@OK1DOM wrote:
First of all, you have to choose, whether the antenna should be for local traffic, or on DX.
Year, exactly. We need to know, what is the antenna for?, only then can we construct it.
@OK1DOM wrote:
It is possible to put a telescopic mast of approx. 10 m on the roof. I don't exactly mean magirus, but such a clicker. This can be easily handled on the roof. A balancing member a is attached to the top 2 dipoles in parallel, one on 80m and the other on 40m.
So this is one of the worst solutions. It will be difficult to debug, in addition, parallel dipoles made in this way can give up to 1S weaker signal, than a single dipole – there are simply too many conductive things in that maximum radiation.
Nice, A workable and systemically clean solution is the use of the Open Sleeve technique. I described it in PE5/2011. The basics are covered in Gary Breed's patent K9AY US5489914. Pull out the dipole for 80m, parallel to it, a dipole for 40m. It doesn't matter, when it will be inverted V, important is, to make it symmetrical about the center. The default distance between them will be approx 120 cm. Throw the whole thing into MMANA and you can finish it there, but personally I would rather recommend 4nec2, which with the PM kernel runs about 5x faster and if you run the whole thing under Linux, it's even 2x faster. Of course, we only supply the dipole for the lowest frequency and that via a high-quality balun (here I would use e.g. 8 cont. RG-174 on FT240-43 toroid). The design of such an antenna is then on 10 minutes and above all it works and can be set very conveniently.
On the other hand, I have not been able to set up parallel dipoles with a common power point more than once, this is a deprecated level solution “gum editions” Svazarm, sri.