Weep holes are often overlooked, and in my opinion, a simple yet highly important thing people overlook with "outside" electronics of all types.
Bob W7OTJ
On Wed, Feb 8, 2023 at 7:52 AM Zach Metzinger via AMSAT-BB < [email protected]> wrote:
On 2/7/23 17:58, Joseph Amato via AMSAT-BB wrote:
I recently built two low noise amplifiers (2 m and 70 cm) for satellite work, hoping to mount them right at the antennas. They are in small Hammond die cast aluminum boxes. To mount the boards inside, I had to drill several 4-40 thru holes through each box. I’m worried about slow water seepage through these screw holes. Can you suggest a good way to seal them?
Hello Joseph,
Instead of drilling holes in the box for screws, I've used 1/2" standoffs (threaded) and JB-Weld-ed them to the bottom of the box.
Rough up the general area where the standoffs will go in the box when attached to the board and then screw the standoffs to your board. Use that as an approximate template as to where they'll hit inside the box and mark that with an indelible marker. Remove the board and put a generous glob of JB-W in those four locations. Then put your board in, submerging the standoffs in the JB-W. Let the whole assembly sit, undisturbed, overnight. It will be nearly impossible to remove those standoffs from the box, but you can easily unscrew the PCB for servicing.
Also, you have to assume that any sealed box is not perfect and that you'll eventually get some moisture inside of it. So, I drill a small weep hole (1/8") in the side which will face down and cover it with window screen on the inside to keep out the spiders, etc. That will allow the box to breathe.
I have an SGC ATU (CPVC/fiberglass box) and several other projects outside which have had this treatment. They've all survived for more than a decade with no observable corrosion or water inside the box.
Might I ask: Which LNAs did you build?
73,
--- Zach N0ZGO
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org