ZL1RS - Antennas

A 9 element Yagi for 6m

 

A 9 element Yagi for 6m

 

Built in October 2021 ... but please read the Foot Note at the bottom of this page.

 

Background: the F/R on the 6m5_3v array is not so good. As a result, 6m EME reception at moon rise to the east is ruined by local QRN to the south west that runs for 12 hours every night. To try and improve the situation, another antenna was built with a better radiation pattern, erected at a lower height, and located with buildings and higher ground blocking the noise source.

 

There are some very good "G/T" designs for 2m with very clean radiation patterns. Two of them from DG7YBN's excellent web site were scaled to 6m and the computer plots were compared against the existing 5/5/5 array. One was a 12 element 2m Yagi that scaled to a 20m long boom on 6m, and the other was a 9 element 2m Yagi which scaled to a 12.5m boom on 6m. The 12 element design would have provided 1dB more gain than the 5/5/5, but its 20m long boom would be impractical at our exposed hill top location.

 

The 9 element design had a little less gain than the 5/5/5 array, but a far superior F/R radiation pattern ...

 

 

In addition, the broader ground gain lobe of the 9 element Yagi at a lower height provides much longer moon rise and moon set 'windows', and a better chance of completing an EME contact ...

 

 

Material for the 9 element Yagi was recovered from the 'antenna graveyard' behind my shed. The elements were mounted well off the aluminium boom on HDPE blocks with Stauff clamps, so no Boom Correction Factor was required.

 

The DG7YBN design uses a bent driven element to increase the feed point impedance to 50 Ohms allowing a split dipole feed point fed with 50 Ohm coax cable via a Grounded Quarterwave Line concept Balun. I used RG-393 Teflon coax and several large, HF rated ferrite cores sealed inside heavy duty glue-lined heat shrink tubing ...

 

 

The Yagi boom is supported with two sets of top truss ropes and mounted at 7m high on a 60mm diameter steel pipe and a short 'stub mast' above a thrust bearing. The mast base is fixed to a wooden post with a hinge and was raised using the hydraulic 'arms' on my tractor. The antenna is manually rotated and fixed in position with a light rope tied to the back of the boom ...

 

 

The antenna was built to the nec file dimensions and produced the following SWR and Rs curves without any adjustment ...

 

The 'neigbour's noise source' has been reduced by about 10dB.

The wider ground gain pattern provides the longer moon rise and moon set 'windows' that were anticipated

(EME signals from 5 to 16 degrees of moon elevation)

 

Foot Note: After building this 9 element 6m Yagi, DG7YBN has released another of his fine designs with 9 elements on a similar boom length, but with a straight driven element which will simplify construction. The "YBN 50-9m Yagi with Straight Dipole".

 

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