RTL-SDR for HF WWV Propagation – Telecommunications, Navigation & Electronics

Introduction

Recently I was in Costa Rica (Ref.1) and I used WWV to set my watch for UTC time to accurately read my sextant. We tend to take time for granted now with the Internet & GPS, but time stations like WWV still provide an essential service. WWV (Ref.2) can also be used to study propagation. In previous posts I used the Canadian time Station CHU (Ref.3).

WWV Station Parameters

Frequency	Power
2.5MHz	2.5KW
5.0MHz	10KW
10.0MHz	10KW
15.0MHz	10KW
20.0MHz	2.5KW
25.0MHz (Experimental)	2.5KW
Transmission: AM_DSB , 50% Tones, 100% Secs, 75% Voice
Antenna: 1/2 Wave Vertical Omnidirectional
Latitude = 40.68degN Longitude = 105.04degW

Fig.1 WWV Station Parameters

Figure 1 lists the WWV station parameters and frequencies used. Transmit power is 10KW on all bands, except 2.5/20/25MHz where the power is 2.5KW. Antennas are 1/2 wave verticals, with the 25MHz antenna as a 1/2 wave vertical dipole (Ref.2). Figure 2 shows the path between WWV and my home QTH on Google Earth.

RTL-SDR Reception

Fig.4 RTL-SDR WWV Special Signals HR:08min

Figure 3 shows WWV reception at 2.5/5.0/10.0/15.0/20.0MHz. The carrier shown at 2.5MHz is not WWV but probably a harmonic/intermod of the RTL. There is no signal visible at 5.0/10.0MHz. A small carrier signal was seen at 15.0MHz and a clear signal at 20.0MHz. Figure 4 shows reception at 20MHz with the special propagation signal sent at 8min past each hour.

VOACAP

VOACAP is a powerful HF propagation program originally developed for the Voice of America (Ref.4). It can be used as stand alone or with an interactive web interface. Figure 5 shows the web interface for propagation analysis between WWV and my home QTH. Figure 6 is the resultant propagation wheel and Figure 7 is the Propagation chart.

Band Meters/MHz	Prop Reliability %
10m/30MHz	0
12m/25MHz	10
15m/20MHz	60%
17m/17.6MHz	80%
20m/15MHz	70%
30m/10MHz	60%
40m/7.5MHz	30%
60m/5.0MHz	0%
80m/3.75MHz	0%

Fig.8 Propagation Wheel Results 15:00UTC

Figure 8 shows the propagation reliability figures taken from the Prop Wheel in Figure 6. The RTL-SDR receive levels indicate a good signal at 20MHz, very weak signal at 15MHz and no signal anywhere eles. This corresponds to the propagation wheel results.