Archive for November, 2015

2.4 GHz Diversity Receiver Using a Simple Circuit

Tuesday, November 17th, 2015

RC Model Reviews, a YouTube Channel, created an FPV diversity project. Bruce does a great job explaining this little project and the circuit does a very good job switching between the two video sources. Here is a link below:

Part 1:   DIY FPV diversity project (part 1)

Part 2:   A $1.29 FPV diversity controller (build video)

Part 3:   A $1.29 FPV diversity controller (improvements)

I built one of these  boards for my 5.8Ghz video setup using the RC832 5.8Ghz AV receiver by Boscam.

After building this circuit, I found it work very well and I was impressed. When one of the RC832 receivers started to have phase lock loop problems, I decided to get the Immersion Duo 5800 V4 Diversity Receiver. After a couple of flights with this system, I found that the receivers lack sensitivity and switch wasn’t as clean as the previous circuit. I ended up buying another RC832 and going back to the previous setup.

I also starting using 2.4Ghz video transmitting for longer range. I purchased a TBS Lawmate 2.4Ghz receiver but missed the diversity setup and I wanted to experiment with different 2.4Ghz antennas. I decided to purchase another Lawmate R2400 receiver and build another diversity controller.

I opened up the Lawmate receiver and did some searching on the web and came up with the RSSI (Signal Level) connection for the module.  Here is the connection for RSSI:

350px-Lawmate_comtech_rssi_output

NOTE: You need to solder the module pin connection to the board pin connector (on the side)  as they are just touching. They should be soldered like the other pin connections.

Here is the schematic Diagram of the Diversity Controller which I redrew. This has a couple more parts that Bruce’s original design to filter any noise of the 5V source. The parts are easy to obtain and the board can be built using many different techniques.

Click on schematic for greater resolution.

diversity_controller

You can download a pdf file for the above circuit.   Circuit Schematic PDF Download.

Here are some photos of of the board. As I indicated and if you watched the YouTube Videos, there are different ways to build this circuit. I tried to keep the board and layout simple as possible. Remember the old RC832 5.8 Boscam receiver, I used the old case to mount the board.

IMG_20151113_204553


IMG_20151113_204706

 

Here is a photo of the connections to the first Receiver (RX1): This also provides 5V to the controller. The left side red lead is the RSSI signal, the black wire is the ground, and the white wire is the video signal. The right side red wire is +5V and the black wire is ground. These will be connected to the Diversity board.  I used some servio extension cables for these connections. Also note, you need to solder the Modules Pin 9 to the circuit board Pins as they are not soldered. (Sorry no picture, but refer to above’s module picture.)
IMG_20151111_193202

 

Here is the connections for the second receiver (RX2). Again, I used servo extension cables.

 

IMG_20151111_210348

 

The final layout of the Diversity Boad with the two Lawmate receivers. It was mounted together with mounting tape and a Plexiglas base :

 

IMG_20151114_152407

IMG_20151114_152358 IMG_20151114_152346

2.4Ghz Diversity Receiver Ground Station Completed

IMG_20151115_141900