# iSDR vs RST Decoder

The clearest difference is price: RST Decoder at Free against iSDR's $0.99. RST Decoder also leads on rating (5.0 vs 2.5) and in-app purchases (none vs 1). iSDR's advantage is ads (none vs shown) and device support (3 vs 1). On ratings volume and update cadence there is nothing between them.

RST Decoder is free to download; iSDR costs $0.99 up front. iSDR sells 1 one-off in-app purchase. RST Decoder asks for nothing beyond the download.

RST Decoder holds the better App Store score, 5.0 against 2.5. Both are backed by a comparable volume of ratings — 11 and 7 respectively. Written reviews point the same way: 52% of iSDR's written reviews are positive against 67% of RST Decoder's.

iSDR ships an update every 3 months, RST Decoder every 2 months. The most recent releases landed on October 4, 2026 and October 6, 2026 respectively.

## The numbers

| Metric | iSDR | RST Decoder |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | [2.5 (11 ratings)](https://appshunter.io/ios/app/isdr/id480077371/reviews) | **[5.0 (7 ratings)](https://appshunter.io/ios/app/rst-decoder/id1519587362/reviews)** |
| Number of ratings | **11** | 7 |
| Positive reviews | 51.7% of reviews | **66.7% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | **No** | Yes |
| Update frequency | Every 3 months | **Every 2 months** |
| Monetization | Paid | **Ad-supported** |
| Size | 36 MB | 6 MB |
| Requires iOS | **9.0** | 17.0 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 17+ |
| Developer | [Digital Confections LLC](https://appshunter.io/developer/480077374) | [koji kamogawa](https://appshunter.io/developer/1488210713) |

## What reviewers say

### iSDR

[App page](https://appshunter.io/ios/app/isdr/id480077371)

This app allows experimenters and amateur radio enthusiasts to build a portable software-defined radio receiver using their iOS device. It processes radio signals using the device's processor and offers various display and filtering modes. Additional hardware is required for live signal reception.

**Highlights:** 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

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

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


### RST Decoder

[App page](https://appshunter.io/ios/app/rst-decoder/id1519587362)

This application decodes Morse code from your microphone, acting as a practice tool to verify your keying accuracy. It offers advanced features like BPF and FFT decoders with automatic frequency and gain control, allowing for fine-tuning of reception parameters.

**Highlights:** Microphone Morse code decoding, Morse practice and keying check, BPF and FFT decoder options, Auto Frequency Detector (AFD), Auto Gain Control (AGC), Real-time CW signal display, Input signal recording/playback

**In-app purchases:** none


## Frequently asked questions

### Is iSDR free?

iSDR costs $0.99, and also offers in-app purchases.

### Is RST Decoder free?

RST Decoder is free to download, with no in-app purchases.

### Which has better reviews, iSDR or RST Decoder?

RST Decoder is rated higher. iSDR averages 2.5 out of 5 from 11 ratings, while RST Decoder averages 5.0 from 7 ratings.

### Do iSDR or RST Decoder have ads?

RST Decoder shows ads; iSDR does not.

### Which is updated more often, iSDR or RST Decoder?

iSDR ships an update every 3 months, and RST Decoder every 2 months. Most recently, iSDR was updated on October 4, 2026 and RST Decoder on October 6, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*