Tuesday, April 9, 2019

The quest for a homemade multiband beam

The butternut HF5B I use now.
I've been looking for a multiband directional antenna since my antenna tower is finally standing. I've seen several commercial options, some of them are expensive, some less expensive. Last year I had the opportunity to buy a commercial made HF5B antenna. It's a 5 band antenna 20,17, 15, 12 and 10m. It should be directional on 20m, 15m and 10m and a dipole on 17m and 12m. In reality I found the antenna only being directional on 15m and 10m actually, on 20m it is behaving like a dipole. I would like to have a antenna with some more gain and a good front/back ratio. Most ideal would be a antenna like the SteppIR urbanbeam but the price is much too high for a average radioamateur like me. Ultrabeam makes similair beams for example the 20MX which is sold for about the same price as the SteppIR.





LZA10-5 with  a price of only €470 a good alternative
if room is no issue 
A bit cheaper are the aluminium beams like the Force12 XR5, LZ antenna 10-5 or Optibeam 10-5M.  But viewing the specs of those last 3 I think it's just as good as the HF5B. No one will ever see or hear the difference between 3 or 4 dB gain, however front/back ratio will be much better I guess. Even cheaper are multiband wire beams like the hexbeam but due to the unusual shape it is not always a antenna for everyone. Let's be honest, look at the specs from all these wonderfull antennas, they all have nearly the same specs which are not even far away from the HF5B I have in my tower now. Buying or building a multiband beam with better specs is just a dream which will never come through. But building my own antenna would be just more satisfying! So, that is what I'm going to do. Building my own 5 band directional antenna with specs that are as good as a commercial one.

Since a fullsize horizontal 5 band beam is no option here I'm thinking of a alternative by using lineair loads or capacitive hats . I've used the lineair load principle on my alutape multiband vertical in the past with success. There are several designs that can be found but which one suits me best? I think it is a trail and error path because what works well at someone else could be not working at all at my QTH. Other possebilities are capacitive hats and helical loading. I have to investigate these options. I don't like antennas with coils so that is something I absolutely want to avoid.

Best photo I could find from a 3 band BBQ quad
Another option is to build a 5 band cubical quad. I made quads in the past and also used a PDL2 quad on 11m and 10m. It was all with mixed success. The homemade quads didn't do what I expected and the PDL2 quad did but was of course only suitable for just 2 bands. The nice thing is that quads don't need that much height to work well on DX. The width of a 20m quad is about 5,5 meters measured from side to side when the antenna is configured as a cubical. That is reasonable and I think I can have it in the mast. If it is still too big I can downsize it using lineair loads. A good example has been made by Degen BBQ quads in the past. However as far as I know they don't make them anymore, at least they are not listed on their website. The concept is interesting though especially for those that have not much room. The lineair loaded 20m quad is only 3,4 meter wide.

I will study these options and there might be even more? Anyone have any ideas? I prefer to build the antenna by myself but any commercial option is fine, I guess it can always be build, However time is as always a issue. But as always....let me dream on...

7 comments:

  1. Hi Bas

    It might be worth considering the Moxon? Easy to build and the centre X will support different bands. Maybe try mono-band versions first to see what they are like? Supposed to have a very good F/B ratio. Also very cheap to make.

    John, EI7GL

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    1. Hello John, tnx for the reply. I considered a moxon but unfortunately it is too wide. I don't have room for a antenna which is 7,7m wide. Though I guess a moxon can also be downsized with lineair loading. Will have another look. 73, Bas

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  2. An interesting post, and something that I want to achieve at my countryside shack, too. A 20m quad is big, ugly (to neighbours) - and wine prone! I thought a 10m version would be OK, but when I built it, it was ridiculously big compared to a Yagi. I never deployed it.

    A variant on the quad is a Pfeiffer (linear loaded) quad. I never had time to properly test a 15m 2-element antenna I once built, but the 1-element version did work succesfully. Size reductions are potentially (if the antenna actually works!) dramatic.

    Have you thought about a VK2AQB beam? I suppose it's too much like the size of a Moxon, for which you say you have no room. I also don't know if it works very well. I guess if it did, we wouldn't be making the much more visually-intrusive Hexbeams!

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  3. Did I say 'wine prone'? Ha ha! Well, some wine usually helps antenna work!

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  4. Hello John, I agree a cubical quad has a visible impact on the environment. But I don;t care what my neighbours think about it. I've had a 84m long NVIS square loop around my garden for years, that was very ugly as well. I've been looking at the Pfeiffer quad as well and at the HB9CV quad. It could be a alternative though the problem with those antennas is multibanding. The VK2AQB is in fact a moxon. Some interesting designs are explained at DJ0IP's site. http://www.dj0ip.de/wire-beams/wire-beam-types/. 73, Bas

    You can keep the wine....;-) I prefer to stay sober doing antenna work.

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  5. Heb je al eens naar een logperiodic antenne gekeken:

    Acom heeft een 8 elements en ook Tennadyne.

    Ik heb zelf al jaren een Tennadyne T8.
    (zijn goedkoper dan multiband beams.

    Kees PA5CW

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    1. Hallo Kees, langste element 11m !!! Vergeet het maar! Kan ik moeilijk kwijt, in de lucht wel maar niet als ik de mast naar beneden heb. Ik heb er dus inderdaad al eens naar gekeken. Heb zelfs al bijna een T8 eens gekocht maar bleek achteraf niet meer te vervoeren omdat de boom niet meer uit elkaar wou. 73, Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas