Wi-Spy Spectrum Analyzer

I've been playing with a Wi-Spy Spectrum Analyzer for a few hours.

$99 plus shipping. I installed it on my Panasonic M34 laptop running W2K and did some really crude testing. Some initial comments:

1. It's fairly fast which is a BIG plus. It's much faster and better than my Proxim 7400 card. I set my access point to beacon once every second instead of the usual 10 times per second. It was easily detected but took a few sweeps for wi-spy to coincidentally end up on the same exact frequency as the access point. One can't see the sinx/x DSSS spectra, but it's close enough.

1. It can easily pickup my Panasonic KX-TG2257 2.4GHz cordless phone and microwave oven from anywhere in the house (2 floors). Sensitivity, even with the tiny antenna, is quite impressive.

2. Dynamic range sucks but that's understandable. The noise floor is about -60dBm while the SA saturates at about -32dBm. That's 28dB of dynamic range which is really bad compared to my ancient HP140T spectrum analyzer with about 60dB of dynamic range. However, I would not expect much more from such a unit. What this means is that there will need to be some form of attenuator to deal with close in sniffing, and possibly an adjustable gain amplifier for long range work.

I can just barely see my neighbors client radio at about 200ft with a

2dBi antenna and a tangle of wet trees in between. I'm sure that with an external antenna on the wi-spy, it would be detectable.

I had my neighbor across the street (about 50ft) fire up their Uniden something 2.4GHz cordless phone. I could see it, but just barely. Again, more antenna gain would be helpful.

1. The software appears to be stable and quite useful. Whomever wrote it apparently has used commercial spectrum analyzers. I had some problems restarting the application after hibernation, but a reboot solved that. I can run my Netgear WG511v2 PCMCIA card at the same time. It makes for an interesting display, especially when the card is scanning for access points.

1. I won't post any AVI recording files until I get a reproducible setup and possibly butcher the unit with a better antenna. The ones on the web site should be sufficient for now. |
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1. The display is either by channel number or by frequency. It will display all 14 UK channels, but when set to frequency, it reverts to the 11 US channels (2400 to 2483.5).

1. I couldn't resist taking it apart and analyzing the hardware. It's actually a DSSS wireless mouse receiver. The radio module is made by Unigen: |
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   had to apply for permission to download their secret data sheet. Maybe later.

Photos at: |

square thing in the picture is a push button, usually used to synchronize a wireless mouse with a USB adapter. The RF chips is a Cypress Semi CYWUSB6934-48LFXC: | The antenna is the wiggly affair on the right of: | appears that I can easily attach a small coax pigtail for an external antenna. Of course, the usual coffee can or dish reflector can also be used. Some notes on the antenna design: | Bottom line is that it works and seems to work well enough. It will need some modifications to attach an external antenna in order to make it suitable for interference detection and location. It may take a while for me to use it in the field (it's raining). However, the fact that it can easily detect my leaky microwave oven and 2.4Ghz cordless phone means that it is sure to be useful.

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Posted 5 years ago by Jeff Liebermann in Wireless Networking

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