Vtx temperature

[Edgeflyer]

I am using a TBS unify pro 5g HV race and within a minute it gets too hot to hold. It is currently set to 200mw so I could set it at 25mw and have low range but how much difference does it make and is there any point? Do any vtxs run cooler?

[Paul De Tourtoulon]

I have a few on different frequency's and power outputs, mine all get hot, so they are out in the airflow.

[Denis Watkins]

From the manual concerning hot running

 

Installation / Mounting 

When installing the Unify Pro, please ensure adequate airflow and - most importantly - heat transfer. This 

means mounting the Unify Pro with a bit of pressure against a flat piece of carbon will give you the best 

results. Proper mounting will allow the video transmitter to run for extended periods of time while sitting 

on the ground, both with 25mW and 200mW power levels. On 500mW / 800mW power levels, we 

recommend to start flying after a maximum of 1 minute, so that the airflow can begin to provide adequate 

cooling. 

When video transmitters heat up they start transmitting with less output power. There is also chance of 

the power supply circuit overheating. Don't worry, the Unify Pro will detect excess heat and shut down 

until it recovers. But that will also mean the video transmitter will not transmit. If you are experiencing 

that the video transmitter shuts down, check your installation. Ensure that heat can be drained well and 

make sure that there is a bit of airflow access to your VTx.

[Edgeflyer]

Thanks. I have created an air scoop and mounted the vtx in between 2 heat sinks in such a way that it sits in the cooling air stream. I am also going to incorporate a sold state switch to allow me to switch on the vtx when wanted when airborne.

[Edgeflyer]

My other query is does the vtx antenna have to be outside the fuselage? Is it hidden from the video receiver on the ground by the wing or fuselage? Does that interfere with the transmission?

[Denis Watkins]

The antenna is fine in a foamy, and should be laid out straight and not folded.

A range test should show up any problem

The scoop looks good, just don't hang around after switch on, and fly

[Edgeflyer]

Here's my layout. I'm wondering if the vtx antenna is too close to the GPS antenna.

[Nimiq4]

On 08/12/2023 at 16:10, Edgeflyer said:

I am using a TBS unify pro 5g HV race and within a minute it gets too hot to hold. It is currently set to 200mw so I could set it at 25mw and have low range but how much difference does it make and is there any point? Do any vtxs run cooler?

- If the transmitter is designed to work at 200mW then it may simply need some airflow around it. I'm guessing it operates at 5.8GHz?
- As installed maybe the antenna isn't radiating well and a poor match to the transmitters output FET - try placing the antenna outside and away from metal objects, battery and receiver. Similar problems occur if the antenna connectors are dirty, worn, damaged or not tightened.
- Maybe locate the antenna to the underneath of the glider and orientated to ensure the radiation pattern is downwards to your receiver. You may then get away with a 25mW setting? A hemispherical pattern antenna radiating downwards is probably the best option for a glider.

Just be aware, transmitting at 200mW in the 5.8GHz band in UK would require a licence, the limit for unlicensed at 5.8GHz is 25mW:
https://www.ofcom.org.uk/spectrum/rules/licence-exempt-radio-use/licence-exempt-devices/Radio-controlled-models

and scroll to the table at the bottom.