Monthly Archives: March 2017

Airspy & SpyVerter: A serious love affair


24 broadcast channels demodulated in parallel on shortwave – And Airspay and SpyVerter do need just a quarter of PC’s power!

For a much too long time, I had overlooked Airspy and the matching up-converter, namely SpyVerter. Found no explanation for this my blind spot. Now I am focusing my view onto this 10-bit SDR, covering 24 MHz to 1.800 MHz (just Airspy) plus 1 kHz to 60 MHz by help of Spyverter (+120 MHz). What I see from my first tests is a sensitive combo with a surprisingly lot of dynamic range, ending up in clear recpetion of up to a nearly 10 MHz wide band. This may be recorded and eventually played “as live”.

I am still tuning up and down the bands, trying this and that. It will end up in a test report in due time. For now, just have a look at the screenshot on top, showing 24 demodulators (Synchro-AM) in parallel, covering many broadcast channels in English from Asia. Have also a look at the fine print on the right at the bottom: this all needs just the quarter of the power of an able PC.

So, for now, just a a sentence at half-time: Don’t overlook this combo if you are in search for a “low cost, high perfomance SDR”. Yes – that’s exactly  the way Youssef and his team advertise it, but it is one of the rare cases where such a claim meets reality. Stay tuned.

LimeSDR: First Experiences on HF

One hour in the 20 m ham radio band with LimeSDR and SpyVerter, zoomed out of a one hour’s recording of 30 MHz width. Antenna: quadloop of 20 m circumference.

LimeSDR is a Crowdsupply project – delivering an SDR which covers 100 kHz to 3.8 GHz with bandwdiths of up to 2 x 30 MHz. I was interested almost exclusively in the range 100 kHz to 30 MHz. The board arrived on March 17th, and I already have done some tests with it. From these very first results & a recommendation:

  • Installing is easy (W10), if you follow the instructions.
  • Without modification, LimeSDR is simply useless on HF. It’s deaf near to a dummy load.
  • The producer recommends a “modification” by just removing one SMD. Then some life came into this range. But it was hard to sort the ghost stations from the real ones.
  • Even a low-pass filter from Heros didn’t helped that much.
  • Just before selling the board on ebay, I connected the antenna first with Spyverter – a state-of-the-art up-converter with an IIP3 of +35 dBm, transferring the band of 0 – 30 MHz to 120 – 150 MHz. This is a range, where LimeSDR sees some light.

So, if you are disappointed by the near-non HF performance of naked LimeSDR: an able up-converter will change the game. Recording and sonagrams had been made with V3.

30 MHz live with LimeSDR and SpyVerter shows that it generally works. Same antenna as above.

“Ghost signals” make it sometimes difficult to distinguish them from real signals. This sonagram has been made with SpyVerter. Broadcast stations are easy to find out (in their majority). But it gets difficult to sort the ghost stations from the few real ones in the left part.