2.4 GHz wireless audio link 1 KM range

[vigyanabikshu]

I want to make 2.4 GHz mono wireless audio link having 1 KM range. I think NRF2460 will be fine for me, but the range is less than 100 Mtrs. Can I use some RF amplifier ICs like RF2126 to increase the range to 1KM?

 

[jiripolivka]

Much easier way is to use a directional antenna on both sides. For 1 lm range I would suggest to use a parabolic antenna, e.g. a satellite TV dish. Commercial antennas are also available, with a gain up to >20 dB.
Two such antennas add >40 dB to your link, much easier than adding the transmitter power.

 

[vigyanabikshu]

Much easier way is to use a directional antenna on both sides. For 1 lm range I would suggest to use a parabolic antenna, e.g. a satellite TV dish. Commercial antennas are also available, with a gain up to >20 dB.
Two such antennas add >40 dB to your link, much easier than adding the transmitter power.

Thanks for your good suggestion. But I want to implement it in schools, colleges etc, so that every class room, I have to put receiver and each may be located far.A single Transmitter and more than 25 Receivers around.

 

[crutschow]

Is there any legal problem with broadcasting at that frequency at a higher power where you live?

 

[FvM]

I don't believe that Indian telecommunication regulations permit increased transmitter power required for 1 km range in the 2.4 GHz band.

It should be also noted that most applicable standards for small radio devices are field-strength respectively e.i.r.p. related. Using a directional antenna would enforce a reduction of transmitter power to keep the limit values of these standards.

 

[jiripolivka]

I don't believe that Indian telecommunication regulations permit increased transmitter power required for 1 km range in the 2.4 GHz band.

It should be also noted that most applicable standards for small radio devices are field-strength respectively e.i.r.p. related. Using a directional antenna would enforce a reduction of transmitter power to keep the limit values of these standards.

Mostly in and around the schools, people are concerned of irradiating children by a higher RF power at >1 GHz. Technically there may be multipath problems, too.
If your task is to distribute an audio signal, I would suggest to use a low-power FM transmitter at 88-108 MHz band. Such designs are widely used, require ~1W to cover > 1 km square area, and pose no danger. Low-cost FM receivers can be used.
Or, use a cable-distributed system, like describe in the thread "Photodiode noise reduction" elsewhere on Edaboard.

 

[vigyanabikshu]

Mostly in and around the schools, people are concerned of irradiating children by a higher RF power at >1 GHz. Technically there may be multipath problems, too.
If your task is to distribute an audio signal, I would suggest to use a low-power FM transmitter at 88-108 MHz band. Such designs are widely used, require ~1W to cover > 1 km square area, and pose no danger. Low-cost FM receivers can be used.
Or, use a cable-distributed system, like describe in the thread "Photodiode noise reduction" elsewhere on Edaboard.

There are a lot of devices available in Indian market like XBee modules having range from 100mtr to 10,000mtrs! working in 2.4GHz without any problem. I have used many XBee 1KM modules. So I did not believe there will be some legal problems in ISM band 2.4GHz. In my case the device will broadcast only few seconds every hour. Actually the deivice is a voice enabled bell ringing system used for bell ringing and for some short announcement only.

I have tried the FM transmission, but I want high quality digital transmission not only audio signals but also control signals like volume controling, speaker addressing etc here. I have also tried powerline audio also, but due to some reasons it is not good to use in commercial products.

 

[D.A.(Tony)Stewart]

The path loss equation is well known and there is a tradeoff with the Signal Bandwidth, SNR and BER.

In case you forgot or are just learning, for 1Km distance the IDEAL path loss neglecting moisture loss and fading loss ( deadspots from multipath cancellation)

f (MHz) 1km 100m Path Loss (dB)
10 ...... 53 ... 33
100 .... 73 ... 53
1000 .. 93 ... 73

A 30 dB boost in power from 1W means 1kW is required assuming all else equal. But as we know as f increases, fading losses and weather, trees, ground reflections etc.. become more problematic so you need at least 10dB of margin.