6m Yagi - YU7EF EF0606
12 November 2020
With the summer 6m DX season fast approaching and having no 50 MHz Yagi on hand, I had a look at some popular designs for a quick solution. The YU7EF EF0606 Yagi is a scaled version of the YU7EF EF0206 Yagi that I built and tested in early 2019 ... and there just happened to be a suitable boom for the 7m boom length version of the 6m Yagi in the 'antenna graveyard' behind my shed. A quick dabble with 4NEC2 showed a promising result:
Material in 'full lengths' for 6m Yagi elements was in short supply, so checked with 4NEC2 if half lengths of 3/8" diameter aluminium tube could be joined with 3" long center sections of 1/2" tube without requiring a significant 'taper correction'. The difference was insignificant, so the 5 parasitic elements were built accordingly. In addition, 8" long 1/4" diameter aluminium tube inserts were added at the middle for extra strength at the 1/2" to 3/8" tube transitions. The tubes were permanently fixed/locked together using a crimping tool.
A 'Metallic Boom Correction Factor' for the element mounting system used (Nuxcom) was not added because previous experience with them indicated that the Yagi response would move 'up the band' by about 100 kHz which would suit the new axis of activity with FT8:
A pre-assembled split dipole driven element also came from the 'antenna graveyard', and a DG7YBN coax line balun (the 'Pro' Version) was made from RG-141 Teflon coax with some suitable ferrite cores (4 x Fair-rite 623-2643625202 and 5 x Laird 28B0375-000):
The Yagi was assembled and mounted on a mast located at the edge of a gully on our property that would increase the effective height of the antenna in the direction of South America to about 2 or 3 wavelengths on the 6m band:
Here is the final result as measured in the shack with a SARK110 antenna analyser. Two resonant points (X=0) at 50.170 and 50.400 with very low reactance in between :
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