[BC] recommended fluxes for silver soldering ground system/radials?

[Milton R. Holladay Jr.]

A carburizing oxy-acetylene flame will strip the oxygen out of the darkest
tarnish; crusty green will require brushing after a good heating.
Stay-silv/Silfos is the stuff to use in whatever % silver you like. If you
need flux or abrasion on clean copper, you're not doing it right.
You can forget the Weller and propane with these rods; Mapp and Prestolite
will work, some fashion.

Cad-weld is preferable for ground rods, but a honkin' big torch tip will do
the job: Dig out about a foot below the attachment point, twist the strap up
vertical, make a tight omega shaped bend around the rod, clamp it in place.
Heat the top of the rod until good and hot, then move down and flow the
solder up and down the width of the strap on both sides of the ground rod
(This will require some skill not to have the solder dripping out of the
joint.) If you're doing it right, the molten solder will flow into the joint
all the way around the contact area........
M