Application Note: Using Handheld Spectrum Analyzers To Find Hidden Signals

Placing a bug near a high level signal can be a very effective way to make it very difficult to detect. There are several potential reasons for this. Most handheld spectrum analyzers exhibit fairly poor phase noise characteristics. These phase noise skirts are very effective at hiding a transmitter. Failure to have sufficiently narrow resolution bandwidth filters makes it impossible to detect signals close to a strong carrier. The ability to sweep quickly also provides major benefit since you can to a wide sweep without taking a long time. For example, you can use the Anritsu MS2722C to get a 9 GHz sweep in less than 0.5 seconds. Those limitations in many instruments make them ineffective for finding this sort of hidden transmitter.