FM Transmitter does not work while plugged into charger
 

I bought Radio Shack branded a micro usb car charger for my N900 today. I tried to use the N900s FM Transmitter while it was charging. I was surprised that it did not work at all.

Has anyone tried the FM transmitter with an official Nokia car charger? Does the official charger have a FM antenna built into it?

Re: FM Transmitter does not work while plugged into charger
 

The problem is the FCC. Plugging a wire can act as an FM antenna and then people in other cars might be able to hear you playing your Britney Spears albums. :rolleyes:

Re: FM Transmitter does not work while plugged into charger
 

Ugh.. well there goes one of my purposes of the n900. I wonder if there is a way to bypass that with a hack if it's not limited by the hardware.

Re: FM Transmitter does not work while plugged into charger
 

There has to be a way around that, its completely unreasonable.
Who is NOT going to have their N900 on charge while in the car?

Its totally insane to expect people to drain their batteries while near an outlet. Especially as iPod FM transmitters come with car adapters, although I think they factor in the cable as you get no reception at all without it plugged in.

But that just proves the point, surely you just factor in the likely signal boost from the cable and drop the output strength accordingly while charging. There is always the possibility of interfering with other people, it all depends how well shielded your car is to begin with.

Re: FM Transmitter does not work while plugged into charger
 

I use my n900 with the nokia dc-6 car charger and fm transmitter works fine.

Re: FM Transmitter does not work while plugged into charger
 

Hmm the n900 doesn't charge with a power pin like the older tablets and other Nokia phones does right? So it's not a matter of plugging into USB vs. power pin since there is no power pin option.

Re: FM Transmitter does not work while plugged into charger
 

It may not be the N900 itself. It might be the car recharge and the usb data cable which is the culprit. I have a nice little DC/AC power adapter which provices Fireware and USB powers. I use this to recharge my old phone and NITs. But when I tried using it with N900, it doesn't work. The N900 doesn't kick into recharge mode. And like the OP, it's kills my FM Transmitter. After I disconnect it, it seems the FM transmitter power output is also drastically reduced. I have to reboot the N900 to FM transmitter back to normal.

I suspect that the data connections in the USB data cable are confusing USB hardware or drivers. Does anyone know if the AC recharge only has the power connections wired on USB port? If not how are the data connections wired?

Re: FM Transmitter does not work while plugged into charger
 

It [fmtxd] checks to see if a charger is in by listening to D-Bus (and, perhaps; a sysfs entry). Feel free to look at fmtxd's strings.

Re: FM Transmitter does not work while plugged into charger
 

I have an original Nokia car charger lead and find that the N900 FM output works but is badly attenuated when the charger is plugged in.

This is a serious problem for me because I planned to use the FM transmitter to listen to podcasts while on long drives.

Until reading this thread I had assumed it was something to do with the power cord grounding the N900 to the car.

Re: FM Transmitter does not work while plugged into charger
 

Repost:

I'm not sure if this has been pointed out in another thread or not but I thought I'd mention it since it's really helped me out.

Currently, the N900's FM Transmitter either deactivates or is reduced to an unusably low power level when and AC adapter is plugged in to the Micro USB port. This sucks since transmitting over FM burns your battery and there's usually a cigarette lighter socket nearby just begging you to charge off of while you listen & drive.

Well, I noticed that if you install fm-boost and execute it AFTER plugging in the power adapter, the N900 resumes FM transmission at the full power level of 118 even while charging!

Re: FM Transmitter does not work while plugged into charger
 

This would mean the initial theory is correct, that the transmitter is still on, but the power has been reduced to a very low number. echo'ing 118 into that file (cant recall the location) would have the same effect then (as that is was fmboost essentially does)

So that's good to know. Easy to fix.

Re: FM Transmitter does not work while plugged into charger
 

I have an Official Nokia Car Charger for the N900 and the FM transmitter works fine when plugged in.

Re: FM Transmitter does not work while plugged into charger
 

I thought FCC was US only (Wikipedia agrees), so does this only happen in the US? Is it international? Is the charger really used as an antenna? Shouldn't that bother USB data stream?

Wouldn't is be easier to simply use a lookup table and just lower volume if nmatch() finds 'spears'? Or simply reboot the phone.

That would be nice; to see the threads "My N900 reboots while playing .. uhmm.. some random MP3".

Re: FM Transmitter does not work while plugged into charger
 

I have several issues related to car charging:

1. I have the DC-6 car charger; the first one I had stopped working after a week - literally went up in smoke. I got a replacement, but note that it is running very hot - not usual for a car charger. If anyone else has the official DC-6 12v car charger from Nokia, check to see if the round portion that plugs into the car is running warm or hot.

2. Not all 3rd party chargers will work with the N900. I tried a clever, tiny USB jack that barely protrudes from the cigarette lighter jack in the car. Using a known good USB cable, the N900 refuses to charge. This is the Beljkin Micro Auto Charger for the iPod, F8Z446.

Using another generic micro USB car adapter however did seem to work.

3. My Nook and Kindle readers use the same micro-USB connection. Their AC chargers will charge the N900.

4. The N900 doesn't always recognize the Nokia AC charger. Unplug/replug is sometimes necessary.

My conclusion: I did read the other thread concerning the need for smart chargers. I'm just a little concerned that the official DC-6 from Nokia runs very hot, and I already had my first one go up in smoke. I have yet to try the Nokia CA-146C converter; I did see another note about one of these going up in smoke, too.

As for the FM transmitter - I have not had much success using it in the car, so I have been using the 3.5mm headphone jack to connect to the car audio system. I know the FM transmitter is working, since I tested it with another desktop radio. The signal is simply not strong enough in my car - whether using the charger, or not.

Re: FM Transmitter does not work while plugged into charger
 

Read the Output mA (on the label) of the AC (wall) charger. You will notice that it is 1500 mA, which = 1.5 amps. most, if not, all aftermarket chargers are only, wait for it... 500 mA. This is only one THIRD of what is required to charge and operate the N900. That is probably what smoked your charger.

as an electrician, I recommend, using a DC to AC inverter. Then plug the AC charger into that.

Re: FM Transmitter does not work while plugged into charger
 

The FM transmitter is programmed to reduce power when a car charger is plugged in to, I believe to stop the charger cable acting as a antenna and so boarding casting the signal outside of the vehicle.

However there is a script on either this forum or Nokia's own which overrides the power reduction and I have been using it without any issues for the last 6 months or more.

Found the link now but only do this if you are confident you know what you are doing as there is a danger you could mess up your transmitter


http://discussions.nokia.co.uk/t5/Ma.../755743#M18280