Every Monday night, join us on the MichiganOne DMR Tech Net as we try to make Digital Mobile Radio (DMR) fun to use and easier to understand!
Monday night, May 5th, the MichiganOne DMR Tech Net team will discuss SDR (Software Defined Radio). We’d love to hear you share your thoughts and comments.
We’re on Brandmeister Talk Group 31266 (Michigan Nets channel) for the combined MichiganOne DMR Tech Net every Monday, starting with check-ins and comments at 7:30 PM ET followed by the DMR Tech Net portion after that.
DMR Tech Net upcoming topics:
- May 5 Using Software-Based Radios to connect to DMR with John VK1JT
- May 12 Robert Bretzman K4WZV and Steve Smith KWØZ answer your questions about the TGIF Network & TGIF Products Store
- May 16-18 Dayton Hamvention
- May 19 Dayton Hamvention 2025 recap
- Tuesday, May 20 DMR Tech Net TV on Zoom with Steve Smith KWØZ about the TGIF Network
- May 26 How to learn more about DMR
- June 2 What is HamShack Hotline & Hams Over IP?
- June 9 Stan WB8QJZ explains AllStarLink (https://www.allstarlink.org/)
- June 16 Handheld & mobile Antennas for DMR radios
- Tuesday, June 17 DMR Tech Net TV on Zoom with Benoit Sylvestre VE2VB from BrandMeister
- June 23 Using a Bluetooth headset with DMR
- June 30 DMR mobile radios hints and tips
- Jul 7 DMR apps to use on your cellular phone
- Jul 14 Maidenhead Grid Square location system
- Tuesday Jul 15 DMR Tech Net TV on Zoom going over the Open GD-77 firmware
- Jul 21 Using your radio’s side/hot keys
- Jul 28 Simplex vs Duplex Hotspots
- Aug 4 TOT, the Time-Out Timer feature
- Aug 11 Brad KE8WNV goes over the Open GD-77 firmware for your radio
- Aug 18 Tom N8TJ will discuss Q-codes
- Tuesday Aug 19 DMR Tech Net TV on Zoom about Maidenhead Grid Squares
- Aug 25 Using your Digital ID to make a Private Call or create a talkgroup
If you have a topic suggestion for a future DMR Tech Net, please let us know! Send an email to [email protected]
To read the whole newsletter, open the attached .pdf or visit our website: https://MichiganOnedmrtech.net/
Table of Contents
✅ Benefits of Using SDR with DMR: 3
Software Defined Radio (SDR) in the context of Digital Mobile Radio (DMR) refers to radio communication systems where components traditionally implemented in hardware—such as modulators, demodulators, filters, and signal processors—are instead implemented in software, typically running on a computer or embedded system.
Here’s how SDR relates to DMR specifically:
🔧 How SDR Applies to DMR:
- DMR Signal Processing in Software:
- DMR is a digital voice and data protocol that uses TDMA (Time-Division Multiple Access) to split a 12.5 kHz channel into two timeslots.
- An SDR can transmit or receive DMR signals by processing these digital signals using software (e.g., decoding voice and control data), instead of requiring a dedicated DMR chip or radio.
- Flexibility in Modulation and Protocols:
- With SDR, you can switch between analog, DMR, P25, NXDN, etc., using different software without changing hardware.
- This is especially useful for hobbyists, developers, and network gateways.
- Popular SDR Applications for DMR:
- Receiving DMR: Tools like DSD+, SDR# (SDRSharp), and GQRX allow users to decode DMR transmissions from SDR receivers like the RTL-SDR dongle.
- Transmitting DMR: Advanced SDRs like HackRF, LimeSDR, or USRP can be used with software like GNU Radio to transmit DMR signals, though this requires proper licensing and more technical setup.
- Monitoring and Analysis:
- SDRs are often used to monitor DMR networks, analyze repeater activity, decode talkgroups, and scan frequencies more dynamically than with traditional radios.
✅ Benefits of Using SDR with DMR:
- Cost-effective for receiving and experimenting with DMR.
- Customizable for specific scanning, decoding, or logging purposes.
- Useful for learning how DMR works at the protocol level.
