Jazzsinger, you do have a point. it is commen antenna knowledge.
Shockwave is always quite enthousiastic about sirio (nothing wrong ment with that though)
im sure he is very enthousiastic about other things aswell.
Attached you can find the different eznec diagrams of the antenna at 27,5 Mhz.
There is over a dB "loss" if one does not change the element spacings.
But only element length.
If one doesnt change the element spacing but only the element length
The entire antenna becomes too high in frequency.
The best gain and FB would be around 28 Mhz and so is its resonant frequency.
(with only the different element sizes)
The impedance drops to about 18 Ohms at 28 Mhz. At 27,5 a reactance comes into the game and optimum performance cant be expedted.
Ofcourse it would be possible to match the antenna but in that case it is again a beautifull antenna with a beautifull SWR but with less than optimum Gain and FB figures.
Im not sure if it is easy to change the element spacing or not of that antenna.
If not, a answer from Sirio refering to the original spacings and only (optimal)different element lengths would be more appropiate, as im sure one is able to get 7,5 dBI around 25 dB FB and a resonant frequency of 27,555 without changing the spacing.
Perhaps specific question towards them will give a answer.
Otherwise there are quite a few on this forum who could model it.
Element diameter in this case doesnt effect the antenna in a way one can notice.
It will be difficult to measure if that is possible at all.
Kind regards,
Henry
11 meter Dx antenna systemx
