The TS-870 features high-performance circuitry for DSP-based digital processing from the IF stage onwards. The intermediate frequency of the quadruple superheterodyne system are as follows: 1st IF 73.05 Mhz, 2nd IF 8.83 Mhz, 3rd IF 455 Khz and 4th IF 11.3 Khz.
This modification permit to transform the IF output for the SM-230 station monitor (HF 8.83 Mhz) in IF output (BF 11.3 Khz).
It is now possible to connect directly this output to the sound card input of your computer and demodulation numeric radio on short wave. This output is suitable for others applications.
For use with DRM software tune your receiver on selected frequency and select FM mode. This is due to select width band switch.
Warning, proceed at your own risk.
If you not are sure - don't touch !
Details of modifications
- Disconnect power supply, antenna cable and any other cables and wires connected to the TS-870.
- Turn the TS-870 upside down.
- Remove bottom cover.
- Disconnect all wires on RF unit (X44-3210-00), dismount plate and unsold coax cable W2 (see Fig. 1)
- Remount plate and reconnect all wires.
- At the end of coax cable W2 sold a resistor (1 K). Isolate GND with the tubing.
- On the TX-RX unit (X57-4620-00) sold resistor to C144 (see Fig. 2)
Fig. 1: W2 coax cable.
Fig. 2: 1 K resistor with tubing
Fig. 3: General view of modifications.
Fig. 4: Schematic diagram showing the 1 K resistor.