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.