yagi_const

	VHF / UHF Yagi Construction

On this site are some Yagi designs for VHF and UHF. Most of the designs are from a German ham, Martin Steyer DK7ZB. His designs are very popular in Europe. The dimensions are given in metric. I could convert them but it is easier to just purchase a tape measure with metric/English units. It is easier to get an accurate length with the metric scale than in English units. It is easier to measure 1022mm than it is 40 7/32". On 440 antennas it matters if the elements are not exact, if you want to get the maximum gain etc.

Most of the designs I have chosen are for a Driven Element impedance of 28 ohms. This gives better gain and pattern than a 50 ohm design. It is easily matched to 50 ohm using two 1/4 wavelengths of 75 ohm coax in parallel. This design has the Driven element as a simple dipole (easier to construct & match).

The tubing in the design is metric, below is a table to convert metric tubing into our tubing sizes. Most of the time the only difference in the design is the bigger tubing is a little shorter (positions are usually the same).

_{_Metric}	_{_{English Units}}	_{_{Recommendations}}
3.2 mm	.126"	use #8 solid copper wire = .125" 1/8" Aluminum welding rods
4 mm	.157"
5 mm	.197"
6 mm	.236"	use 1/4" Tubing = .250"
8 mm	.315"
10 mm	.394"	use 3/8" Tubing = .375"
12 mm	.472"	use 1/2" Tubing = .500"

	For the 3.2mm elements I use 1/8" aluminum welding rods. They come in 3 foot lengths they are too short for the elements. I cut them at 20 1/2" and join them with 5/32" brass tubing. I use a piece of 2" tubing and then I crimp them using a coax connector crimper. This provides a very good mechanical connection. You can cut your brass tubing using a Dremel cut-off wheel (this will prevent warping the tubing).

	DK7ZB web site is: http://www.qsl.net/d/dk7zb/start1.htm

	Below are designs for Light weight beams. These can be made from PVC pipe and small elements. These antenna are usually used for portable operations. These are all 50 ohm drivers (no matching network).

	4 Element - 2M - 50 ohm - Light Weight

Element	Position	2.4 mm	3.2 mm	4 mm	6 mm
Reflector	0 mm	1022 mm	1022 mm	1020 mm	1016 mm
Driven Element	260 mm	977 mm (4 mm)	977 mm (4 mm)	977 mm (4 mm)	980 mm (6 mm)
Director 1	470 mm	941 mm	935 mm	930 mm	924 mm
Director 2	985 mm	921 mm	915 mm	910 mm	890 mm

	5 Element - 2M - 50 ohm - Light Weight

Element	Position	2.4 mm	3.2 mm	4 mm	6 mm
Reflector	0 mm	1038 mm	1037 mm	1036 mm	1034 mm
Driven Element	280 mm	995 mm (4 mm)	995 mm (4 mm)	995 mm (4 mm)	988 mm (6 mm)
Director 1	430 mm	959 mm	954 mm	949 mm	939 mm
Director 2	950 mm	949 mm	944 mm	939 mm	929 mm
Director 3	1480 mm	935 mm	929 mm	923 mm	912 mm

	6 Element - 2M - 50 ohm - Light Weight

Element	Position	3.2 mm	4 mm	5 mm	6 mm
Reflector	0 mm	1028 mm	1030 mm	1030 mm	1030 mm
Driven Element	260 mm	1001 mm (4 mm)	1003 mm	995 mm	993 mm
Director 1	395 mm	956 mm	952 mm	944 mm	940 mm
Director 2	845 mm	940 mm	934 mm	931 mm	927 mm
Director 3	1470 mm	940 mm	934 mm	931 mm	927 mm
Director 4	1980 mm	914 mm	908 mm	904 mm	900 mm

	7 Element - 435 MHz - 50 ohm - Light Weight

Element	Position	3.2 mm	4 mm	6 mm
Reflector	0 mm	341 mm	340 mm	336 mm
Driven Element	115 mm	336 mm (4 mm)	337 mm	335 mm
Director 1	165 mm	312 mm	310 mm	305 mm
Director 2	330 mm	302 mm	299 mm	293 mm
Director 3	545 mm	299 mm	296 mm	290 mm
Director 4	785 mm	302 mm	299 mm	293 mm
Director 5	960 mm	295 mm	292 mm	285 mm

	9 Element - 435 MHz - 50 ohm - Light Weight

Element	Position	4 mm	6 mm
Reflector	0 mm	337 mm	334 mm
Driven Element	140 mm	336 mm	332 mm
Director 1	195 mm	313 mm	308 mm
Director 2	365 mm	300 mm	294 mm
Director 3	610 mm	294 mm	288 mm
Director 4	875 mm	291 mm	286 mm
Director 5	1130 mm	291 mm	285 mm
Director 6	1385 mm	293 mm	288 mm
Director 7	1580 mm	280 mm	273 mm

	Notice that the only difference between sizes of tubing is that the bigger tubing is a little shorter, but uses the same position.

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