. Very bare complectation, overpriced cost, bad service and problems with guarantee take place. So on garmin.ru are many info that do not correspond with reality.
But I hear what model with built-in traffic receiver sold in many country and it have problems with SW in opposite to external GTM. But angelozip wrote that built-in traffic receiver work with JM:

Originally Posted by angelozip

​Models of series 24x5 and 25x5, for sale in the United States, now comes with the Traffic receiver embedded in the body of the GPS, as well as the Nuvis 140/150 Europeans.

The cable carrier is a simple power cord (TA20), but Traffic does not work with non original Garmin cable (still need to test the cables GTMxx with receivers ).

The good news is that the receiver built-in accepts keys generated by JetMouse.

Question is only in SW version for traffic receiver. For external GTM problem is fully investigated on this forum. But not for built-in version. You must post ad that the experimental rabbits is required.

...............
The good news is that the receiver built-in accepts keys generated by JetMouse.

Either i missed that in Angelo's post about the NA 24x5/25x5 with traffic receiver on-board accepting JM subs or had forgotten it. That's essentially the same hw as 14x/15x i think [same PCB P/N anyway] so probably all of them share the same traffic module including 2xx7 i guess, so Philipych can be the experimental rabbit if he chooses.

Friends , makes sense the TA-20 cable also serve as antenna, but would make more sense if there was at least a small antenna embedded in the body of the gps, as exists in much smaller devices like mobile phones ( that have GPS antennas and others.. ), that is, would have felt the traffic work without the cable connected, even if partially. The fact is that the traffic receiver built-in GPS does not work without the cable, then it's likely that it also have some power line specifies in the cable to the receiver traffic. It is also worth remembering that, as already mentioned, a user received of garmin a report that another cable with a different part number manufactured for years (I think ), would also serve as a substitute for the TA- 20 [Only registered and activated users can see links. ] post # 13. It seems so strange that a power cable produced at long ago has embedded antenna and serve to activate the GPS receiver traffic of recent gps, ie, I suspect about the veracity that the function of the cable is only to serve as an antenna .
A likely need of extra power supply to the receiver could be the major energy consumption that would degrade the battery, or Garmin's strategy to force the use of its accessories (cables). To solve the question only opening the other mentioned cable (and a TA- 20) and to see if in fact they have built-in antenna. By the way, the GTMxx cables are divided into two parallel parts visible externally, where a corresponds to power transmission and other for antenna (I've opened some to check out as well). As the receiver is in the cable has felt the main antenna, and connector for an auxiliary, stand in the cable also.

Your EN is better than Giomen's and i understand him just fine.

Thanks for reporting back. Glad you have your added traffic sub working.

PS: Our humour is an acquired taste though. Even native English speakers don't really get it so don't worry ...

Philipych, like you I also assume that TA-10/TA-20 "are not simply battery charger, and at the same time serves as an antenna-feeder path", ie, assume that it serves as an antenna probably, but it has an extra function besides feeding the battery: energizing the traffic receiver, this is the hypothesis.
In short, what I meant was that the receiver built into some models of garmin PERHAPS work with other vehicular GARMIN CABLES (or other duly modified) have they or not antenna. An example of cable "alternative" was the cable that I mentioned and was indicated as a substitute to TA-20 by Garmin and which, it appears, has no antenna. All this because the receiver only works with a power cord connected, strong principle it depends on external power line from a cable. With other Garmin original cables if it works, will certainly be in a limited way, as backup for emergencies or for testing. Of course just only testing with any other vehicular cable from Garmin to check this hypothesis. Also in the Traffic Receiver Status screen you can check if the receiver is initialized and the intensity of the tune.

I go back to my original theory that the principle is the same as the FM radio use in a mobile phone which uses the earphones cable as an aerial/antenna to receive the FM signal [actually, they all use the shielding on the cable i think, not the actual audio wire inside]. There seems to me to be no good reason why it would be any different with on-board traffic receivers in Garmins, other than they are using the shielding of the power cable. Alternatively, they may be using one power wire somehow with some kind of RF filter to separate the FM radio signal, maybe via dedicated choke coils in the 'TA' designated cables. I really don't know nor pretend to fully understand how any of this works at a deep technical level, so much of this is supposition but it does make sense to me.

So, if it uses the wire's shield [screen] as an aerial that would be the simplest because it's already floating free.

If it's using one of the power wires then FM signals need to be separated via a filter of some kind [my car uses the rear window's inbuilt heater to receive it's radio signals via an RF filter. Another less comparative example is ADSL signals over plain copper telephone wires with a filter at our end to separate the ADSL from the voice transmissions. Either way it's using a wire for two purposes and then separating them].

Regardless of the method used, there is no 'dedicated' antenna/aerial as such if my hypothesis is correct. It's the secondary function of an existing part of the cable. Also the aerial needs to be within certain lengths to properly receive the target frequency. This is why Garmin state that the lead needs to be uncoiled. Try bundling up the aerial wire on your FM radio, you'll lose or markedly degrade the reception. If the shielding is used, provided the cable is within the required unwound length then any shielded cable should work and then as reported in the other thread it is as Garmin states, i.e. older cables can do the job.

Certainly there could also be an internal function in the device itself which when it is sensed that the external power is missing no battery power is fed to the traffic receiver. That power sensor's already present in all battery powered Garmin units so it wouldn't be difficult for them to use it to isolate the traffic module from the battery power as Angelo's mused.

Further testing is probably needed as Angelo said, and if anyone is interested it should be in the other thread [Only registered and activated users can see links. ], or even a new one, but a bit OT here now.