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 Radios8U Series Radios8J Series Radios9C Series Radios9Z Series RadiosFN Series RadiosYou 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!

There is more than meets the eye in Jordi's setup!! Copy it EXACTLY or know what you are doing. JB, Jordi's Microwave/RF Guru, INGENIOUSLY designed in to the system about 5 dB of required padding thru the careful selection of ABC lossy RF cables & connectors!! If you don't incorporate this in your 2.4 GHz 'footwarmer' design with the prescribed components, you will inadvertantly turn your Microwave Amplifier into the ARC of the COVENENT "whether you like it or not" (famous quote by SFO Mayor)! The maximum rated input of the WIFI Power Amp is +15 dBm. This is burnout rating only and does not take into account signal quality. With the rated GAIN of the amplifier you are well into signal COMPRESSION with maximum rated input. SPEKTRUM RF Module's output is rated @ +20 dBm. So...................If you want to use a "short connector" between the module and the booster" you will need at least a 5dB pad (attenuator) on either end of the cable. Run an extended ground range check through at least a couple of battery discharge cycles before flying! Good luck! And get a HAM license to legally radiate that much power!

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Admin

Morli August 22, 2010 at 8:22am

Dennis, John is right, The length of cable between TX and amp if long enough can act as attunator else amp burnout is real danger. I would rather attempt to keep the amp further down. The easiest way to do that is use external wifi antenna mount (for wifi PCI card used in normal computers without wifi). The simple wifi base comes with few meters of cable( RG48!! ) which IMO should be do the job attunator.& you can mount 7+Dbi antenna to enhance. I do the same without the amp. If real long distance is desired then look at Thomas LRS or similar system.Good luck
JOHN PIZZICARA August 20, 2010 at 10:15pm

There is more than meets the eye in Jordi's setup!! Copy it EXACTLY or know what you are doing. JB, Jordi's Microwave/RF Guru, INGENIOUSLY designed in to the system about 5 dB of required padding thru the careful selection of ABC lossy RF cables & connectors!! If you don't incorporate this in your 2.4 GHz 'footwarmer' design with the prescribed components, you will inadvertantly turn your Microwave Amplifier into the ARC of the COVENENT "whether you like it or not" (famous quote by SFO Mayor)! The maximum rated input of the WIFI Power Amp is +15 dBm. This is burnout rating only and does not take into account signal quality. With the rated GAIN of the amplifier you are well into signal COMPRESSION with maximum rated input. SPEKTRUM RF Module's output is rated @ +20 dBm. So...................If you want to use a "short connector" between the module and the booster" you will need at least a 5dB pad (attenuator) on either end of the cable. Run an extended ground range check through at least a couple of battery discharge cycles before flying! Good luck! And get a HAM license to legally radiate that much power!
Dennis Smith August 20, 2010 at 8:00pm

Hi Morli, I have been reading through this thread and just joined the forum and have a question that maybe in here somewhere but have not seen it yet. I am flying with a Futaba 8 UHS and have a spektrum module and also an Assan module. To boost the signal for both of these Tx's I actually have 2 I just need to get a booster and then power it with a lipo and a bec to control power. I already have a connector on the back of the modules so just need a short connector between the module and the booster, a switch to turn it on and I am in business?
Admin

Morli June 16, 2010 at 6:42am

Like inline amp with auto bypass, that I am not sure bu any decent design should take this as standard consideration. But let some one else confirm it first.
GC9n June 16, 2010 at 6:15am

Thanks ..
i want to ask a last question..
IF for some reason the Booster dont work (in flight time) the TX will operate thought it and "without" it?
in another words the TX will be dead or will operate like stock?
Thanks in advance
Admin

Morli June 16, 2010 at 2:37am

GC9n , check here or @ RF comm
GC9n June 15, 2010 at 11:53pm

hi guys i am looking for a cable to connect TX with booster but with Angles to remove the stock booster wire , with a angle one...
i am trying to find somethng on ebay but i can't
Rana June 14, 2010 at 5:46am

Mark, Presently I have used X-bee's wire antenna removed from X-bee 2.4GHz and soldered at the output of the amplifier.

For schematic, I have already answered.

Mark, this amplifier is a bidirectional Wi-Fi amplifier dedicated for 2.4GHz use only and do can not be modified for 900MHz operation.

This amplifier has a switch synthesized using chip, which bypasses the power amplifier stage and connects the antenna to the LNA when there is no TX signal at the input of the amplifier. The switching is very very fast and the the antenna gets connected to the output of the amplifier immediately if the ampliFier is receiving any rf input.

In other words I would say only this type (bidirectional) of amplifier can be used with X-Bee and no other type as the X-Bee is transmitting and receiving.
Rana June 14, 2010 at 5:31am

Morli, raw image files;
500mW X-Bee 2.4, Photo_1.JPG 500mW X-Bee 2.4, Photo_2.JPG
Developer

Mark Colwell June 14, 2010 at 5:30am

Rana, Could you please post a schematic off your Xbee boosters mods. Do you need a shield on ground Xbee setup. Maybe a better antenna on both ends would add more reliable link at longer range?
Can these Boosters be modified for 900mhz Xbee?

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