Mysterious AP problems

RouterOS Wireless Networking
1

I’m experiencing intermittent high ping times / packet loss on an AP that previously was one of my best. Clients are getting anywhere from 3 to 30 percent packet lose intermittently. My hardware is as follows:

All the clients are CB3s
3 120 degree sector antennas
3-way splitter to feed each sector (worked fine for over 18 months)
NL-2511MP Plus 802.11b Prism card
When the site was running properly, we upgraded the AP from a RB532A to a mini-itx solution with 512MB Ram and a 1GHz cpu (lots of clients). Everything was fine for a couple of months. Since the issue arose, we have switched to another routerboard in case the AP was damaged, but it had no effect.

The issue:
About 2 weeks ago, we had several thunderstorms go through the area. The water tower the AP is installed on lost power and the AP dropped offline. We went over and discovered the switch wasn’t plugged into the UPS. We plugged the switch in and the AP came back up. Then we discovered that we had lost a backhaul that was on the water tower due to the lightning. After it was replaced we patted ourselves on the back and thought everything was fine. The problems seem to have started that day.

Since then we’ve replaced the card, the amplifier and the AP itself. We did discover some water in the sector antennas, but have dried them out and sealed them. We looked for interference but haven’t noticed anything unusual. It does seem that clients don’t associate as quickly as they used to. We have also updated to 2.9.42.

We will replace the sector antennas as soon as possible. Does anyone have any other suggestions?

2

Also check your cables and connectors for water ingress, if in doubt replace them. When replacing make sure all exposed connections are wrapped with self-amalgamating tape (also known as self-vulcanising tape).

In case you’ve never used self amalgamating tape before, it is a soft rubber tape which when stretched will self bond leaving a waterproof layer.

Ordinary electrical insulating tape is not good enough, heat causes the glue to soften and leave gaps, cold causes the tape to become brittle.

To apply, start a couple of inches from the connector, as you wrap the tape stretch it to half its normal width.


Regards

Chris Macneill

3

aside from stating the obvious as cmacneill has about waterproofing your connectors, I wouldn’t trust the antennas if they have already taken on water…
And if the antennas took in water, then it is likely that your cables have also sucked some water - replace the lot… corrosion will have begun to set in, and they will probably never be the same again…