To set up an SDR system for receiving and decoding DMR signals, you’ll need a few things:
- SDR Hardware
Choose one of the following:
- RTL-SDR dongle (cheap and popular; ~$30)
- Airspy, HackRF, or SDRplay (better performance, higher cost)
- Antenna
- A wideband VHF/UHF antenna suitable for the 400–470 MHz UHF range (where most DMR repeaters operate)
- Software
You’ll need:
- SDR# (SDRSharp) or GQRX (for signal tuning and demodulation)
- DSD+ (Digital Speech Decoder) or DSD-FME (for decoding the digital DMR voice/data)
- Optionally: Fast Lane version of DSD+ for advanced features like voice follow and trunking support
- Virtual Audio Cable
- To route audio from SDR# to DSD+ (e.g., VB-Cable or Virtual Audio Cable)
✅ 1. Install SDR# and Drivers
- Download from https://airspy.com/download
- Run the Zadig utility (included) to install the right driver for your RTL-SDR dongle
✅ 2. Launch SDR# and Tune to a DMR Frequency
- Use www.radioreference.com or a local repeater list to find DMR frequencies
- DMR signals sound like rapid digital buzzes—find one and note the frequency
✅ 3. Install and Configure Virtual Audio Cable
- Route audio output from SDR# to a virtual cable
- Set DSD+ to use that virtual cable as its input
✅ 4. Run DSD+
- Open a terminal or shortcut to run DSDPlus.exe
- It should automatically begin decoding when a DMR signal is present
- You’ll see decoded info like talkgroup IDs, slot number, voice/text messages, etc.
- Use DSD+ Fast Lane to monitor trunked DMR systems and multiple frequencies
- Add a scanner list or group follow mode to track specific talkgroups
- Run Unitrunker alongside for trunked system analysis
Using a Software Defined Radio (SDR) comes with a range of benefits and some trade-offs depending on your goals, budget, and technical comfort level.
✅ Pros of SDR:
- Flexibility
- Tune to any frequency within the device’s range.
- Support for multiple modulation types (FM, AM, SSB, DMR, P25, etc.) via software.
- Cost-Effective
- RTL-SDR dongles start under $30—very affordable for beginners or hobbyists.
- Upgradable
- New features and protocols can be added with software updates—no need to replace hardware.
- Educational Value
- Excellent tool for learning radio theory, digital modes, and spectrum analysis.
- Useful for ham radio operators, students, and developers.
- Multi-Purpose
- Works as a scanner, spectrum analyzer, weather satellite receiver, ADS-B tracker, and more—all in one device.
- Wide Community Support
- Lots of open-source tools and tutorials available (GNU Radio, SDR#, DSD+, etc.).
❌ Cons of SDR:
- Limited Transmit Capability (for most low-cost SDRs)
- Most entry-level SDRs (like RTL-SDR) are receive-only.
- SDRs that can transmit (HackRF, USRP) are much more expensive and complex.
- Learning Curve
- Requires setup, drivers, and routing audio between programs.
- May be overwhelming for users not familiar with radio or digital audio processing.
- Latency
- Some SDR setups introduce slight delays, which can be an issue for real-time applications.
- Sensitivity and Selectivity
- Cheaper SDRs may be more prone to interference and have lower dynamic range compared to dedicated radios.
- Computer Resource Usage
- SDR decoding and real-time processing can be CPU-intensive.
