Posted by Jordi Muñoz on December 2, 2009 at 2:00pm
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!
Answer #1: Is not that critical because those devices are build to work all day, all the year constantly. Also i'm sure that total power applied to the booster is a lot less than the calculated. But yes the idea of the long cable is to reduce the input power, and also will let you walk around your ground station.
Answer #2 Yes, from the output side of the AMP to the antenna you want to use the shortest cable to increase the range.
#1. The output of the TX is a little more than the input of the amplifier prefers. But using a few connectors and a few feet of cable will reduce the input to the amp. This is good.
#2. After the amp we want to get as much of that power radiated as possible. So use the best, shortest cable and connectors you can get for between the amp and the antenna.
No i'm not joking, and you don't have to solder anything. Only a coaxial cable with SMA connectors so you can move around of your booster/antenna (like a video game controller cable, you play a few feet's from the console) and at the same time you will attenuate the signal from the transmitter, because is strong for the booster.
You say “anyway he gave me coaxial cable used for a satellite project and it REALLY improved the range of the system. SO the secret is use the shortest cable possible (mine is about 8 inches long “ Is this the cable which goes from the transmitter to the amplifier?
“In the case of your Spektrum 2.4Ghz you want to use the worse cable and a lot of connectors to attenuate the signal ;-) “
Are you joking? Or should I solder the 8” cable from the 2.4 transmitter to the amplifier?
Means that you may damage the amplifier. But if the amplifier is the same as mine it can really handle 20mW... Using a long cable from the RC to the AMP you will attenuate the signal down.
Comments
Answer #1: Is not that critical because those devices are build to work all day, all the year constantly. Also i'm sure that total power applied to the booster is a lot less than the calculated. But yes the idea of the long cable is to reduce the input power, and also will let you walk around your ground station.
Answer #2 Yes, from the output side of the AMP to the antenna you want to use the shortest cable to increase the range.
You are 100% right! ;-)
To help clarify. 2 separate issues.
#1. The output of the TX is a little more than the input of the amplifier prefers. But using a few connectors and a few feet of cable will reduce the input to the amp. This is good.
#2. After the amp we want to get as much of that power radiated as possible. So use the best, shortest cable and connectors you can get for between the amp and the antenna.
You say “anyway he gave me coaxial cable used for a satellite project and it REALLY improved the range of the system. SO the secret is use the shortest cable possible (mine is about 8 inches long “ Is this the cable which goes from the transmitter to the amplifier?
“In the case of your Spektrum 2.4Ghz you want to use the worse cable and a lot of connectors to attenuate the signal ;-) “
Are you joking? Or should I solder the 8” cable from the 2.4 transmitter to the amplifier?
Matthew
I will let you know the results !
I'm using it with a ar500 spektrum receiver
Thanks
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