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-   -   Automatic choosing best frequency for FM Transmistter? (https://talk.maemo.org/showthread.php?t=52602)

harelm 2010-05-13 19:29
Automatic choosing best frequency for FM Transmistter?
 
Hi, I had a little idea.
is it possible to program a little feature that will scan the FM spectrum with the FM Receiver,
and then automatically and dynamically choose the best one for the FM transmitter?
That way you can travel forever without the need to mess with the
transmitter settings, it will just always be on the best frequency available :)

does the device can handle using both receiving and transmitting the same time?
is it possible to build anything like that?

kylepsp 2010-05-13 19:32
Re: Automatic choosing best frequency for FM Transmistter?
 
I'd like this, similar to the itrip.

hopbeat 2010-05-13 19:36
Re: Automatic choosing best frequency for FM Transmistter?
 
This has already been talk about this.
It is not possible to use transmitter and receiver simultaneously, this could however be done by switching temporary to only receiving mode.

The problem is with antena that is necessary for fm reception...

harelm 2010-05-13 19:37
Re: Automatic choosing best frequency for FM Transmistter?
 
well silly me... i forgot all abut the radio tuning :\
but you have a point, most car's radio have a remote controll,
with i assume uses IR.. so this will be a little trickey - but possible :)

edit:
why is the antena is a problem? you can't just keep the headphones pluged in for reception?

joshv06 2010-05-13 19:44
Re: Automatic choosing best frequency for FM Transmistter?
 
Yeah can't there be a way to scan all off the frequencies and see which has less static? Or some program that shows a graph or how much or less a frequency is being used?

imax 2010-05-13 19:52
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by harelm (Post 657349)
well silly me... i forgot all abut the radio tuning :\
but you have a point, most car's radio have a remote controll,
with i assume uses IR.. so this will be a little trickey - but possible :)

edit:
why is the antena is a problem? you can't just keep the headphones pluged in for reception?
Plugging in headphones disables the fm transmitter.

nosa101 2010-05-13 19:56
Re: Automatic choosing best frequency for FM Transmistter?
 
This is actually a pretty good idea. Maybe the fmtx developer can help with this.

Strutten 2010-05-13 19:56
Re: Automatic choosing best frequency for FM Transmistter?
 
If there was a program that could change frequency like this, there shouldn't be any problem having it as a widget that displays the current frequency and beeps 5 seconds before changing, should it?

Bratag 2010-05-13 19:59
Re: Automatic choosing best frequency for FM Transmistter?
 
http://fmchannel.sirius.com/servlet/FMFind

Perhaps this page (or there are others) could be used.

southwalesboy 2010-05-13 20:06
Re: Automatic choosing best frequency for FM Transmistter?
 
isn't it just easier to use like 107.x ? Don't know about where you live but i've never noticed any stations up near the top end of the FM spectrum

pycage 2010-05-13 20:20
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by southwalesboy (Post 657407)
isn't it just easier to use like 107.x ? Don't know about where you live but i've never noticed any stations up near the top end of the FM spectrum
I don't know where you live but here in south Germany the whole FM band from 87.5 up to 107.9 is heavily polluted by stations and mirrors of mirrors of stations. Scanning through the whole range it's not rare that you'll find the same stations at four or more frequencies.

To answer the question about scanning for frequencies, the FM receiver would not be needed as signal strength detection is also a feature of the FM tuner hardware. It just has to be utilized.

atilla 2010-05-13 20:20
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by Bratag (Post 657396)
http://fmchannel.sirius.com/servlet/FMFind

Perhaps this page (or there are others) could be used.
something like that for germany???

rmerren 2010-05-13 20:25
Re: Automatic choosing best frequency for FM Transmistter?
 
I'd be happy even if this idea were dialed back a notch. How about an app that simply scans the FM bands and reports back the most likely candidates, perhaps rating them on whether there are other stations adjacent, etc. Then you click one of the choices and it sets the FM transmitter frequency for you.

