ZAP CHECKER 270
The frequency specificity and directionality of the ZC-270 is controlled by the external antenna connected to its SMA input. The optional LOG Periodic Antenna works well in this manner. Using a ˝ meter 2.4 GHz loop-yagi antenna improves the sensitivity 6 fold at 2.4 GHz and narrows the detection width to about 5 degrees. The ZC-270 can be directly connected to such antennas or connected using a flexible cable.
Avoid measuring transmitted signals which are directly connected to the SMA input. The signal levels of such devices can be large enough to damage the sensitive receiver input of the ZC-270.
Directional antennas usually have increased sensitivity along their longer axis. Pointing the front of the antenna towards the transmitting device gives the strongest pickup – but there is also an enhanced pickup 180 degrees away from that direction to the rear of the antenna. The differences between the front and rear sensitivities are usually specified by the front to back ratio in dB. More directional antennas, (usually longer in length), tend to have higher front to back ratios. When specifying the direction of the signal source, be aware of the diminished signal enhancement directed from the rear of the antenna.
The Zap Checker 270 is an extremely sensitive instrument which detects signals that are coupled to it in any manner. In this way the ZC-270 is more like a wideband receiver with an antenna input. The proximity to a metal cabinet, desk, or automobile can affect the reading. Also, the proximity of your hand or body may increase the reading, acting as the antenna and coupling a stronger signal to the input. It is even possible to reflect signals directed toward your body and redirect them to the ZC-270. Be aware that although an external antenna is optimized to enhance reception within a particular band of frequencies, it is also capable of detecting stronger signals from out-of-band frequencies.
When initially using the ZC-270, it is often perplexing why detected signals appear so fickle. By moving closer to the window, the signal strength increases (the walls of the room tend to shield the outside signals). The walls of the room define a resonant cavity – the room itself. Radio waves bounce off the walls, ceiling and floor to give enhanced “hot” spots (where the signals converge) or “cold” spots which are devoid of signals. Different frequencies have their own hot and cold spots. When moving the ZC-270 just a few cm the detected signals may change dramatically due to these intensified and rarefied signal regions.
Polarization effects may also be apparent with the ZC-270, especially when an external antenna is used. Polarization effects are noted when rotating the antenna from a horizontal to a vertical plane. The change in signal strength gives an indication of the polarization of the transmitting source. It is even possible to note changes in signal intensity in outdoor wide-open spaces. Buildings, trees, people, mountains, etc. all reflect signals that produce variations in signal strength. It is important to consider these other factors when detecting and locating weak covert signals. Experience with use will overcome many of the hurdles.
The Zap Checker 270 speeds up and simplifies the installation of wireless devices – from security cameras to wireless computer networks. With wireless installations the ZC-270 verifies the signal strength of the transmitting device. It identifies the hot and cold spots in the region. Hot and cold spots are usually undesirable as transmitters or receiver sites. It measures the baseline level of RF at these sites and detects any interfering signals (RFI) that may occur. Besides detecting the RFI, the ZC-270 also can identify its source.
The ZC-270 with directional antenna optimizes the radio link between a wireless transmitter and receiver. It is also helpful in selecting a hub site for solid communication with its multiple secondary WLAN sites. Corporate security officers use the Zap Checker to identify potential hacker-sites outside their facilities and to help shield and position wireless transmitters to eliminate those hacker-sites.
The Zap Checker 270 is instrumental in identifying radio frequency interference sources from coronas and arcing insulators on utility poles. By using a directional antenna on the ZC-270 an offending insulator can be located from the ground. This enables utility personnel to quickly and easily identify the problem from a safe distance. (Even bolts of lightning are detected by this instrument.)