I just replaced my Xfinity Internet cable modem with a Wintek fiber optic modem. I use an Airport Time Capsule to run my wireless network. If I

Firstly, before you worry about fine tuning the wireless.. the absolute top speed you can get is around 350Mbps down due to processor limitations in the TC. I am assuming the fibre optic modem is a pure modem.. not a router?? Even the AC model Time Capsule is well behind modern wireless routers currently available.

You really need a new router for gigabit internet.. the older models will not have a powerful enough processor.

Just to give you an idea the Last Airport Apple made, AC tower, which we call Gen5, runs a 1Ghz processor. It is not possible to get 1000Mbps throughput without a processor that works faster than that.

Worse.. and worse, Apple wrote their own firmware which makes it super slow. In normal setup Broadcom has a trick to help get speeds higher but Apple lost access to it. You need newer type router with >1.7Ghz processor with full NAT engine speedup access firmware to get gigabit internet.

We can make suggestions if you give us idea of what you need.

The TC can be bridged and setup just for backups. It is not really useful otherwise.

How old is the iMac? Older Macs would be limited to the 270-300 Mbps range for WiFi.

How old is the Time Capsule? An older version would have the same WiFi limitations.

I assume that the 270 Mbps WiFi speed is being checked with the iMac in close proximity to the Time Capsule with a line of sight relationship to the Time Capsule, correct?

Unfortunately, there are no settings on the Time Capsule that need to be "updated". About all that you can do is reset the Time Capsule back to its factory default settings and then set it up again to see if that will result in any improvement.

If still no luck, you could use the Time Capsule just for backups, as La Pastenague has suggested, and get an up to date router that will deliver much higher WiFi speeds. In that regard, even if you have the most recent "tower" version of the Time Capsule, that product was designed in 2012 and introduced in 2013. Apple made no improvements in the hardware on the Time Capsule from the time that it was introduced to the time that it was discontinued in the Spring of 2018.

Just had a post disappear again.

Unfortunately I really like managing the network through Airport Utility.

Then you need to move to better end products.

Have a look at Ubiquiti particularly the Dream Machine router along with a couple of UAP wireless access points.

Or look at TP-Link Omada series.. which is cheaper and a bit easier to learn. It is without a router at this point.

Or just get one of the high end domestic routers like Asus RT-AX88U and use it with a couple more Asus units since it has unified configuration.

Hold down the option key on your iMac while you click on the WiFi menu at the top of the screen

Look for the Transmit Rate which is abbreviated Tx Rate and note that figure

This is a theoretical maximum speed at which your iMac can connect to the Time Capsule over WiFi. It does not tell you anything about your actual Internet connection speed though, which might typically be half or less than the Transmit Rate.

You can buy the modern equivalent.

Ubiquiti is a brand that many people are moving to.. certainly a lot more complicated to setup but uses a controller that gives you overall control of the whole network including switches and routers if you buy USG series along with UAP WAP.

It is pricy for high end router that will handle gigabit ethernet. They do however have a home equivalent UDM which is worth a look.

TP-Link has a cheaper version of the same thing which is a lot easier to setup and also works very well. The router is not included in management yet.

Note you need in both cases all ethernet wired WAP. This is not mesh in using wireless backhaul but does do the same thing in terms of roaming and handoff.

If you want a single point setup I would be looking at Asus RT-AX88U or similar units.. which have good control via excellent gui and run either AP or mesh system to other units. The difference is this is domestic type where the above are semi pro type.

First thing is to check the wired Ethernet speed by connecting a computer directly to one of the 3 LAN ports on the Time Capsule and check speeds that way. Make sure to turn the WiFi off at the computer when you do this, to insure that the connection will be over Ethernet.

This will give you a baseline for potential speed on the network. Depending on whether the Time Capsule is set up as a DHCP and NAT router or as a "bridge", the top potential speeds can range from about 300 Mbps to the 700-800 range.

Check the wired connection speed first, then we will proceed. What are your results when you check this way?

Unfortunately, if the Time Capsule is set up as a DHCP and NAT router, it is one of the slowest routers on the planet.