To enable Wireless-AC mode on your adapter you'll need to confirm the following settings:
Wireless Mode: 6. 802.11a/b/g
HT Mode: VHT Mode
However, this is not the only thing that may keep you from achiving your maximum connection rate.
In order for us to take a full look at your settings, please download and run the https://downloadcenter.intel.com/download/25293/Intel-System-Support-Utility Intel® System Support Utility while connected to your network, and share the report with us.
To enable attachments your will need to switch to the "advanced editor" while replying.
I couldnt find the "advanced Editor" option, but here's the wifi info
*DeviceSleepOnDisconnect Sleep on WoWLAN Disconnect Disabled (0)
*PacketCoalescing Packet Coalescing Enabled (1)
*PMARPOffload ARP offload for WoWLAN Enabled (1)
*PMNSOffload NS offload for WoWLAN Enabled (1)
*PMWiFiRekeyOffload GTK rekeying for WoWLAN Enabled (1)
*WakeOnMagicPacket Wake on Magic Packet Enabled (1)
*WakeOnPattern Wake on Pattern Match Enabled (1)
ChannelWidth24 802.11n Channel Width for 2.4GHz Auto (1)
ChannelWidth52 802.11n Channel Width for 5.2GHz Auto (1)
CtsToItself Mixed Mode Protection RTS/CTS Enabled (0)
FatChannelIntolerant Fat Channel Intolerant Disabled (0)
IbssTxPower Transmit Power 5. Highest (100)
IEEE11nMode HT Mode VHT Mode (2)
MIMOPowerSaveMode MIMO Power Save Mode Auto SMPS (0)
RoamAggressiveness Roaming Aggressiveness 3. Medium (2)
RoamingPreferredBandType Preferred Band 1. No Preference (0)
ThroughputBoosterEnabled Throughput Booster Disabled (0)
uAPSDSupport U-APSD support Disabled (0)
WirelessMode Wireless Mode 6. 802.11a/b/g (34)
Could you please run the SSU again, but while connected to your wireless network?
If you're disconnected we don't get enough details to troubleshoot.
Thank you for running that report again. We were now able to narrow down the issue to between your network (router/access point) or your internet service. Your wireless adapter looks to be performing as it should.
Despite your adapter having wireless-AC enabled, it's currently connecting to an 802.11n network. Meaning it will need to operate in Legacy Wireless-N mode in order to be able to connect.
If your router/access point IS wireless-AC capable, then you might need to look into it's settings or a firmware update in order to troubleshoot to find out why it's broadcasting in legacy mode.
If your access point is not 802.11ac capable, then you will need to upgrade it to a newer model in order to achieve your adapter's full potential.
In this configuration, the maximum achievable connection rate for this adapter will be of 300 Mbps (as compared to 867 Mbps for an 802.11ac network). Please keep in mind that connection rate refers to the speed data is being transfered between your adapter and it's wireless access point. Download speed simply looks at one layer of the packet and measures how fast it's copied from the web over to your computer, not accounting for packet overhead.
If you have a high connection rate, but a slow download speed, the issue will likely need to be addressed by your internet service provider (ISP). However, low signal strength can increase latency due to RF interference, which can heavily affect your download speed in high density environments.
What is the model of your current access point or wireless router?
Its not the access point, we're using Meraki commercial networking gear with their access points. My Samsung Galaxy S8 phone gets 867 Mbps. Other laptops with AC Wifi adapters can get 700-800. I believe some laptops with other models of Intel adapters (7260?) are getting in that range as well. It just seems to be specific to these laptops that have the 8260ac adapter.
Please keep in mind that the drivers provided through our Download Center are generic versions. If you believe the issue is the driver, then our next best recommendation will be to contact your computer manufacturer and install the latest OEM specific driver instead using the clean installation method.
1. Download the latest wireless driver provided by your computer manufacturer.
2. Under Programs and Features in the Control Panel, uninstall any instance of the "Intel® PROSet/Wireless Software." When prompted, choose to "discard settings."
3. Go to the Device Manager > Network Adapters > Right click on your Intel(R) Dual Band Wireless-AC 8260 and uninstall it. Make sure to select the option to "Delete the driver software for this device."
4. Clear out your temporary files: Press the Windows* Key + R to open the run box. Type Cleanmgr.exe and press OK. Here you will need to make sure Temporary Files are checked, you may uncheck everything else (unless you're ok with the extra wait) and press OK.
5. Reboot your computer.
6. Install the drivers from your OEM.
You may also want to check to make sure that your access points are not being set with access control or priority list (QoS/Access List). It's not uncommon for a commercial grade AP to broadcast multiple networks with the same SSID, then inteligently assign clients to a slower connection or only allow them limited bandwidth depending on QoS lists.
So at home I have a Netgear AC1900. My phone gets 700-900 but the PC only gets 144.
I set the "prefer 5GHz Band" option to "Yes" and it shot up to 300 for a short time and dropped back to 144.
The second SSU.txt I sent in was from my home (which is AC capable). I am trying different settings at difference locations (and comparing to my phone). I also have Wifi Analyzer on my phone so I can measure signal strength to an AP, etc.
If the issue continues regarless of which network or driver you're using, then we can definitely suggest for you to contact your computer manufacturer. It's very possible for this to be a hardware issue.
On a basic level, if your laptop is no longer in warranty (or you're not worried about voiding it), we can also recommend making sure that both wireless antennas are securely connected to your adapter.
That could be part of the issue, wireless adapter upgrades can be troublesome more often than not. For example, if your previous adapter was a lower end model such as the Intel® Dual Band Wireless-AC 3165 (which is a 1x1 adapter), then it's possible that only one of your antennas is intended for wireless connectivity, while the second will be a lower gain antenna placed for Bluetooth*. The Intel® Dual Band Wireless-AC 8260 on the other hand is a 2x2 adapter (two antennas supporting two simultaneous data streams).
If the replacement was purchased directly from your OEM, there are less things to worry about. Otherwise you may have some mismatched features, as there are some models intended to work with vPro, low power, or LTE platforms. Some are even customized for an specific computer manufacturer. Although I do hope it's just a loose antenna connector, please keep in mind that wireless upgrades are technically only supported through your computer manufacturer.