The problem is the 4g LTE fails when attempting to connect to dual band routers will be sporadic and most often fail. Here's what I did and it worked
This a 3 part solution:
Part 1 on your evo
1) go to "setting"
2) go to "wifi"
3) go to advanced and and click on "Wifi Frequency Band"
4) I chose 5 Ghz only
Part 2 on your PC
Now goto your Wifi Router settings
For Linksys it is Http://192.168.1.1
click on Wireless setup
On the attached page noticed I diabled the 2.4Ghz setting and I have the 5.0ghz set for channel 149
use any channel you want and be sure to save it. Don't change anything else!
Part 3 back to the EVO
Download free program "wifi analyzer"
1) Click on setting
2) Click on Available channels
3) Make sure channel 149 is checked
Your done! This is not a real solution EVO needs to actually fix, but it worked for me at home. And remember if you are at some wifi hotspot that doen't use 5.0 it won't work.
But with Wifi Analyzer you can find whats available and adjust your phone accordingly.
Hope this Helps
PS EVO FIX IT!
It was the first thing I checked, and yes, it's set to "Always." It always has been. It's just happily totally ignoring that setting now. I've tried toggling it to other options and back, but to no avail. Other people have reported the same problem elsewhere, and nothing really seems to fix it.
Logs show that it is in fact disconnecting the wifi in response to a power state change event, so it isn't just some random wifi glitch. It's Jellybean deliberately disconnecting the wifi when the screen shuts off.
Just another Sprint/HTC screwup. You'd think they'd learn to test these things.
Problem is where it does happen on your device every time there are some phones that are not having the issue or where the issue has be resolved. The Symptoms have been different between Devices having issues. At this point I do not have any information on how many people have download the update and how many are rreporting issues. The original poster is having a problem with a dual frequency modem and setting it to 5ghz fixes his issue. for other people making sure it was setting to 2.4ghz fixed issue. We are collecting the data on the different issues. Your issue seem to be a device issue, others have been with interoperability with a certain type of Router.
I am assuming you have done a power cycle on the device to resolve the issue. Have you turned off automatic connections?
Yep. I've disabled automatic connections, disabled the power saver (which re-enables itself after a reboot, which is a separate issue), set "Keep wi-fi on" to "always" and tried different settings for the band and "maximum performance" setting. It doesn't matter which combination of settings I choose. It happens Every. Single. Time.
The easiest way to observe the symptom is to unlock the phone and watch the status bar as the wifi icon disappears, 3G turns on, then the wifi icon reappears, and 3G turns back off. It's enough of a disruption to ***** up everything that's running.
WiFi Fixer's log just shows this:
Build:0.9.5.4a:979 :Sat Dec 15 10:40:11 PST 2012
CatLog shows the wifi disconnecting in response to a power event. It's basically just ignoring the "keep wi-fi on" setting entirely.
I had to turn off auto channel detection on my DLINK D615 router and specify a channel in order for my router to work. It works fine now and seems to be stable. My EVO worked just fine on the WiFi at my place of employment and has all along recognized my neighbors WiFi, just not mine until I performed this fix. Don't know if you're going to address it though so I can go back to auto channel detection.
At this point I would recommend either a factory reset of the device as something in the software is causing this problem. Given the other problems I have seen thus far yours is the only one where the device connects normally then discounts with the screen time out. If others are having this particular problem I would it would help if we could get some information of how many. If there have been other posts with this issue I may have missed them
Of all the things I can recommend I like this one the least. Worst part is I cannot even give you a guarantee this will resolve the issue. Based on your post you have already done everything else I can think of at this point. I certainly understand the problems that come with the reset of the device.
Making some progress... if I do a Factory Reset and do NOT restore my data from my Google account, WiFi seems to be working normally. So some stored setting in my Google account may be corrupt or broken in some way, or there's an off-chance it could be some app I had installed interfering with normal power behavior.
I suppose this means I'll have to re-install all my applications manually, since Google doesn't give you the ability to pick and choose which settings or which applications or which data you want restored... it's all or nothing.
It does explain why a factory reset didn't seem to help though... it would have helped for a few minutes, until the automatic restore put the phone back into the same bad state it was in to begin with.
It's possible it's your previous settings as Google does store them. If your like me, I have about 10 differnet WiFi systems I connect to during the week, e.g. work, home, parents house, brothers house, etc.. These known locations are stored and backed up and when you do a Hard Reset and connect to your Google acct they come back.
I can't remember though where this info is stored to remove it.