The gain between Figure 1 and Figure 2 is clearly 19 db. The gain scales directly with the number of array elements present. If the array elements are connected in series, then a voltage amplifier is required. If the array elements are connected in parallel, then a transimpedance amplifier is required.
Excessive 50/60 cycle hum or interference can saturate or latch high gain preamplifiers. When the array cannot be sufficiently removed from the interference sources, the lower end bandwidth can be limited to positive effect. Electronic filtering on the output will not mitigate a positive effect, since the front end will already be saturated or latched. Another method is to use a magnetic spatial neutralizing filter to cancel out specific magnetic wave frequencies without actually affecting the bandwidth, such as a bandpass filter would do having a finite bandwidth to negative effect. |
