Kenwood TS-480 manual Noise reduction, Demonstrates how ignition noise is reduced by the DNL

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First, the input signal is divided into its low- and high-frequency components. Ignition and other pulse noise tends to be concentrated in the latter, from which amplitude variation is output. The attenuation coefficient derived from this signal is multiplied by the input signal. As soon as pulse noise occurs, the attenuation coefficient rises instantaneously, thus damping the amplitude variation in the input signal. Because of this adaptive processing performed by the DNL and based on the amplitude variation, the output signal has virtually none of the “digital feel” that is often the mark of digital signal processing. It is perhaps only natural to associate this DNL with the old “noise limiter” technology, but as explained it works on a completely different principle, performing the sort of advanced processing that is only possible with DSP.

Because the TS-480 will be often used for mobile operations, DNL parameters have been tuned so as to have maximum effect on ignition noise. However, even when used as a fixed station, it can be very effective on irregular, unanticipated noise, so we recommend that you try making use of it, in combination with the noise blanker as well.

Fig.14 demonstrates how ignition noise is reduced by the DNL.

Fig. 14: The effect of DNL on ignition noise

The DNL works in SSB, CW, FSK and AM modes, and it can be used in conjunction with other interference reduction and noise elimination features.

Noise reduction

There are two methods available for noise reduction: NR1 and NR2. NR1 is a line enhancer that employs adaptive filter technology. By shaping a filter that lets through signals with a certain amount of periodicity, as with voice and CW, it can suppress noise that falls outside the passband. NR2 employs what is known as SPAC (speech processing by auto correlation) technology. What results from looping one cycle of the RX signal’s autocorrelation coefficient is then output as the received audio. What this means is that only periodic signals found in the received audio emerge. In principle this approach can result in a small amount of noise at the “seam” where the periodic signal is looped together, but in practice it proves extremely effective at noise compression.

NR1 is a good choice for SSB and other audio signals, while NR2 is especially effective when used with single frequencies, as with a CW signal.

Figs. 15~17 demonstrate the effect of applying NR1 and NR2. For comparison purposes, the same weak sine signal was received, with the audio output monitored by an FFT analyzer.

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Contents Page TS-480HX TS-480SAT Back to basics The appeal of HF lies in DX’ing Design ObjectivesDetermination to create a unique transceiver 200W challenge Standalone control panelFocus on basic performance Overview of the TS-480 Series Adding appeal to fixed station operationsAchieving 200W output in a compact transceiver Development Objectives for the TS-480 SeriesTS-480 concept began with development of the TS-570? Focusing on HF TX circuits 200W final section CircuitryTX IMD output 200W SPS schematic diagram SPS separate power sources TS-480HX onlyAntenna tuner TS-480SAT Failsafe device some TS-480HX versions only100W final section 200W final section FM circuit FM modulation block diagramRX 1st mixer RX circuitry Front endRX dynamic range RX sensitivity Jumpers for joy Comparison of optional CW filters 500Hz Circuitry after the roofing filterOption installation unit Full compatibility with digital modes data modes Auxiliary FeaturesFeatures useful for 50MHz operations Features useful for mobile operationsNew 5MHz band Ideal for mobile operations DNL Features of the Built-in DSPDSP circuit Demonstrates how ignition noise is reduced by the DNL Noise reductionNR OFF BC OFF Beat cancelRX DSP filters Switching Width During CW operations CW auto tune RX equalizer & TX equalizerTS-480 menus TipsDSP Useful if you want to go on to tune FSK APO Functions that can be assigned to PF keys Assigned Use Split Quick menu Making menus easier to use Menu switchingInternal structure of the main unit Structural FeaturesCooling Cooling diagramUpper side Temperature rise around final transistors Page Design concept Message recording/playback function New Option Voice Guide & Storage Unit VGS-1Constant recording function Voice Guide ResetConfiguration mode for TX output, etc Menu settings Split modeVariable Voice Guide speed Other featuresVFO mode, direct frequency entry Memory channelButton layout & basic operation Main functionsKNS added CW keying Changing memory and registered detailsReading and writing files Compatibility with KNS Kenwood Network Command SystemAccidental continuous TX Setting up KNS on the Arcp sidePage Using a broadband router New Option ARHP-10 Amateur Radio Host Program Freeware Checking LAN settingsUser setup Adjust PC volumePage Network & Operations Problem Solution TroubleshootingCannot get KNS to work Sound Problem Solution Connect a microphone to the computer and bring up TS-480 In-Depth Manual