Last night, I purchased and installed from the Mac App Store the program Network Logger Pro ($9.99). 

Despite my belief that the Airport Time Capsule is not the problem with our connectivity, I still had to consider the possibility that it might be. So I started researching wifi problems with Airport Time Capsules. I compiled a small checklist of wifi settings to try in the Airport Utility (such as changing ipv6 to "link-local only"). 

I also discovered that the ATCs have a lifespan of 3-5 years -- not only for the hard drive, but also for the wifi components. Apparently, they get hot and wear down over years of being on all the time. So the ATC could be part of the problem after all. That is disappointing, but good to know. Time to start pricing another external drive and a new wifi router.

But let's take the ATC out of the equation: if I was relying just on the Frontier modem, would I still  experience network outages?

So I started looking for programs or terminal commands I could use to create a log file to show that the outages are coming from the modem, not the ATC. It was during this research that I discovered Network Logger Pro. 

Therein followed a series of brainwaves.

• Brainwave #1: I already have an extra-long Ethernet cable running from the ATC to the back of the iMac, so that I don't need to be on wifi. 
• Brainwave #2: The modem has an Ethernet port.
• Brainwave #3: If I connect the iMac to the modem via the Ethernet cable, then I'm bypassing the ATC and getting the data directly.
• Brainwave #4: With the ATC out of the equation, the Frontier tech guy has one less confounding variable to deal with.
• Brainwave #5: If the modem-to-Mac connectivity is solid and steady, then the problem is the ATC. If the modem-to-Mac connectivity is choppy, then -- if the line and signal are all working correctly -- then the problem is the modem. (Just thought of another variable -- the Ethernet cable. But it's not pinched or bent anywhere, so that shouldn't be a problem.)

It takes a while for me to put things together...

I installed Network Logger Pro, which has graphs and stuff I can't begin to decipher. 

  <img src="http://tempblogfood.files.wordpress.com/2019/08/2e4c1-network-logger-pro.jpg" alt="" />

Now that my iMac is slurping data directly from the modem, Network Logger Pro records in its log the network up- and downtimes. Yes indeed, connected directly via Ethernet to the modem, I can see that I'm getting outages of several minutes at a time. 

  <img src="http://tempblogfood.files.wordpress.com/2019/08/2c5fd-log.jpg" alt="" />

So now I can call the tech guy, show him this log, and make the case that we should try a new modem. Once we're sure the modem and line are working well on my iMac, then we can tackle any wifi problems the ATC may have.

Update: the Internet went down as I tried to post this from home. So I'm posting this from work.