Kenwood TS-870S User Manual - Page 58

8 REJECTING INTERFERENCE CHANGING RECEIVE BANDWIDTH (CW/FSK/FM) The width of the receive pass band can be changed without altering the current receive frequency. Change the bandwidth by adjusting the LO/WIDTH control. When the control is adjusted, "WIDTH" and the newly selected bandwidth appear on the Display. AGC AUTO CW NB WIDTH CW Bandwidth (Hz) 50 100 200 400 600 1000 FSK Bandwidth (Hz) 250 500 1000 1500 Default values FM Bandwidth (kHz) 5 6 8 10 12 14 ADAPTIVE FILTERS The Auto Notch, Beat Cancel, and Noise Reduction functions accomplish their design purposes by modifying the characteristics of adaptive filters. Adaptive filters adapt or change their characteristics according to the nature of the signal being received at a given moment. Menu No. 18 (TRACK) determines whether the adaptive filters are allowed to change in this manner or not. It is also possible to specify how long the received signals will be monitored before determining filter characteristics. This monitor period is inversely proportional to the response time. The longer the monitor time, the slower the response time and vice versa. Use Menu No. 14 (LINE.ENH) to select a different Line Enhance response time, Menu No. 16 (SP.BEAT) for the Beat Cancel response time, and Menu No. 17 (SP.NOTCH) for the Auto Notch response time. The adaptive filters may not function correctly with signals that have a poor signal-to-noise (S/N) ratio. Under poor conditions, you may find that optimum results are obtained by switching OFF the adaptive filters via Menu No. 18 (TRACK). Note: Only Auto Notch, or Beat Cancel, or Noise Reduction can be used at one time. They cannot be activated at the same time. Also, Menu No. 18 changes to its default setting when the TS-870S power is switched OFF and then ON again. AUTO NOTCH (SSB) Auto Notch automatically locates and attenuates interfering tones within the receive pass band. This function operates digitally at the IF level, hence it can affect your S-meter reading, and may affect (slightly attenuate) your desired signal. If interfering tones are weak, you may find that Beat Cancel eliminates them more effectively. Also, Auto Notch may not notch out signals inside the pass band if signals just outside the pass band limits are stronger. After switching ON the function, selecting a mode other than SSB will switch OFF the Auto Notch function (LED goes out). Changing back to SSB re-activates the function automatically (LED lights). If strong, steady interference is present, switching Menu No. 18 (TRACK) to OFF may improve the notching capability. To block CW interference, switch TRACK to ON, then switch TRACK to OFF to lock the adaptive filter. Interfering tone Receive pass band Notch band Press [AUTO NOTCH] to toggle the Auto Notch function ON or OFF. • The LED indicator in the button lights when the function is ON. Note: The effect of Auto Notch may differ under different receiving conditions even when using the same response time. BEAT CANCEL (SSB/AM) Beat Cancel also attenuates unwanted tones within the pass band, but it is more capable than Auto Notch at removing low-level tones. Also, this function works at the AF level, therefore you will notice there is no S-meter signal loss, although the S/N ratio may be lowered in the AM mode. After switching ON the function, selecting a mode other than SSB or AM will switch OFF the Beat Cancel function (LED goes out). Changing back to SSB or AM re-activates the function automatically (LED lights). Interfering tones Receive pass band Receive pass band Press [BEAT CANCEL] to toggle the Beat Cancel function ON or OFF. • The LED indicator in the button lights when the function is ON. Note: The effect of Beat Cancel may differ under different receiving conditions even when using the same response time. 52