Homedale offers a line graph of the signal levels for each SSID, but no graph is provided for visualizing channel usage. This tool might be most useful when a simple location-aware stumbler is needed, especially if you need to save or log the results.
LizardSystems offers a free edition of their Wi-Fi Scanner application for non-commercial use and a paid edition with more functionality. In addition to Wi-Fi stumbling, it displays statistics and graphics on certain types of packets for the network you're connected to. However, this is only available during the first 30 days of the free edition.
The application has a modern looking GUI that's easy to get around and understand. Two tabs switch between the screens for the stumbler functionality and the wireless information with packet details.
On the Scanner tab, you'll find a list of detected SSIDs. Along with the typical details, it shows signal strength in negative dBm values and percentages. Although it doesn't fully support 802.11ac, it does recognize their larger channel-widths. You can also use the list on the left to filter the SSIDs shown. On the bottom, you can flip between graphs showing signal levels and channel usage of the SSIDs, plus a scanner log.
On the Wireless Information tab, which is only available for 30 days in the free edition, you can see more details on your current wireless connection. This includes graphs and statistics on many different Mac layer and PHY layer packets types.
Overall, Wi-Fi Scanner would be an okay tool for general surveying needs, keeping in mind it won't allow you to save or export the findings, reveal hidden SSIDs, nor fully recognize 802.11ac. It has a user-friendly GUI with capabilities to filter the types of access points should be shown.
The WirelessNetView utility is freeware from NirSoft, offered for personal or commercial purposes. It's a very simple Windows-based Wi-Fi stumbler, available in an installable or portable download.
For the signal strength, it shows negative dBm values and for percentages, it shows values for the last signal received and the average over time. Another unique detail it offers is how often each SSID has been detected, which could be useful in certain situations. All this data can be exported to a simple text file.
Keep in mind, this utility lacks advanced features, like graphs, hidden SSID detection, full 802.11ac support, and recognizing all channels for access points utilizing larger channel-widths. However, it still might be useful for simple Wi-Fi stumbling, especially if you need to save or export the findings.
In Mac OS X Mountain Lion 10.8.4 and later, Apple provides the Wireless Diagnostics tool. It's more than just a stumbler; it can help you detect and fix Wi-Fi issues as well. Best of all, it's a native tool included with the OS.
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