HDSDR Version 2.75 (Stable) Released

The beta 2.75 version of HDSDR was released about two months ago. Now the stable version has just been released. HDSDR is a free general purpose SDR receiver, similar in nature to other programs like SDR# and SDR-Console. HDSDR can be downloaded from hdsdr.de.

The author of HDSDR emailed us with the following release information:

this morning we released the final version 2.75. Here’s the changelog:

Version 2.75 (January 01, 2017)
- more recording options
- support for 8bit sampling format – ideal for RTLSDR, halving RF recording size
- display level / clipping for RF and AF
- additive noise generator for hiding aliases
- Highpass Filter for AM/FM deactivatable – useful for slow digimodes
- configurable gain for I/Q output – useful for digimode decoding weak signals of SDRs with >16 Bit dynamic range
- Uniform “Calibration” dialog for Frequency/S-Meter/DC Removal/Channel Skew
- “Custom color palette” to customize colors of Waterfall/Spectrum and some more
- output soundcard no longer necessary (e.g. for recording or monitoring)
- support for 8k display resolution (7680×4320)
- some new keyboard shortcuts (see )
- extended ExtIO capabilities
- experimental transmit capability through ExtIO API interface
- many fixes and improvements

Some of the new features were introduced especially for the RTLSDR Dongles:

- 8 bit support, of course

- displaying the RF (ADC) level in dBFS allow working with deactivated Tuner AGC – NOT oversteering/clipping the ADC.
This would also ease making good suitable recordings as used in

Especially for decoding this kind of signals (AM/FM) , deactivating the Highpass filter (Ctrl-H) will make the demodulated Audio clearer:
long periods of positive or negative levels will not fade towards zero.
Find attached recordings and screenshots with active and deactivated highpass filter of a garage door opener demodulated in AM.

- additive noise generator (Ctrl-N) is for hiding some alias carriers in scenarios where the ADC does not see real noise from the antenna.
The noise generators level has to be configured carefully for not hiding real signals. A level between -25 to -10 looked fine for me. But that should be measured in a lab.

Below are the mentioned attached images and .wav files.

Highpass Filter - Active
Highpass Filter – Active
Highpass Filter - Inactive
Highpass Filter – Inactive

Highpass Active .wav file (Download)

Highpass Inactive .wav file (Download)


  1. Robert

    To start with I would like to say that I like the program HDSDR and I use it on a V3 dongle . I do have a question about the extended ExtIO capabilities . I am using the 2.75 stable version and I don’t see any extended ExtIO .
    The only ExtIO I see is the one that has always been their . Is the extended ExtIO something that is down loaded form website , if so what site is it ????????

  2. Mario

    Have not downloaded the latest version, but must say that HDSDR which I use with an SDR dongle and Up-converter is an excellent software. I especially like the large “S” meter on the dashboard.

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