Abstract: Wireless communication systems (100, 800) comprise mobile units (118, 802) provided with a directional coupler (206) and circuit (220) for measuring the complex reflectance (phase and magnitude) of antenna (202) of the mobile units (118, 802). The system (100, 800) has, either in the mobile unit (118, 802) or elsewhere, a processor (238, 808) programmed to perform pattern recognition of the near field environments of the mobile units (118, 802) by using the complex reflectance measurements as feature vectors. Information as to the near field environment at the time of wireless connection drops is suitably accumulated and is used in network upgrade planning and/or mobile unit design evaluation. The complex reflectance is alternatively used to discriminate antenna faults. Alternatively, near field environments that tend to degrade wireless communication performance are detected by the mobile unit using the complex reflectance and the mobile unit then alerts the user.

Abstract: A tank to header attachment construction for heat exchangers include T-shaped tabs on the header which extend through slots in a flange on a tank. The top bar of each tab has it ends bent out of alignment with the slot to secure the tank to the header.

Abstract: A tank to header attachment construction for heat exchangers include T-shaped tabs on the header which extend through slots in a flange on a tank. The top bar of each tab has it ends bent out of alignment with the slot to secure the tank to the header.

Abstract: Difficulties in obtaining consistent bonds of high quality between side pieces and tubular headers (10), (12) in heat exchangers are avoided in a side piece (42) that extends between the headers (10), (12) and which has circular recesses (48) at each end (44), (46). The recesses (48) define resilient fingers (56), (58) which may separate to receive the ends of the headers (10), (12) and frictionally grasp the same, eliminating the need for fixturing at this location and assuring a strong consistent gripping of the headers (10), (12), by the end piece (42) to assure consistent bonds of high quality.

Abstract: Difficulties in obtaining consistent bonds of high quality between side pieces and tubular headers (10), (12) in heat exchangers are avoided in a side piece (42) that extends between the headers (10), (12) and which has circular recesses (48) at each end (44), (46). The recesses (48) define resilient fingers (56), (58) which may separate to receive the ends of the headers (10), (12) and frictionally grasp the same, eliminating the need for fixturing at this location and assuring a strong consistent gripping of the headers (10), (12), by the end piece (42) to assure consistent bonds of high quality.

Abstract: A first coil (110) resonant at a first frequency, and a second coil (120) resonant at a second frequency, coupled to a conductive straight portion (140) of an antenna element (130) to form a multi-band antenna structure. The first and second coils (110) and (120) are preferably of different axial lengths and circumferences, wound in opposite directions and coaxially disposed about the antenna element (130). Additional coils can be added to accommodate additional bands and an upper coils (150) can be used to realize a multi-position structure.

Abstract: Multiple helical coils (110, 120, 130) are placed side-by-side and coupled to a conductive straight portion (140) of an antenna to provide a multi-band antenna structure. The helical coils (110, 120, 130) are distanced from one another to sufficiently eliminate coupling interference therebetween. A portable radio capable of communication in many different frequency bands utilizing a single, compact antenna structure is thus realized.

Abstract: A method (100), a device (300), and a radio (500) are described for compensating for modulator frequency drift while allowing for data transmission in a half-duplex frequency modulated communication system. An adjustment is made to a premodulation signal in such a way that when it is passed through a frequency modulator to provide a transmitter excitation signal, frequency drift is corrected. Subsequent to determining a training command, the transmitter excitation signal passes through a switch to a demodulator. The demodulator output is averaged and used in the adjustment.