Hello,
In product specs say that LImeSDR can go from 100KHZ > . Do I need specially made up-converter for lower frequency, or LimeSDR can do that task alone…
No … So im told … you no longer need to build/aquire an upconverter …
With the bandwidth of the ADC and LO can cover quite low in freq …
If you want to go below 100kHz I would recommend using high end audiophile 24-bit sound cards. The Antennas for ELF to VLF are usually magnetic based (large coils of wire).
e.g. a typical ULF (300Hz to 3 kHz) antenna:
And if you were interested in Schumann Resonances (60Hz and below) then you would typically use coils (8-10 kg [18-22 lb] of copper) with a mumetal core as your antenna. Because of man made noise below 100Hz, from basically everything, you need an extremely large dynamic range. So 24-bits would be far more useful than 12-bits. If you are interested in low frequency stuff there are some really good articles at http://www.vlf.it/ (scroll down a bit on the front page).
The LimeSDR not having coverage below 100kHz is not really a problem because the antennas start to get very exotic. 100kHz is a wavelength of 299 meters ( 983 feet), so even a quarter wavelength antenna would be ~75 meters (~250 feet) long. And the lower in frequency you go the longer (and/or more exotic) they become.
Thanks for replay, your answer is excellent, which clarify any doubts about LimeSDR, although I was thinking about domain from 3-30 MHz, but didn’t mention initially :-).
For 3-30MHz [which is a subset of the specified range 100kHz to 3.8GHz], there should be no need for any external up/down converter. The software developers and other people with access to the initial boards have listened to signals at 2MHz, 4MHz, 6MHz without any additional converters (ref: here).