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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.

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???

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.

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.

Re: Automatic choosing best frequency for FM Transmistter?

Quote:

Originally Posted by pantera1989 (Post 657444)

fmtx_client -f89300
to set it to 89.30 (frequency * 1000)

Re: Automatic choosing best frequency for FM Transmistter?

Quote:

Originally Posted by pycage (Post 657424)

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?

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

Re: Automatic choosing best frequency for FM Transmistter?

well yes... this will be excellent as well.
finding the clearest frequency is the hardest part (:

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.

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