Update on Update on P25 Scanner


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 are somewhat long, but modestly descriptive so you should be able to figure out which to download. Once you have the file, unzip it and copy to an 8GB SD card. Put […]

Read More Here! 26

RTL-SDR.com Dongle Measurements (Part 1 — background)

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 the gain setting on receiver performance, and the results are below. First, some introduction. The dongles use an 8 bit analog-to-digital converter (“ADC”). The number of bits sets the dynamic range, […]

Read More Here! 1

Update on P25 scanner — new version, and new installation instructions


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. The new version will run nicely on a Raspberry Pi 3, and probably on an RPi 2 as well. Following are instructions to install it from scratch on the PI. […]

Read More Here! 2

More Solar Eclipse Analysis (HF Propagation)

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 pretty good site for monitoring the high frequency bands. The data was recorded over the eight hours from 1400 – 2200 UTC (10AM to 6PM EDT) on Monday, August 21, […]

Read More Here! 0

First data from Solar Eclipse 2017

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 just under 1 TB (!) of data. Fortunately, disk drives are cheap these days. I’ve done the very first step of analysis on one of the data sets — a […]

Read More Here! 1

Hermes SDR as spectrum analyzer

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 the radio. This is in preparation for the upcoming solar eclipse, where as part of the HamSci 2017 Total Solar Eclipse HF Wideband Recording Experiment I’m planning to use the […]

Read More Here! 1

$20 P25 Trunking Scanner (Part 4)


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. Because you probably only want to listen to a subset of the talkgroups, you can optionally create a file called site_name_wl.tsv with a list, one talkgroup per line, of the […]

Read More Here! 3

$20 P25 Trunking Scanner (Part 3)


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 this path. If you’ve successfully installed Linux, Gnuradio, and op25 on your computer, you are ready to test the system, and then configure it for trunking. The scanner application is […]

Read More Here! 7

$20 P25 Trunking Scanner (Part 2)


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 from the SBRAC radio astronomy group called build-gnuradio. Click on the link, then save the contents of the browser screen (easiest way is to select everything on the web page, […]

Read More Here! 5

$20 P25 Trunking Scanner (Part 1)


A couple of weeks ago at the Dayton Hamvention I bought a fancy Whistler TRX2 scanner that can receive the new P25 digital trunking system that’s been rolled-out statewide here in Ohio. Unfortunately, after a lot of attempts, I still can’t get it to reliably receive the talkgroups I’m most interested in. Out of frustration (and boredom) I decided to research the couple of projects I’d heard about to implement P25 decoding, and after a few hours work (and some […]

Read More Here! 1