Thursday, 29 January 2009

Multi-band loft-mounted dipoles for 40, 20, 17, 15, and 10m

Amateurs are always after the Holy Grail - an antenna that will work on all bands, is inconspicuous, effective, but above all inexpensive. Unfortunately, you seldom find something that fits all these factors.

This antenna has nothing new about its design, but it does bring together quite a few useful ideas and characteristics.

These are:

• Fully no-tune antenna system for five popular HF bands

• Suitable for SWLS, QRP, M3 licensees and PSK31 operating plus occasional useup to 100W, but watch out for RFI at high powers. DO NOT USE A LINEAR!

• Uses non-inductive (zig-zag) loading for 40m

• Feed point balun reduces RF pick-up and interference making it quiet.


  1. Another interesting idea. My approach to HF operation in an attic that looks about the same size as yours is to use the G3OJV 80plus2 design from Waters and Stanton. It is a full-size dipole on 20m, linear loaded on 40m, and end loaded on 80m. I plan to add extra elements for 15m and 10m later, when propagation makes those bands actually useful. The bandwidth is pretty narrow on 80m and performance is quite a bit worse than a full size dipole, but if you know of a better solution suitable for an attic that size please let me know!

    1. Using a Carolina Window 40-10m in the loft works great, especially on 40m.

  2. Hi Steve, I ran across this today while researching alternate attic (loft) mounted HF antennas. Previously I was using a half-wave 40m dipole, bent in a "Z" shape to fit the space. I didn't have it properly supported at the feedpoint, so after a couple years' usage it malfunctioned. I replaced it with a center coil-loaded 40m, and it's nowhere near as good.

    So finding this was very intriguing. But I have some questions I was hoping to ask about.

    Specifically - my house runs dead-set E-W, meaning my roof slopes to the N and to the S. Would there be a difference in putting the rafter-mounted 40m antenna on the North side vs the South side?

    Second, I'm thinking of adding a half-wave 80m along the opposite rafters. The attic over my garage is at a right angle off to the North of my house. Would bending the 80m dipole into an off-center fed horizontal L cause significant issues?

    Lastly - and most importantly -- did you have to lengthen the dipoles on the rafters at all to account for the bends?

    1. Hi. I don't think it will make much difference what side of the rafters you use. The relatively low height means the antenna is a bit of a cloud warmer anyway. That is, the radiation will be mostly straight up.

      The 80m antenna is even more of a compromise so I don't think it will make a difference.

      From memory I don't think I had to lengthen the dipoles. If anything I think I had to shorten them. The only way to know is put it up and test it. You can always extend the dipoles with electrical connectors. Let me know how it goes.