[MOVED] FM transmitter with 10km range in city

[TyomaNb]

Hi! Can't figure out where to start with this project. I want to build some sort of high range remote control.
I can't find suitable circuit in internet, maximum range I saw was only 5 km
Please help me with these questions:
If understand correctly the best option for 10 or more km is frequencies something like 450 MHz, right or wrong?
Another problem with the height, what power do I need to make it work from 4-5 store building window and what antenna I should consider?

Additional info:
There is no need for carrier, this remote control should just turn on and off the device.
About power - I understand that high power transmission is illegal in many countries but I though frequencies from 400 to 500 MHz are used for portable radio transmitters that cam be bought in any shop and they go up to 20km range, so I don't think i need a lot of power for a simple ON switch and I won't interrupt someone on 450 MHz band.

Sorry for stupid questions and thanks for your time.

 

[kripacharya]

Questions :

why do you want it to be FM ?
What exactly do you mean when you say "no need for carrier" ?

One alternative to your requirement - which does NOT try to transmit a high power unlicensed RF signal - is to use the all pervading mobile network.

You can do remote controls by engineering a GSM unit to transmit & receive command/ responses via SMS's, and interface it with some uC based circuit to perform your functions

 

[TyomaNb]

Why FM:
I just thought it would be easier to implement. Talking about GSM receiver unit it seems more difficult to do, though I never tried to do something like this, I should look info in internet. Is is as easy as FM receiver?

By no carrier I meant that I don't need to transmit information in signal, like audio and make filters and etc. Receiver must just catch presence of signal and turn on the device it connected to(like LED and Speaker alarm or something simple like this).

I suppose it maybe easy and cheap to make GSM receiver, but just for the first though making GSM transmitter(if I would like to get feedback for example) is quite expensive and complicated. And overall this idea sounds expensive.

 

[davenn]

By no carrier I meant that I don't need to transmit information in signal, like audio and make filters and etc.

you have a misunderstanding of what a carrier is

from your description you NEED a carrier you DONT need modulation

be aware that for general public use, power is limited to ~ 0.5 - 1.0 watt maximum output ... many countries are a lot less than 0.5 W in their regulations. For the power levels you seem to want you would require your transmitter to be tested and approved by the licencing authorities in your country to make sure it confoemed to their standards. If approved them you would be paying an annual licence to make use of that transmitter

cheers
Dave

 

[KerimF]

Even if your RF system is for on and off only, the received signal should have a specific characteristic (likely a digital key address) so that signals from other transmitters (at the same frequency) cannot turn on or off your device.

 

[davenn]

Even if your RF system is for on and off only, the received signal should have a specific characteristic (likely a digital key address) so that signals from other transmitters (at the same frequency) cannot turn on or off your device.

that is so true ..... I neglected to comment on that in my previous post

the OP is going to need some sort of coded transmission

Dave

 

[kripacharya]

...maybe easy and cheap to make GSM receiver, but just for the first though making GSM transmitter....

No no you misunderstand. I am not suggesting actually MAKING the gsm tx/rx units. I am suggesting that you can buy cheap mobile handsets with a low cost sim card, and interface to these with your uC circuits, which would send command/ responses using sms feature.

There's plenty of projects been done using this concept, and theoretically there is no distance limit !!

 

[TyomaNb]

you have a misunderstanding of what a carrier is

from your description you NEED a carrier you DONT need modulation

oh sorry, oh course I meant I don't need modulation, just was asleep and mixing words

the OP is going to need some sort of coded transmission

basically yes, I'm thinking of some kind of sine wave or short digital code. I meant that I don't need some sophisticated filters or amps like I would need for audio-transmission.
Sorry, I said some bullshit in the beginning.

I looked on prices on all the stuff I would need for gsm sms transmissions and it's quite expensive. Moreover it needs much bigger box and power than FM receiver. So, I don't know... I don't wanna waste 50 dollars on this.

About power level - in my country it is almost not monitored(I'm pretty sure it is not monitored absolutely), so I guess I can use more than 1W power and from human point of view I will not cause troubles to anyone because it is portable radio sets frequencies(400-500MHz)

So the problem is, I can't find any transmitter circuit that implements 400-500 Mhz transmission and I don't know what troubles should I consider if I would like to modify simple 108 MHz transmitter.
I don't wanna take a lot of your time, so basically, could you give me some general advice? I mean - should I stick to 400 to 500 Mhz radio or maybe you know some better way? And also if 400 MHz is the best way - what the circuit will be like - just regular 80-108 Mhz with slight modification or completely different?
Thanks.