Networking – Router drops internet connection if I connect an additional PC

Many devices rotate the WPA or WPA2 group key (the key used for encrypting multicasts and broadcasts) after exactly an hour. As a diagnostic experiment, try switching to WEP or no security and see if the problem goes away. If it does, then you know the problem is likely the group key rotation interval, and you have something useful to discuss with your AP manufacturer.

Make sure you have the latest firmware on your AP. No use fighting a bug that's already been fixed.

Another thing that may be happening after an hour is DHCP lease renewal. If the DHCP server process on the AP is failing, you might not be able to get an IP address lease, which you might perceive as a failure to connect. You could try giving your client machine a static IP address that's within your router's NAT range but preferably outside its DHCP pool range, and see if that resolves your problem.

This sounds more like a "the wifi connection sucks" issue than a "there's no connection" issue, especially since you said you can sometimes get pages to start loading but it's very slow.

Possible problems:

1. Just a hard incompatibility between your laptop's wifi adapter and Router 2's wifi settings or chipset. This can either be something physical that's impossible to resolve without hardware hacking, or it can be something you can fix by tweaking software, most likely config settings in the router's firmware... but without knowing either the router or the adapter's make/model it's hard to be more specific.

2. Too much wireless traffic in your area. Is this an apartment? Apartments are notorious for having too much wifi crosstalk, so even devices sitting right next to eachother can't communicate. Have you ever tried to have a conversation with someone during a heavy metal concert? Changing the wireless channel of your router can sometimes help if you have a nearby access point(s) communicating on the same channel as yours.

3. Cordless phone, bluetooth, or microwave oven interference. More likely to exist if you're on the noiser 2.4 GHz band rather than the relatively less-used 5 GHz band, but still, it's a possibility.

4. Polarization. Wireless signals are "polarized" in the same way sunglasses are, to block light waves in a certain direction.

An intuitive understanding of polarization: take a long piece of Lasagna pasta. It's a wavy piece of material. Now put the pasta into a cast iron mold and let the mold set to a solid. Remove the pasta. Now you have a mold which is shaped like the pasta, but it's a hole where the pasta could go. Now, line up the pasta with the mold and insert it right in. It should go in although you may get resistance due to the wavy nature of it (ignore that part, bad example ;)). Now, rotate the mold by 90 degrees. Now you can't insert the pasta in at all, it just bumps up against the frame of the mold! Because the dimensions don't match up. You're trying to put the width in along the original height axis and vice versa.

To test for polarization, just rotate your laptop slowly in place while measuring performance (ping command, etc). If it suddenly picks up, congrats you have polarization.

5. For the ultra-long answer, see Tom's Hardware