Kenwood TS-870S User Manual - Page 57

REJECTING INTERFERENCE DSP TOOLS SLOPE TUNING (SSB/AM) Changing the positions of the LO/WIDTH and HI/SHIFT controls while in SSB or AM mode changes the cut-off frequencies for the receive pass band. Controlling the pass band in this way allows you to eliminate adjacent frequency interference. Turn the LO/WIDTH control clockwise to raise the high-pass filter cut-off frequency; turn it counterclockwise to lower the cut-off frequency. This is effective in removing interference from frequencies lower than your current operating frequency. LO/WIDTH USB pass band LO/WIDTH f USB pass band f Turn the HI/SHIFT control clockwise to raise the low-pass filter cut-off frequency; turn it counterclockwise to lower the cut-off frequency. This is effective in removing interference from frequencies higher than your current operating frequency. HI/SHIFT USB pass band f HI/SHIFT USB pass band f Using only these controls, you can eliminate a great deal of interference on the phone bands. By using both controls together carefully, you will increase your ability to pick out weak signals from the interference. Adjust Mode Frequency Selections Default Freq. LO/WIDTH Control SSB 0, 50, 100, 200, 300, 400, 500, 600, 800, 1000 Hz (high-pass filter cutoff) AM 0, 100, 200, 500 Hz 300 Hz 100 Hz HI/SHIFT Control SSB 1.4, 2.6, 1.6, 2.8, 1.8, 3.0, 2.0, 3.4, 2.2, 4.6, 2.4, 6.0 kHz 2.6 kHz (low-pass filter cutoff) AM 2.5, 3.0, 4.0, 5.0, 6.0, 7.0 kHz 6.0 kHz IF SHIFT (CW) For CW, the center frequency of the filter pass band can be shifted without changing the current receive frequency. This is an additional method of fighting adjacent frequency interference. Change the CW center frequency by adjusting the HI/SHIFT control. When the control is adjusted, "SHIFT" and the newly selected center frequency appears on the Display. AGC AUTO CW CTRL SHIFT Be aware that shifting the CW center frequency does not automatically adjust the receive CW pitch. Therefore, it is possible to shift the CW pass band such that the selected CW pitch frequency falls outside the pass band. Doing this makes the CW signal inaudible. Example: Before adjusting IF Shift: • CW pitch: 900 Hz • IF Shift: 800 Hz (center frequency) • CW Width: 600 Hz In this example, the pass band would lie from 500 ~ 1100 Hz (from 300 Hz below the center frequency of 800 Hz to 300 Hz above the center frequency). If the CW pitch was set for 900 Hz, the signal would be audible. After adjusting IF Shift: • CW pitch: 900 Hz • IF Shift: 500 Hz (center frequency) • CW Width: 600 Hz 900 Hz pitch 900 Hz pitch 500 800 1100 200 500 800 Now, the pass band would lie from 200 ~ 800 Hz. With the CW pitch set for 900 Hz, the signal would not be audible since the pitch frequency is 100 Hz above the upper edge of the pass band. In this case, to make the signal audible, lower the CW pitch frequency by at least 100 Hz. Mode Freq./ Filter Relationship Frequency Selections (Hz) Default Freq.(Hz) CW Center 400, 450, 500, 550, 800 frequency 600, 650, 700, 750, 800, 850, 900, 950, 1000 51