While at its best the dedicated 5GHz network is indeed a lot faster, the dual-band network by default tends to be more stable, providing generally more reliable connection most of the time
That might be why Apple makes this the default setting for the routers. Most users will get better results with a lot less effort if they leave the router set at the default of using the same name for both the 2.4 GHz and 5 GHz networks.
2.4GHz travels wider and 5GHz travels farther
No, that is not correct. One of the things that users seem to have a difficult time understanding is that everything in wireless involves a compromise. 2.4 GHz signals are significantly stronger....but slower....than 5 GHz signals, so they penetrate walls and other obstructions more effectively than 5 GHz signals and travel greater distances with less loss of signal.
5 GHz signals are obviously higher frequencies that have higher speed capabilities. But, here the compromise is signal strength, since the 5 GHz signals are significantly weaker than 2.4 GHz signals. So, here is all that you need to remember about this. The lower the frequency, the slower the speed, but the stronger the signal. The higher the frequency, the faster the speed capability, but the weaker the signal.
So the bottom line for users is that in general, 5 GHz works best when the router and computer are in the same room, or have line-of-sight with each other. 2.4 GHz will work better if the computer is a few rooms away from the router, or there are more obstructions in the signal path between the devices.
But my dedicated 5GHz network is occasionally limited to an upload/download traffic speed of just a few Mbps
I have never experienced this on a 5 GHz network, so I don't have an answer for you on that one. Some users have reported issues with cordless phones that operate in the 5 GHz region though.
My ISP's techie said that must be a sign of interference.
Possible. But, remember than 5 GHz signals are weaker than 2.4 GHz signals, so it is unlikely that any nearby networks are broadcasting a 5 GHz signal that would be strong enough to bother your network. If the culprit is interference, it is coming from a source within your house.
Try powering off both Apple routers, wait a few seconds, and then powering them up again. When the AirPort powers up, it goes through a process of automatically scanning to find the best available channels to use at the time.
Should I give up the dedicated 5GHz network?
Most users will get better results with a lot less effort if they leave the router set at the default of using the same name for both the 2.4 GHz and 5 GHz networks. This is what I do, and it works fine.....better than dedicated networks for me.
But, some users swear by using a different name for the 5 GHz setting, and they are convinced that it is the best setting to use, even though it is not the default setting that Apple provides. There are very few clear cut answers in wireless.....as I said, everything involves a compromise of one thing or another.
