Inverted V with balun adjustment problem. - AntennaRestrictions Forum at eHam.net

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eHam.net Forum : AntennaRestrictions : Inverted V with balun adjustment problem.

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Inverted V with balun adjustment problem.	Reply
by SW4LRC on October 28, 2006	Mail this to a friend!
Thats my problem, the elements are cut using this formula for inverted Vee http://www.geocities.com/Augusta/7117/antenna.html for 40m. The edges are 15 feet from roof. I use the BU-50 1:1 balun from Diamond. Without using my tuner i have 1,3 SWR in 30MHz!! The balun is feeded with rg-223. My vertical is OK 0 SWR in 7.080MHz with the same cable. I 'm doing somethink wrong? Thanks SW4LRC.

RE: Inverted V with balun adjustment problem.	Reply
by KB9CRY on October 30, 2006	Mail this to a friend!
The calculator gives you the lengths for the "ideal" antenna, one that is in free space with no surrounding interferences. Obviously the overall height and/or nearby objects are affecting it's resonance. Since your low SWR spot is higher in frequency than what you want, you need to lengthen each leg to compensate. Add on wire, I'd say add a foot to each end, and remeasure the SWR. The balun used should do the job and you've already checked out the cable. You'll need to tweak the lengths until it's where you want. Phil

RE: Inverted V with balun adjustment problem.	Reply
by AE6RO on November 4, 2006	Mail this to a friend!
I've never built an inverted V but plan to. I read the length should be 1.06 times the usual formula length for a 1/2 wave antenna. Then you do the cut and trim until you get your SWR where you want it. However, if your resonance (frequency of 1:1 SWR) is so far off the track, I would get rid of the balun. There's probably something wrong with it. As long as your coax is 50 ohm you should be OK. I had some brand new high cost coax which was supposed to be 50 ohm but when I connected it to a dummy load the SWR was 1.6:1, indicating an impedance that was different. Good luck, OM! You'll build a much better antenna than you can buy! 73 AE6RO

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