Do I have to set up the 5Ghz wireless band network or is it automatic?

Question

I'm hoping someone can give me advice on how I should best proceed.....
I have an old (7 years) Belkin 802.11g F1PI241EGau 'gateway' that was provided by my ISP when I switched over to their service in February 2006, which I use to access the Internet via ADSL.  I also have a 500 GB 802.11n Time Capsule Model A1302 which is connected to the Belkin via an Ethernet cable.  Until last week my network also consisted of 2 x 802.11g AirPort Expresses that I used to extend the range of my network throughout my house. Getting any of the devices to achieve reasonable 'reach' is challenging because the house is on three levels, has double brick walls and steel-reinforced concrete floors.
Last week I bought an 802.11n AirPort Express and, simultaneously, one of my 802.11g AirPort Expresses 'died' when I tried to re-configure my network to add the 802.11n AX to it.
I have read that the range of the 802.11n devices is much greater than 802.11g.  I decided to 'forget' my remaining 802.11g AirPort Express and see if my network would work with just the TIme Capsule and the new AirPort Express (both 802.11n).  It does.  The signal to my Apple TV is now only 3 bars, not 5, but it doesn't seem to affect its functionality.
As both the Time Capsule and the new AirPort Express are 802.11n they are both capable of functioning on the 5GHz band.  Is there an advantage to this? What should I do in AirPort Express to 'turn on' the 5GHz band?
Can the 5GHz band have the same wireless network name as the 2.4GHz band?
Apart from the Apple TV, we have two iPads (version 3), one iPhone 3GS, one iPhone 5 and a MacBook (late 2008 aluminium unibody) as 'clients' on the wireless network.
Lastly, when I set up my network I set the Time Capsule to 'Create a Network' but it is in 'Bridge' mode to avoid double NAT problems with the Belkin gateway. The Airport Express is set to 'Join a Network'.
If someone can tell me whether there is a better way to setup my network I would be very grateful.
Cheers
Tricia

Answer 1

Bob said:
  "Nothing....if you have the simultaneous dual band version of the AirPort Express. It is already providing both a 2.4 GHz and 5 GHz signal"
I agree that "nothing" should be done but...
FWIW: Using Airport Utility 6.3.2 I get the following options for my Airport Express 1st Generation.  There is a similar option for Airport Utility 5.6.1 under the "Radio Mode" pull-down.  Using Wi-Fi Explorer ($3 on the App Store) I see that only a 2.4GHz signal is available even when standing directly next to it (vs both a 2.4 GHz and 5GHz signal from my Airport Extreme 802.11ac)
Point being that the Airport Express(n) does not appear to provide both 2.4 and 5 at the same time.
This Airport Express (n) is configured for a "roaming" network, meaning it is connected via ethernet back to the cable modem which also has the Airport Extreme (ac) connected via ethernet.
As an aside, and since I walked all the way over to the barn to check this out, my MacPro appears to still be using the Airport Extreme for its connection even though Wi-Fi Explorer shows a much weaker signal.  I am in the barn now.  The Airport Express is the top line in the graph which when at the house, disappears on occasion although it is always accessible via Airport Utility.  (The Airport Express(n) is the third in the list)
I am using Airport Utility 6.3 which shows that the Airport Extreme (ac) is the AP my Mac is running through.
My MacPro is the third Mac Address in this list 70:56:...
Interesting too, now that I am in the Barn, both Airport Utility applications do NOT have access to the Airport Express (n) even though Wi-Fi Explorer continues to show a strong signal from that system.  (BTW, I also have 4 bars of wireless in the menu bar)  (FWIW: I also quit and restarted Airport Utility)  Based on further information below, it appears that my MacPro is NOT switching to a 2.4GHz network.
As an experiment, I turned off my wireless on the MacBook and turned it back on again.  Airport Utility now shows me connected to the Airport Express(n) in the barn.
Here is Wi-Fi Explorer as I return to the house (approximately 125ft)  Note the colors have been reallocated and don't match the previous screenshots.  The list has also changed.
At this point, my menubar on the MacPro usually shows 2 bars but often rises to 4.  However, it is clear my MacPro is still connected to the Airport Express in the barn because response is horrid and Airport Utility still shows that AP is servicing my MacPro.  (I cannot show that screen shot since it is a popup that disappears when I move the cursor.)
To switch back to the Airport Extreme (ac), I have to shut the wireless on my Mac off and turn it back on again.
I assume that I am connected to the 5GHz subnet since Airport Utility shows my data rate is 450Mps.
Something I had noticed until now, it also shows that my PHY is 802.11a/n.
This brings up several questions, which I should post somewhere else since my only purpose here was to suggest that an Airport Express (n) does NOT broadcast in both wireless ranges at the same time.