UPS (Uninterruptible Power Supply) Adversely Affects WiFi Performance?

[jzchen]

I recently purchased a BQ16 Pro to patch up (horribly) poor WiFi speed in my sleeping quarters. I plugged it into the 120 V wall outlet typical of here in the USA. Everything including WiFi ran great. Then I decided to shore it up with a UPS so if power went out my ASUS network would not shut down. I did not get a pure sine wave version so it is specifically what's called a simulated sine wave (non-pure sine wave) UPS. Low and behold, TERRIBLE WiFi speed!

Ethernet does not seem affected but WiFi becomes terrible!!! (See attached speed test screenshot).

I think I finally found the root of my home WiFi problem. (Some AC adapters may be immune while others sensitive. A recently added RT-AX5400 continued to use the same AC adapter from my old RT-AC68U as they listed the same V and A output, so I guess the older ones may be the non-sensitive ones. The new ones tend to cause grave issues with WiFi).

 

[bbunge]

FWIW - I have a CyberPower AVRG750U which runs a NAS, router and a RPI3 with no issues. We had a power outage of almost an hour a couple of weeks ago and the UPS kept everything running. The UPS is one of those Simulated Sine Wave devices.....

 

[Squall Leonhart]

the frequency of the sine wave (50/60hz) isno where close to the harmonics of a 2.4 or 5Ghz radio

 

[jzchen]

FWIW - I have a CyberPower AVRG750U which runs a NAS, router and a RPI3 with no issues. We had a power outage of almost an hour a couple of weeks ago and the UPS kept everything running. The UPS is one of those Simulated Sine Wave devices.....

Hmm. Thank you. I added a RT-AX5400 a few months ago. I reused the AC adapter from my EOL RT-AC68U. (That one is really old). It has been working great...

 

[jzchen]

the frequency of the sine wave (50/60hz) isno where close to the harmonics of a 2.4 or 5Ghz radio

I've been searching for two things- pure sine wave UPS, $$$, and replacement AC adapters, order of one decimal less, $$. The BQ16 Pro came with a 12V 5A AC adapter. This particular combo is available on Amazon. Do you think it's worth a shot? (My phone is WiFi 7 so likely on the 6 GHz band, is that one a concern)?

 

[jzchen]

I can't believe I've been living with terrible WiFi over this....

 

[jzchen]

Definitely seems to have an effect...

 

[jzchen]

These are with the AC adapter rotated 180 degrees (so plugged into Surge protector ONLY side).

 

[degrub]

Is this the router based speed test or an app in the phone ?

The link rate only changed by about 10%. So i would not expect the local environment to be much of an issue.

Signal strength increased by 2 dB which suggests the client being very close to the AP in the second run and in a different location in space relative to the AP. If you are holding the client and your body position changes, that can affect the RF reception.

Does the change in bit rate hold for any location in the area (room/house/apartment) ?

 

[degrub]

the frequency of the sine wave (50/60hz) isno where close to the harmonics of a 2.4 or 5Ghz radio

It would be the square wave approximation that introduces high frequency noise. We noticed the potential issue long ago when we were switching from transformer based UPSs to the cheaper square wave synthesized. Most PC power supplies can handle the issue now, but maybe some of the cheap wall warts do not.

 

[degrub]

I recently purchased a BQ16 Pro to patch up (horribly) poor WiFi speed in my sleeping quarters. I plugged it into the 120 V wall outlet typical of here in the USA. Everything including WiFi ran great. Then I decided to shore it up with a UPS so if power went out my ASUS network would not shut down. I did not get a pure sine wave version so it is specifically what's called a simulated sine wave (non-pure sine wave) UPS. Low and behold, TERRIBLE WiFi speed!

Ethernet does not seem affected but WiFi becomes terrible!!! (See attached speed test screenshot).

I think I finally found the root of my home WiFi problem. (Some AC adapters may be immune while others sensitive. A recently added RT-AX5400 continued to use the same AC adapter from my old RT-AC68U as they listed the same V and A output, so I guess the older ones may be the non-sensitive ones. The new ones tend to cause grave issues with WiFi).

Did you unplug the UPS from the wall to force it on battery ?

Is the ups plugged into the wall directly or through a plug bar or other device with filtering circuit ?

 

[Tech9]

Did you unplug the UPS from the wall to force it on battery ?

Good question because most common UPS models in Stand By mode have power output directly connected to the main power. They switch the power output to whatever wave they generate only on main power interruptions. In this case what @jzchen is experiencing may be some noise generated by the UPS electronics itself even in Stand By mode. With so many UPS devices available on the market there is no good way test and know.

 

[jzchen]

Is this the router based speed test or an app in the phone ?

The link rate only changed by about 10%. So i would not expect the local environment to be much of an issue.

Signal strength increased by 2 dB which suggests the client being very close to the AP in the second run and in a different location in space relative to the AP. If you are holding the client and your body position changes, that can affect the RF reception.

Does the change in bit rate hold for any location in the area (room/house/apartment) ?

Phone app speed test. Ethernet seems unaffected but as an FYI everything is 10 Gbps ethernet except routers that do not support it and the 5 Gbps port on the AT&T BGW320-500. Service is 1 Gbps fiber.

 

[jzchen]

Did you unplug the UPS from the wall to force it on battery ?

Is the ups plugged into the wall directly or through a plug bar or other device with filtering circuit ?

No I did not try forcing it to battery power. The effects of just using the battery side were (to me) obvious.

The UPS is plugged into the wall directly. Prior I was using a cheap surge strip, (but I had forgotten to mention).

If it wasn't clear the UPS, a CyberPower S175UC (Sam's Club if that matters) has two columns of plugs, one side surge only, the other side battery backup. The results were gotten trying to approximate the same signal phone to router, just plugged into battery in one set, and surge in the other.

 

[jzchen]

It would be the square wave approximation that introduces high frequency noise. We noticed the potential issue long ago when we were switching from transformer based UPSs to the cheaper square wave synthesized. Most PC power supplies can handle the issue now, but maybe some of the cheap wall warts do not.

There's some harmonics in engine design, (by background I am studying automotive technology), but by the time they start talking about secondary harmonics based on cylinder firing, my mind starting being somewhere else...

 

[Tech9]

No I did not try forcing it to battery power.

Must be the UPS itself then. The waveform is unchanged in Stand By. There is a fast relay there switching between main power and battery. You perhaps can hear it clicking on main interruption or self test. Most general use UPS devices work this way.

 

[degrub]

Good question because most common UPS models in Stand By mode have power output directly connected to the main power. They switch the power output to whatever wave they generate only on main power interruptions. In this case what @jzchen is experiencing may be some noise generated by the UPS electronics itself even in Stand By mode. With so many UPS devices available on the market there is no good way test and know.

Looking at the spec, it is a bypass design, which means there would be no difference from running plugged into the wall. Something else is/was the issue.

 

[Tech9]

Looking at the spec, it is a bypass design

Yes, the ones with controlled output are much more expensive and not commonly sold in computer stores.

 

[degrub]

Must be the UPS itself then. The waveform is unchanged in Stand By. There is a fast relay there switching between main power and battery. You perhaps can hear it clicking on main interruption or self test. Most general use UPS devices work this way.

Likely a solid state relay rather than a physical coil / contacts. Expensive to use physical one with high switching speed.

 

[Tech9]

At home I use a few APC Back-UPS CS-series and they have a mechanical relay. Quite loud, actually. I can hear them clicking on power fluctuations in the next room over. They boost the feel something is working really hard there for you, ready to die for you if necessary...

My APs are all far from the firewall/switching though and no ill effects on Wi-Fi quality.