Heatsink upgrade for 800mW* 1.3GHz Transmitter

[Skimmer]

Hi guys,

I've posted this on OpenPilot, I though people might like it. It could be a future product upgrade for RMRC to improve the weight of the product.
I'm sure your all know the 1.3Ghz transmitters from RMRC I bought the following one and like it alot
800mW* 1300MHz Transmitter - NEW CUSTOM READYMADERC US VERSION

I was doing some work to replace the loose wire harness that connects my battery and video camera with an old USB cable so I could have the power,audio and video in a single 4 conductor shielded cable. I noticed on the transmitter that the loose wires disappear into the side of the box.



so I opened it up and this is was I saw

Yep its a regular 300mw transmitter box with the output beefed up to 800mw at 14V I guess (well 600mw at 12V which is probably what most of us will use if you are using a 3cell lipo.)



Anyway You'll notice the whole unit weighs 74 grams and the box weighs 53 grams!!! Plus all those shims are not the best way to conduct heat from the smaller transmitter box to the outside case. We can do better than that!!

So why not take a CPU heatsink from my old old, OLD desktop computer which I've been looking for a reason to decommission and chop it up to fit on the actual transmitter box? When that little silver box uses 800mw it gets hot to the touch for sure.


UPDATE:
I've been looking for a heatsink that might fit the dimensions for you guys. I found one!!! So after digging and digging I found one the exact size you need 50mmx25mmx10mm. Turns out this is a heatsink designed for a LM2596 power module (what ever that is @#$!!) and will handle 2-3 watts!! NICE! This could handle enough heat coming out of a 1000mw or 1500mw transmitter if needed.
Here is a link to one here: just do a search for LM2596 Heatsink... about $2US.


Anyway I used my good old desk top band saw (with new blade ) and my sanding station on my CPU headsink, here is what I came up with. Again heatsink dimensions are 50mmx25mmx10mm tall. You'll notice I made the base about .125" thick, that's plenty thick to distribute the heat though the fins.



Now the fun part, We need a thermally conductive epoxy to glue the two parts together. I happen to have some Cotronics Duralco 128 Ceramic Filled Epoxy which is crazy expensive. But man it is good and strong!! you can call up Cotronics, number is on the bottle in the photo, you only need 5 grams of mixed epoxy. I think they sell 1 ounce packages. You can get the same effect with some JB weld. I've seen overclocker guys use a dab of thermal grease at the center of a heat sink and then use a tiny about of JBweld around the perimeter to bond the headsink to the part and seal in the thermal grease.


So here is the heatsink glued onto the transmitter. Once I got the heatsink in place and the glue was setting I plugged in an antenna and power and let the transmitter heat up the glue to help cure it.


Here is the final weight not bad!! 42grams. I just took roughly and once of weight out of this thing and you can easily hold it in your hand with the power on, plus once it's in my quad it will get even more cooling.


Here is the final install in the back of my HT-FPV the 1/2" height on the heat sink worked out really well. Anyway I hope this helps!

[viper522]

Very nice DIY. I installed my VTX on the arm of my hex which is under the swing of the 10" prop, so it's cool to the touch when it lands. But a mod like this would allow me to install it away from crash danger. I've got about a dozen heatsinks to carve up. The next evolution would be copper heatpipes

[aeryck]

Nice! Radio shack carries TO220 size heatsinks that work well, and i've used JB Weld to glue them on, but i don't know just how well jb weld conducts heat.

[Wearyman]

Nicely done.

I did something similar, only I used some pre made heat sinks with thermal tape on them. (Originally made for PC video card memory chip cooling.) I also put heat sinks on the front and back as mine have much shorter fins than yours and I'm using it on my FPV truck where it will get less airflow.

[Dsiee]

I also did something similar as wearyman however I went all out and did the ESC's on my tri aswell. Works nice, dissipates the heat much better than the aluminium plate that was there befor.
Not a bad mod for little money (none if you butcher up old gear

[bolt]

Thanks for shearing , and taking the time to post all the photos!

[Skimmer]

Thanks for shearing , and taking the time to post all the photos!

No problem!! It was a fun little project

[h0tr0d]

Just so you know, Tim also sells a Heatsink that fits those and it's thermal adhesive backed, so no mucking about with messy epoxy. I typically put one on my higher power vtx's since I live in Texas and frequently fly when it's 100+ degrees F outside. You can actually buy them cheaper at digikey, but it's cheaper to grab one from Tim if you're only picking up one. You can fit two on most of them if you're not worried about weight, but one works fine.

[slowjet]

I have that same vTX (from bevrc) and have never had any trouble without a heat sink. Even sitting there for an hour on the ground while I fiddle with stuff. How necessary do you find this mod to be?

[viper522]

I have that same vTX (from bevrc) and have never had any trouble without a heat sink. Even sitting there for an hour on the ground while I fiddle with stuff. How necessary do you find this mod to be?

Depends on your ambient temps, supplied voltage and airflow. On my RV 800mW Vtx, in the sun, 94F temps, no airflow, 12.6v on a fresh battery, it will probably boil water.