Why is signal from the 5 GHz AC radio so poor?

  • Just got my Alien the other day and I was surprised to find that the 5 GHz AC radio was disabled by default. What's the point of making this a tri-band router if the 3rd band isn't even used by default, I thought.

    Well, unfortunately, I might have figured out why it's off by default. I thought I would create a separate SSID with the 5 GHz AC radio and move some of my 5 GHz smart home devices to that network since they don't need to roam to 2.4 GHz and it would help ease congestion on the 5 GHz AX radio where I want things like my phone and laptop to get maximum performance. The very first devices I moved over were some Amazon Echo Dots and Echo Show 5s, and to my disappointment, they went from having a great signal when connected to the 5 GHz AX radio to having a horrible signal on the 5 GHz AC radio, so much so that I'm afraid to put devices on that network now because I suspect the performance would be a lot worse.



    I was expecting the performance to be about the same for WiFi 5 devices, but I guess the 5 GHz AC radio just has an awful antenna or something? What's the deal with that? Is there something wrong with my Alien or is that radio just useless? Seems like they should have just left that crap out and charged $299 for an Alien instead of $379.

  • So I did some testing with my laptop, and it appears the signal from the 5 GHz AC radio is only about 2 db weaker than the signal from the 5 GHz AX radio in most places around my house. Could there be a bug in the signal % and Rx / Tx rates shown in the app? I don't see how a 2 db difference is showing as going from 71% signal to 26% signal, unless the WiFi chips in the Amazon Echos just don't play nice with the 5 GHz AC radio. I guess I'm going to add some other devices and see how they do.

  • Solved. Looks like this is a bug in the AmpliFi app for iOS. When I look at one of my Echos connected to the 5 GHz AC radio in the app, it shows 53% signal, but when I look at the same device in the web interface, it shows 95% signal, so while the 5 GHz AC radio does have weaker signal than the AX radio, it’s not a huge difference and the app seems to be over exaggerating it, whereas the web interface seems more accurate.

  • @gtg465x That may be a specific instance. With my Amplifi app all devices are showing an expected signal strength. Right next to the Alien -100 or maybe 99%. 20 feet away 80-90 %. In my bedrooms that are about 30 - 40 feet away and through walls mid 70s. I only have iOS devices and an HP printer which is the furthest away but uses the 2.4 band, no Alexas so I couldn’t speak to that.

  • @John-Pappas You should check to see if the signal % shown in the app matches what's shown in the web UI. I found another person reported the same issue here: https://community.amplifi.com/topic/3152/signal-discrepancy

  • @gtg465x You are correct. On my furthest device, the printer, on the app the connection is shown as 76%, on the web 85%. On my iPhone 11 Pro Max about 15-20 feet away the app shows 91% and the web 100%. So they are indeed different but not so much that I would have suspected so if I hadn’t seen your post.

  • I also wonder if the lower reading from the app is what the Alien is using to trigger band steering as well. I have noticed myself and in posts from others that devices with pretty good 5 GHz connections (over 200 Mbps) are sometimes getting steered to 2.4 GHz, dropping speeds to 30 Mbps. Maybe it's band steering to 2.4 GHz too soon because the signal readings it's using for that logic are 10-15% off. Wish I could move this topic to the bug report section so some UI employees could look into this theory.

  • @gtg465x That does seem logical and another reason I chose not to use the Common SSID function. I’m fortunate that in my apartment the 5GHz band reaches just about everywhere and on my devices I have made them “forget” the 2.4 separately named band. Otherwise I’m certain my phone would latch onto that every time I come back to my apartment from being outside. I left the band steering toggled on but since the devices can only connect to the 5 band it’s irrelevant. Only my Apple Watch and the printer use the 2.4 band.

  • @John-Pappas Having separate SSIDs doesn’t make sense in my case. I own a house and actually want my devices to connect to 2.4 when I’m outside in the yard where 5 GHz doesn’t reach.

