Video range - How to work yours out

[Coyote]

Its that burning question, the one everyone always asks at one point or another is what range can i get with my system ?

Its really not as easy as that but you can get a maximum range possible. Then of course where you fly, how high you have your antenna etc etc comes into play and changes it some what. Never more always less though :(

So here`s what to do.

First gather some information about your system :

1) Video transmitter frequency, this will be F.

If your using 2.4GHz then F = 2400
If your using 5.8GHz then F = 5800

2) Video transmitters dBm, to do this find the mW rating of your Vtx and use the figures below :

  10 mW = 10dBm
100 mW = 20dBm
500 mW = 27dBm
1000 mw = 30dBm

This will be PTX

3) Your transmitter antenna gain (GTX). Most will be using a 3dBi Rubber Ducky so GTX = 3. Even if your using a Dipole or Inverted Vee antenna its still a 3dBi antenna so just use this figure

4) Receiver sensitivity ( SRX ). Almost all 2.4GHz receivers are -85dbi so if you don't know leave around this

5) System Impedance (Z). All our systems over here are 50 ohms

6) Receiver Gain (GRX). The gain of your receiver antenna. Again rubber duck = 3 All else will be obvious a 8dBi patch = 8 and so on

If you have a Helical antenna and can not remember the gains just count the number of turns and work it out using the details below :

Gain

Gain ~ 4.5 + number of turns (3 turn minimum, 12 turn max)
3 turns = 7 dbi
4 turns = 8.5dbi
5 turns = 9.5 dbi
6 turns = 10.5 dbi
7 turns = 11.25 dbi
12 turns = 12.5 dbi

The rest of your figures are already default into the link below so just leave as is.

Now with your 6 values you have go to this link and put the values into the boxes. The formula will now tell your your theoretic best max range possible.

Now use this link below :

Range Calculator

Of all the calculators Ive seen so far, this ones on the money for me, its the most accurate Ive found or have used

Ill do an example to put in, so you can check your putting the right info in the right box.

Ill go off my system to be used abroad ay L'Aigle later next year.

1) F=      2400 because I`m using 2.4GHz Video link
2) PTX = 27dBm because I`m using a 500 mW Video Transmitter
3) GTX = 3dBi I`m using a standard rubber duck
4) SRX = -85dBi Sensitivity of a Firstpersonview.co.uk receiver
5)   Z  = 50 ohms
6) GRX = 14dBi because I`m using a 14dBi Yagi

If you put this into the columns correctly the range at the bottom should display : 23.78421 Km

If you get the same result you have entered the values correctly, then re do to your own system and find out how yours will perform

For any interest

1) The Firstpersonview 10mW flightbox will get .94 km straight out the box

If you upgrade your receiver antenna to a 8dBi Circular Polarized Patch you now get nearly 1.7km, that's over 1 mile from just swapping your receiver antenna :)

This has as most have seen been proven through video and GPS so we know the calculator above is in fact pretty accurate.

2) The newer version complete with Video transmitter will do 2.995 km straight out of box

If you upgrade your receiver antenna to a 8dBi Circular Polarized Patch you now get nearly 5.32km, that's over 3 miles from just swapping your receiver antenna :)

What people must understand is these figures are accurate. But don't take into any consideration of local RF influences to where you are flying or range reduction through your own RC radio link being positioned badly.

Another note is I`ve said to use -85 dBm as your receiver sensitivity. Some 2.4GHz Rx say they are -91, -93 dBm. This is probably inaccurate and if they are not which is highly probable then affect the sums to give you a much bigger figure. If you use -85 then you know the figures will be safe.

Also please stick to the rules regarding range flying. This is for pure theoretical understanding of what your equipment can do.