Hi Gianfranco,
The results are too good to be true
I felt vicarious pleasure being to be able to copy and paste that happy comment!
Regarding the last table of results I posted that you have asked me to check, the significant difference would likely be feeding it from the bottom directly against ground as per your test. That latest 'guesswork' model was with the feed arrangement at the top of the vertical, all my other figures and models were with the feed point at the grounded end of the vertical.
Trying to guess the layout of your earth wire and the 2m extra horizontal piece wouldn't help, but then I'm also not sure of your wire layout at the far termination end.
One of the Beverage characteristics is that short bottom fed vertical wire radiator (in your case being 6m) so a meter or two of spare wire is a reasonable percentage of that distance and thus may influence behaviour more than expected.
Feeding it at the bottom seems the logical thing to do, you could stick to HF and put your favourite balun / transformer outside at the feed point and use a nearly invisible run of RG174 or similar for the run inside, it's useful stuff, I use a bit of it.
Alternatively bring in a run of 300 ohm ribbon from the bottom feed point so as to keep your frequency options open and play balun swapping inside?
BTW when playing with creative antenna layouts I always keep reminding myself that
the radiated electric field strength E is proportional to the integral of the current distribution along the antenna. The current at the center is just the driving current I=I0e−it and the current must drop to zero at the ends of the antenna, where the conductivity goes to zero. For a short antenna, we can make the approximation that the current declines linearly from the driving current at the center to zero at the ends
From the link below, couldn't find a shorter one but the whole article is interesting, skipping the maths and just going for the meat!
https://www.cv.nrao.edu/course/astr534/ ... heory.html
In other words the part of an antenna that radiates the most is the part where the current is at it's highest and as the current swings to zero, the voltage swings to it's maximum. So the radiation diminishes, following the sine wave voltage/current transformation curve along the antenna. High current + maximum radiation at the centre of a dipole, high voltage and no radiation at the ends of a dipole.
In your antenna the high current part is supposed to be at the bottom of and in the short vertical because that's where it is meant to be fed, my guess is that's why it's vertically polarised as per the model though that would only be the majority, there obviously would still be plenty of horizontal. And as we know transmit and receive current flows and hence radiation patterns behave the same way.
That's why the ends of a dipole can be bent around or drooped without too much compromise and also why loading coils at the bottom of shortened verticals make such antennas incredibly inefficient - not only do they consume lots of precious RF by turning it into heat by virtue of their radiation resistance / impedance losses but also they simply eliminate a huge swathe of the antenna's ability to radiate anything. Even the best screwdriver or mobile antenna on HF radiates almost nothing, all it has left is just the tiny tip! So much for mini-whips on HF! / end soapbox
--
So you are now officially on notice about the importance of those loose wires coming in your window and the part they play, the mathematically perfectly equal current flow† on that insignificant looking blue ground wire is radiating just as much RF as the current flow on that insignificant looking extra 2m of "antenna" wire, starting at the current maximum at, your balun
Sincerely, Phil
† except for the other currents we'll politely ignore (both transmit and receive) on any coax braid inside the house and USB braid and internal earth wires, all also happily radiating.