For this year’s ARRL Field Day event I was looking to put up a homebrew antenna that was easy to construct‚ easy to deplay‚ and give me multi-band support. I settled on an 80 meter Off Center Fed Dipole antenna. Watch the video to see how I do it:
The OCF or Off Center Fed Dipole antenna is much like a conventional dipole antenna in that the formula you use to calculate the length of it is the same. That is: 468 / Frequency Mhz will give you the overall length of the antenna. For a conventional antenna I would normally split this wire in half and place a feed point in the center. Doing so will give you classic antenna with single band coverage.
![](https://www.jpole-antenna.com/wp-content/uploads/2020/07/OCF-Antenna-Plans.jpg)
The benefit of an Off Center Fed antenna is that if you move the feed point away from the center‚ you can find a spot that will allow the the antenna to resonate on multiple bands. So if we move our feedpoint so that one leg of the antenna is 1/3 long and the other is 2/3 long‚ the antenna will now resonate on 80‚ 40‚ 20‚ 10 and 6 meters usually without a tuner. Using an antenna tuner will give you the other bands: 30‚ 17‚ 15‚ 12 with not a lot of losses. Normally as you move the feed point of the antenna the impedance will change‚ so you will need to use a 4:1 current balun with this antenna.
Finally‚ if an 80 meter antenna is too long‚ as it is 133 feet in this example‚ you can use the same formula to build a 40 meter version which will only be about 67 feet long. You’ll forgo one band‚ but you’ll end up with an antenna that is easier to deploy.
Links/items mentioned in the video:
MFJ 913 4:1 balun: https://amzn.to/3hplfbn
Isotip butane soldering iron: https://amzn.to/3e1QWFJ
Rigexpert AA-600 antenna analyzer: https://amzn.to/3e2RoUa
Weaver Leather Throw Weight: https://amzn.to/2CigRek
Support Ham Radio Q&A by shopping at Amazon: http://amzn.to/2kO6LH7
![](https://www.jpole-antenna.com/wp-content/uploads/2020/07/OCF-Antenna-Pin-683x1024.jpg)
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