[Sensitive SDR receiver for sensitive information]

Sensitive SDR receiver based on the DRU-244A digitizer SDR hardware platform

The DRU-244A digitizer board was designed and implemented for building radio receivers. It contains a 16 bit resolution low-noise Analog-to-Digital Converter (ADC). It has a low-noise input preamplifier and an input attenuator in front of the ADC. The low-noise preamp provides input sensitivity as low as -111 dBm in SSB reception mode with 2.1 kHz bandwidth and 10 dB SNR. With external preamplifier it could be as low as -122 dB. If you would like to see more detailed test results on SDR receiver sensitivity click here:
http://spectrafold.hu/quadrus/digitizer-hardware/sdr-receiver-sensitivity-test

Practical results for receiving weak signals

I’ve already made some practical tests with my very simple inverted-V shaped wire dipole antenna. It was used in the country side, so there was less human made noise than in the crowded city or urban area.

Sensitive SDR receiver as long range DRM SDR

If you are not a professional radio enthusiast with a vast knowledge of exact broadcasting carrier frequencies, one of the easiest ways to find some DRM radio stations is to just look for its unique spectrum in the HF band. The DRM spectrum is a very typical, noise like, wide band signal. This is exactly what I did; I simply connected the antenna to my receiver through a 30 MHz low-pass input pre-selection filter, and started visually looking for DRM radio signals in the spectrum. I was really surprised when one of the first signal received turned out to be be coming from India and the next one was from South Africa. Not bad. The SDR receiver seems to be real sensitive if I am able to decode these signals in the middle of Europe.

If you are interested in how the SDR receiver was connected to the Dream DRM decoder software, please read these posts:

http://spectrafold.hu/quadrus/radio-software/virtual-audio-connection/

http://spectrafold.hu/quadrus/radio-software/sdr-drm-receiver/

Sensitive SDR receiver for secret transmissions

One of my other favorite signals in the HF spectrum is the UVB-76 Buzzer on 4555KHz.

https://en.wikipedia.org/wiki/UVB-76

http://priyom.org/military-stations/russia/the-buzzer.aspx

http://www.wired.co.uk/magazine/archive/2011/11/features/enigma?page=all

As the frequency is well known, I could simply dial it in to the SDR receiver software, and immediately see the transmission on my screen and hear the famous “Buzzer” tone on the speaker with very high Signal-to-Noise Ratio (SNR).

There are a lot of mysterious signals in the HF spectrum. The sensitivity of our receiver – especially with an external, low-noise per-amplifier and a good antenna – makes it possible to listen to even the most remote signals.