Tagged: iOS

January 13, 2026

Echo – A Native iOS Client for KiwiSDR & OpenWebRX

Thank you to Mark Garrison Jr. for writing in and sharing with us a new iOS app he's developing called "Echo". Echo is an app designed to provide a streamlined mobile companion for the KiwiSDR and OpenWebRX ecosystems. Note that the app is currently not yet released, but Mark is planning a TestFlight beta in February. Follow his Twitter/X @SDRecho for updates, and sign up to the beta tester waiting list if you are interested.

OpenWebRX is a piece of server software that allows you to access and share SDRs over a network connection, such as the internet, via a web browser interface. OpenWebRX is a core component of the KiwiSDR, an SDR designed to operate as a shared receiver over a network connection. Around the world, many people have set up public KiwiSDR, RTL-SDR, and other SDR systems that can be accessed via OpenWebRX. Echo is designed to make searching for and viewing public OpenWebRX receivers easy on iOS devices.

Mark writes:

[Echo] is a native iOS app built entirely in SwiftUI, designed to provide a streamlined mobile companion to the KiwiSDR and OpenWebRX ecosystems.

The goal is to offer a modern interface optimized for iPhone, making it easier to explore the spectrum on the go.

Key Features:

• Global Connectivity: Access any public KiwiSDR or OpenWebRX server via a live global map with 500+ active stations.

• Smart Scans: Station scanner with presets for Shortwave, Ham, and Military bands.

• Audio Intelligence: Integrated recording with speech-to-text transcription for logging signals.

• Native Performance: 100% SwiftUI for smooth waterfall rendering and low battery impact.

The app is currently in active development. I am sharing progress updates and will be announcing the upcoming TestFlight beta over on Twitter at @SDRecho. I’m planning to launch a beta in February.

Echo for iOS: The Native SDR Experience

Watch this video on YouTube

May 5, 2021

MagicSDR: A new Android and iOS RTL_TCP Client

Unlike Android devices, Apple iOS devices can't run RTL-SDRs directly through their USB ports. However, they can still connect to another networked device such as a PC or Raspberry Pi running an rtl_tcp server. In the past we've seen two rtl_tcp clients for iOS released [1 , 2].

Now a third client called "MagicSDR" has just been released, and this one is cross platform for Android and iOS. The app is free on the Android store (with in-app purchases), and costs US$14.99 on the Apple App Store. The developer writes:

MagicSDR makes it possible to interactively explore RF spectrum using panadapter and waterfall visualization, demodulate and play AM, SSB, CW, NFM, WFM signals, collect frequencies. Built on the principle of plug-in architecture, MagicSDR - powerful and flexible next-generation SDR (software-defined radio) application. Typical applications are dx-ing, ham radio, radio astronomy, and spectrum analysis. Explore the spectrum everywhere!

MagicSDR processes signals that are streamed over the local network from the rtl_tcp server, which is running on the host computer. The smartphone itself, on which MagicSDR is running, can act as a host computer.

To start playing with MagicSDR, you need to set up a server on a host computer to which SDR peripherals (rtl-sdr dongle) will be connected or connect SDR peripherals directly to a smartphone via a USB OTG cable. To try application without SDR peripherals, MagicSDR can emulate a virtual radio device.

May 2, 2018

RTL_TCP SDR: iOS Software Defined Radio App with Spectrum Display

In the post a few days ago about the newly released "SDR Receiver" app for iOS, we briefly mentioned that another iOS app called "RTL_TCP SDR" has just been released out of beta and put onto the Apple store as well.

"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.

Over on his Reddit discussion thread he also mentions:

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+.

HotPaw's "RTL_TCP SDR" running on an iPad.

April 30, 2018

New RTL-SDR Receiver App for iOS Released

A new RTL-SDR compatible app for Apple iOS (iPhone, iPad) has recently been released on the Apple App store. The app is called "SDR Receiver", costs US$9.99, and is used together with an RTL-SDR (or Airspy HF+) server running on a separate networked device such as a Raspberry Pi or PC. Limitations by Apple mean that the RTL-SDR can not run directly on iOS devices. The software description reads:

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.

March 9, 2018

New Apple iOS (iPhone/iPad) RTL-SDR rtl_tcp Client App in Beta Testing

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.

Contact info for beta testing can be found here: http://www.hotpaw.com/rhn/hotpaw/

Source code to librtlsdr and rtl_tcp can be found in many repositories on github, but zero support for finding or installing such, and/or setting up your Raspberry Pi, will be provided by me.