My home router acts as an access point with an Intel Dual-Band Wireless-AC 7260 wireless card. This card supports 802.11ac (on the 5 GHz band) and 802.11n (on both the 5 GHz and 2.4 GHz band). While this seems a very decent card to use in managed mode, this is not really a great choice for an access point.

$ lspci -k -nn -d 8086:08b1
03:00.0 Network controller [0280]: Intel Corporation Wireless 7260 [8086:08b1] (rev 73)
        Subsystem: Intel Corporation Dual Band Wireless-AC 7260 [8086:4070]
        Kernel driver in use: iwlwifi

TL;DR: Use an Atheros card instead.

Limitations§

First, the card is said “dual-band” but you can only uses one band at a time because there is only one radio. Almost all wireless cards have this limitation. If you want to use both the 2.4 GHz band and the less crowded 5 GHz band, two cards are usually needed.

5 GHz band§

There is no support to set an access point on the 5 GHz band. The firmware doesn’t allow it. This can be checked with iw:

$ iw reg get
country CH: DFS-ETSI
        (2402 - 2482 @ 40), (N/A, 20), (N/A)
        (5170 - 5250 @ 80), (N/A, 20), (N/A)
        (5250 - 5330 @ 80), (N/A, 20), (0 ms), DFS
        (5490 - 5710 @ 80), (N/A, 27), (0 ms), DFS
        (57240 - 65880 @ 2160), (N/A, 40), (N/A), NO-OUTDOOR
$ iw list
Wiphy phy0
[...]
        Band 2:
                Capabilities: 0x11e2
                        HT20/HT40
                        Static SM Power Save
                        RX HT20 SGI
                        RX HT40 SGI
                        TX STBC
                        RX STBC 1-stream
                        Max AMSDU length: 3839 bytes
                        DSSS/CCK HT40
                Frequencies:
                        * 5180 MHz [36] (20.0 dBm) (no IR)
                        * 5200 MHz [40] (20.0 dBm) (no IR)
                        * 5220 MHz [44] (20.0 dBm) (no IR)
                        * 5240 MHz [48] (20.0 dBm) (no IR)
                        * 5260 MHz [52] (20.0 dBm) (no IR, radar detection)
                          DFS state: usable (for 192 sec)
                          DFS CAC time: 60000 ms
                        * 5280 MHz [56] (20.0 dBm) (no IR, radar detection)
                          DFS state: usable (for 192 sec)
                          DFS CAC time: 60000 ms
[...]

While the 5 GHz band is allowed by the CRDA, all frequencies are marked with no IR. Here is the explanation for this flag:

The no-ir flag exists to allow regulatory domain definitions to disallow a device from initiating radiation of any kind and that includes using beacons, so for example AP/IBSS/Mesh/GO interfaces would not be able to initiate communication on these channels unless the channel does not have this flag.

Multiple SSID§

This card can only advertise one SSID. Managing several of them is useful to setup distinct wireless networks, like a public access (routed to Tor), a guest access and a private access. iw can confirm this:

$ iw list
        valid interface combinations:
                 * #{ managed } <= 1, #{ AP, P2P-client, P2P-GO } <= 1, #{ P2P-device } <= 1,
                   total <= 3, #channels <= 1

Here is the output of an Atheros card able to manage 8 SSID:

$ iw list
        valid interface combinations:
                 * #{ managed, WDS, P2P-client } <= 2048, #{ IBSS, AP, mesh point, P2P-GO } <= 8,
                   total <= 2048, #channels <= 1

Configuration as an access point§

Except for those two limitations, the card works fine as an access point. Here is the configuration that I use for hostapd:

interface=wlan-guest
driver=nl80211

# Radio
ssid=XXXXXXXXX
hw_mode=g
channel=11

# 802.11n
wmm_enabled=1
ieee80211n=1
ht_capab=[HT40-][SHORT-GI-20][SHORT-GI-40][DSSS_CCK-40][DSSS_CCK-40][DSSS_CCK-40]

# WPA
auth_algs=1
wpa=2
wpa_passphrase=XXXXXXXXXXXXXXX
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

Because of the use of channel 11, only 802.11n HT40- rate can be enabled. Look at the Wikipedia page for 802.11n to check if you can use either HT40-, HT40+ or both.