A self-calibration circuit and associated method for testing an RF device includes the RF device to be tested having transmit and receive sections, and a built-in self test circuit coupled to the transmit and receive sections of the RF device on the same chip. The first transceiver selects a signature sequence from a set of signature sequences, incorporates the signature sequence into a signal, and transmits the signal to the second transceiver. A plate is secured onto the recess, with the plate having a slit. Each of the plurality of securing members has a plurality of snap fit openings. The methods generally involve ionizing DHT in a sample and detecting and quantifying the amount of the ion to determine the amount of DHT in the sample. The method and system also include the capability to process the service request based on the availability of wireless bandwidth.