Dual band 6m-4m Yagi based on 6jxx6 from Sandro I0JXX.
This antenna was optimized with the goal to minimize any changes
in 6jxx6 impedance/lobes.
The result is a 7 el on 70 MHz with a little loss of gain comparing
with the other monobands of the same lenght.
If you don't have so much space on your mast, like me, a dual
band antenna can be a nice solution.
I chose to separate the sources of the 2 antennas because i have
two rigs attached.
The 4m antenna has an impedance of about 27 Ohm, so we must
use a matching circuit.
The easiest way is to use a quarterwave line of
about 35ohm, achieved with a parallel of 2*75ohm cable.
I simulated the antenna with nec2 engine and the results are
very close to the real values.
Thanks to Sandro I0JXX for hardware and Pino IK0SMG for help
in matchbox assembling.