Richard Clark wrote:

I do use some small stuff, like RG-174 and precision hard line, but
you are right, this is not for RG-58 which I commonly use. The 101
size is Amidon's reference for a multiplier for other forms.

I wind about 10 turns of RG-174 type coax on a core having an OD of a
bit more than an inch. Works fine up to at least 300 watts with a
reasonably matched antenna.

Roy Lewallen, W7EL