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Kenwood DSP-100 Modifications:
The Kenwood DSP-100 is what makes the 850 such a flexible transceiver and is key in producing Extended-Band SSB (ESSB) Hi-fi quality audio. You could simply use the DSP-100 as is and still get excellent results. The usual way the signal is routed is as follows:
Mic > 850 Mic input / 850 ACC1 output > DSP-100 Controller Input / DSP-100 DSP3 output > 850 DSP3 Input
However, the Kenwood 850 internal mic amp has a severe low frequency response roll-off below about 150 Hz. Additionally, there are some minor inherent noise and distortion properties associated with the 850 preamp section.
If you are a purist and want to circumvent these problems, it was determined that bypassing the 850 mic preamp by feeding the audio chain's Line-Level signal directly to the DSP-100 input would be advantageous in the following three ways;
1) Eliminate the low frequency roll-off inherent in the 850's internal mic amp, lowering the frequency response down to 20Hz
2) Eliminate any distortion properties inherent in the internal 850 mic preamp
3) Eliminate several signal cut/gain stages through noisy and lossy components
This page describes in detail how to perform the mods mentioned above.
(Click here to see an after mod KA0KA on-air spectral analysis)
DSP-100 Modifications Instructions:
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