Two ways to Build a 6m 2-Element Yagi
Here’s a nice little starter project for anyone wanting to get some directivity on 6m. For 6m, the antenna is small and compact with a boom length of around 0.75m length and can be turned with the smallest rotator. You should be able to build this for around £30 – maybe less.
Two element Yagi designs come in quite a few different flavours. The constructor has the choice of either a ‘driven element and reflector array‘, or a ‘driven element and director‘ setup. There’s not a huge difference between the two.
The ‘Classic 2-element‘ Driver/Reflector design has been around for many years. It’s simple to construct and uses a hairpin match to bring the natural impedance of the array [around 30 ohms] down to the required 50 ohms match at the feed point. Our design pictured above is typical with a boom length of 75cms and distance between the elements of 60cms. Bandwidth is nice with well over 1MHz 1:1.5 SWR band edges and gain is quite high at around 6.50dbi although the front to back ratio is only around 11 or 12db at best. Saying that, it’s a low ‘Q’ antenna, meaning it’s forgiving under varying weather conditions and you are unlikely to get much [if any] swinging in SWR during rain or damp conditions.
If you felt the resonance was slightly low, constructors could reduce the end tips of the driver and reflector by 1.25cm on each side which would push the resonance up the band by about 300-400KHz making it nicely useable up to 51MHz and beyond.
Click here to download the data sheet 6M2 YAGI LIGHTWEIGHT CLASSIC
As an option, builders have the choice to build a Driver/Director version which has similar gain, but with a little better front to back ratio [but a slightly reduced bandwidth] – so a trade-off exists. Online sites such as DK7ZB [highly recommended] show this type of antenna and also offer builders the dimensions. We modelled the original figures but made some minor adjustments mainly due to our use of different diameter tubing that was also telescopic [12 and 16mm]. We also set the center frequency slightly higher at 50.300Mhz.
DK7ZB also offers a solution to match your antenna to 50 ohms by using a coaxial balun transformer. The transformer you require is the 28 to 50 ohms match which uses 2 x 75 ohm lengths of coax [in parallel] to construct a fully symmetrical match.
Remember, when building the match – you must take into account the velocity factor of the coax. If all this seems a little overwhelming, then alternatively, you can use the ‘Hairpin Match‘ shown above which will also do the same job in providing a match to unbalanced coax, but you’ll need a feed point 1:1 choke balun – so a couple of choices.
Click here to download the data sheet 6M2 YAGI by DK7ZB
Click here to download the EZNEC file for the DK7ZB Yagi