I don't need constant scanning, but I do find the occasional search tiresome enough that I don't really use the transmitter much.

pantera1989 2010-05-13 20:30
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by imax (Post 657379)
Plugging in headphones disables the fm transmitter.
You don't need the FM transmitter to be actually enabled for this to work. You just need N900 in built FM module to scan the frequencies and then edit whatever it has to edit so that the FM transmitter is set to that frequency. I'm sure that info is saved somewhere since the transmitter loads to the previous frequency set.

MohammadAG 2010-05-13 20:33
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by pantera1989 (Post 657444)
You don't need the FM transmitter to be actually enabled for this to work. You just need N900 in built FM module to scan the frequencies and then edit whatever it has to edit so that the FM transmitter is set to that frequency. I'm sure that info is saved somewhere since the transmitter loads to the previous frequency set.
fmtx_client -f89300
to set it to 89.30 (frequency * 1000)

rpgAmazon 2010-05-13 20:37
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by pycage (Post 657424)
I don't know where you live but here in south Germany the whole FM band from 87.5 up to 107.9 is heavily polluted by stations and mirrors of mirrors of stations. Scanning through the whole range it's not rare that you'll find the same stations at four or more frequencies.

To answer the question about scanning for frequencies, the FM receiver would not be needed as signal strength detection is also a feature of the FM tuner hardware. It just has to be utilized.
Then you have the key to do it possible.
Car's audio with RDS active could search for "n900" or "mediabox" if fmtransmiter decides to change frecuence, I'm wrong?

JonWW 2010-05-13 20:43
Re: Automatic choosing best frequency for FM Transmistter?
 
Perhaps what is needed is a databse that can map GPS locations to free frequencies. Then if the radio transmiter (being an RDS transmiter) could send out an alternative frequency signal to the receiving radio, everything could be automated and you wouldn't need to touch anything.

I know little if anything of how RDS works or even if the N900's transmiter can send out an alternative frequency (assuming it even works this way)

Just thought

harelm 2010-05-13 20:54
Re: Automatic choosing best frequency for FM Transmistter?
 
well yes... this will be excellent as well.
finding the clearest frequency is the hardest part (:

tzsm98 2010-05-13 21:00
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by southwalesboy (Post 657407)
isn't it just easier to use like 107.x ? Don't know about where you live but i've never noticed any stations up near the top end of the FM spectrum
107.7 is a strong station in my market.

http://www.radio-locator.com/cgi-bin/vacant

Is good for locating vacant frequencies in the USA.

Making that URL a bookmark in the browser and then manually entering the results would be almost as good as a built-in functionality

For the radio to automatically pick the best frquency it would have to scan the entire band, recording signal strength for each frequency and then select the frequency with the lowest signal. To select any empty frequency would require scanning until it found a frequency with low signal.

I'm no coder but I believe the first option would flow like this:


a- create database with record name =n and value =x
b-Turn on radio receiver
c- mute speaker
d- set frequency to 87.90
e- 87.90 = n
f- create record n
g- read signal strength
h- signal strength = x
i- write x to database record n
j- n=n+.05
k- if n <108.00 then goto to f
l- if n = or > 108.00 go to m
m- sort database descending order of x
n- read n of top cell in database
o- n=f
p- set radio transmitter frequency to f
q- unmute speaker
r- turn off radio receiver
s- end

This ought to yield the frequency with the lowest signal without having to listen to it scan frequencies. How long this program rests at each frequency before recording the x value will impact how long it takes to run and how accurate it is. This is a single sample routine. A more accurate routine would include x= average of three readings at n.

There are several different ways of implementing this sort of function

1- A GUI button to call it from the FM transmitter application
2- Make it part of the FM transmitter application startup routine ( no GUI required)
3- A GUI Toggle for using it on next start-up of the FM transmitter, default is off

This assumes there is a way of measuring FM signal strength directly from the FM chip.

JonWW 2010-05-13 21:06
Re: Automatic choosing best frequency for FM Transmistter?
 
Why is it crazy? If you drive around listening to a station and that station fades out of range, then there is (I assume) a list of alternative frequencies being tranmited by that station so that the radio can tune to, so you can continue to enjoy the same station.

