# iSDR — A Software Defined Radio App

> Software-defined radio receiver app for iOS devices requiring external hardware. (iPhone/iPad app by Digital Confections LLC.)

- Source: https://appshunter.io/ios/app/isdr/id480077371 (this page in markdown: same URL + `.md`)
- Developer: [Digital Confections LLC](https://appshunter.io/developer/480077374)
- Category: Education, Utilities
- Price: $0.99 with in-app purchases
- Rating: 2.50/5 from 11 App Store ratings · 58 written reviews indexed
- Age rating: 4+
- Requires: iOS 9.0 · 36 MB
- Languages: American English
- Released: 2011-11-18
- Data updated: 2026-08-22
- Monetization: paid
- User reviews in markdown: https://appshunter.io/ios/app/isdr/id480077371/reviews.md

## What is iSDR?

PLEASE READ THE ENTIRE DESCRIPTION BEFORE PURCHASING. iSDR is the first and only software-defined radio application compatible with the Apple iPhone®, iPod touch® and iPad™. iSDR is for experimenters and amateur radio enthusiasts looking to construct a truly portable software-defined radio receiver. Additional hardware is required to receive live signals. Currently, iOS devices will not work with RTL-SDR USB dongles, and they are not supported by iSDR.

PLEASE NOTE: Receiving live on-air signals using iSDR requires purchasing or constructing a "quadrature sampling detector (QSD)" RF front-end device, and connecting it between an antenna and the microphone input jack. Alternatively, iSDR can be used to implement a panadapter for use with a compatible radio receiver. Without a QSD RF front-end or a connected radio, iSDR will only play I/Q recordings of actual radio signals. Additional recordings can be loaded into the app using iTunes file sharing - some recordings are available free to download from the Internet. Visit the support web site for more information.

iSDR includes a sample I/Q recording featuring 30 seconds of a ham radio contest. This is for demonstration purposes only. It is not meant to fool you! It is to allow you to experience how the app works without having to do anything yourself: just turn it on. You can download and play your own files if you like. Please see the support page for details. AND PLEASE contact us directly if you experience any issues with using this app. We will respond promptly when provided with details.

When iSDR is used to receive live radio signals, receiver performance will depend largely on the quadrature sampling detector and antenna that you use.

iSDR is a software-defined receiver application for use on mobile handset devices and iPad. Despite its extreme portability, the app utilizes the same digital signal processing techniques found in PC-based SDR receivers. It does frequency domain filtering using a theoretical "brick wall" sinc filter algorithm to provide steep and deep bandpass filtering. iSDR doesn't utilize any DSP hardware but instead uses the iOS device's processor to implement DSP algorithms.

Features

o Six receive mode settings: USB, LSB, CW, AM, FM* and Binaural.
o Selectable bandwidth settings for each mode.
o Signal strength meter covering 120 dB of dynamic range with peak and average power indication.
o Three AGC settings: fast, slow, and off.
o Three display modes: Spectrum, Waterfall and Oscilloscope.
o File sharing** supports downloaded audio-format spectrum files synced using iTunes.
o Most PCM file formats are supported, including .wav and .caf.
o Embed the center frequency in your file names and iSDR will automatically display the correct frequency!
o Tune quickly using a single touch to the display screen, or tune precisely using the rainbow tune bar.
o Change radio settings with a simple double-tap action to the red cursor, mode text, AGC indicator or signal grid!
o Up to 44.1 kHz of available spectrum bandwidth.
o Dimmable semi-log or linear spectrum grid (native Settings app only).
o Adjustable CW offset (native Settings app only).
o Monaural microphone input automatically adjusts the display to 22 kHz bandwidth.
o Automatically detects if external audio is available for receiving live signals (menu selectable).
o Reverse I/Q stereo input logic (menu selectable).

*FM mode is not supported for monaural signals, and will not appear as a mode selection unless stereo audio (live or recorded) is available. Narrowband FM only: 16 kHz or 11.2 kHz bandwidth.

Please contact Digital Confections with your questions and suggestions!

## Key features

- Six receive mode settings (USB, LSB, CW, AM, FM, Binaural)
- Selectable bandwidth settings
- 120 dB dynamic range signal strength meter
- Three AGC settings (fast, slow, off)
- Spectrum, Waterfall, and Oscilloscope display modes
- Supports downloaded audio-format spectrum files via iTunes
- Embed center frequency in file names for automatic display

## Pricing and in-app purchases

Base price: $0.99.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Wi-Fi Radio Control | Free | one-time |


## Chart rankings

- #200 in Top Paid · Education (US App Store)

## Recent user reviews (10 of 58)

All indexed reviews: https://appshunter.io/ios/app/isdr/id480077371/reviews.md

### 1/5 — Unsupported OUT OF DATE

*2025-02-10, version 5.1*

Unsupported. Last update years ago. Website out of date and does not answer emails.  It would be useful if updated.  Falsely claims to be the only add program for iPhones and iPads.  See SDR RECEIVER and peel-SDR received in the AppStore.

### 1/5 — Junk

*2022-11-18, version 5.1*

This is junk. Will not work at all. Just get a blank black screen. Would like my money back

### 5/5 — Belka DX panadapter... Excellent!

*2022-03-15, version 5.1*

Have a Belka DX spy radio and can feed the iq output through irig HD2 to the software to create a panadapter visual interface on my iPhone.   
All other SDR require dongle and server this removes this into one very small neat package but needs power as the irig chews phone battery.
The app could have a few improvements as it can be clunky but nothing on market to match it at moment

### 5/5 — Very useful!

*2021-09-20, version 5.1*

Exactly what I was looking for. I plan to use this app with KX2, QCX, and QSX in the future. Although I currently have none of these radios, the demo file gives me a very good understanding of what this app can do. Mind blown with the sdr/dsp stuff.

### 3/5 — Outdated

*2019-10-13, version 5.0*

I wish the developer would release an update with iPhone X display support. Goes to show how long it’s been since this app was updated.

It’s nice to see my Xiegu G90’s waterfall on a larger screen (the radio only has a 1.8” display), but frustrating knowing it could be larger still.

### 3/5 — Needs FT-8 mode

*2018-03-02, version 5.0*

Any chance you would consider making an FT-8 encoding / decoding iPhone app?

I think this would be very popular.

73!

Jim - KH2SR 

Needs support for Apple Watch

### 1/5 — Absolute garbage.

*2017-09-19, version 5.0*

Absolute garbage.

### 3/5 — AM geht schlecht

*2017-09-12*

Für SSB ist die App ja durchaus zu gebrauchen, allerdings sind die beiden Bandbreitenstufen etwas gering und man sollte vorallem für AM selbst die Filterbreite auswählen können. Auch scheint das AM eher so eine Art DSB zu sein da dort immernoch ein Träger mit dazugemischt wird was AM beinahe unbrauchbar macht.

### 5/5 — Nettes und faszinierendes Spielzeug

*2016-07-07*

Als SDR-interessierter Funker hab ich mir die App zugelegt, um die SDR-Fähigkeiten meines Handscanners Alinco DX-J11 auszunutzen.
Das geht jedoch nur mit einem Stereo-Eingang, den iPhones und iPads nicht haben. Also musste ich mir ein externes Soundmodul zulegen (Sonic Port, ca. 70 Euro). Damit spielt iSDR einwandfrei als SDR-Demodulator. Leider ist das Kabelgeraffel mehr als nervig, sodass ich das nur ganz selten einsetze.

