Handheld cordless phone

Hello guys,

I am trying to build a walkie talkie. My idea is to be able to communicate with 10 people or 7 at least, without any interference from other then the guys who has the device.
(Q1) What transmitter should i use that willl achieve high range ? ...

i was looking up FM transmitters and i thought at 433MHz will be the highest range, with the proper antenna. but now am confused ?!
(Q2)iIsnt FM in the range of 87.5 to 108.0 MHz ? why then 433MHz , 315 , 868MHz availability ?

(Q3) will arduino be suffecient for such project ? i already built the amplifiers and such , just the transmitter is missing and if i will use arduino , then i have to do dsp programming

Peace

Hi,

A few concepts:

FM (Frequency Modulation) can be used at any RF frequency; 88-108Mhz is commercial FM broadcasting in USA.
Many different modules that operate at many different frequencies are available. You probably need to experiment.

And Questions:

  • What is "Highest Range"??
  • What would the Arduino do?
  • What Digital Signal Processing do you expect to need? Why?
  • How many users? How would you organize "Who is talking now"??

Usual Engineering: More questions at the start!

terryking228:
Hi,

A few concepts:

FM (Frequency Modulation) can be used at any RF frequency; 88-108Mhz is commercial FM broadcasting in USA.
Many different modules that operate at many different frequencies are available. You probably need to experiment.

And Questions:

  • What is "Highest Range"?? more then 500meters is good, the highest the better . so if 2 km line of sight i think it will be perfect but if less then it is ok .. As far as i understand the lower the frequency the higher the range (with factors like :antenna gain , Rx sensitivty , tx gain)... the factor i want to avoid is an ugly big antenna,

  • What would the Arduino do? The arduino will work to process the voice (ADC in ) (DAC out) and program the transmitter... if you have a better option then that please enlighten me

  • What Digital Signal Processing do you expect to need? Why?
    if you mean by modulation techniques such as FSK ,PSK, frequency hopping .. then i cant decide yet.. whatever that can give secure communication and reduce or prevent interference.... i think so far frequency hopping is the best , but i have 0 experience programming any actually..

  • How many users? How would you organize "Who is talking now"??
    users upto 10 ... the one who switches first the talk button (transmit) the rest must listen

Usual Engineering: More questions at the start!

Thanks dear terryking228 for the quick smart response. please check my answers above