N900 Radio Transmitter: ways to amplify the radio signal
 

Hey,

From the threads on the forum, it is obvious that even though some people have awesome experiences with the radio transmitter, and in some cases the transmitter is way too powerful (like a friend driving behind you being able to tune in), the experience of others (including me) have been disappointing.

The fm transmitter only works when my N900 is literally touching the radio's antenna. Using the transmitter in a car, or anywhere more than 10cm away from the antenna is impossible.

Through software, would it be possible to amplify the radio signal? Or would it be possible to override the transmitter not working with a headset problem to amplify the signal through some changes to the driver, or OS?



Another thing to note is that maybe each country (or even state) has different regulations, and the transmitters are powered down according to where the N900 is sold. That would explain the discrepancy between the experience of users.

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

could be your antenna on the car ..

i dont think that they would dumb down the power for each state .. maybe country .. but not state .. too much work ..

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

At best I'd expect the most granular this would be is by firmware.

Would be interesting to test multiple firmware localizations on the same n900 in a fixed location with fm transmitter.

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

that's a pretty good idea actually.

Btw, I have tested with multiple radios, in different frequencies and the result is the same. Moreover, I've read most of the threads on the issue and there are people with similar experiences, so it's either hardware issue, software restriction, or maybe in places where the fm band is crowded the radio works much harder (but then some people have pointed out before that their n900 can overpower radio stations at close range).

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

I am using 89.1 in North Dallas, TX, USA.
Becasuse N900 cannot broadcast on the 87.9 which is the free wave here in states. Mine is not that strong where my friend can tune in the same channel when they are driving behind me but I do not need to touch the phone and antenna of the car.

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

I've been using 88.1 in the UK. It was perfect in a Honda Civic, but not so great in a Mercedes A5. A Toyota was ok and a Jag was average as well. I think it may be to do with the location of the aerial on the car? It's ok at short distances from my DAB radio at home, but even 6/7 feet away, it starts breaking up. Perhaps someone else knows the optimal frequencies to use in different cities/countries.

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

... from reading the forum on this issue it really does sound like the FM transmitter's range is tied to the local markets laws ... I'm in the UK ... and my FM transmitter experiences static when it's more than a couple of feet from a radio ... and in the car is useless unless I hold it, and touch the radio with the other hand ... there's no way in the world my FM transmitter could be capable of transmitting to the car behind me!

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

Which frequencies have you tried?
I think the trick may be to find an "empty" frequency, if such a thing is possible in the UK.

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

maybe its important how the n900 is faced toward the antenna? :>
maybe it transmits the signal in a focussed direction rather than broadcasting it 360 degrees, so if its not pointing to the antenna the right way, you'll have bad reception.

just a thought though, still dont have a n900 to prove this theory to myself.

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

i use 107.3 in cambridgeshire area and east london.sound quality is quite good in my volvo v70...

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

That's an interesting theory, I just tested it myself with the stereo in my room.

I first walked the farthest before I heard static. (pretty much out of the room, the stereo is on the opposite end). Car length wise it'd be about 1.5 Toyota Camrys (yes I know a odd measurement) length.

When the N900's screen is facing the user, and the back is facing the stereo the signal was clearer (no static). If I flipped the N900 around so the back was facing me and the screen was facing the stereo then I could hear static.

Though having tested the transmitter in a car being in a metal car does reduce its range a bit. I've had trouble getting it to work without static even when say resting on the middle compartment (between the two front seats). Toyota cars have their receivers in the back of the car.

Edit: And if you get in the way of the signal there's static too. E.g. position the N900 between you and the radio receiver.

I live in the USA (for clarification's sake). So whatever regulations for transmissions come from the FCC.

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

89.1 - N900 placed on the drive side dash and pushed back to meet the windshield.

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

Yea i got to admit...transmission is not that great and i always get static signal along with the music. I didn't bother to fine tune it though as i was busy driving. But from my first experience...that's what's what happened.

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

ok

when im using the stereo in my home the signal is lost if i hold the n900 more than 10cms awasy from the antenna in any direction.

by signal loss i mean a complete loss and not just simple noise that happens at 5 cm

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

I can confirm I can get it to work, but I need to be +-50cm from the antena. I find the relative volume to be soft, magnifing the static because I have the volume so high.

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

I've generally stuck to 88.1 ... although I did try it on a higher frequency on a radio that didn't go down that far ... any suggestions for a good frequency for Bristol in the UK?

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

Found this today: https://bugs.maemo.org/show_bug.cgi?id=6792#c9

When FM transmitter is on, the following sys file is present:

/sys/class/i2c-adapter/i2c-2/2-0063/power_level

You might could try fiddling with this value and see what happens. Of course you do so at your own risk and I take no responsibility for you frying device or getting frog-walked/fined by the FCC.

