 |
||||||
 |
 |
 |
 |
 |
 |
 |
 |
||||||
|
Mani Product Specializes in the manufacture of FM-SCA Receivers. In addition, we manufacture receivers for SAP, TVPRO, RDS/RBDS, and EAS applications. Our receiver designs cover frequencies up to 800 MHz for subcarrier, wideband and narrowband applications. To maintain a position as a major manufacture & supplier of world-class consumer electronics product Mani National has become technology leader in SCA, SCMO and Narrowband products. Mani Technology SCA & SCMO Mani Technology is new to the market. The reason is our unique approach to the reception of SCA. In the mid 1980's it became clear that the traditional methods were inadequate. When a signal is received, it contains not only the subcarrier(s), but the main channel, the stereo, the RBDS, and a lot of noise. Before the signal can be recovered it must filtered from all the other contents of the station's transmission. This requires a filter that is wide enough to include all the components of the SCA signal and narrow enough to rejects everything else. The only practical method of making filters at subcarrier frequencies is with coils, capacitors and resistors. The complexity and expense of an ideal filter would make the receiver too expensive. There are, however, inexpensive filters made of ceramics that are nearly ideal, but their frequencies are too high. The solution was to use a process call heterodyning. This process allows two frequencies to be added or subtracted to achieve a new frequency. Thus if the subcarrier is 67 kHz and the inexpensive filter is 455 kHz, a third frequency of 522 kHz will cause the 67 kHz subcarrier to become a 455 kHz signal that can easily be filtered. (522 - 67 = 455) The result is a simple and inexpensive replacement for the coils, capacitors and resistors. Because the filter is almost perfect, the signal has excellent frequency response, low distortion, and low noise. Furthermore, alignment is simple and will not drift over time, temperature and vibration. This approach makes mass production of quality SCA receivers a reality. The quality of the Mani receiver is also a result of careful design. The problems encountered by the users of SCA receivers can be traced to specific causes and then rectified. We have sought out and rectified those problems and the result is a nearly ideal receiver. On our Products Specs page, we show typical performance characteristics. In reality, these values are almost worthless. There is no standard method of measuring SCA performance, and laboratory tests do not accurately simulate real-world conditions. We can only recommend a real-world evaluation. VHF NAS station transmitters, in a technical sense, operate under similar arrangements to land stations in the Land Mobile licence type VHF NAS Frequency Assignment Criteria in Australia Frequency assignment criteria for NAS stations in the VHF bands are the same as those for standard single frequency land stations in the Land Mobile service with the exception that transmission may be continuous. While mobile receivers are not normally protected from interference, IMM services are primarily safety-orientated and will be protected, especially in areas where a NAS station site is in very close proximity to IMM equipment. Mani Receivers support segments F and W of the VHF High Band Frequency Band Plan in Australia.
|
|
