Comparison

rtl_tcp SDR vs smartDF

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

rtl_tcp SDR

This app acts as a software-defined radio receiver for iOS devices, allowing you to listen to various radio signals and view RF spectrum data. It connects to external SDR peripherals via a network protocol, requiring a separate server setup.

Highlights
  • Listen to AM, FM, SSB, CW signals
  • View RF spectrum and waterfall
  • Connect to networked RTL-SDR peripherals
  • Supports Airspy HF+, SDRPlay, LimeSDR Mini
  • Direct connection to Hermes Lite 2
Features
Read full description

An RTL-SDR Software Defined Radio receiver app for iOS devices.  Listen to AM, FM, SSB and CW radio signals. View an RF spectrum and waterfall. Connect, via the rtl_tcp network protocol, to networked RTL-SDR USB peripherals. This app requires an external rtl_tcp server. iOS devices do not currently support the direct connection of USB peripherals 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. This allows a Raspberry Pi (or Mac) to act, essentially, as the USB port adapter for your iOS device. The rtl_tcp SDR app can also connect to hfp_tcp for the Airspy HF+, rsp_tcp for SDRPlay devices, and lmm_tcp for the LimeSDR Mini; see GitHub for server source code. This app can also connect to a Hermes Lite 2 QRP transceiver directly, if it has a known IP address, or through an hl2_tcp server. No support is provided for installing any of the rtl_tcp or other tcp software needed to use this app (with a Raspberry Pi, or otherwise). Please do not download this app unless you are already familiar with Software Defined Radio, have an RTL-SDR or equivalent USB SDR peripheral, and have already installed and tested rtl_tcp on your Raspberry Pi, Mac, or other server. Note that this app requires a very high bandwidth network connection in order to receive streams of real-time RF samples from an RTL-SDR. It is recommended that your rtl_tcp server be on a wired connection rather than on the same WiFi as your iOS device.

About

smartDF

Features
Read full description

iPadOS application designed in cooperation between certified developer Carlos Lago and Rhotheta International Inc - www.rhothetaint.com - for the remote control and monitoring of Rhotheta radio direction finders via Bluetooth (BLE) or Wi-Fi. A modern UI for direction finder (DF) products increases crew productivity and enhances mission awareness during search-and-rescue, law enforcement, and special missions. DF sensor data is conveniently displayed over maps with state-of-the-art graphics.

Screenshots

rtl_tcp SDR3 screens

Verdict

The call

The clearest difference is price: smartDF at Free against rtl_tcp SDR's $12.99. smartDF also leads on update cadence (weekly vs every 4 months). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

smartDF is free to download; rtl_tcp SDR costs $12.99 up front. Neither carries in-app purchases, so what you see is what you pay.

UpkeepUpdate frequency

rtl_tcp SDR ships an update every 4 months, smartDF weekly. The most recent releases landed on October 23, 2026 and October 25, 2026 respectively.

Scorecard2 real differences · 8 level
rtl_tcp SDR versus smartDF: the parameters behind the verdict, then further details
Parameterrtl_tcp SDRsmartDF
Price$12.99Free — better
Rating3.9 (32 ratings) — better—
Positive reviews40.0% of reviews—
Number of ratings32 — better—
Update frequencyEvery 4 monthsWeekly — better
AdsNoNo
In-app purchasesNoNo
MonetizationPaid—
DevicesiPhone, iPad — betteriPad
Requires iOS16.615.4 — better
Further details — not scored
Size3 MB59 MB
Age rating4+4+
DeveloperHotPaw ProductionsCarlos Yordanis Lago Gonzalez

In-app purchases

None

rtl_tcp SDR

No in-app purchases

None

smartDF

No in-app purchases

Questions

Is rtl_tcp SDR free?
rtl_tcp SDR costs $12.99, with no in-app purchases.
Is smartDF free?
smartDF is free to download, with no in-app purchases.
Do rtl_tcp SDR or smartDF have ads?
Neither rtl_tcp SDR nor smartDF shows ads.
Which is updated more often, rtl_tcp SDR or smartDF?
rtl_tcp SDR ships an update every 4 months, and smartDF weekly. Most recently, rtl_tcp SDR was updated on October 23, 2026 and smartDF on October 25, 2026.

Other comparisons