Introduction
Recently I was approached for advice on frequency scanning. My first thought was a traditional approach of starting at the base frequency, stepping by the channel spacing and doing a power evaluation. If greater than a threshold, then hold and attempt a decode. Before building a prototype in GNU Radio, I thought I would look at current SDR scanners to see how they operated. In this post I will look at SDR#/FMS Frequency Manager Suite.
VHF Marine Band
| Channel # | Ship Tx Freq MHz | Shore Tx Freq MHz |
| 0..step 50KHz | 156.000 | 160.600 |
| 1 | 156.050 | 160.650 |
| 16 | 156.800 (distress) | 156.800 (distress) |
| 28 | 157.400 | 162.000 |
| 60..step 50KHz | 156.025 | 160.625 |
| 87 | 157.375 | 161.975 |
| 88 | 157.425 | 162.025 |
| Wx Channels | 161.650/161.775/162.400 162.425/162.475/162.500 162.525/162.550/163.275 |
Figure 1 shows a table of Marine VHF radio band frequencies that cover from about 156 – 162 MHz (varies between countries) and are assigned to Channels 0 – 88 (Ref.1).
SDR#/FMS Scanner
In previous posts, I have covered using SDR# which is an extremely versatile SDR receiver software that works well with the RTL-SDR (Ref.2). The latest version at the time of writing is 1901 and can be downloaded from Ref.3. In order to perform the scanning function, there is a versatile Plugin “Frequency Manager Suite” that can be added to SDR# (Ref.4). Download the zip file, unzip and read the installation instructions. Then unzip the next file and place the folder in the SDR# directory folder “Plugins”. Previously, to add Plugins it was necessary to add a “magic line” to an xml config file. This is no longer necessary.
Figure 2 shows SDR#_1900 with the FMS PlugIn installed. The Frequency Scanner menu is very straightforward. You can configure a group of channel frequencies via buttons F1-F10 (say Marine frequencies that you want to continuously monitor) or scan a range of frequencies in this case 157 – 162.4MHz. There is a detailed instruction manual contained in the second unzipped file and you can configure all the scanner parameters in the “Tools” menu. Figure 3 YouTube Video “” shows the operation.
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References
#1. – “Marine VHF Radio”,
https://en.wikipedia.org/wiki/Marine_VHF_radio
#2. – “RTL-SDR for VHF Air & Marine Bands”,
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-vhf-air-marine-bands/
#3. -“SDR# Download”,
https://airspy.com/download/
#4. – “Frequency Manager Suite for SDR#”,
https://www.freqmgrsuite.com/
