Transmitting Power??

[Meee]

:) Hi guys

Can any body till me how to calculate the power needed to transmit!!
>>>> I want to transmit a signal with a range of 400m , but I am not sure about the power??

[audioguru]

hi Meee,
Welcome to our forum. ;D

Transmit power and range depend entirely on whether the modulating signal is analog or digital, the RF frequency, AM or FM (or fancy digital types), and wideband or narrowband.
Of course it also depends on the sensitivity of the receiver, if there is an obstuction between the transmitter and receiver and what quality is acceptable. ;D

[prateeksikka]

hi Mee!
What kind of modulation are u using for your signal?
In case its FM u have to compromise with the range

[Guest SM2GXN]

Audioguru you forgot to mention one of the most important things that will affect the range namely the antenna,  without antenna you are going nowhere  ;D
400m is quite short distance so a couple of hundred mW will do the trick if there is no objects between receiver and transmitter.

[Meee]

:) ;D audioguru,prateeksikka and 4-1000A >>> Thank you very much for your response.

I believe I have to give more info. about my project to get help, so this is a brief summary about my project:

[Shahriar]

Hi

The Most importat parameter between The DC power and Output power in a transmitter is called Efficiency. the best transmitters have efficiencies near 60%. the

Efficiency = Output Power / Input power

The most power disspation occures in RF Amplfier Section: Class E RF amplifiers have the best Efficiency.

Anyway I recommand you to use a Long range remote control because they have a SAW resonator and works an 433Mhz or higher and have very good stability. If you build one yourself without a resonator then It is possible that sometimes your Remote control doesn't act because of the oscillator Shift Frequency and the person in Ambulance say goodbye to everybody :-((

HTH - Shahriar

[Guest Alun]

If you don't feel like building a transmitter you can buy some nice modules to save you the hassel.

There are other ways of doing this, like detecting the siren or blue flashing light, I've been told that if you flash your headlights at the right frequency at some of the traffic lights in our town in they change to green I haven't tried this and it might also be illegal I don't know.

[binkabir]

i have successfully constructed the time beeper that was published in this web in fun anough IT DIDN'T WORK. could any help me out  ???

[audioguru]

All traffic lights in my city have a little sensor with a "baseball cap" on it, shielding it from the sun, I guess. It probably detects the flashing strobe lights on emergency vehicles.
I am waiting to see what will happen if two emergency vehicles arrive at an intersection at right angles at the same time. The traffic light controller will have a heart attack and need to be re-booted. ;D

When an emergency vehicle comes along behind me, I move over to let it go by (unlike many morons who just stop in front of it), then move in behind it to follow it through all the green traffic lights. ;D

[Meee]

Thanx everybody I got some ideas from your replys, and I appreciate you all ;)