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I'd like to put up an antenna in my attic for the 30 meter band. My attic is about 55 feet/16.5 m long, roughly east-west. Does anybody have a recommendation for an inexpensive antenna, preferably homebrew? |
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N3JIM, my suggestion for you is that one of the easiest and cheapest antennas to make is a Dipole in an 'Inverted-V' configuration with the center insulator or Balun placed at the highest point in the middle of the underside of the roof, suspended by a hook if you can reach it or by use of a pulley for easy access to lower the center for maintenance or repair. Using #14 AWG THHN wire, each dipole leg will be approximately 22', 2 1/4" on each side of the center insulator/Balun for an antenna cut at the center frequency of the 30 Meter band which is 10.125 MHz. If you use 50 Ohm coaxial cable as your RF feedline, I also suggest that you cut the wire length of each leg about 1 foot longer than needed, so that you can attach the legs to end insulators at the 22' 2 1/4" length and check the feed point impedance by using a SWR meter. Adjust the leg lengths for the lowest SWR possible by shortening or lengthening the leg ends if needed to adjust the antenna feedpoint impedance for the best possible impedance match to the coaxial cables characteristic impedance of 50 Ohms. By checking the SWR meter after every adjustment you can observe the SWR created on your feedline by the impedance mismatch. If possible try to obtain a SWR of 1.5:1 or less, but anything equal to or less than a 2.0:1 will suffice. K4RFE Larry |
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Stephen, I would put a dipole or inverted vee in the attic fed at the center,you can fold it,turn it whatever just as long as it is not folded back inside each leg to close,then with a tuner ,tune the antenna for 20,17,15,12 and 10 mtrs it should work fairly good.Have fun. |
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Here is one site that was able to do it with confined space, but you might run into a snag with a height restriction... I'll update as I find things though. http://www.midcoast.com/~w1gql/hex/thirty.htm and another that might be useful with this Hope this helps, Stephen KJ4RAU Here is a quote from one of the forums about this subject "by W2DIP on March 22, 2007 Interestingly enough I have tried other dipoles but none seem to work as well as this one does. I have 8 antennas in the attic and have tested even more. It appears that there is no predicting what will work until you try it and then when you find the magical combination of antenna and positioning it just seems to work better than imagined." |
