The fact that VTX nowadays are getting smaller, it means there is less surface area to let the heat go and often cause overheat issues. This is especially the case with high power units like the TS5828 600mW. In this post we will share some tips how you can prevent VTX overheat. Same principle should applies to other VTX and electronics.
Video transmitter overheats
When I first received my TS5828 (a tiny yet high power VTX), I powered it up with a 3S battery, so it was no more than 12.6V. Even though it’s rated up to 24V, only after a few minutes of use, the transmitter was getting so hot it almost burned my fingers. (Antenna was connected).
I measured the temperature with a digital thermometer and it showed 90 degree Celsius, I cannot imagine what would happen if we run 24V on it as the excessive voltage will turn into heat.
I thought it was a faulty unit, but after some research on forums and reviews, I found out that the overheat issue is happening not only to mine but almost every unit.
Why is overheat bad?
- Your VTX can burn out during FPV flights and cause crashes
- Running at this high temperature while in contact with other electronics in your aircraft could damage them
- It affects your range and transmitter efficiency as they depend on the working temperature
Solution to Fix your VTX Overheat
We can’t reduce the heat VTX generated without changing the design of the VTX or lowering the power, but there are a few easy and cost effective ways to improve heat dissipation.
This is the best way to decrease operational temperature. Insert a small heat sink to the transmitter which lets the vtx remain light weight as only add 1-2 grams.
- Remove the factory heatshrink from the transmitter
- Apply some thermal conductive paste/greese on the VTX
- Put the new heatsink on the VTX, and secure by a zip-tie
Lower input voltage
Most VTX has built-in linear voltage regulator, they burn excessive input voltage into heat. To minimize this it’s always a good idea to provide the VTX with the lowest voltage possible (closest to its working voltage).
For example for the TS5828:
- The lowest input voltage it can take is 7.4V, so if you are running 2S lipo you can just connect your VTX directly to the main battery
- If you are running 3S, and there is no way you can get anywhere near 7.4V, feeding the VTX with your battery voltage should be fine (max 12.6V), that’s not the end of the world
- However if you are running 4S, max voltage is 16.8V, and that’s pretty high for the VTX. I would recommend converting the voltage down to 12V for the VTX. Most PDB these days provides 12V and 5V outputs so it’s not hard to find
Decent airflow has significant cooling effect on your electronics, try to place the transmitter in a position with maximum airflow. This is the same principle when talking about where to mount your ESC’s.
The rule of thumb is that you never place your VTX too close to any other components which also generate heat without good airflow.
To get best result you should consider all 3 options above. These techniques can be applied not only in the case of the TS5828 video transmitter, but any other electronics devices.
Other causes of overheat?
Please be aware that there are many other issues that can also cause your VTX to overheat. It’s always a good idea to check the below as well.
Never ever power on your VTX without antenna, all the energy sent to the antenna will bounce right back when the antenna is absent, and instantly cause overheat and might permanently damage your video transmitter.
Wrong antenna connector type
Always make sure that you are using the right connectors between the VTX and antenna. For example the TS5828 is sold with both RP-SMA and SMA connectors.
It does not matter which one you bought however you need to buy the antenna with the correct connector for that. The reason is that some connectors have a pin inside, and the matching connector should have a hole inside. But if you accidentally used 2 connectors with holes, the antenna and VTX are actually not connected, as if you are not running an antenna at all.
Bad/damaged VTX antenna
The VTX antenna can be tuned to a certain frequency, and if you are broadcasting at that tuned frequency your VTX should run cooler. But unless your antenna is really that bad, this normally shouldn’t be a huge difference.
Another problem with antenna could be the bad/broken solder joints in the antenna, resulted from poor quality manufacturing or crashes.