Ambient, Baseline Signal Levels
Transmitted signal strength drops off rapidly (in an exponential manner) from the signal source. Powerful transmitted signals, however, can still broadcast to far distances. There is a concentration of powerful signal sources in and around urban areas. Larger cities and towns have baseline (ambient) signals that register as constantly high signal levels on the AAG0.

Signal Detection in High and Low Ambient Signal Zones
In order to detect weaker signals in high ambient signal zones, a change in intensity of the signal on the analog meter or lighting of the LEDs is needed. Alternately, one can move the instrument closer to the signal source to get higher signal strength, and hence more easily detected signals. The VCO is ideal for detecting subtle changes in signal intensity. The VCO can be used to detect a weaker signal in a strong ambient signal zone. A small change in the pitch of the VCO is often easier to appreciate than a change in the visual displays.

If one has control over turning on and off the signal source, even a weak signal can often be detected in the midst of a large ambient signal zone. By turning on and off the transmitting signal source, (such as a security monitoring transmitter) the change in the detected signal is more readily appreciated. In this manner, adjustments can be made to the positions of the signal source and the receiving site to insure the strongest RF signal-link.

In weak ambient signal zones it is easier to detect very weak signals from low powered transmitters such as hidden transmitting cameras or wireless computer devices. In these zones, the SENSITIVITY level on the AAG0 can be set higher without being overwhelmed by the ambient signal level. The weak ambient signal level will not be high enough to mask or conceal the low-powered transmitted signal.

LOG, LINEAR, MID Detection Modes
The level of signals detected by the model AAG0 is directly related to the type of RF detection being used. In the LINEAR mode, the weakest signals are detected. This is the mode to use when trying to detect weak-powered transmitters or RF signals from a far distance.

In the LOG (logarithmic) mode, the detection is such that both weak signals and strong signals are observed on the meter scale without overloading at the higher meter readings. In the LOG mode, the weaker signals are seen at the low end of the meter scale and signals 1,000 times stronger are observed on the higher end of the scale. This allows the LOG mode to be used to pinpoint the location of the signal source at close distances to the transmitter without overwhelming the AAG0’s measurement capabilities.

The signal strength from the transmitter drops off in an exponential manner from a high level near the transmitter to a low level at a distance. The LOG mode uses a logarithmic amplifier and detector which detects the weak signals with very high amplification, and detects the strong signals using very low amplification. The exponential RF signal drop-off is cancelled by the logarithmic amplifier-detector of the AAG0 such that the meter reading in the LOG mode increases in direct proportion to the distance to the transmitter. That means the meter reading goes up in a controlled manner as the transmitting source is approached without overloading the measurement. Hidden, covert devices or weak-powered transmitters are thereby easily located.

If the signal reading in the LOG mode increases as the user walks with the AAG0 in a particular direction, that direction is getting closer to the transmitting source. A maximum increase in the meter reading occurs when moving in a direction directly pointing to the transmitting source. The maximum signal reading occurs (without meter over-loading) when the AAG0 is directly over the transmitting source, pinpointing its location. This is an effective way to localize and pinpoint covert devices and can also be used to locate interfering devices causing RFI (Radio Frequency Interference).

The middle detection mode (MID), is a combination of both LINEAR and LOG modes together. It is often used when a moderate signal level is being detected and localized. If a weak signal detected in LINEAR mode become too high on the meter scale as the transmitting source is approached, switching to the MID mode will reset the meter reading to a lower, more measurable position. Similarly, signals which become too strong for measurement in the MID mode are reset by switching to the LOG mode.

AUDIO SIGNAL OUTPUTS, AM and VCO
The AM detection mode is used to detect Amplitude Modulation of RF signals. This is especially helpful for signals used below 54 MHz by amateur radio and citizen band operators. The audio content of the AM signal can thus be appreciated.
The AM detection mode is also very important in the detection of higher frequency signals. The higher frequency signals have their own characterizing sounds to them which are heard in the AM detection mode. These characterizing sounds help to identify the type of the transmitting device. Signal characterization also aids in identifying and sorting through different RF signal sources that are present at the same time.

The VCO (Voltage Controlled Oscillator) provides an audio output signal whose pitch (frequency) varies with the detected signal level. We can get a good idea of what the signal strength is by listening to the VCO. The VCO is especially useful for detecting small changes in signal strength since it is easier to recognize a small change in pitch than a small change in the meter display.

ANALOG AND DIGITAL SIGNALS
Analog signals are “on” all the time, conveying information by modulating the frequency or amplitude of the signals. Digital signals are pulsed on and off rapidly to convey their information content. A higher reading in the Digital mode compared to the Analog mode is an indication that the signal is a digital signal. The simultaneous bright illumination of both the red and the green LEDs also gives an indication of a digital signal. The LEDs are lighting alternately at a fast rate due to the “on-off” pulsing of the digital signal. By comparing the difference in signal measurement between the Analog and Digital modes, we get an idea of how often the digital signal is pulsed “on.” If the digital signal is pulsed on about 1/3 of the time, then the Digital reading will register about 3 times greater than the analog reading.

SILENT VIBRATOR
When switched ON, the silent vibrator is useful for the unobserved detection of transmitting surveillance sources. Thus a AAG0 may be carried in a pants pocket or purse and be used to detect a covert transmitting source. The vibrator intensity varies with the signal strength and vibrates stronger as the signal source is approached. This is how a body-worn transmitter or the site of a covert signal source is identified without any indication that such an identification is being made.

Companies regularly supply their officers and sales staff with ZC products to detect covert cameras and bugs on trips to foreign destinations. The silent vibrator is also useful when holding the unit is inconvenient, such as lines people identifying RFI sources on top of utility poles.