In this article I will show you how to build a 1.2GHz/1.3GHz to 5.8GHz wireless relay (repeater). It’s an ancient idea but a powerful DIY hack that can bring various benefits to your FPV experience if you are a 1.3GHz user.
What does it do? Basically it takes a video signal through this train.
1.3GHz VTX => 1.3GHz VRX => 5.8GHz VTX =>5.8GHz VRX => Goggles/Display
If you are new to using 1.3GHz for FPV, please see my beginner’s guide first.
The Benefits of 1.3GHz to 5.8Ghz Repeater
First of all, it allows further separation between the pilot (radio transmitter) and the 1.3GHz video receiver. This minimizes interference, and no dangling cables!
If you also fly mini quad, you probably already have a pair of Fatshark style goggles with your favourite 5.8GHz receiver module. The 1.3 to 5.8 relay allows you to use existing gear without buying additional equipment.
What Do You Need?
In the simplest form, all you need are
- 1.3GHz video receiver: http://bit.ly/2KTPEPb
- Any cheap, low power 5.8GHz VTX, like this one: http://bit.ly/2QPHkl0
You can put in additional components to “improve” your setup later on, like voltage regulator, filters and all that kind of good stuff, that’s entirely up to you.
Building 1.2GHz to 5.8GHz Relay
Basically you want to re-transmit the video signal from the 1.3GHz VRX using the 5.8GHz VTX, to your FPV goggles wirelessly.
Simply connect the output of the VRX, to the input of the VTX like so:
And that’s it.
The latency of VTX and VRX is measured to be only 1 to 2 milliseconds, which is negligible for long range stuff.
Things to Consider
Don’t forget to find out if 1.2GHz is a legal FPV frequency to use in your country.
You are creating more points of failure with this hack, so bear that in mind. Check your setup thoroughly before each flight.
When choosing a VTX, get one with very low power. Generally speaking, 25mW, or even 10mw is more than enough. Anything over 25mW is really an overkill, unless you plan to stand hundreds of meters away from the 1.3GHz receiver?
Keep in mind that you can affect other people’s video if they are also using 5.8GHz (and the other way round is possible too). Therefore it’s important to use a lower power VTX if you do fly with others.
I recommend putting a heatsink on the back of the VTX to keep it cool: http://bit.ly/2QLQ0sI
Since most 1.2GHz VRX are rated for 12V, you might want to get a VTX that can be powered by 12V as well. Most modern 5.8GHz VTX have a wide input voltage these days, from 2S to 4S, or even 6S so that shouldn’t be a problem.
Maybe it’s a better idea not to use 12V voltage regulator (BEC), use a 3S LiPo if you can. Firstly it’s another point of failure. Secondly some voltage regulators can produce RF noise that affects your video receiver.
Since you are already feeding the video signal from the VRX to the VTX, you don’t want to split that signal and use it for something else. It might work but that might affect video quality. If you insist you might want to get a proper video splitter which amplifies the video output: https://amzn.to/2RHTMYD