Those interested in using LimeSDR to receive and/or transmit on HF bands can find performance details, along with suggested easy fixes to greatly improve receive performance, at:
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I think there may be a typo in Table B (carried over from other posts).
From the schematics I think MN14 should perhaps be MN25.
Good article - it does give us a sense of where we (and by ‘we’ I mean the Amateur Radio community, not Lime Microsystems) need to work the transmit strip on the LimeSDR or have ample preamplification off-board to drive larger amplifiers. It was my assumption all along that transmit was a side benefit of the LimeSDR - that no one could expect 100kHz to 3.8 GHz at 0dBm to +10dBm. From the LTE response it’s apparent that at (about) 3 MHz to 9 MHz the LimeSDR is averaging -40dBm, give or take a few dB. My first inclination would be to review the output circuit on the LimeSDR and determine if it’s (easily) tailorable to HF - if not, then study the preamplification, with ALC, that would be necessary off-board to have a constant drive level from 2 - 30 MHz @ +10dBm. Again - all that would be determined by anyone wanting that kind of performance, It’s not on LMS to make that happen. Frankly, I’m actually looking forward to researching this and posting on it when I have something solid to offer. But the article does put things into perspective for transmit and does a good job on the recap of the ‘EasyFix’ for receive, too.
73 de Marty, KN0CK
Marty, what you see in the LTE plot is the power density. You have to integrate that over the BW of ~5 Mhz to get the output power.
In 2.2.1 the “SSB output power” is given. It varies from -10 dBm for 2 MHz to +10 dBm for 30 MHz. I suppose SSB output power means CW on the low side of the LO. Unclear is if this is the saturation power or the output power for more linear operation.
On the Lime website I found another document
www.limemicro.com/wp-content/uploads/2015/08/LMS7002M_Measurements-v1_05.pdf
it gives a lot more information about measurements of the LMS7002M in the LMS7002M Evaluation Board
Cornelis
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@andrewback , do you know if the latest LimeSDR and its Mini variant had this HF performance issue fixed by default or it still require the user to do so personally? Just ordered 2 LimeSDR Mini and could be using low frequencies.
Also the wiki page shows performance up to 1G Hz and a slight trend of dropping for various fix method, would the fix impact higher frequency performance up to 2.4G?
No, this would not be the default, as it compromises performance elsewhere. Also note that Mini is only specified down to 10MHz.
I believe so.