Thread: Automatic choosing best frequency for FM Transmistter?
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tzsm98 is offline tzsm98
2010-05-13 , 21:00
Posts: 500 | Thanked: 437 times | Joined on Nov 2009 @ Oklahoma
#19
Originally Posted by southwalesboy View Post
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.
Last edited by tzsm98; 2010-05-13 at 21:13. Reason: change receiver to transmitter