I’ve noticed that my SDR setup, an Apache Labs Anan-7000DLE transceiver used with the PowerSDR software, seems to rest the S-Meter at a quite high level when there is no signal present. This is unnerving when I try to compare my local noise floor with others who claim noise levels
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SDR
Since my updated post on building a P25 trunking scanner with a Raspberry Pi and an RTL-SDR dongle, I’ve created a copy-and-play image file that gets you up and running in minutes.
I’ve put it (along with a couple of other RPi image files) at http://febo.com/pages/os_images/. The filenames
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I’m using several USB “dongle” SDR sticks from RTL-SDR.com. These nifty $20 devices can receive from 100 kHz to above 1700 MHz. They have a low noise amplifier in the front end that is adjustable from 0 to about 50 dB gain. I wanted to determine the impact of
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Since I posted my original articles on configuring the Gnuradio-based op25 P25 trunking scanner, there’s been a lot of progress in the code. In particular, there is a new fork that changes the program to a command-line version, which saves a lot of CPU resources and also offers added features.
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I’ve continued processing the data generated from software-defined-radio recordings I made during the 2017 solar eclipse at my fairly isolated and low-RF-noise location on Beaver Island, Michigan (45 38 38 N, 85 29 24 W, grid square EN75gp). The nearest AM station is about 28 miles away, so it’s a
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I set up a smaller version of my mad-scientist stuff at our cottage on Beaver Island, Michigan (45 38 38 N, 85 29 24 W, grid square EN75gp), to record the RF spectrum before, during, and after the eclipse on August 21, 2017. The recordings were successful, and I captured
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I was fussing about signal generator output accuracy because I wanted to calibrate my
HPSDR Hermes software defined radio (“SDR”) so that I could calculate the absolute power input in dBm, assuming a 50 ohm load impedance) based on the dBFS (db full scale of the ADC chip) output from
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With op25 successfully decoding the control channel, now you just need to set up the trunking configuration. To do this, you’ll probably need to set up three files:
1. trunk.tsv defines the sites to be monitored.
2. site_name.tsv provides a table of talkgroup numbers and names for that site.
3.
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The info in this and in part 4 was aided tremendously by several folks on the “op25-dev” mailing list. Without their help, I would not have even known where to start in getting my system running. I hope that what I’m documenting here will be helpful for others going down
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Here’s how to install the OP25 scanning software. If you don’t already have Gnuradio installed on a Linux system, do those two things first.
Any current Linux distribution works. I use Linux Mint which is very similar to Ubuntu.
The easiest way to install Gnuradio is to use a script
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