| Feature | SDR Advantage | SDR Limitation |
| Flexibility | Multi-mode, multi-band | May require software swapping/setup |
| Cost | Affordable entry point | Transmit-capable units cost more |
| Ease of Use | Powerful if configured | Not plug-and-play for most setups |
| Performance | Excellent for RX learning | May lack analog radio fidelity |
| Upgradability | Software-based mods | Depends on active community support |
To learn more about Software Defined Radio (SDR) effectively, especially for use with DMR and other digital modes, here are solid resources and pathways broken down by level:
📘 Beginner-Friendly Resources
- RTL-SDR Blog & Guide
- Website: https://www.rtl-sdr.com
- ✅ Massive collection of tutorials
- ✅ Focuses on RTL-SDR dongles
- Topics: DMR, trunking, ADS-B, weather satellites, SDR# setup
- SDR# (SDRSharp) Quick Start Guide
- Included in the Airspy SDR download package
- Learn how to install drivers, tune frequencies, and visualize the spectrum
- YouTube Channels
- Tech Minds, SignalsEverywhere, TheSmokinApe
- Excellent walk-throughs on SDR setup, digital modes (DMR, P25), and SDR projects
- Reddit Communities
- r/RTLSDR – very active with help and examples
- r/amateurradio – broader scope including SDR use
📚 Intermediate to Advanced Learning
- GNU Radio
- Site: https://www.gnuradio.org
- Open-source toolkit for building your own SDR applications from scratch
- Great for developers and experimenters
- SDRangel
- Software platform for advanced SDR use, including digital decoding, transmit, plugins
- Good for HackRF, LimeSDR users
- Books
- “Software Defined Radio using MATLAB & Simulink and the RTL-SDR” by Robert W. Stewart
- “The Hobbyist’s Guide to the RTL-SDR” (free eBook from RTL-SDR.com)
🧪 Hands-On Projects (Best for Learning by Doing)
- Monitor local DMR repeaters with DSD+ and SDR#
- Track aircraft with ADS-B using RTL-SDR and dump1090
- Decode NOAA weather satellite images
- Use SDR to identify unknown signals in your area
A Ten Band SDR Transceiver for Homebrewers
February 26, 2025 by Jenny List
Making a multi-band amateur radio transceiver has always been a somewhat challenging project, and making one that also supported different modes would for many years have been of almost impossible complexity best reserved for expensive commercial projects. [Bob W7PUA] has tackled both in the form of a portable 10-band multi-mode unit, and we can honestly say he’s done a very good job indeed.
As you might expect in 2025 it’s a software defined radio (SDR), but to show how powerful the silicon available today is, it’s all implemented on a microcontroller. There’s a Teensy 4 with an audio codec board that does all the signal processing heavy lifting, and an RF board that takes care of the I/Q mixing and the analogue stuff.
Band switching is handled using a technique from the past; interchangeable plug-in coil and filter units, that do an effective job. The result is a modestly-powered but extremely portable rig that doesn’t look to have broken the bank, and since the write-up goes into detail on the software side we hope it might inform other SDR projects too. We might have gone for old-school embossed Dymo labels on that brushed aluminum case just for retro appeal, but we can’t fault it.
It’s not the first time we’ve looked at a small multi-band SDR here, but we think this one ups the game somewhat.
Thanks [Pete] for the tip!
https://hackaday.com/2025/02/26/a-ten-band-sdr-transceiver-for-homebrewers/
If you can’t join us live for the DMR Tech Net, you can always listen to us via BrandMeister’s mobile Hoseline app or their Hose desktop software: (https://hose.brandmeister.network/).
We do record the show, so if you miss out and want to listen, or re-listen, to it, you can. The audio link is on our website, located at the very bottom of this post (after the show ends). We also have the AI interpretation/transcription of the audio, so you can read along.
You can always chat with the MichiganOne Tech Net team on TGIF talk group 31268, the MichiganOne DMR Tech Net channel or Brandmeister talk group 31266, the Michigan Nets channel.
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To see previous newsletters, check out our website: https://michiganonedmrtech.net/
On May 5th, the MichiganOne DMR Net will be moving to BrandMeister Talk Group 31266, the Michigan Nets Channel and combined with the DMR Tech Net. The bottom line is that the DMR Tech Net and MichiganOne DMR Net are flip-flopping times.
The new combined net will be renamed as the MichiganOne DMR Tech Net. We will start the combined net with the check-in portion for your comments at 7:30pm. After all check-ins, re-checks, and comments are completed, we’ll switch to the DMR Tech Net segment (we estimate 8pm ET).
- May 5 Steve KC8WXM kicks off the new MichiganOne DMR Tech Net beginning at 7:30pm on BrandMeister talkgroup 31266 (Michigan Nets channel)
- May 12 Allan N4ALK
- May 19 Brad KE8WNV
- May 26 Rick AD8KN
- We’re looking for more net control operators to help us with the check-in portion of the combined net. If you are interested and would like to volunteer, notify any member of the DMR Tech Net team and/or send an email to [email protected]. Stay tuned as more changes are coming.
https://www.michiganonedmr.net/
