Sorry, I missed the 100 kilohertz. [Linked Image]

Discones won't give fantastic performance below VHF. A long wire (e.g. an inverted-L) would certinly be a good cheap antenna for the MF and HF ranges. Bearing in mind your comments about neighbors in the general area, it's also worth considering that a long wire is fairly unobtrusive (tell 'em it's a big washing line! [Linked Image]).

You could add an ATU to help tune to the band you're scanning at any one time.