>I'm not sure, the router doesn't appear on the list of available networks so I'm not sure how I'd check.
You'd probably have to access your router's firmware from a connected device and view the connected device list if you're completely unable to see the network with those PCs. I see you're using what looks like an ISP provided router, so I have no idea what kind of access they give to the firmware as that can sometimes be locked down.
Do you know what model router you have? If nothing else
>Do you have a suggestion on which one to use?
I've not looked in to new apps in years, I still have access to the old free version of inSSIDer but I've also used Wifi Analyzer from farproc (Android only I believe). Cannot vouch for the quality or safety of either at this point.
I upgraded to a mesh system (Google's mesh routers) for about $200 and that system works phenomenally for me with Nest cams. But before going that route, try some troubleshooting: check the channel your wifi is on. If you have an Android phone you can download Farproc WiFi Analyzer for free (http://a.farproc.com/wifi-analyzer/) and it'll tell you how busy each nearby wifi channel is, and what the strength of the wifi is when you walk out to your outdoor cam.
Do you have a tablet or other device that runs Android?
If you do then I recommend downloading this app called WiFi Analyzer. This app will give you an excellent view of the wifi space around you. It can also tell you which would be the best channel(s) to use for both 2.4 and 5 GHz (there are 8 other channels beside 1, 6 and 11 on 2.4)..
I like it's real-time signal meter.. good for tracking down dead zones and whatnot.
One thing, if you want a full picture of the 5GHz wifi space, you'll need to configure the app to make it report on all the available channels, for some reason only a few are selected by default. Other than that I think it's a great tool to have for troubleshooting wifi issues.
If you are PC only, there is Acrylic WiFi that does a similarly decent job showing what the wifi in your area looks like (the free version is limited but it gives enough info to figure things out).
It might be worth using something like (since inssider went to a paid app :(( ) Wifi analyzer http://a.farproc.com/wifi-analyzer to guide you on what channel on your router is going to provide the least interference.
Wifi signal strength isn't a big enough problem for all that. The mid to high end routers they sell now have no problem reaching out to hundreds of feet. Bad connections are more likely caused by interference from the locally oversaturated radio spectrum, and you can easily solve that problem with simple apps like WiFi Analyzer.
If you are going to to a good bit of trouble shooting you might as well scan for interference of other routers using Wi-Fi scanner (windows) LinSSID (Linux) or WiFi analyzer (android)
Ideally you would use another computer/smartphone to test signal strength and interference