This fixed it for me immediately. The problem is the nature of wifi adapters.
The solution. It involves using the Registry Editor. Be careful not to change anything else except for the things that are listed.
1. Open Registry Editor (Windows 8/8.1, right click where Start button was, click Run, type regedit. Windows 7, click Start, click Run, type regedit)
2. Head to 'HKEY_LOCAL_MACHINE \ System\ CurrentControlSet \ Control \ Class \ {4d36e972-e325-11ce-bfc1-08002be10318} [Be sure to expand the 4d36e.... folder]
3. Inside will be a number of folders named 0000, 0001, 0002, etc. Look through all these folders until you get one that says Intel(R) Dual Band Wireless-AC 7260 in the registry.
4. Once the device has been found, search for a value called ScanWhenAssociated.
5. If you see this value, set it to 0 on hexadecimal. If you don't see the value, click edit from the top, select new, and click DWORD (32-bit) value. Rename this value to ScanWhenAssociated (exactly as shown). Make sure this value is set to 0 on hexadecimal.
6. Restart the computer. This is important. The changes won't take effect unless you do.
You can test by cmd running ping 192.168.0.1 -t (or whatever your router gateway is) and you will see that the ping spikes have gone.
Calix