Re: N900 Radio Transmitter: ways to amplify the radio signal
 

this pretty much sums up my experience on the device...

how come we have such a huge difference in use experience of the radio transmitter?

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

Different receivers?
Have you tried your phone with other cars, or car with other transmitters?

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

Hi All!

My first post...

I just tried the "cat /sys/class/i2c-adapter/i2c-2/2-0063/power_level" command and it returned 112...

I'm in the UK and when I tested the FM transmitter inside the car and my house I was disappointed to say the least.

Is 112 the maximum signal strength?

Cheers,

Daniel

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

The preset power level was 114 for me (scandinavian sales SW).

Setting it to 118 removed almost all of the audible static and made the signal strong enough to be captured decently in all cars I tried it in (and older Golf, a Scudo and and shiny new Insight; only the Scudo initially struggled with it).

One thing to remember with the numbers is that the chip may have some kind of built-in Tx power management by monitoring the actual power pushed to the air vs. power reflected back from the antenna. As the antenna itself seems to be a just a metal sliver with carefully formed shape suited for antenna use and the contact is a standard metal-gold-spring-loaded touch-gold-nickel-copper contact, it is subject to variance in quality from device to device and also WILL vary as the device ages and gets dropped, dusted, humid, squeezed, dipped in beer and so on. The Tx power can quite likely be controlled to some degree by the chip itself, though the problem here is not frying the gain stage - even the maximum output is but a candle compared to the supernova-like relative luminosity of the "real" transmitter stations - but power usage that should always be minimized.

One nasty thing I noticed about the transmitter is that there's quite little fitering from the main power net of the phone to the transmitter. I noticed this when I was trying it with the not-that-good-but-adequate minihifi set I use as computer speakers and not that low sound level as I wanted to hear if the static changed as I played with the settings - the bundled charger distorted the transmitted signal to a horrible shriek that made my cat go from sleepy rest to VERY puffy in about 3,8 µs and resulted in eight bleeding deep puncture wounds on my shoulder, lots of swearing and bodily pain due to the shock from the shriek and the cat wanting to suddenly delocalize itself, which in turn resulted my computer chair toppling over and me lying on the floor, bleeding and wondering what the hell had just happened - and the shrieking just wouldn't stop until got up from the floor and pulled the charger cable - it was closer than the power button for the speaker set.

Perhaps this is why the SW is not sure whether to allow the FM transmitter to work while a power-carrying cable is plugged in? :D

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

Hahah! Well i'm glad to hear you survived that attack!

Would you mind sharing how you changed the default power level? I'm a total n900 / linux noob! :(

Do you think changing it could invalidate the warranty?

*EDIT* I should probably just learn to UTFSE! Sorry!

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

Noob Question:
How to change it manually ?
is it something like this ?

sudo gain root
cat 118 > /sys/class/i2c-adapter/i2c-2/2-0063/power_level

Thanks

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

I think you're going to get a file not found error with that command.

I tried using vi to edit the file but got scared when I got a file could not be opened fully error... (or something to that affect)

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

close.

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

Hello Guys

Are you sure the changing the contents of that file is going to change the Power Level ?

I think that that file is not a "config" file but it is a Log file, if you notice that file is updated whenever you start the FM Transmitter, so the only thing that that file is telling you is the current power-level.

The contents of my file where:

0

And after i started the FM Transmitter it changed to 111.

So i really think is a Log file

Maybe it cannot be changed this easily

Re: N900 Radio Transmitter: ways to amplify the radio signal
 

I've tried echoing 118 to that file whilst the device is connected to the charger. Before echoing 118, cat returns 88, and the signal is weak. Echoing 118 increases the signal strength so that the receiver is fully quieted.

So, it works for me :)