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 SDR-Radio.com 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.

 

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