Note:

There are many ways to achieve this and in this tutorial I follow two flash method.

Preparation:

• This guide assumes you are on stock firmware.
• If you are already on DD WRT or Tomato, ignore step 2 of procedure.
• Doesn’t matter whether you are on Windows, Linux or Mac. Everything happens in browser
• Make sure you are connected to the router over one of WAN ports
• It doesn’t matter which firmware version you are currently on. My router came with V1.0.3.XX, which I later upgraded to V1.0.4.28_1.1.64.
• Download these two files:
  1. Tomato Initial CHK file (.chk), which upgrades your NetGear firmware to Tomato - link.
  2. XWRT TRX file (.trx), which upgrades Tomato to XVortex’s AsusWRT-Merlin (the thing you finally want). Current latest version is v378.53_0. The zip file contains .chk and .trx files, you can ignore the .chk for this guide - link.

Procedure:

1. Login to your router. Reset it to factory settings (Advanced > Administration > Backup Settings > Revert to factory default settings).
2. Flash the .chk file, after this procedure firmware will be upgraded to Tomato. (Advanced > Administration > Router Update > Browse > Apply)
3. Now flash the .trx file which upgrades to XVortex’s Firmware. You will see ‘successful’ message at end.
4. Now if your router is not being detected, do manual reboot of the router.
5. Connect to the router, if there are any IP conflicts it will be displayed. It should now show you the Installation Wizard. Either follow it or skip it. But it will require you to set the WPA creds.
6. Do another reset (Administration > Restore/Save/Upload Setting > Factory default OR http://<router_ip_address>/Advanced_SettingBackup_Content.asp).
7. Repeat step 4 if necessary.
8. Follow the installation wizard at your wish, same as in step 5.

That’s all!! :D

Post installation:

To set TX power to 30%-50%, for both bands:

1. Go to Wireless > Professional > Tx power adjustment (or http://<router_ip_address>/Advanced_WAdvanced_Content.asp).
2. Set Tx power adjustment to 30% - 50%.
3. Change Band to 5Ghz and do step 2 again.

Hope this helps.

Credits:

Check this thread where I originally wrote this tutorial. Thanks to @XVortex for this fine firmware. Thanks to @slidermike who actually introduced me to this, or else I was going to try Tomato. Thanks to @ManiDhillon, @freibooter and @mito for answering my noobie questions and giving me instructions.