Extreme 5GHz extend to Express 5GHz & 2.4Ghz?

if I extend this 5GHz network with the new Airport Express, does the 2.4GHz on the Airport Express still work and that my iPhone 4/S would able to connect to the network if it's in the Airport Express's range?

No. If you extend the 5 GHz network with the new AirPort Express, it will only extend 5 GHz. It can only extend what it receives.

If you want the Express to extend both the 2.4 GHz and 5 GHz signals, then the AirPort Extreme needs to be configured so that both bands use the same wireless network name.

In other words, you must uncheck the option to assign a separate name to the 5 GHz network. Then, the Extreme will broadcast both bands using the same wireless network name.

Configure the Express to extend that network, and will extend both bands...assuming that it is located where it can receive a strong signal.

No. In your case, the Express will work only on a 5G channel.

Why not set up the Extreme to use a 2.4G channel? You'll get greater distance than with a 5G channel.

Why not set up the Extreme to use a 2.4G channel?

It already is if it is a simultaneous dual band Extreme. The Extreme is always broadcasting on both the 2.4 GHz and 5 GHz bands simultaneously.

So, it is not possible to turn one band "on" and the other "off". Both bands are always "on".....unless you turn both "off"

Thanks. I'm not familiar with the old Extreme and I accepted the OP's words at face value: "...and set it up as 5GHz network only."

It is possible that he does not have a dual band AirPort Extreme and that only one band.....either 5 GHx....or....2.4 GHz can be selected at a time. Then your suggestion to use 2.4 GHz would be a good one. But, then the "new" AirPort Express would only extend 2.4 GHz.

We need to find out what version of AirPort Extreme is being talked about here.

Using an older Airport Extreme

Please look on the bottom of the AirPort Extreme for the Model Number so we have a clear idea of what is.....and what is not possible here.

I am assuming that you have a dual band AirPort Extreme, but it is dangerous to assume.

Right now I'm doing this:

- Airport Express 2012 - WDS Main, 5GHz & 2.4GHz (living room)

- Airport Express 1st Gen - WDS Remote, 2.4GHz (living Room)

- Airport Extreme - WDS Remote 5GHz (bedroom)

So there is a simultaneous dual band "new" AirPort Express in the living room to cover that area.....and.....there is also a single band AirPort Express extending 2.4 GHz in the living room as well?

Is this really needed?

What happens as an experiment if you move the single band AirPort Express to the bedroom.....where you note that you need more 2.4 GHz coverage?

This still may not help the iPhone becasue iOS devices tend to want to hold on to their original connection. They do not "switch" among multiple access points that well....and sometimes not at all unless you power them off and then restart.

Looks like replacing the Airport Extreme in the bedroom with a simul-dual band station is the way to go

I agree.