7135 kHz Technical Roundtable: Waterproofing Antenna Joints

Yesterday’s technical roundtable on 7135 kHz was joined by VU3LKZ, VU3LKT, VU3ATD, VU23KM and
VU2LSK. Main discussion centered around waterproofing of antenna cable joints. I had mentioned that I had a bad experience of my RG213 cable for 40m antenna getting damaged by rain water seepage. Antenna system which was functioning well became very bad after that. Earlier VU2LID/N8LI had suggested that he uses three layers of covering with Teflon, rubber and electrical tapes. Antenna joints sealed like that look like new 10 years later even if buried underground or left on the ground.

VU3LKZ suggested Teflon sealing tape being used by plumbers, followed by covering with COTRAN adhesive tape. VU3ATD mentioned that similar tapes are being used for submersible pumps of bore wells. I have located both plumber tape and COTRAN Mastic tape online and will be trying them out in future projects. Mastic tape is a highly conformable, self-bonding, rubber-based tape used for creating durable, waterproof, and airtight seals, primarily for electrical insulation, moisture proofing, and corrosion protection on cables and connections. It is known for its excellent adhesion to irregular surfaces, UV resistance, and self-healing properties, allowing it to stretch and mold over joints to build up insulation and seal gaps effectively, often outperforming standard tapes.

I have used silicone tape as suggested by VU2THF after my antenna cable fiasco. That tape has to be stretched about twice before winding tightly over the joint. I am also applying adhesive tape on top of that to prevent the silicone tape from slipping off before it gets set in position. I found it useful also for my DIY plumbing for drip irrigation!