VHF Optimized Yagi Antenna for the 6-meterband (50 Mhz)
RE-A50Y3
By Guy, de ON6MU

Click to enlarge (Hernan, LW5DTZ)

Schematic fig1

Highlighted


click to enlarge (Greg, SP5LGN) click to enlarge (Greg, SP5LGN)

 

 

Parts list for the long yagi antenna RE-A50Y3

Note: there are many ways to build your antenna and I'm sure some can come up with better mechanical designs then described here although the design and material used here is cheap and easy to find. Also, the diameters of the tubing described here is not too critical.

Links of interest:

Click to enlarge (Greg, SP5LGN)
Gamma-match

When the dipole is the driven element of a Yagi parasitic array, the impedance that appears at the center of the driven element will usually be quite different from that of the isolated dipole. The reason for this is that the Yagi antenna is equivalent to a number of resonant circuits tuned to different frequencies and coupled together. The self-impedance of the parasitic elements and mutual impedance between parasitic elements and driven element cause resistance and reactance to be coupled into the driven element.
A gamma-match tube act's like a capacitor. The "capacitor's" sole purpose, is to oppose unwanted inductive reactance. It is a series-tuned LC circuit between the coaxial cable's center conductor and the gamma's connection point at the driven element hence getting a pure Ohms resistance. So, a gamma match taps a point on one side of the center of the driven element and connects the feedline to that point through a capacitor. In this design a tube with a copper wire inside acts as air-spaced capacitor. Another advantage is to allow the center of the driven element to be directly grounded to the antenna's boom, making driven element assembly easier and no static build-up on the driver.

To tune the gamma-match to a desired frequency for best SWR you will need to experiment with the placement of the strap on the driver (feedpoint) and the position of the strap relative to the feedpoint.
If you build the yagi antenna according to above specs, then you should be pretty close (if not spot-on) to a ideal match.
Click to enlarge (Hernan, LW5DTZ)
How Hernan, LW5DTZ did the Gamma-match

Specifications ON6MU 50 Mc wide-spaced yagi antenna RE-A50Y10

Be sure to seal everything up to avoid moisture, corrosion etc...

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..................................... .Please take a look at my 50mc vertical antenna

This is how Greg, SP5LGN made my 50mc long-yagi:
click to enlarge click to enlarge Click to enlarge
please click the images to enlarge

Take a visit to Greg, SP5LGN his website:
http://www.sp5lgn.ampus.pl

Thanks Greg for the photo's!!

This is how Hernan,LW5TDZ made it:
Click to enlarge (Hernan, LW5DTZ) Click to enlarge (Hernan, LW5DTZ)
Thanks Hernan foir the pictures!



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