They are French pseudo CB'ers / 'Freebanders' / Echo Charlie operators.
There are unlicensed operators from loads of different countries using that segment of the spectrum. 6660.00KHz LSB is typically used as a calling channel.
Other frequency segments also get used by 'Pirate operators' they very often stick to fairly narrow frequency limits which may partially be because they use simple resonant antennas and don't want to have to use a tuner. Some of these 'Pirate' bands have been running for many years.
Some examples include:-
'Zender' stations using AM and broadcasting traditional music from 1600KHz to 1800KHz.
Russian CB'ers using ex military equipment mainly between 2900KHz to 3200KHz AM /USB / LSB and calling on 2920.00KHz
Filipino fishermen speaking in Tagalog 16540/16545/16550KHz USB
Could be Indonesian village radio 10940KHz +/- 100KHz USB
I think Phil's suggestion of a last used frequency memory would be useful.
I often find that I listen to one frequency whilst scrolling up or down the adjacent spectrum. If I quickly tune to a new frequency to hear what's been transmitted, it would be good to be able to quickly go back to the previous frequency without having to scroll back or retype the frequency (which I've often forgotten anyway).
Would it be possible to add something like a browser 'back' and 'forward' function below the frequency entry box, which would allow you to scroll between frequencies that have been entered during the current browser session whilst using the SDR ?
I've tried to assist where I can by sending personal emails to admins where I think I can help improve things.
But unfortunately in some cases the Admins are more software orientated than having any real interest in the hardware or RF side of things. So it's very difficult to try to get them to improve things when either they aren't really that interested. Sometimes this is because they don't really know what sort of performance to expect, or alternatively they don't have a good enough understanding of RF to be able to understand the nature of the problem and how to go about fixing it. Just stuffing a random length of wire in to the KiWi antenna socket and hoping for the best shouldn't be the default position.
I have offered to make up filters and send them free of charge to some Admins (where I thought the SDR was otherwise OK apart from some local overloading or interference that could be filtered out), but so far there has not been any take up (I don't to make a wide announcement and then spend all my time sending free stuff where it's not going to make any difference).
Maybe we could collectively write up some more detailed guidance notes for SDR Admins or folks considering buying a KiWi (as I notice that Farnell / Newark are now stocking the boards and kits) who are not well versed in the RF dark arts ?