Allerdings habe ich (nur mit dem eingebauten Mikrofon) eine ganz neue Anwendung für iSDR gefunden: Man kann es als Ultraschallempfänger  benutzen. Spannend ist es, Jagd auf (fast) unhörbare Signale zu gehen, beispielsweise zirpende Schaltnetzteile, unerwartet im nahen Ultraschallbereich emittierende bewegte Teile oder auch die von Virenjägern entdeckte Ultraschall-Kommunikation von Viren über den PC-Lautsprecher (da hatte ich jedoch noch kein Jagdglück...)
Außerdem habe ich als ebenso nette wie unnütze Spielerei entdeckt, dass ich Musik und Sprache unhörbar per Ultraschall über meine Stereoanlage im ganzen Haus mit iSDR hörbar machen kann. Dazu muss ich die zu übertragenden Musikstücke vorher mit dem Plugin "Frequency Shifter" z.B. im Audioeditor "Audacity" in den nahen Ultraschallbereich verschieben. Allerdings muss man entweder mehrfach um 5kHz verschieben oder man muss die 5kHz-Grenze des Plugins durch einen Hack in der Konfig-Datei überwinden. - Okay, das ging jetzt erheblich über eine normale Rezension hinaus, aber ich wollte meine Begeisterung für diese App irgendwie plausibel rüberbringen, auch wenn ich den ursprünglich vorgesehenen Anwendungszeck kaum nutze.
Mein Fazit: nettes Spielzeug, das mir neue faszinierende Möglichkeiten im Ultraschallbereich eröffnet hat.

### 2/5 — ISDR

*2016-07-01, version 4.4*

Disappointing performance, as I had to buy a fairly expensive sound card to make it work with my radio, and then I found it allowed no control of the radio and a very limited range on screen which needs to be reset when tuning through the band.

Of only limited use and not worth the effort. Spend out on a proper pan-adaptor.
Les

## Frequently asked questions about iSDR

### What is iSDR and what does it do?

iSDR is a software-defined radio receiver application for iPhone, iPod touch, and iPad. It allows users to process radio signals using their iOS device's processor, offering features like frequency domain filtering, various receive modes, and signal display options. It is designed for experimenters and amateur radio enthusiasts.

### Do I need any extra hardware to use iSDR?

Yes, additional hardware is required to receive live signals. You will need to purchase or construct a "quadrature sampling detector (QSD)" RF front-end device and connect it between an antenna and the microphone input jack. Alternatively, it can be used as a panadapter with a compatible radio receiver.

### Can I use iSDR with RTL-SDR dongles?

No, iOS devices will not work with RTL-SDR USB dongles, and they are not supported by iSDR. The app is designed to work with specific QSD RF front-end devices or as a panadapter for compatible radio receivers.

### How can I load my own radio recordings into iSDR?

You can load your own I/Q recordings into the app using iTunes file sharing. Most PCM file formats are supported, including .wav and .caf. If you embed the center frequency in your file names, iSDR will automatically display the correct frequency when the file is played.

### What are the key features of iSDR?

Key features include six receive modes (USB, LSB, CW, AM, FM, Binaural), selectable bandwidths, a 120 dB signal strength meter, three AGC settings, and three display modes (Spectrum, Waterfall, Oscilloscope). It also supports downloaded spectrum files and allows for quick or precise tuning.

## Version history (last 5 releases)

### 5.1 — 2019-11-25

o Fixes a crash when using native Settings
o Provides WiFi functionality without in-app purchase
o Updates for iOS 9 and above
o Support for iPhone 11 and iPad Pro

### 5.0 — 2016-09-25

o Updated for iOS 10
o iPad Pro support
o Keep frequency displayed in waterfall by tapping it once
o Move between display modes without losing frequency setting
o Minor bug fixes

### 4.4 — 2014-10-20

o Updates for iOS 8 and iPhone 6 and 6 plus devices. 
o Resolves issues with audio when playing files, and various screen layout issues, with iOS 8

### 4.3 — 2014-07-11

o TCP Port value can now be set in the app as well as in native Settings
o CW Offset adjustments for KX3 owners 
o Minor bug fixes and acknowledgements edits

### 4.2 — 2014-07-02

o In-app Store features optional Wi-Fi Radio Control feature (additional hardware is required to use this feature)

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## More apps by Digital Confections LLC

- [Map-n-Compass](https://appshunter.io/ios/app/map-n-compass/id691748599)
- [Make My Trail](https://appshunter.io/ios/app/make-my-trail/id862806834)

All apps by Digital Confections LLC: https://appshunter.io/developer/480077374

## Related topics

[confections](https://appshunter.io/ios/topics/confections)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-22.*