As far as I can tell this is almost instant, so the radio will not be scanning for the name of a station as it can take time for a radio to decode the station name, ther must be a list of alternate frequencies

So the question is: If the N900 changed frequency could the radio follow it and if so what is the timeout period for bad reception for the radio to change frequencies. Could there be a delay making it unusable

MohammadAG 2010-05-13 21:07
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by rpgAmazon (Post 657458)
Then you have the key to do it possible.
Car's audio with RDS active could search for "n900" or "mediabox" if fmtransmiter decides to change frecuence, I'm wrong?
afaik RDS is "downloaded" after tuning into a station, not while automatically tuning. Not sure about it though.

Rapparee 2010-05-13 21:17
Re: Automatic choosing best frequency for FM Transmistter?
 
I was thinking about this as well...

I also thought can we use the headphone jack as a means to create better reception for the FM trnasmitter?

tzsm98 2010-05-13 21:46
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by Rapparee (Post 657530)
I was thinking about this as well...

I also thought can we use the headphone jack as a means to create better reception for the FM trnasmitter?
Are you thinking of a plug-in FM transmit antenna for the 3.5 jack? That antenna could include an amplifier. If the signal from the transmitter can be moved to the 3.5 jack that would be the end of "the FM transmitter is too weak" complaints.

imax 2010-05-13 21:46
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by pantera1989 (Post 657444)
You don't need the FM transmitter to be actually enabled for this to work. You just need N900 in built FM module to scan the frequencies and then edit whatever it has to edit so that the FM transmitter is set to that frequency. I'm sure that info is saved somewhere since the transmitter loads to the previous frequency set.
agreed the scanning part will work without the transmitter being enabled, but if the op is wanting to travel round with the transmitter automatically selecting the best frequency, unless the headphone override on the transmitter can be turned off, you'll need to keep plugging in and disconnecting the headphones.

still can't see how the car radio would be retuned. AFAIK, the auto retune works by selecting the strongest signal within a predefined range for a specific station, once a previously free frequency was no longer suitable, a significant change in frequency would be needed, which falls outside the use of auto frequency functions.

ceroberts75 2010-05-13 22:09
Re: Automatic choosing best frequency for FM Transmistter?
 
this would be great. i use 104.1 here in the bay area most of the time. only run into challenges when i travel.


the ability to tap the screen of a widget and have it "search on demand" and pop up 1-3 freqs to use and then tap that freq should you want to use it, then change your radio station as needed would be awesome.

IzzehO 2010-05-14 00:30
Re: Automatic choosing best frequency for FM Transmistter?
 
I still don't understand why so many people have issues with the FM transmitter. With FM Boost enabled I can drive through the middle of the CBD of Sydney and not have the slightest bit of interference

YoDude 2010-05-14 01:45
Re: Automatic choosing best frequency for FM Transmistter?
 
I don't BTW need to go below 88.0 and use a web app if I find I'm a stranger in a strange land and need a new vacant channel.

>> http://www.radio-locator.com/cgi-bin/vacant

>> http://frequencyfinder.org.uk/

>> http://fmchannel.sirius.com/servlet/FMFind

( I found fmchannel.sirius^ not as good as www.radio-locator. YMMV )

With all that^ said... I'm wondering if a 4 or 5 button preset app that launches FMTX set to one of the presets would be more realistic and easier to put together. It could be a status bar app that drops down with the volume slider, Clock & Alarms, Etc.

juise- 2010-05-14 09:53
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by tzsm98 (Post 657579)
Are you thinking of a plug-in FM transmit antenna for the 3.5 jack? That antenna could include an amplifier. If the signal from the transmitter can be moved to the 3.5 jack that would be the end of "the FM transmitter is too weak" complaints.
I think wanting to be weak is actually the reason why transmitter is disabled when there's any antenna substitute plugged in. It might actually become too effective, and there are regulations to follow.

YoDude 2010-05-14 15:22
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by juise- (Post 658092)
I think wanting to be weak is actually the reason why transmitter is disabled when there's any antenna substitute plugged in. It might actually become too effective, and there are regulations to follow.
I think we may over think this stuff and come up with reasoning to suit our desire that all behaviors are by design.

