Hello i want to design a tx and rx distance will be 2.5 miles(4 KM),frequency 10-20Mhz using FSK.what will be the power needed i just need guess value.or should i use another technique

 

Unlicensed RF transmitters generally have a range of only a few meters and are limited to 100mW in most countries. They're also only legal within certain frequencies and power outputs.

You could buy a pair of XBee pro modules which with the right antenna and line of sight you might get 4kM.

 

i dont wanna use it in daytime & its pc to pc communication just to check & learn.Is there anyway by which government can track us & what are its consequences? thanks for the answers!

 

Hello,

I can only speak for Holland.
When you get caught with an illegal transmitter here, you get a fine, the transmitter and everything connected to it will be taken away.
So if you have connected your computer to the transmitter, you will loose your computer too.

Bertus

 

As I said a pair of XBee pros can be linked for a PC to PC RF network.

 

For most here, RF solutions should be purchased instead of built, other than the near range FM transmitters and similar items.

I saw a video where 2 802.11b routers were connected something like 10 miles apart using 2 parabolic dish antennas between two mountains. All I can remember for location was somewhere in South America.

Also, the 10-20Mhz band is reserved without a license, generally, the only "open" frequencies for hobbyists are 27Mhz, 49Mhz, 75Mhz, 900Mhz, and 2.4Ghz. The last two are not easy to work with due to the short wavelengths involved.

 

i want to design my own TX & RX so that i could learn something & government wont allow me.ok what about if i take ham license then will that be possible & i want to know how can they trace us?do they have any detectors etc.thanks for the reply's

 

Getting your Ham license is an excellent start. When you have it you'll also understand why you need it and how your transmitter can be located.

 

i want to know how can they trace us?do they have any detectors etc.

can anyone answer this question.Thanks!

 

Yes they have detectors and can triangulate on a signals source.

 

It is VERY easy to get traced.

No problem at all

Look up triangulation.

2 known points, they can find you in under a second.

If your transmission acidentially causes a plane to lose communications with the tower, or peoples garrage doors start opening and closing, or all the radios start squeeking, you will be in jail quick.

If they just catch you, they will fine you 3 years wages and probably jail your parents.

You want to take on a project. Thats good.

But, you are need to learn the hows and whys of the technology, not just getting caught.

Triangulation

 

yeah i am 19 all right so i would probably go to jail if i break the rules.do these people even check at night i promise i wont go beyond 50MHZ

 

Hello,

Checks can be done all around the clock.
When you stick to the rules and buy certified equipment, nothing will happen.

Bertus

 

The checks are not done by humans.

Computers monitor the bands.

As soon as you power up, you are seen.

Is this line of sight?

If so, you should consider using light.

A laser pointer can be hacked to transmit data to distant location as long as it can be seen.

There are many legal ways of doing this.

Also, what country are you in?

If there is currently military action or war happening, the military will also be monitoring the bands ESPECIALLY at night looking for spys that are trying to transmit info.

How do you like waterboarding?

Night is the worst time, because you DEFINITELY look like you are hiding something.

You can look up the info on the laws in your country to let you know what power you are allowed to use without a license, and what bands you can be active on.

Also, you can get info on how to get a license.