{"id":5395,"date":"2012-07-31T08:00:43","date_gmt":"2012-07-31T12:00:43","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=5395"},"modified":"2012-08-29T08:25:34","modified_gmt":"2012-08-29T12:25:34","slug":"water-and-rf-do-not-mix","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2012\/07\/water-and-rf-do-not-mix\/","title":{"rendered":"Water and RF do not mix"},"content":{"rendered":"

Last year, the main antenna and transmission line for WSPK was replaced.\u00a0 I was, therefore, somewhat surprised to hear that there was an issue with the new transmission line.\u00a0 And yet, problems there are.\u00a0 Most likely, some ne’er do well has shot the transmission line with a bullet making a hole, which, when it rains, allows in water.\u00a0 Said water then accumulates in the bend at the bottom of the tower.\u00a0 When enough water is present to fill the gap between the center conductor and the outer conductor, this happens:<\/p>\n

\"Foward<\/a>
Foward and Reflected power meters, WSPK, Mount Beacon, NY<\/figcaption><\/figure>\n

For those of you keeping score at home, that’s 980 watts forward, 375 watts reflected or about 4:1 VSWR.\u00a0 Obviously not a good load, in fact the transmitter shut down.\u00a0 Fortunately, the backup transmitter and antenna system worked flawlessly.<\/p>\n

This began happening last month, usually after a heavy rain storm.\u00a0 Thus, I went out to the base of the tower and shook the transmission line and sure enough, water was sloshing around in there.\u00a0 Last time time it happened, a tower crew was summoned to inspect the line.\u00a0 Inspect it they did, but did they find any holes? No, they did not.\u00a0 Perhaps the issue is with the antenna itself, in which case the entire thing will have to be removed from the tower and lowered to the ground.\u00a0\u00a0 In the mean time, my boss drilled a small “weep hole” at the bottom of the bend where the line comes off the tower.<\/p>\n

I uncovered this weep hole and pressurized the line and viola, lots of water came out:<\/p>\n

\"WSPK<\/a>
WSPK 1 5\/8 inch air dielectric transmission line, Mount Beacon, NY<\/figcaption><\/figure>\n

A bit unconventional, but effective nonetheless.\u00a0 The first video is of the water dripping out:<\/p>\n