How hot can vtx get?

[Pyrzi]

So how hot it normally vtx is? After few minutes my vtx is so hot that I can barely touch it. I am afraid that I will fry it. I tried to remove rubber around the antenna so pin would go deeper but nothing changed. Even plastic cover around vtx is starting to peel out because of high temperature. Is this normal?

Thank you!

[Bajadre]

Very hot unless there flying and have some airflow etc
I try not to leave it on while testing without flying for too long

[atomiclama]

Think I measure mine at 65degC on the bench.

But as mentioned once flying and some airflow it just gets warm to the touch.

Oh yeah I have the metal can removed on mine so get better air flow.

The components should be good for 85 degC but the power output drops off the hotter it gets

[Andy7]

I suspect that keeping the metal can on is a good idea to prevent RF noise escaping. I swamped my RX recently by having the VTX too close, even WITH the can on. You might get some unexpected failsafes if you have too much noise.

Also, I wonder if the can has some heatsink capability?

[Two-Six]

I stuck a little heat sink on mine.  You can buy them from Maplin I think.  I made mine from an old PC chipset heat sink.
http://www.multi-rotor.co.uk/index.php?topic=15675.msg143221#msg143221

[Revs]

As said they get bloody hot, usually causing the image to fizzle out if left long enough with zero air flow. But they usually need only a slight air flow to keep cool and functioning. Obviously the higher the power the faster they heat up.

Some VTX';s like the TBS Unify cut off at a certain temp to avoid damage. Really handy if you break an antenna.

[atomiclama]

I suspect that keeping the metal can on is a good idea to prevent RF noise escaping.

And that relatively big antenna sticking out the back doesn';t let RF noise out 

Not really sure or convinced about the pros/cons of the shield.

Also, I wonder if the can has some heatsink capability?

Nah it makes things worse, it traps a small pocket of air around the components insulating them.

Best way to cool them and still keep the can is to drill some holes in it. It will still keep the shielding properties but allow the air to circulate a bit.

[Andy7]

And that relatively big antenna sticking out the back doesn';t let RF noise out 

Actually, signal noise IS a problem in electronic design. I put my VTX on top of my RX and it knocked the signal out from leakage even with the can on.

[Sweet Pickle]

I';ve got one Eachine one that could pass as a soldering iron it gets that hot.
It';s one of the ones in a metal enclosure and the case is supposed to act as a passive cooler by the look of it. When stripping down there was some cheap and nasty thermal paste on which I cleaned and replaced. Temp dropped by a couple of degrees but still mighty hot.

[Gav]

On one of my vtx';s I soldered the antenna direct and used hot gun glue to protect the soldering - glue melts n goes squidgy when I power up lol

end up with glue cob web strands, if I grab the quad in the wrong place after a flight.

[Andy7]

I wonder if the input voltage might be a factor? If you';re powering directly from a 4S and there';s a linear regulator inside, that will get hotter than if you take 12v from your PDB.. or wil it run from 5V?

[atomiclama]

Most VTX have a SMPS on them which are fairly efficient and don';t generate much heat. So shouldn';t matter if running from 4S

But can if badly designed generate electrical noise. Maybe that was the source of your problem Andy7 ?

There is a linear regulator inside the can on the RF module. This along with the RF modulator and output PA generate the heat. Wish my works thermal camera would save it';s piccies so I could post them up.