Code may have unintended consequences and if these bugs remain unidentified... they never get fixed. Until then, all we can do is cobble together work arounds.

I believe this is a bug based on the fact that if FMTX is invoked while the charger is plugged in, TX power level is unchanged. Unplug the charger and then plug it back in... TX power level goes in the toilet.

If it was designed to eliminate the cable as a possible TX antenna it fails when FMTX is invoked while already on charge or plugged in.

... a bug either way you look at it. :)

tzsm98 2010-05-14 18:19
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by juise- (Post 658092)
I think wanting to be weak is actually the reason why transmitter is disabled when there's any antenna substitute plugged in. It might actually become too effective, and there are regulations to follow.
I was thinking for testing purposes only:rolleyes: of course we do not want to oversaturate the area around our N900 with illegal, overpowered FM transmissions. If it is that hard to find an empty frequency now, just imagine how tough it would be if your neighbors all put a 1 watt amplifier on their N900.;)

pycage 2010-05-15 14:48
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by YoDude (Post 657769)
Do European stations broadcast below 88.0?
Is 87.5 ~ 87.9 heavily populated?
Unfortunately yes... :(

~phoenix~ 2010-05-16 12:59
Re: Automatic choosing best frequency for FM Transmistter?
 
hmm... what about a widget button with "use next avaliable frequency"
when you press it the fm reciever will measure the signal strengh of the next 20 frequencies.... if there is a frequency with signal strengh under a specified value then set to the freq with lowerst value... else search next 20...

another thing is my radio automatic switches freq when signal is to low.... ex. radiostation sends on 105,3... after 50kilometres it sends on 98.5... for some way my radio automaticly tunes in 98.5 when i leave the 105,3 area.... normaly it search up... but for some strange reason it changes freq to 98.5 to recieve the same radiostation...

how is this feature workin? can we build in that feature in the n900??

sry for my bad english...

southwalesboy 2010-05-17 13:42
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by pycage (Post 657424)
I don't know where you live but here in south Germany the whole FM band from 87.5 up to 107.9 is heavily polluted by stations and mirrors of mirrors of stations. Scanning through the whole range it's not rare that you'll find the same stations at four or more frequencies.

To answer the question about scanning for frequencies, the FM receiver would not be needed as signal strength detection is also a feature of the FM tuner hardware. It just has to be utilized.
I live in south wales (uk) and i think the entire FM spectrum here has about 6 radio stations lol. probably too high tax for local commerical stations knowing the UK law!

korhojoa 2010-05-17 14:10
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by ~phoenix~ (Post 660785)
hmm... what about a widget button with "use next avaliable frequency"
when you press it the fm reciever will measure the signal strengh of the next 20 frequencies.... if there is a frequency with signal strengh under a specified value then set to the freq with lowerst value... else search next 20...

another thing is my radio automatic switches freq when signal is to low.... ex. radiostation sends on 105,3... after 50kilometres it sends on 98.5... for some way my radio automaticly tunes in 98.5 when i leave the 105,3 area.... normaly it search up... but for some strange reason it changes freq to 98.5 to recieve the same radiostation...

how is this feature workin? can we build in that feature in the n900??

sry for my bad english...
http://en.wikipedia.org/wiki/Radio_D...implementation

That.
I've been wondering why it doesn't send any information to the radio when you change the frequency.
It would make sense to first send the alternate frequency information and then change over the transmitting frequency, so that no fiddling with the tuning would be required.

Is it possible to implement at least this?

stlpaul 2010-05-17 14:28
Re: Automatic choosing best frequency for FM Transmistter?
 
Quote:
Originally Posted by tzsm98 (Post 658714)
I was thinking for testing purposes only:rolleyes: of course we do not want to oversaturate the area around our N900 with illegal, overpowered FM transmissions. If it is that hard to find an empty frequency now, just imagine how tough it would be if your neighbors all put a 1 watt amplifier on their N900.;)
I wish my N900 would become illegally overpowering enough that my car radio could actually receive its signal clearly one day. :D

maxximuscool 2010-08-16 22:48
Re: Automatic choosing best frequency for FM Transmistter?
 
illegal N900 = the best!!


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