I  need to extend the range of my 72 mhz Radio till around 4 Kms  because now we are looking at moving  to FPV beyond visual range .
last week  pushed till  the easy glider was a spec in the distance  with direct FPV tx input into Saju's Portable LCD TV.

Now  we want to push beyond visual range  but can't take that risk  without RC range enhancement , the Carona gives a range of 1.6 KM but   going beyond visible  range may be pushing it to its max as well , hence without a safety margin I am  not comfortable  

Any  ideas that can be tried 

I read it somewhere that if you have a GPS, auto-pilot, and fail-safe mechanism then,

1) Auto-pilot notes down the flight's starting point via GPS.
2) fail-safe mechanism detects that the radio communication has been broken.
2) Auto-pilot kicks in and by using GPS navigates the plane and brings it back to the starting position.

If these three elements are present in your plane then you don't have to worry about your plane getting lost due to "out-of-range" issues. 

Is a safety measure that needs an auto pilot , but I don't have  an auto pilot .
I am looking at plain FPV flying  with RC beyond visual range

1. Increasing the output of Tx may be a violation of the WPC norms (well for 2.4G, its 4W!! )
2. Nevertheless:
  a. Increase the length of the antenna. make is double, say
  b. Better still use a 'Highly directional Antenna" like Yagi (used in broadcast TV), Cubical Quad etc, instead of the default omni directional retractable antenna.
  c. Best, make an auxiliary linear amplifier. This would involve lots of Electronics R&D. You may easily find circuits for 27/72Mhz Amps using commodity FETs, but matching the impedance from the Transmitter (acting like pre-amp) and that for the final antenna would require help from a seasoned Radio engineer or the neighborhood HAM! But Hey Mr Sai, you can market those Amps yourself!!

[Add]
Somebody across the Himalayan wall already doing it :
http://www.rcgroups.com/forums/showthread.php?t=1073115
[/Add]
If you finally if you do  succeed, hope you not interfere those flying in Bangalore, Thissur etc from Chennai!  

Did a bit of searching and came up with this :
http://www.rcgroups.com/forums/showthread.php?t=759494

Looks like greek and latin twice over
Sai

Sai,
Just a basic question. How do you intend to control the bird that is outside the visual range?

Pankaj

Quote from: PankajC on February 09, 2010, 08:29:50 PM
Sai,
Just a basic question. How do you intend to control the bird that is outside the visual range?

Pankaj

That is  FPV  

You  see from the Bird  not  the bird  

That is what we did last Sunday but stopped short of going beyond visible range  
You fly  looking at a Monitor  and using land marks  visible from the air .
Like sitting inside your RC plane

Quote from: ujjwaana on February 09, 2010, 08:11:52 PM

[Add]
Somebody across the Himalayan wall already doing it :
http://www.rcgroups.com/forums/showthread.php?t=1073115
[/Add]
If you finally if you do  succeed, hope you not interfere those flying in Bangalore, Thissur etc from Chennai!  

Thanks  Ujjwal  this looks promising    more suited for a  person like me

Sai

Sai,

You definetely need a high power RF amplifier. Also, as Ujjwana said you need to match the amp to the antenna. There is a lot of tech stuff involved so, homebrewing might be difficult unless you have first hand experience with radio electronics.

Further, increasing the range might be not be legal. If you do so, better not to publicize it and attract too much attention.

I have modified some old airtronics transmitter. Just replaced the RF transistor to 2N3866 and it worked like a charm. Calculated power dissipation from the transistor was about 3W!.. more than enought for 4 Km line of sight. It might or might not work for you. Ask an electronics saavy person to look at 2N3866 specs. At Rs14 a peice its unbeatable value for money.

-Ismail

-Ismail

Looking at all this  seems way beyond my abilities   .
Got  to get some one to  help  

Legality apart I just wanted to know if such a thing is do able .

All you tech guys  say it is possible  that is encouraging

Now  I need to start hunting for a  electronics expert with RF experience  

Quote from: izmile on February 09, 2010, 09:05:11 PM
Sai,

I have modified some old airtronics transmitter. Just replaced the RF transistor to 2N3866 and it worked like a charm. Calculated power dissipation from the transistor was about 3W!.. more than enought for 4 Km line of sight.
-Ismail

Was chaning the RF Transistor enough ? sounds like music to ear! but yes, if you can find Trasistor with similar characteristic, but higher power rating, that THE straight forward method! I wish I had a FM Tx/Rx module! I could have done the RnD. I am too scared to mess up with my 'microwave' 2.4 Ghz Tx stuff as all I have done till date is within HF/VHF spectrum. And trust me, just doubling the Freq in HF takes you to VHF (14Mhz to 27Mhz) but the challenges become 8 times!!

Yes chaining should also work, but I did not venture into that. I just replaced the transistor and lowered the emitter resistor value. It made the transistor to go warm. So, it required a heat sink on it. But the range is superb!

some one here is looking for serious trouble! i would suggest all the parties to break away for this discussion and more over THE FREQUENCIES MENTIONED ARE SOME OF THE MOST TRACKED BY GOI

what is max practical range achived in a 2.4 Ghz Futaba 6EX and 7C and what is the Tx power ?

Quote from: sundaramvelar on February 09, 2010, 10:22:07 PM
what is max practical range achived in a 2.4 Ghz Futaba 6EX and 7C and what is the Tx power ?

Power is 100mW. 

Range is dependent on a bunch of factors (receiver model is a big one).  For a full range receiver, it is claimed to be well over where you cannot see the model clearly. Close to a mile is a good number being discussed, although small tweaks have made it possible for people to go up (double that and more).

http://www.rcgroups.com/forums/showthread.php?t=904535

Thanks Mr Anwar. Here when flying from top of a small hillock 200 m dia base and 70 m tall in the field firing ranges from where one can see area around for about 8 - 10 kms with a clear field of view without any obstruction, never been brave enough to try beyond a KM.

Since any amo or any object falling in the ranges is immedietly picked up by local people picking up scrap amo for the scrap contractor.

FPV...... man this is way beyond my imagination right now. Can't even fly a trainer straight which I am looking at. So flying the model looking through the model - :S to hi-tech stuff

saw a video in youtube for this search in it .all information about autopilots.