HF SDR-IQ for Olivia 64-2000 – Telecommunications, Navigation & Electronics

Introduction

During the past several years I have received broadcasts from Short Wave Radiogram using the RTL-SDR and SDR-IQ receivers. These broadcasts featured transmissions using MFSK32/64 which I decoded with FLDIGI and Multipsk (Ref.1/3). These broadcasts illustrated the amazing noise performance of MFSK. Last week Short Wave Radiogram added a segment using OLIVIA 64-2000 (Ref.4). So it was interesting to compare this to the other formats.

Equipment Layout & Transmission Schedule

Figure 1 shows the equipment setup. I received SW Radiogram Program 452 on June 6th at 2300UTC on 9455KHz. I pre-tuned the HF Loop antenna to that frequency. In order to study the transmission, I received the signal using the SDR-IQ receiver with Spectravue software. I recorded the received audio using the Spectravue record feature. Afterwards I played back the .wav file with Audacity and sent the audio via VBcable to FLDIGI & Multipsk.

Reception Results

Fig.5 FLDIGI Decode of MFSK32 Program Summary

Figures 4/5 show the RF spectrum and decode for the MFSK32 program summary. Figures 6/7 show the RF spectrum and decode for the OLIVIA 64-2000 segment and Figures 8/9 show the RF spectrum and decode for the MFSK64 portion. Notice the different transmission bandwidths:
BW_MFSK32 = 1250Hz – 1750Hz = 500Hz
BW_OLIVIA 64-2000 = 500Hz – 2500Hz = 2000Hz
BW_MFSK64 = 1000 – 2000 = 1000Hz

OLIVIA 64 – 2000 is described in Ref.4/5. It is a robust two layer modulation scheme consisting of two layers. The first layer consists of 64 MFSK tones and the second layer is for FEC using Walsh functions. In the next post we can examine how robust this mode is using a GNURC channel model.