Radwave is a recently released Android App for RTL-SDR dongles. It provides a real time waterfall of the RF spectrum, and it's defining feature is that you can easily zoom, pause and rewind the spectrum at any time. The software is currently in beta, and doesn't demodulate any signals, but the work and ideas behind the spectrum display features is really interesting.
Radwave utilizes RTL-SDR dongles and the RTL2832U driver app to allow people to interactively explore the RF spectrum. You can dynamically zoom in and out in time and frequency, pause, and go back in time - all without losing any samples. If you find something cool, tag it and share with friends.
Radwave core technology is its interactive real-time spectrogram. It shows all the spectrum - utilizing every sample1 - for the entire collection2. Frequencies are aligned over time as you change the RF center frequency3, helping you make sense of what you see.
Over on YouTube, channel Null Byte has uploaded a video showing us how to use an RTL-SDR V3 on an Android smartphone. In the video he discusses the hardware and software required to get started on Android and demonstrates the free SDRoid Android app (based on RFAnalyzer) by tuning to several signals including a voice signal. Later in the video he also shows an ADS-B app for receiving aircraft positions. The video is intended for people new to RTL-SDR so it is a little basic, but it's a great introduction.
He notes that the next video (which will probably be released in a week) will show RPiTX being used with the RTL-SDR.
Use an RTL-SDR Software-Defined Radio Receiver with an Android Smartphone [Tutorial]
"RTL_TCP SDR" is a little different to "SDR Receiver" because it contains a full spectrum analyzer and waterfall display, whereas "SDR Receiver" only allows you to listen via presets or manual tuning. Both apps can not access the RTL-SDR directly on the iOS device due to Apple limitations. An external server on a Raspberry Pi or PC running rtl_tcp is required. Programmer HotPaw writes about his App:
An RTL-SDR Software Defined Radio receiver for iOS devices (requires an external rtl_tcp server). Listen to VHF AM and FM radio signals. View a waterfall of the RF spectrum. Connect, via the rtl_tcp network protocol, to a networked RTL-SDR USB peripheral.
iOS devices do not currently support the direct connection of USB devices such as an RTL-SDR. Thus, the use of this app requires network access to a server, such as a Raspberry Pi (or Mac), with an RTL-SDR unit plugged into its USB port, and running the rtl_tcp protocol at an TCP/IP network address accessible from your iOS device. The Raspberry Pi acts, essentially, as a USB port adapter for your iOS device.
No support is provided for installing any of the software needed to use this app with a Raspberry Pi. Please do not download this app unless you are already familiar with Software Defined Radio, have an RTL-SDR USB device, and have already installed and tested rtl_tcp on your Raspberry Pi, Mac, or other server.
Since Apple's iOS doesn't allow an RTL-SDR to be plugged directly into a Lightning port (even with a USB adapter), an rtl_tcp adapter, such as a Raspberry Pi (or Pi Zero) server is required.
This app is an experiment in real-time DSP and SDR coding using Apple's Swift and Metal GPU-shader programming languages. It includes a spectrum waterfall, and supports demodulating FM, AM, and SSB. Also, includes beta test support for the AirSpy HF+.
SDR Receiver, a new iOS app for RTL-SDR and Airspy HF+, is now available on the App Store. The app works with an RTL-SDR or Airspy HF+ that is attached to a host Mac, PC or Raspberry Pi running the rtl_tcp server or equivalent. The iOS device, which may be an iPhone or an iPad, communicates over the network with the host computer which may be anywhere on the network that is reachable by TCP/IP and that can sustain the required bandwidth.
SDR Receiver demodulates AM, narrowband FM and wideband FM signals. Key features include:
Easily entered and managed lists of stations to simplify station selection.
Adjustable squelch that works for both AM and FM signals.
Adjustable LNA gain for RTL-SDR.
Adjustable audio high pass and low pass filters.
Signal strength indicator that shows power level in the signal passband.
Multiple sampling rates down to 240Ksps for RTL-SDR.
Sampling rate of 768Ksps for Airspy HF+.
Streaming from an RTL-SDR requires installation of the librtlsdr package including the rtl_tcp utility on the host computer. Streaming from an Airspy HF+ requires installation of server software on the host computer that supports the Airspy HF+ and that streams data according to the protocol used by the rtl_tcp utility. One such server has been made available by Ron Nicholson in source code form on GitHub.
Requires an RTL-SDR or Airspy HF+, a host computer and server software which are not provided with the application.
Another RTL-SDR client for iOS is "RTL_TCP SDR" by Ron Nicholson which we posted about back in March when it was still in beta testing. RTL_TCP SDR includes a spectrum analyzer and FFT display. SDR Receiver appears to have no spectrum display, so is mostly useful for listening to preset frequencies, whilst RTL_TCP SDR appears to be more useful for spectrum exploring.
