How to boost your 2.4Ghz Spektrum/JR Transmitter signal!



I love my Spektrum Dx7 and my 2.4Ghz JR XPS9303 and i refused to trade its solid rock performance by a 72mhz radio just to increase range of my FPV/UAV. So in collaboration with my friend JB we find out the cheapest and secure way to amplify the signal, it even works in some Futabas and virtually with any 2.4Ghz radio, but some modifications are required. Lets see some options:

-Spektrum Dx7 this is the cheapest solution for a very reliable 2.4Ghz radio, i used it for about a year and i never had any signal glitch (unless i fly beyond 2000 feet). The problem with this one is that you have to modify it, you need a SMD to U.FL adapter, drill a hole in the side of your radio and just connect and screw the adapter, no soldering required. If you have more than 5 hours of experience with Legos your qualified to do this job. Then you just need to connect the booster. The one in the picture (middle) is already modified.

-If you have the awesome JR radio but is 72Mhz you can buy the Spektrum 2.4Ghz module and just insert it in the back of your TX, personally this is my favorite setup. It's a good deal because includes a $99 dlls receiver for free! Note that JR TX alone cost around $600 dlls, but you can get it for less, i got mine for 300 bucks with Spektrum Module included on R/C Groups =P. Remember you are looking for the JR XPS9303.

If you have one of the fallowing Futaba radios:
7U Series Radios
8U Series Radios
8J Series Radios
9C Series Radios
9Z Series Radios
FN Series Radios
You can just go and buy the Spektrum 2.4Ghz module, easy and with no hassles. It's also a good deal because includes a $99 dlls receiver for free!



One of the advantages of the Spektrum receivers is the build in diversity system, you can even buy one with 4 satellites like this one, or buy a super tiny, tiny setup like this one, or the traditional one.
The diversity is crucial to have a reliable link when you are flying far away, also Spektrum has a receiver for Carbon Fiber airplanes (Carbon Fiber blocks RF signals).

The idea is to have the best reliable hardware with an SMA connector and the SMA extension cable, after that you are ready for the final step: Get an amplifier. But we are talking about a few hundred dollars here, if you get the weakest one of 100mW it will cost you around $150 dlls. This is not pocket friendly in my point of view. So again our Asians friends come to the rescue, after making some research around the net I've found on eBay and a home Wireless Amplifier, so i decided to give it a chance and i bought it for 60 bucks including shipping! Wow that's a good deal! The one i got is this one.

Note that the amplifier needs 6Volts to work, you can get a cheap 6V power regulator from here and just make the adapter. A 3 Cell LIPO is enough to supply it for a long time.


After receiving the AMP i did some tests, here are my results:

Before using the amplifier, i was able to fly around 3000 feet away (~1 km) using a 900Mhz@500mW Video transmitter. I never lost the video signal, only the radio link...

Using a 1.3Ghz@1Watt Video transmitter i was unable to fly more than 2000 feet away (~600meters). So the 1.3Ghz Video transmitter reduces my 2.4Ghz Spektrum range...

Then i got my cheap Asian amplifier and using a 2.4Ghz Patch Antenna i was able to fly around 2.6 miles (4.18Km) away without a single glitch, but i was unable to continue because now my video was causing me problems, hehe!

Not bad at all! Honestly i don't need more than 2 miles of coverage, is really a long way for an EasyStar. In conclusion the maximum range for my setup still unknown, but the range achieved is more that 2.6 miles and the +2 extra miles of coverage gained for less than $100 dlls is really a good deal for me!


Now just remember this:
-The range will be different in other setups.
-Never turn on your radio without antenna.
-Never turn on the Amplifier without antenna.
-Note that in some country's this amplifier may be illegal.

Thanks for watching!

Views: 96275


Moderator
Comment by Morli on December 2, 2009 at 4:24pm
Jordi, I am using/testing similar setup without external amp.I used straight 7dB rubber omni, 9 dB FG base antenna and 14 dB patch w/o any amp , did notice considerable increase in range. but Didn't know I could use a wifi inline amp :)) . , How did you power your amp as it requires 6V @200 mA? thank for bring this up.
Comment by mook on December 2, 2009 at 4:26pm
Great post, I was just looking for a similar solution for my dx6i. 100 dynamic link libraries is not too shaby ;) I wonder if you could write a WRT54g firmware to somehow make one antenna a receiver and the other just a repeater that's amplified

3D Robotics
Comment by Jordi Muñoz on December 2, 2009 at 4:27pm
You can use this selectable 5V / 6V regulator and a 3 cell LIPO:
http://hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=4319...

Moderator
Comment by Morli on December 2, 2009 at 4:38pm
Rhanks Jordi, will try it,
@Mook , WRT54g AP if is what you are talking about then it has diversity system I guess, even if such a F/W can be written, would not make much of difference since they( both the antenna) are almost few c.m apart and there fore at the same distance from rx , so defeating the purpose of repeater( which usally is between TX and RX to increase the range by repeating) further more close of TX proximity to repeater would desensitize the repeater input stage ! , there is one hacked f/w for another brand AP to increase its power from 100mW to 500 mW.
Comment by mook on December 2, 2009 at 4:47pm
@Morli, I meant use a connector from the rc tx to one of the antennas, and in firmware have the other antenna just amplify what is coming in the one hooked up to the tx. I know you can go up to 250mW not sure how noisy it gets.
Comment by Jack Crossfire on December 2, 2009 at 4:51pm
A lot of problems would be solved if someone just told 2.4Ghz manufacturers to sell turnstile antennas instead of dipoles. It does require quadrature hybrids & their use is not documented online but a turnstile antenna would go farther than diversity dipoles.

Moderator
Comment by Morli on December 2, 2009 at 5:01pm
@hook, ok, that would pratically become in line booster/amp which is what Jordi's amp will do ( cheaper) , there are some more model/brands too. The product/brand I have used( not same model) is here which is smaller too , the performance/quality of this brand is some thing I can vouch :)
Comment by Austin Laws on December 2, 2009 at 5:03pm
Would this work with the DX6i lol? Noooo idea

3D Robotics
Comment by Jordi Muñoz on December 2, 2009 at 5:08pm
DX6i, yes i should, but you must modify it like the DX7.. Open it and look for the U.FL connector.

Moderator
Comment by Morli on December 2, 2009 at 5:08pm
if it does with dx7 , I don't see why not , the concept is same :)

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