RTL-SDR for HF Beacons

Introduction

Fig.1 Solar Cycle 25 (Ref.1)
Fig.2 NCDXF/IARU HF Beacon Network Locations (Ref.4)
ContinentCall SignLocationLocator
North AmericaVE8ATInuvik, NWT, CanadaCP38gh
4U1UNUN, New York, USAFN3Øas
W6WXMt. Umunhum, CA, USACM97bd
KH6RSMaui, Hawaii, USABL10ts
South AmericaYV5BCaracas, VenezuelaFJ69cc
OA4BLima, PeruFH17mw
LU4AABuenos Aires, ArgentinaGFØ5tj
EuropeOH2BLohja, FinlandKP20eh
CS3BSão Jorge, MadeiraIM12mt
Africa5Z4BKariobangi, KenyaKI88ks
ZS6DNPretoria, South AfricaKG33xi
Middle East4X6TUTel Aviv, IsraelKM72jb
AsiaRR9ONovosibirsk, RussiaNO14kx
JA2IGYMt. Asama, JapanPM84jk
VR2BHong Kong, HKOL72bg
4S7BColombo, Sri LankaMJ96wv
AustralasiaVK6RBPRolystone, AustraliaOF87av
ZL6BMasterton, New ZealandRE78tw
Fig.3 NCDXF/IARU Beacon Location Data (Ref.4)

This past year I spent most of my time in the VHF/UHF/uW bands. Last night for a change, I did a quick tune across the HF frequencies. I was really surprised, I was picking up strong short wave broadcast stations on 17MHz at 19:00hrs local time. Looks like solar cycle 25 has really started to kick in! Figure 1 shows the cycle and the greater than predicted activity in 2022 (Ref.1). In previous posts I examined how the RTL-SDR with an up converter can be used to receive the LF/MF/HF bands (Ref.2/3).

The NCDXF/IARU International Beacon project consists of HF beacons located all across the world. They transmit at predefined times which allows an HF user to determine propagation conditions between his QTH and the remote transmitters. The station locations are shown in Figure 2 and station details in Figure 3 (Ref.4).

HF Beacon Reception Planning

Fig.4 HF Equipment Layout
Fig5. NCDXF/IARU WebPage Active Transmission & Beaconmap PA1ARE
Fig.6 Beacon Sched 0-30min
Fig.7 Beacon Sched 30-60min

Figure 4 shows the HF equipment setup. A balcony mounted HF buddipole is connected to the 125MHz upconverter using RG-58. The upconverter feeds the RTL-SDR version 2. Reception is by SDR# with a shift of -125MHz to compensate for the upconverter. The transmission schedule can be accessed directly from the NCDXF/IARU webpage Figure 5, or by a stand alone application like Beaconmap by PA1ARE (Ref.6). Another method is to download the transmission spreadsheet for a complete hour as in Figures 6/7.

Each station transmits for 10 seconds, with the call at 22wpm followed by four one second dashes. The call and first dash is sent at 100W, the next dash at 10W, the next at 1W and the final at 100mW. Each station transmits on each band once every 3minutes. After transmission it shifts to the next higher band.

HF Beacon Reception SDR#

Fig.8 SDR# Rx YV5B CW BW=1000Hz
Fig.9 WAV File in Audacity
Fig.10 YV5B Callsign 22wpm
Fig.11 VOACAP Point to Point Prop Study YV5B to Toronto
Fig.12 VOACAP Prop Wheel YV5B to Toronto April 12th_2022

On April 12th at approx 18:00hrs local EDT, I was able to pull in Venezuela YV5B very clearly. Figure 8 shows the SDR# screen, Figure 9 shows the saved WAV file in Audacity and Figure 10 is the playback. A quick VOACAP study between YV5B and my QTH is shown in Figures 11/12.

Fig.13 YouTube Video RTL-SDR for HF Beacons

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References

#1. – “Solar Cycle 25”
https://en.wikipedia.org/wiki/Solar_cycle_25

#2. – “RTL-SDR for LF Beacons”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-lf-beacons/

#3. – “RTL-SDR for HF 0-30MHz”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-hf-0-30mhz/

#4 – “NCDXF/IARU International Beacon Project”
https://www.ncdxf.org/beacon/

#5. – “NCDXF/IARU Beacon Schedule”
https://www.qsl.net/sm7nwj/NCDXF-IARU-BeaconMonitoring.html

#6. – “Beaconmap by PA1ARE”
https://www.qsl.net/pa1are/software.html

#7. – “VOACAP Propagation Analysis”
https://www.voacap.com/

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.