HF OLIVIA 64-2000 Channel on GNURadio

Introduction

In the previous post I received an OLIVIA 64-2000 transmission as part of a ShortWave Radiogram broadcast (Ref.1). I know from my work with MFSK how robust this mode is, so I thought it would be interesting to see how the OLIVIA 64-2000 compares to MFSK64 using the same channel model I used to evaluate MSK144 (Ref.2).

OLIVIA 64-2000 Channel Test Setup

Fig. 1 Channel Test Setup
Fig.2 GNURC Channel Test Model

Figure 1 shows the channel test setup. FLDIGI is set to OLIVIA 64-2000 mode and transmits an old fashioned data test pattern that I am familiar with. This is saved in Audacity as a .wav file. Vb cable is used to connect the two. This .wav file then feeds GNURadio as in Figure 2 which adds Gaussian noise. A QT GUI Entry block allows you to adjust the noise level (std.dev = rms value) during run time. The GNURadio output now feeds into FLDIGI in receive mode again using Vb cable. Noise is adjusted till character errors occur which is the threshold.

OLIVIA 64-2000 Channel Test Results

FIg.3 GNURC Noise Amplitude = 0
Fig.4 FLDIGI No Errors for Noise Amplitude = 0
FIg.5 GNURC Noise Amplitude = 1.8
Fig.6 FLDIGI Errors for Noise Amplitude = 1.8

Figures 3/4 show the test results for no added noise, with FLDIGI showing no errors. Figures 5/6 show results for threshold noise = 1.8 with FLDIGI just starting to take errors. We can calculate the threshold SNR:

Vsig_peak=1.0
Vsig_rms=Vsig_peak/1.414=0.707
Vnoise_dev= Vnoise_rms=1.8
SNRrms=20log10(Vsig_rms/Vnoise_dev) = -8.1dB

MFSK64 Channel Test Results

FIg.7 GNURC Noise Amplitude = 0
Fig.8 FLDIGI No Errors for Noise Amplitude = 0.0
FIg.9 GNURC Noise Amplitude = 1.3
Fig.10 FLDIGI Errors for Noise Amplitude =1.3

Figures 7/8 show the test results for no added noise, with FLDIGI showing no errors. Figures 9/10 show results for threshold noise = 1.3 with FLDIGI just starting to take errors. We can calculate the threshold SNR:

Vsig_peak=1.0
Vsig_rms=Vsig_peak/1.414=0.707
Vnoise_dev= Vnoise_rms=1.3
SNRrms=20log10(Vsig_rms/Vnoise_dev) = -5.3dB

Fig.11 YouTube Video HF OLIVIA 64-2000 Channel on GNURadio

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References

#1. – “HF SDR-IQ for OLIVIA 64-2000
https://jeremyclark.ca/wp/telecom/hf-sdr-iq-for-olivia-64-2000/

#2. – “Meteor Scatter MSK144 Channel on GNURadio”
https://jeremyclark.ca/wp/telecom/meteor-scatter-msk144-channel-on-gnuradio/

#3. – “The Draft Specification For The Olivia HF Transmission System”
https://www.arrl.org/olivia

#4. – “Olivia MFSK”
https://en.wikipedia.org/wiki/Olivia_MFSK

By Jeremy Clark

Jeremy Clark is a Senior Telecommunications Engineer and Advanced Amateur Radio Operator VE3PKC. He is the author of E-Books on Telecommunications, Navigation & Electronics.