Kenwood TS-870S User Manual - Page 85

APPENDIX A: LEARNING ABOUT DSP First-time users of a DSP transceiver may feel bewildered by the quantity of functions that they have never encountered on previous transceivers. When combined with the collection of new terminology that accompanies DSP, even an experienced operator may become frustrated. The purpose of this section is to offer a few examples that help you to begin learning about the effects and benefits of DSP. It's best to read this section after you are comfortable with using the Menu system, and after you are fully familiar with the controls and buttons on the TS-870S. This manual will not make you an expert on using the DSP functions; that knowledge will come as a result of hands-on experience with the TS-870S. Regardless what style of operating you prefer, DSP can help you. What operator doesn't want the quiet, low-noise pass band offered by DSP operating in the IF stages? Who doesn't want to effortlessly eliminate interfering tones caused by others tuning up near their operating frequency? Why wouldn't anybody want to narrow their CW bandwidth to a razor-thin slice of spectrum if they can still listen to a pleasing CW note without analog filter "ringing"? These are only a few examples where DSP shines. To begin with, the default Menu values chosen for the DSP functions on the TS-870S Menu have been carefully considered by the design engineers. They are good starting points. If you have already changed many Menu items as you've experimented with your new transceiver, do a Temporary Menu Reset {page 24} or a Full Reset {page 63} so that you know you are starting with the default Menu values. Switch over to an Amateur band with lots of activity. Tune in an SSB station with reasonable signal strength. Press [N.R.] to activate Noise Reduction. You will hear a drop in the background noise that makes listening to the signal much more pleasant. If your station is located in an electrically noisy city, this function alone may make you a DSP believer. Assuming the default Menu values are selected (due to the reset above), you are now using the Line Enhance function (Menu No. 13 is ON). This function is "tracking" (Menu No. 18 is ON) the signal as the unwanted noise is removed. Try changing Menu No. 14 to reduce and increase the response time of the Line Enhance function. What do you notice? Maybe little change can be heard with this signal or maybe you hear an important change. The longer you allow DSP to monitor the signal, the better the adaptive filters can determine how to fight the noise that is present. But there are tradeoffs. Monitoring a particular signal for too long will mean that the transceiver responds too slowly. Experiment and listen. Switch OFF Menu No. 13. You are now using the SPAC filter. Listen for a change in audio quality as you switch Menu No. 13 OFF and ON. While Menu No. 13 is OFF, change the setting for Menu No. 15 to select a different correlation time for the SPAC mode. If you can't hear a significant difference for the current receiving situation, then select a longer SPAC time for better audio quality. Although you may prefer the audio produced when, for example, the Line Enhance function is ON, remember APPENDICES ● that different signal and band conditions can produce different results. Try not to come to any conclusions about which settings are best at this early stage. Keep an open mind until you've done a lot more experimenting on various bands with different propagation conditions. Widen the receive pass band by turning the LO/WIDTH control counterclockwise and the HI/SHIFT control clockwise. Try to find a QSO in progress between two stations who are experiencing interference from a third station that may be tuning slightly off frequency but within your pass band. Press [BEAT CANCEL]. You may think the tuning station stopped transmitting. Press [BEAT CANCEL] again to switch OFF the function. The station is still tuning and you can hear it again! Beat Cancel can be so effective at automatically finding and canceling tones that are audible in the pass band that you may not be aware of the "interfering" stations at all. With Beat Cancel ON, experiment by changing the Beat Cancel response time via Menu No. 16. The response time of the function decreases as the setting number increases (selection 0 has the fastest response time). Press [AUTO NOTCH]. Since Auto Notch functions in the IF stages, it may work better or worse than Beat Cancel for a given situation. Compare the effect of Auto Notch versus Beat Cancel with the same interfering tone or tones. Change Menu No. 17 to try different response times for Auto Notch while that function is activated. Experiment and listen. If you are a CW operator, switch to the CW section of a band and search for a crowded portion. With the CW mode selected and the LO/WIDTH control turned clockwise to select a 1 kHz bandwidth, tune to a frequency where two or more stations are audible. Now turn the LO/WIDTH control counterclockwise to reduce the bandwidth. Forget old ideas associated with analog filters for how narrow you like the bandwidth when operating CW. With the minimum bandwidth, you may need to tune a little to center the desired signal in the pass band. Press [FINE] to reduce the tuning step to make tuning easier. Listen to the quality of the chosen signal. Can you believe the bandwidth displayed on the Front Panel? There are other functions to help you fight CW interference (such as IF Shift) but this example is to illustrate the benefits that DSP offers when using extremely narrow bandwidths. After reading this manual, you should be equipped with the basic knowledge to begin learning how to use DSP to your advantage. The DSP benefits that you enjoy will be related to the amount of time that you spend experimenting with DSP while operating. 79