# Doppler Effect Calculator vs NTRIP STX

The clearest difference is price: NTRIP STX at Free against Doppler Effect Calculator's $2.99. NTRIP STX also leads on update cadence (every 10 months vs every 26 months) and iOS requirement (15.0 vs 17.6). Doppler Effect Calculator's advantage is in-app purchases (none vs 2). On ads and device support there is nothing between them.

NTRIP STX is free to download; Doppler Effect Calculator costs $2.99 up front. NTRIP STX sells 2 in-app purchases, starting at $4.49 per month. Doppler Effect Calculator asks for nothing beyond the download.

Doppler Effect Calculator ships an update every 26 months, NTRIP STX every 10 months. The most recent releases landed on October 8, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | Doppler Effect Calculator | NTRIP STX |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/doppler-effect-calculator/id1410084954/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 26 months | **Every 10 months** |
| Monetization | Paid | — |
| Size | 1 MB | 109 MB |
| Requires iOS | 17.6 | **15.0** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Nitrio](https://appshunter.io/developer/321121189) | [ITS Geo Solutions GmbH](https://appshunter.io/developer/1362963860) |

## What reviewers say

### Doppler Effect Calculator

[App page](https://appshunter.io/ios/app/doppler-effect-calculator/id1410084954)

This physics and math calculator helps determine the frequency of sound waves when the source or observer is in motion. It provides instant calculations with copyable results and includes reference formulas. The app supports various units and high precision, working seamlessly on iOS devices.

**Highlights:** Instant calculations, Copyable results, Reference formulas included, Supports 16 decimal places, Multiple unit support, Ad-free and private

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

**In-app purchases:** none


### NTRIP STX

[App page](https://appshunter.io/ios/app/ntrip-stx/id1606816934)

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Professional - Monthly | $4.49 | per month |
| Professional - Annual | $46.99 | per year |


## Frequently asked questions

### Is Doppler Effect Calculator free?

Doppler Effect Calculator costs $2.99, with no in-app purchases.

### Is NTRIP STX free?

NTRIP STX is free to download, with in-app purchases available.

### Do Doppler Effect Calculator or NTRIP STX have ads?

Neither Doppler Effect Calculator nor NTRIP STX shows ads.

### Which is updated more often, Doppler Effect Calculator or NTRIP STX?

Doppler Effect Calculator ships an update every 26 months, and NTRIP STX every 10 months. Most recently, Doppler Effect Calculator was updated on October 8, 2026 and NTRIP STX on October 25, 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.*