Also would be curious to know what the value in this file is for different people:

With fm transmitter on do (this will not change anything, it's just a way to see what the current level is):

And report back what number comes back, I get 112 (also the number referenced in that bug report)

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

This meshes with my experience in a Rental with a top roof antenna.

I only got a decent signal by clipping the n900 to the headliner in my e51 case, and signal was better with screen down instead of screen up.

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

I finally tried the FM transmitter.

1. 2003 F250 Truck - Pretty good
2. 2008 F450 Truck - Kinda crappy
3. 05 and 08 CL65's - Couldn't hear anything playing.

This leads me to believe that different cars have different RF insulator qualities for the antenna cable going into the head unit.

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

i have had fm transmitters that transmit at 87.9(and a car with the pick up ability for 87.9)- and it wqas great..

i cannot find any really good signal in london.. best is 154.1

its not great.

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

112 here as well.

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

Might be helpful to include firmware localization as well

I'm at 112 on US firmware PR1.0

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

I'm sitting at 111.

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

mine was 111 with US firmware. The datasheet (http://www.datasheetdir.com/SI4713+Rf-Transmitters) lists a programmable transmit output voltage to be 118dBuV typical with a test condition of 102-118 dBuV for the accuracy spec. I'll go out to the car in a bit and see if I notice any diff setting this to 118.

Interestingly, /sys/class/i2c-adapter/i2c-2/2-0063/region_bottom_frequency contains 87500 but the GUI only goes down to 88.1 .. i'd love to be able to use the 87.5-87.9 freqs too...

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

Ok, I noticed a decent improvement of 118 over 111 or 112. It cut the static down quite a bit...

Anyone find a way to manually control the tx freq to force, say, 87.9?

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

Did it keep your changed power level after a disabling/reenabling of the transmitter?

After a reboot?

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

no, as soon as i turned off the fm transmitter, power_level got set back to 111. you'll need to find a solution to keep setting it

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

112 - in the UK.

Have rotten reception - none in the car (Saab 95) and dreadful on my one remaining FM radio in the house - has to be touching the radio to work.

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

Do You have original volvo radio? I have SC-816 with rear side window antenna and when n900 is on dash FM transmission is very poor quality...

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

Firmware 51-1 here and the value now is 118 on the pre-production device and 113 on the Summit one.
Kinda weird.

It's set a 90.5 on the Summit one and 88.1 on the pre-prod one.

If I disable the FM Transmitter, tough, that profile is still there.

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

Btw, it sucks on both.

Today I used my K850i from SE as Radio (it also has RDS).
I had to place the N900 right on the headset cable (the 'antenna') to have clear audio in the 'radio' (the K850).

If I kept the N900 in my hands, sitting at the table, thus few cm away from the 'radio', the quality would drop a lot.
Rotating the N900 did affect the quality (from nothing to good quality) of the audio in the 'radio'.

And I was in my room... not in a shielded car.

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

Hey, i'm from the uk and i'm at 113, curiously as soon as i plug in the charger it drops down to 88, do you think changing it back up would solve the issue of the transmitter being unusable when charging?

I use my transmitter in my C3 at 107.3 with pretty decent reception, i occasionally get a bit of static, mainly when other pirate stations cross the frequence. I drive in the essex area and about the north m25 with my n900 sitting besides my steering wheel.

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

Yes, this information was gleaned from a Bug relating to that exact issue:

https://bugs.maemo.org/show_bug.cgi?id=6792#c9

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

Does it transmit while charging?

Mine in on charge now, FM Transmitter is off, level is 113.
I can't activate the FM Transmitter (as per the bug) while charging.

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

I get the same behaviour, but apparently some people are able to have their FM transmitter on at reduced power while charging.

I wonder if it's a difference in charging through a 'dumb' charger vs. a USB Host.

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

Uhm.. indeed.

Anyway apparaently that has been fixed in 51-5, but I can't test it.

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

Ah I just plugged the wall charger in and it works.
If I plug in the USB cable (attached to a computer) than it complains... Interesting.

And yes, the power_level dropped from 118 to 93 on the pre-production and to 88 from 113 on the Summit one.

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

Bug https://bugs.maemo.org/show_bug.cgi?id=7425 entered. I am in region 2. /sys/class/i2c-adapter/i2c-2/2-0063/region_bottom_frequency is 87500

If you have a region_bottom_frequency less than 88100 and 88.1MHz is the lowest frequency available to you in the FM transmitter GUI and you want to set a freq below 88.1, please vote for bug 7425.

If you are able to set a frequency below 88.1 by the GUI (or other means), please post to this thread.

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

i thought i had seen a bug for that (88.1 being lowest selectable in GUI) but I can't find it now. I've voted for 7425.

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

According to the N900 manual the limit is 88.1 - 107.9.
According to Wikipedia an FM Transmitter "can broadcast on any FM frequency from 76.0 to 108.0 MHz (or 88.1 to 107.9 in the US)"

Weird as right now Nokia's selling only the Euro version of the device.