I'm still looking for a good solution to build a 5 band quad. However I made some unsuccessful attempts in the past (27 years ago). The main problem is how to tune the reflector for max. gain/front-back. There are several tips that can be found on the internet, most are theoretically but in real life it almost couldn't be done. So in the end it's trail and error.A while ago I came across the DK7ZB quad. It's quite a different design and easier to build. The drawback might be the open line that feeds the director but when using a autotuner and a 1:1 balun it could be easier to accomplish. Another option would be connecting it to the ladder line of the inverted-V through a remote switch.The specs are almost the same as any other 2 element 5 band quad.
Specs of the DK7ZB compared to a Big Signal 2BS-5B tradional quad as example:
| DK7ZB | 2BS-5B | |||
| Band | Gain dBd | F/B dB | Gain dBd | F/B dB |
| 10 | 6,3 | 30 | 5.19 | 18,6 |
| 12 | 6,2 | 14 | 4,9 | 12,6 |
| 15 | 5,8 | 17 | 5,1 | 14,4 |
| 17 | 5,5 | 21 | 4,6 | 13,5 |
| 20 | 5 | 30 | 4,95 | 13,1 |
I just took the 2BS-5B as example since this quad is popping up everywere on the internet these days. But there are many other manufacturers selling 2 element 5 band quads with almost the same specs. I could have picked any other one as example.
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| PDL2 quad used in 2008 @PE4BAS |
it is a lot lighter as insulated copper wire. The main advantage of isolated cu wire is that it is cheap and strong. The disadvantage is that it is heavy, you need a strong construction to hold it. But to make a strong construction for a quad antenna is not easy. It is expensive as well if you want to buy special fabricated glasfiber tubes.
Personally I just want to experiment to see if this quad would be interesting to have in my tower. But it shouldn't cost me too much. So, the idea is to use cheap glasfiber telescopic fishing rods and 1mm alu welding wire because of the weight. This way the antenna might be a bit flimsy but good enough to test things. If the prototype antenna is doing the job for me I can always decide to invest more money in a final version.
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| Previous 1993 attempt to build a quad on 11m, it didn't work well... |
7 comments:
Hello Bas,
It's too bad the high bands are in such poor condition. Besides offering great DX possibilities, 10m was a good band for prototyping antennas (especially quads) due to the small size. If results were satisfactory, those techniques and results could then be scaled to other bands. 10m was a great badn for experimentation and will be again - someday...
73 - John
It all sounds very familiar, Bas! Strange that your 11m quad didn't work very well. I wonder why? I have a 2-ele 50MHz quad which is really perfect. The trouble with the lower band quads is the wind resistance they offer. There's no way I could use anything bigger than 6m from my QTH, unless it was tilted every time after use.
I agree John, 10m is still a great band to test antennas. But I have done a lot of experiments on that band already. I want to go to the next level. 73, Bas
Hello John, I did wonder why at that moment as well. Didn't have the experience I have now. After all I think, or am shure, I didn't tune the reflector well. I really didn't know how to do it in 1993. Remember there was nothing like internet, everything was from books and drawings others made. The PDL2 worked well though, but that is a complete different design and it was not home made. 73, Bas
good luck bas. i have a 10m quad in my garage...flat packed as too big for the qth..lol
Imagine Stu, this quad is twice the size of a 10m quad....73, Bas
yup thats a big beasty. i may one day turn it into a 6m quad when i move qth.its strong as iron with fibreglass spreaders.just couldnt get it onto the mast and mounted, too much weight !!
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