Having just written again on skin effect and copper clad steel (CCS) conductors on HF, and the potential for less than copper performance, it was interesting to note a thread on QRZ where the OP asked for advice on the issue with budget CCS RG-11.
Two late posts as I write this were:
There really is no real issue with skin effect on HF bands with copper clad materials.
At 1.8 MHz, the skin depth in copper is 0.654 micro-meters (.0000654 mm), so the copper cladding on the center conductor of most RG-11 type coaxial cables is more than sufficient for any of our current bands.
The specific advice above looks interesting, convincing even… but thankfully, the skin depth in copper is nowhere near either of the figures he gave.
If it was 0.654 micro-meters as he first states, the RF resistance of a 1.6mm solid copper centre conductor would be 2.5Ω/m.
If it was .0000654 mm as he secondly states, the RF resistance of a 1.6mm solid copper centre conductor would be 25.6Ω/m.
In fact the skin depth in copper at 1.8MHz is 48.6µm, and the RF resistance of a 1.6mm solid copper centre conductor would be 0.0349Ω/m.
You do have to be discerning in what online advice you swallow.
To the original poster’s question, if the cladding is more than say 100µm in thickness, it will have almost copper like performance at 1.8MHz.
I measured a piece of quad shield RG-6 yesterday to have 10µm cladding, copper like performance above about 150MHz, certainly sub-optimal for HF, much less MF.
Copper thickness is relevant on CCS conductors at HF and MF, and the problem is that lost of cables lack either specifications for matched line loss or cladding thickness data down to low HF and MF. If the datasheet stops at 30MHz, it is a warning that it may be significantly poorer than copper at lower frequencies.