I’m interested in using the LimeSDR at frequencies of a few MHz.
I understand that the supported way to do this is to set the LO frequency to ~30MHz and use the NCO to downconvert.
I’m wondering though if there might be another option. In figures 15 & 16 in the Programming and Calibration Guide, it looks like the LO output can be swapped to signals:
LOCH_OP_T, LOCH_ON_T, LOCH_OP_R and LOCH_ON_R.
about which I can’t find any information. I’m guessing though that these are outputs of some dacs? If the LO output could be set to constant values, could low frequencies be generated directly by the NCO (or by hand)?
So my questions are:
Is there any documentation on these signals, and on the muxes they connect to?
What will the LO I/Q generators do with dc inputs?
Will the mixers after the LO I/Q generators work with dc inputs?
As an alternative, would just powering down the LO VCO do the job (expecting that the LO I/Q generator might provide a dc value to the mixer?)