6/27/2007 - Updated Table 2 with WiSpy resolution bandwidth
|At a Glance|
|Product||MetaGeek Wi-Spy 2.4x Spectrum Analyzer|
|Summary||Second generation of (relatively) inexpensive 2.4 GHz USB spectrum analyzer with improved resolution and range|
|Pros||· Inexpensive compared to alternatives
· Improved frequency resolution
· Improved amplitude resolution and range
· Record and playback capability
· Can't control sweep rate
· Can't manually set view amplitude
· Price will put off some buyers
It's been almost a year and a half since MetaGeek's original Wi-Spy 2.4 GHz spectrum analyzer hit the street. I thought it was one of the coolest and most useful products I'd seen in a long time, especially for the $99 price. And I urged anyone who had been needing or thinking about 2.4 GHz spectrum analysis to buy one.
Since that review, MetaGeek doubled the price to $199, which caused much tooth-gnashing and garment-rending among its fan base. But the increase corrected a price that was probably way too low to begin with to support a viable business and further development.
Well, it looks like the Geeks put the extra money to good use to develop the Wi-Spy 2.4x, with better performance and the ability to use higher-gain antennas. But they also have once again done the price-doubling trick and set the 2.4x' price at $399. So let's see if it's worth it, shall we?
What it is
The 2.4x maintains its USB flash-key size, but now sports an RP-SMA antenna connector onto which you screw the small, swiveling 2 dBi dipole that comes with the module. The original Wi-Spy was a JUNO-USB dongle, manufactured by Unigen, that used a Cypress Semi radio and USB microcontroller.
Figure 1: Wi-Spy 2.4x board
The 2.4x' board shown in Figure 1 is a home-grown design using a Chipcon CC2500 2.4 GHz tranceiver and Silicon Labs C8051F326 (PDF link) USB microcontroller with 16K of flash built in. The design is so integrated that there are components on only one side of the board and nary a switch or even an LED in sight.
A summary of the key differences between the original and 2.4x are shown in Table 1 below, which I copied from the MetaGeek website.
|Bandwidth||2.4 - 2.482 GHz||2.4 - 2.4835 GHz|
|Frequency Resolution||1 MHz||328 KHz|
|Amplitude Range||-97 dBm to -50.5 dBm||-110 dBm to -6.5 dBm|
|Amplitude Resolution||1.5 dBm||0.5 dBm|
|Sweep Time||~120 msec||~165 msec|
|Supported Operating Systems||Windows, Mac OS X, Linux||Windows, Linux, Mac OS X BETA|
Table 1: Wi-Spy vs Wi-Spy 2.4x
While there are significant improvements in frequency resolution (3X), amplitude range (> 2X) and amplitude resolution (3X), I found the most noticeable and useful improvement to be the frequency resolution. The next most useful is the extension of the lower end of the amplitude range, which helps to sniff out low-level signals. There is significant range extension on the high-signal side, too. But since through-the-air signals rarely top -40 dBm or so, the high-side extra range isn't very useful.
2.4 GHz (802.11b/g)
|2.4 GHz (802.11b/g)||2.4 GHz (802.11b/g)|
|Minimum Signal Level||-110 dBm||-97 dBm||-110 dBm|
|Frequency Resolution||10 kHz||1 MHz||328 kHz|
|Minimum Resolution Bandwidth||156 kHz||320 kHz||337.5 kHz|
|Views & Charts||Views
- Real Time FFT
- FFT Duty Cycle
- Power vs. Freq
- Power vs. Time
- Active Devices
- Devices vs. Channel
- Devices vs. Time
- Duty Cycle vs. Channel
- Duty Cycle vs. Time
- Planar (spectrum)
- Planar (spectrum)
|Plot Traces||- Max
- Max Hold
- Max Hold
- Max Hold
|Multiple Simultaneous Views||Yes||Yes||Yes|
|Record / Playback||Yes||Yes||Yes|
|Device List ||Yes||No||No|
|Auto Interferer ID ||Yes||No||No|
|Device Finder ||Yes||No||No|
|Saved Data File Format||Proprietary||Proprietary, but documented||Proprietary, but documented|
Table 2: Cognio vs. Wi-Spy vs. Wi-Spy 2.4x Specs and Features
 Device List is essentially that same analysis capability put to use, but for identifying and displaying valid Wi-Fi devices.
 Auto Interferer ID represents the ability to analyze the signals being captured, match them against signatures of interferences sources such as cordless phones, microwave ovens and other RF sources, and display an indication of devices found.
 Device Finder allows you to choose an identified valid device or interferer and physically track it down by displaying a signal strength vs. time chart and real-time signal strength meter to be monitored as you wander around in search of your quarry.