RTL-SDR Versions
The RTL-SDR receiver is a simple but very useful device. It can receive signals from 25MHz to about 1700MHz. Various versions exits. Figure 1 shows the two that I have. The first version was purchased about 7 years ago, and consists of a plastic dongle with a USB connector on one end and a very small CMX insert-able antenna connector on the other end. A small whip antenna is supplied with the unit. The newer metal version has a USB connector on one end and an SMA on the other end. It can connect to the Nano Up-Converter via an SMA M-M adapter. The Nano can be powered from the RTL (requires a Bias-Tee) or via a separate USB connection.
Antenna Connectors
The RTL-SDR requires different types of antennas depending on the type of reception wanted. The wavelength of an EM field is given by the equation:
Freq x Wavelength = c = Speed of light = 10^8m/sec
Wavelength = 300/(Freq_MHz) is another form of this equation.
In order to receive signals at a particular wavelength, the antenna you use should be somewhere between 1/4 to 1/2 a wavelength for good reception.
So for instance if we want to receive an HF signal at 7MHz or approx. 40m, then we need an antenna of at least 10m to 20m long to get a good signal. A simple 50ft hook up wire tossed in a tree can do this. For Air/Marine reception at about 150MHz, then you need about 0.5 – 1m antenna. Here polarization is important, so a vertical antenna is necessary. Various antennas and connectors/adapters are show in the YouTube Video of Figure 3.
| Freq MHZ | Wavelength m(cm) |
| 1 | 300m(3000cm)/Antenna=75-150m |
| 10 | 30m(300cm)/Antenna=7.5-15m |
| 100 | 3m(30cm)/Antenna=0.75m/1.5m |
| 1000 | 0.3m(3cm)/Antenna=0.075m/0.15m |
Please send your comments, questions and suggestions to:
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References
#1. -“RTL-SDR for VHF Air & Marine Bands”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-vhf-air-marine-bands/
#2. – “RTL-SDR for EPIRB”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-epirb/
#3. – “RTL-SDR for LF Beacon”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-lf-beacons/
#4. – “RTL-SDR for HF 0-30MHz”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-hf-0-30mhz/
#5. – “RTL-SDR for Marine HF Weather Fax”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-marine-hf-weather-fax/
#6. – “RTL-SDR for AIS”,
https://jeremyclark.ca/wp/nav/rtl-sdr-for-ais-2/
