Very Very slow 5ghz on RT-AC88U with Merlin

[John Harvey]

Ive had this router since right after it was released. Its been working fantastic and never had any problems. Ive had 380 firmware for as long as I have had it. My internet speed is 200 down and 20 up but I usually get about 220 down and 25 up with ethernet. Recently I noticed that my phone was unusable on 5ghz. I did a speed test and consistently for days only get about .5 mbps download. Yes that is half a mbps. I only had 2 google homes connected to 5ghz so I unplugged them to see if that was the issue. My speed jumped to a whopping 5mbps max and hovered around 2-3 on average. WHen I connected to 2.4ghz I get around 120-150mbps download and 25 upload. Ive tried factory new firmware, turning off QOS and disconnecting every divice in the house and nothing seems to help. Any ideas what could be causing such slow speeds at 5ghz? I was thinking maybe interference from a neighbor or something but I did a site survey and dont see any 5ghz signals anywhere.

 

[ScottW]

I have an 88U with 380.69, haven't had that problem before -- but here are a couple things to try (which may or may not help...):
1) If you have 5ghz channel width set for "Auto 20/40/80", try setting it to 40 and see if things improve.
2) On your iPhone, go to Settings, WiFi. Click the "info" icon at far right for your 5Ghz connection, choose "Forget this network". Then setup the connection again.

 

[John Harvey]

Thank you so much for the response. I did try "Forgetting" the network and rejoining several times and nothing changed. I also see the problem when connecting a laptop to the 5ghz channel. Changing auto to 40 actually made a HUGE improvement. I tested both my Google Pixel 2 and my laptop and both are getting around 50mbps download and 25 upload now but nowhere near what it use to get at around 130 or 140 mbps download. Any other ideas to get the full speed? 2.4ghz still gets around 120mbps when I switch to that.

 

[John Harvey]

Ok I tried switching to 80hz and it dropped back down to 3mbps download and 25 upload. Something seems to be up with the 80hz. I switch back to 40 and its back up to around 50mbps download.

 

[ColinTaylor]

It could be RF interference as you previously speculated. Not the Wi-Fi kind, so you won't see in on a site survey. Do you have any USB devices attached to the router?

 

[John Harvey]

No USB devices plugged in. Thank you for the segguestion though. Im wondering if there is just something physically wrong with the 5ghz radio. No settings have been changed in probably a year but this just recently started happening.

 

[ColinTaylor]

Try setting the channel number manually. Compare 36 to 100 to 136 for example.

 

[ScottW]

It does sound like interference (per @ColinTaylor's posts, try different channels). The fact that changing channel width to 40 improved things is supportive of that theory, although even at 40 you should easily exceed 100mbps speeds (mine is at 40, and my iPhone gets my cable's full 120mbps download speed anywhere in the house).

With good signal strength, 40Mhz should support your 200mpbs isp speed just fine -- and will be more resilient to any external interference, since it needs half the amount of clear frequency. If it is interference, a combination of setting 40Mhz channel width AND setting a fixed channel may provide the best solution.

>> I'm wondering if there is just something physically wrong with the 5ghz radio
Certainly possible, but most posts here about 88U radio exhibit a "complete failure" rather than a speed problem when the radio fails.