I do have a Limesdr usb modified on LNAL input (removed one coil as approved by lime)
until version 3.0.6 it works perfect from 100 khz and up .
From version 3.0.6 tx is not working ok below 30 mhz. in March 2019 I used version 3.0.6 but with the SDRSourceLime.dll from version 3.0.5 and that works OK.
About that time I had a discussion with Simon about it on this forum. (you can trace it back under limesdr).
With the arrival of the Oscar 100 I focused only on that and thanks to Simons usbrelais and geostationair beacon window etc it it working perfect with the Oscar 100, .
Today I focused again on working on 80 meter (3.630 khz). No ok tx with 3.0.22 so i replaced the DRSourceLime.dll with the old one from 3.0.5..
And it is working OK !!! (RX LNAL TX Band 1 Bandwidth 6.144 Mhz). The Lime gives about 20 miliwatt output that goes to a little amp (2N5109)
output about 2 watt and then to a linear output 20 watt. This evening I made a lot of qso's with dutch hams on 3630 khz and I got very nice reports.
So no converter is needed.
Perhaps this is useful info and I like to receive comments.