Constraints on the low frequency spectrum of FRB 121102 L. J. M. Houben, L. G. Spitler, S. ter Veen, J. P. Rachen, H. Falcke and M. Kramer A&A, 623 (2019) A42 Published online: 01 March 2019 DOI: 10.1051/0004-6361/201833875