Has anyone modified the filters on limesdr mini for hf?


#1

I thoiught i would ask here before i pop the shield off of my mini and attempt this.

thanks,
Rich N2RV


#2

@richcatena - Rich,

Unlike the traditional LimeSDR, the LimeSDR Mini was designed to work from 10 - 3.5 GHz right out of the chute without modifying anything. The Mini-Circuits matching transformers that exist in the Lime-Mini are good from 2.0 MHz to 3.0 GHz but the specs of the 'Mini suggest that 10 MHz is the start point of its optimal receive range. Some have experimented with that and have found that it’s good down to 60m (5.0 MHz) but it falls off sharply for receive sensitivity for anything below 60m - I think someone tried tuning it to 75m/80m (3.5 to 3.999 MHz) and it was pretty deaf. I cannot vouch for my Lime Mini as my setup is in mothballs at the moment, but I expect to get back onto it in the next month or so.

I really would suggest that you not try to pry the lid off and play - it’s not going to gain you much over what you have now. The only reason the original LimeSDR required the ‘HF Mod’ was because the matching transformers and associated capacitors were optimized for cellular and WiFi frequencies, but the underlying LMS7002 was designed for 100 kHz to 3.8 GHz and once the ‘HF Mod’ was done to that board it truly could work well into 160m and the US AM Broadcast Band (540kHz to 1.6 MHz). But the Mini isn’t that optimized for that, so what you see is what you’re going to get.

Hope this helps, Rich - 73, de Marty, KN0CK


#3

Hi Rich,

I also opted not to mess with the hardware on the lime mini. Instead did some experiments a while ago with up converting the signal with the 40 mhz clock using a mixer. Maybe this could also help you to achieve your goal.