Last year we posted about QuestaSDR, which is a simple SDR multi-mode GUI that is compatible with the RTL-SDR. Since then QuestaSDR has evolved, and is now available on Android devices as well. It looks to be a nice alternative to RF Analyzer and SDR Touch which are the most popular RTL-SDR Android apps. The description of Android QuestaSDR reads:
QuestaSDR - powerful and flexible, cross-platform Software Defined Radio Application (SDR). Built-in scheduler architecture provides integrate plugins, plugins kits and multi - UI. Typical applications are DXing, Ham Radio, Radio Astronomy and Spectrum analysis.
Support Hardware: - RTLSDR Dongle
Main features: - Dark, Ligth, Universal, Material application style - Many spectrum settings (FFT size, waterfall FPS and color theme) - AM/SSB/NFM/WFM demodulator - RDS decoder - Record AF file - Frequency bookmarks - Web remote - Supported IF-adapter, upconverter, downconverter hardware - Rig samplerate, frequency, level and iq disbalance calibrate
To start using QuestaSDR, you will need: - RTL-SDR dongle - USB OTG Cable - used to connect a RTLSDR to your Android device.
Connect the USB dongle to the USB-OTG, then insert the free end of the cable into the USB port of your Android device and launch the QuestaSDR! Now you can listen to live frequency range shortwave, VHF, UHF.
Feedback and bug reports are always welcome.
Please note that I am not responsible for any legal issues caused by the use of this application. Be responsible and familiarize yourself with local laws before using.
Over on our forums poster hotpaw2 has released news about his new RTL-SDR app for iOS (iPhones/iPads). If we're not mistaken, this will be the first app that enables RTL-SDR usage on iOS. However, as iOS devices don't allow RTL-SDRs (or any arbitrary USB device) to connect directly to devices, you still need to use a Raspberry Pi or other network connected computing device as an rtl_tcp server. So the RTL-SDR does not plug directly into the iOS device. Currently he is looking for beta testers to help test a pre-release of the software. Hotpaw2 writes:
Hi. A first version of my iOS SDR app is nearing completion. So I'm interested finding a few users who would like to beta test a pre-release of the app, and provide some feedback. The beta test requirements are having a 64-bit iOS device (iPhone or iPad) running iOS 11.2.x or newer, having Apple's TestFlight app installed, having a Mac, PC, Raspberry Pi (or other Linux box) that already has rtl_tcp installed and ready to run. (And an RTL-SDR obviously.) The rtl_tcp server must be on a fast WiFi network reachable by your iOS device. Note that iOS TestFlight app distributions do have an expiration date.
iOS does not recognize arbitrary USB devices such as an RTL-SDR. This is even true when using Apple's Lightning Camera Connection kit to provide an iPhone with a wired USB port. So an adapter must be used. I use a headless Raspberry Pi 3 running rtl_tcp as the USB adapter to provide raw IQ samples from the RTL-SDR to the iOS app. A Raspberry Pi Zero W would also work. I then connect to the server either over WiFi, or via wired ethernet.
This iOS SDR app is fairly simple. I've been experimenting with developing low-level DSP code in Swift. So this SDR app was written from scratch in the Swift programming language. Because the app is targeted for the iOS App store, it uses none of the existing SDR C++ code base.
The app currently demodulates AM, N-FM, and mono W-FM. It also displays a spectrum and rudimentary waterfall, and allows one to swipe-to-tune. There are not a lot of controls, as screen real-estate on an iPhone is quite limited. But I can walk around the house and, from my iPhone, monitor if my RTL-SDR or AirSpy HF+ are picking up any interesting signals.
QRadioLink is a Linux and Android compatible radio app that can run on smartphones. It can be used to receive and transmit digital radio signals with a compatible SDR such as an RTL-SDR (RX only), or a LimeSDR Mini (TX and RX). The following video by Adrian M shows QRadioLink running on an Android phone with a LimeSDR Mini connected to it. An external battery pack is also connected to maintain power levels over a longer time.
In the video Adrian shows how this combination can be used as a fully portable radio transceiver. The video first shows him receiving broadcast FM, digital amateur radio voice (Codec2 & Opus is supported), narrowband FM and SSB signals. Later in the video he transmits a digital voice signal using the microphone on his Android phone. He notes that an external amplifier would still be needed if you wanted more transmission power.
Portable SDR transceiver: LimeSDR-mini, mobile phone and QRadioLink
As part of their senior project Matthew May & Brendan Harlow of Champlain College worked on a project that involved creating their own software defined radio based portable cell phone network. If you're interested their setup is nicely documented on their project page. Basically it consists of a bladeRF software defined radio and Raspberry Pi running the YateBTS base station software. This is nothing new in terms of work done before, but the clear documentation makes it a good starting point for anyone looking at building their own SDR based cell basestation.
A custom cell basestation may be useful for those in remote areas without commercial cell phone reception, during disasters or even just to create a type of secondary network in your home.