I’ve read some posts about people finding water inside their outdoor enclosures because cool temps pull moisture into the enclosure and then it has no way to drain out.
I plan to put a Raspi and SDR in a plastic 10x6x4" IP65-rated box at the Texas coast and was planning to add a vent hole at the bottom but haven’t decided how big of a drill bit to use. Too big and bugs can get in - any recommendations? Would 1/16" or 1/8’ be too small?
My box has two tiny holes in the bottom. I don’t know the exact size but they are very small, maybe 2mm maximum.
When I took it down a few weeks ago after around eighteen months I was pleased to see that the inside was perfectly clean and dry with no sign of any bug infestation. I was half expecting a few spiders but no, nothing.
A 1/16" or 2 mm weep hole should do the trick.
i just installed a box outdoors for my LNA…i used Amphenol LTW IP67 vents. mounted on a vertical section of the box.
https://www.amphenolltw.com/p2-products-series.php?product_series_sn=34
Several methods I’ve either used or seen include:
Not as good as the amphenol vent, but easier to find!
i found the Amphenol LTW vents thru Newark (Element 14). they were very low cost. took about 1.5 weeks to 2 weeks to get. they had to ship from the UK to the states
Drilling a tiny hole is just as effective, cheaper and quicker 
I live in the tropics. When the wet season starts, ants move into anything warm and dry.
A 2mm hole in a plastic box looks like a Welcome mat.
That’s a fair point!
hi keithma, i agree re the tiny hole. my objective was to attempt to vent heat as well. i used two of these Amphenol vents on the vertical front of the box. one down low and the other high in the hopes of providing a nice path for hot air to rise and escape the enclosure. since i just have the LNA in this box i didn’t want to mess with active cooling (ie a fan)
I’ll probably start with a 1/16" hole to equalize the pressure so no moisture will be pulled into the box.
Also, I decided to thermally conduct the heat from my 2 SDRs through 2 metal L brackets and big washers from Home Depot - the antennas are mounted inside the box …
I like the idea, but the setup as shown cannot perform very well.
The thermal coupling between the SDR and bracket is insulated by an airgap and plastic case.
The steel ‘L’ bracket will work, but aluminum will perform about 6x better
The washers on the outside have a very small surface area and and are only coupled via two small screws.
Could I suggest replacing the brackets with Al angle say 4~5mm thick.
You could use some finned heatsink extrusion on the outside, but a similar sized Al angle as on the inside would be a good start.
Then bolt it together with a pair of 10~12mm brass bolts (copper if you can get them).
This fancy heatsinking is not the best solution in my opinion.
A rather simple sun shade, as in another box around the box will reduce the box temperature much more.
The sun shade box does not need to be water tight and so can have openings at the top.
That means the inside box will more or less be at shade temperature.
A huge improvement compared to the box being baked in the sun.
Even if the box is double walled giving it shade is still an improvement.
Have to agree with this. The thermal coupling will be poor regardless and (assuming the box is out in the open), sun on a heatsink will conduct more heat into the box .
A dual skin is a very simple and effective cure for direct sun heating.
I drilled two 1mm holes in the lowest face and inside the enclosure glued a small piece of open cell foam to stop bugs.
Have also used the same idea on a high power transmitter balun enclosure.
Works fine for me.
Agree there are lots of ways to make it better - I did fold up some aluminum foil to go in the slim air gap between the SDR and the L-bracket.
I stress-tested this setup in my attic a few days ago when it was 90’F outside and the attic air was 120’F and the outside washers were definitely hotter than the plastic box - the Raspi CPU temp was 72’C.
When I finally mount it outside, I will try to find the location with the most shade.
Any location with natural shade will have bad reception.
It won’t be natural shade - it will be mounted at the far end of this pergola that’s on the roof of this condo …
If the antennas are in the box, the box needs to overlook closeby objects for best performance.
Anyway nice shed 
What’s the reason for having the antenna inside the box?
The antenna is too close to RFI generating components. Moving it outside will improve performance. It does not need to be by much, if you are concerned about cable losses.
This way you can install the box in the shade as well.
Then, why not add an FA antenna?
