In TSCM one of the more interesting technical issues to address is that of noise, and how it effects our TSCM activities. Everything in nature creates noise, all of which must be considered when selecting equipment, or when performing a TSCM service. The two basic types of noise are shot noise, and thermal noise.
Shot noise is caused by current flow flowing though any type of load or resistance.
Of course you can dunk all of your instruments in liquid helium for the cryogenic cooling effect, but it's awkward to drag 800-lbs tanks around. The noise floor may be further reduced by the use of preamplifiers, tracking pre-selector, and highly directional antenna. Of course low loss cables, and antenna's suitable for the bands being measured are also critical to facilitate sensitive measurements. Instrument sensitivity is directly related to the system bandwidth, which may or may not match signal bandwidth. Using the above table it's easy to see why may products used to find bugs are relatively deaf when they utilize very wide bandwidths.