This has been tested to be a very good design. It is simple to make and is very reliable.
All elements should be made with Ø10 mm aluminum pipes.
The impedance of the antenna is 28Ω, so it is required to have BalUn with two 75Ω cables in parallel. See more about that in the BalUn section.
The critical for this model is that elements must be on the isolated standoff, but have connection with the metal boom on one central point. The screw should be Ø3 mm. Plastic isolator – standoff – should be maximally 3mm thick.