At Series match for a half wave dipole I mentioned that RG6/U may have a copper clad steel (CCS) centre conductor, and may have significantly more loss at HF than expected based on datasheets and calculators.
Above is a comparison of matched line loss based on measurement of a length of RG6/U Quad Shield CCS cable and prediction from Simsmith of Belden 8215 (also CCS). The ripple is due to measurement system error.
The first cable was obtained from a trade supplier with the common 21% IACS CCS inner conductor, it is low cost, a good reliable product good from VHF (30MHz) through to L Band (2GHz), but its copper cladding is insufficient to give copper like performance at HF (eg MLL=0.027dB/m @ 1MHz where we would expect more like MLL=0.006dB/m from a solid copper RG6/U).
The Belden 8215 is worse than solid copper, but not as bad as the sample cable measured.
So, be aware that CCS cables have no real minimum copper specification, or loss characteristic, and many economy products intended for VHF to L Band TV are not too good at the lower half of HF.
This caution applies also to RG11 which is now often sold in a CCS form.
There are reports of CCS cables being sold with copper cladding substantially less than the common 21% IACS which was plotted above, and you might expect that the performance to be even poorer.