Rock salt, copper or magnesium sulfate were the dope's of choice in the ARRL antenna Handbook page 199 12th edition <c> 1970. IMHO, I doubt it is worth it though. 73, Craig Clark, K1QX RADIOWARE AND RADIO BOOKSTORE PO BOX 209 RINDGE NH 03461 603 899 6957 WWW.RADIO-WARE.COM