Here is a trick how to do it. On the pdf you attached, zoom it up to 400%, and using the Snapshot tool (camera) select, copy, and paste to a photo editing program. Save it as jpeg (using lowest compression, for high resolution).
It will to be a big file ~7Meg (see the attached)
I found this: Google for Smith_chart_bmd.svg and amongst the first hits you'll get a link with foreign characters (not sure which country).
Anyway, download it, and then Inkscape lets you delete individual lines and numbers, to get it to exactly the level of detail that you need,
and then you can do "Save a Copy" to save in many formats.