{"id":6184,"date":"2024-01-31T19:07:58","date_gmt":"2024-01-31T13:37:58","guid":{"rendered":"https:\/\/johnsonfrancis.org\/techworld\/?p=6184"},"modified":"2024-02-13T11:04:19","modified_gmt":"2024-02-13T05:34:19","slug":"does-a-coil-of-coax-change-swr","status":"publish","type":"post","link":"https:\/\/johnsonfrancis.org\/techworld\/does-a-coil-of-coax-change-swr\/","title":{"rendered":"Does a Coil of Coax Change SWR?"},"content":{"rendered":"

I had made a modified inverted V 40 m antenna<\/a> recently with highest point about 1 m to one side of the feed point. This was made so just to suit the space constraints in my location. Highest point was attained using a 6 m GI pipe on to which a nylon rope was attached to host the antenna. Another 3 m of CPVC hot water pipe was used to elevate the region of the feed point away from the first floor fence. I had used two lengths of 10 m HLF 200 coaxial cable with PL 259 connectors at both ends as the feedline. The two cables were joined together using an SO 239 barrel connector. Surplus cable was placed in U pattern on the terrace, almost at right angles to the antenna orientation. The initial SWR was 1.6:1 at the lower end of the band and 2.7:1 at the upper end of the band. Wanted to see if making the surplus cable into a coil would change the SWR.<\/p>\n

\"\"<\/p>\n

After checking the initial SWR, the extra cable was made into a coil of about 6 turns of 21 cm diameter and tied to the CPVC mast. Repeat measurement showed that there was slight increase in the SWR at the upper end of the band to 2.8:1 and slight drop in SWR at the lower end of the band to 1.5:1. SWR at the middle of the band was unchanged at 2.2:1. As the values were within the range of the built-in automatic antenna tuner of FT-710, I could tune it for going on air and check into Silicon City Net with a 5,9 report from Bangalore. As usual, after tuning the SWR meter in the radio<\/a> showed an\u00a0 SWR near 1:1 while the external SWR meter connected in series showed the original SWR of about 2.2:1 on Silicon City Net frequency of 7088 kHz.<\/p>\n","protected":false},"excerpt":{"rendered":"

I had made a modified inverted V 40 m antenna recently with highest point about 1 m to one side of the feed point. This was made so just to suit the space constraints in my location. Highest point was attained using a 6 m GI pipe on to which a nylon rope was attached […]<\/p>\n","protected":false},"author":1,"featured_media":6189,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,19],"tags":[],"class_list":["post-6184","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-amateur-radio-ham-radio","category-antenna-and-propagation"],"yoast_head":"\nDoes a Coil of Coax Change SWR? - Johnson's Techworld<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/johnsonfrancis.org\/techworld\/does-a-coil-of-coax-change-swr\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Does a Coil of Coax Change SWR? - Johnson's Techworld\" \/>\n<meta property=\"og:description\" content=\"I had made a modified inverted V 40 m antenna recently with highest point about 1 m to one side of the feed point. 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