  • @gtg465x I understand. I would do the same in your situation. But in a condo apartment with multiple 2.4 networks around me performance is significantly degraded if my phones or iPads connect to that. For my watch and printer there’s really no such issue.

  • @gtg465x I replied to the other thread about why there is a signal % difference. They are different readings.

    I have also noticed the signal % anecdotally seems low for WiFi5 5ghz (viewed through the app). Is it correct? I have no way of knowing. But their WiFi experience algorithm seems to be more representative of what kind of throughput you can expect. Even when I’m showing in the 60s% (possibly lower) signal strength & 90s% WiFi experience, I still get maximum throughput on my current plan. 300 down/350 up. So I’m not stressing over it.

    If you’re having band steering issues that’s more complicated but check to see if you’re still getting max speeds with a low signal % through the app.

  • @Gofast @gtg465x I had previously checked what was indicated on the web interface versus the app and found that the percentage displayed on the web was higher than what’s shown in the app. But I’m not certain they’re referring to the same things. Just now out of curiosity I checked the web interface and found a number of my devices as shown being connected to wifi 5, which is incorrect. I had earlier today enabled the additional 5GHz band just to test download speeds. Seeing no real difference I turned that off again and made sure my devices had reconnected to the correct wifi-6 5GHz band as before which they had. So there is no wifi 5 network to connect to even though the web interface shows that several are.

    This convinces me that for my purposes the app is probably more reflective of my reality and more useful for my needs. Even the signal/connection strength indicated in the app appears more reflective of what’s going on since it matches what I had experienced when checking my devices with Apple’s Airport Utility when I was using my previous router. On the web checking what was indicated for my phone which is currently located in a bedroom a good distance from the Alien the signal was shown as 100% and that’s just not possible. That value may reflect some other parameter but the 80% shown in the app is more realistic.

  • @John-Pappas The “Connection” column of the web interface shows the capability of each device, not the capability of the radio they’re connected to. So if a WiFi 5 device connects to the WiFi 6 radio, it will still show WiFi 5 for that device, which is how it should be in my opinion. You can tell which radio it’s connected to by looking at the “Interface” column, which will show “5 GHz” for the WiFi 5 radio or “5 GHz AX” for the WiFi 6 radio.

    Thanks @Gofast! That makes sense that one is showing experience and one is showing signal. They should note somewhere in the web UI that they’re showing experience % and not signal %. I still find it odd that when I switched that device in the first post from the AX radio to the AC radio, the signal % dropped so drastically, even though testing with my laptop in the same location only showed a 2 db difference, which isn’t a lot. It’s possible the Echo just has a worse antenna than my MacBook and it did actually see a bigger signal decrease, which would be a bit disappointing.

  • I think the signal % may be calculated based on the incoming Tx rate from the connected devices compared to their theoretical maximum rate. Those Tx numbers correlate strongly to the signal %. The formula for signal % could even be a weighted average of actual Rx and Tx vs max theoretical Rx and Tx. A 12% Rx weight and 88% Tx weight would produce the correct numbers in my example... signal % = 12 * (Rx / Max Rx) + 88 * (Tx / Max Tx)

    So for my screenshots:
    71% = 12 * (433/433) + 88 * (292/433)
    26% = 12 * (292/433) + 88 * (87/433)

  • @gtg465x said in Why is signal from the 5 GHz AC radio so poor?:

    So if a WiFi 5 device connects to the WiFi 6 radio, it will still show WiFi 5 for that device, which is how it should be in my opinion. You can tell which radio it’s connected to by looking at the “Interface” column, which will show “5 GHz” for the WiFi 5 radio or “5 GHz AX” for the WiFi 6 radio.

    Ah, thanks that does clear it up then. All devices are shown connected to the AX Wifi 6 radio.

  • If you look at the spec sheet the low-band 5Ghz radio is 1dBm lower on max TX than the high-band.


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