All HELIAX coaxial cables are jacketed for direct burial or for corrosive
This was taken from the following URL:
If the FSJ is considered HELIAX, it appears it can be buried.
I've been using it in an outdoor environment for fifteen years and see no
signs of degratation. I have two runs about 30 feet long buried.
73 de Larry K7SV
TowerTalk mailing list