432MHz 8 Element Quagi Antenna

432MHz 8 Element Quagi Antenna ...


How to build a 432 Mhz Quagi

The boom is made from wood.{Do not use any type of metal for this.} This boom length is 61 inches and 1/2 inch thick. Mark the boom as to where the elements are to be spaced and drill a 1/8 inch hole in the center of the boom material.After you have done all this apply a few coats of stain. This will preserve the wood from the abuse of the weather. Use #12 wire to form the quad elements. Cut the wire to the correct lengths (see chart below). The quad elements are supported at the top and bottom of the element with a Plexiglas strip with a hole centered at both ends. The bottom of the quad the feed point. Apply a little epoxy to where the wire passes through the support holes. An alternate method would be to place element in boom to correct position and use some Super Glue to secure the elements in place. The Super Glue will wick into the hole and should secure the elements properly. Either technique will secure the wire so it will not move around.

Next solder one end of the wire to the center of an type-N conector feed it through the holes in the Plexiglas and bend it into shape. Then finish the element by soldering the loop closed to the ground tab on the N connector. An alternative to the N-type connector to save cost would be to solder the coax directly to the feed point. Be sure to secure coax to boom or mast to prevent deforming the loop. Coax should exit perpendicular to loop element. On the reflector just solder to two ends of the wire together.

You will note that this is a balanced feed antenna which we are feeding using unbalanced coax. In practice this has not been a problem but if it is not in your nature to do this, you can place some ferrite beads on the coax to form an inline 1:1 Balun. Make sure the beads are good at 432 MHz. I suppose a coax 1/4 choke could also be used so check the ARRL handbook if you want to try one of these.

The directors are mounted through the boom. Epoxy or Super Glue them as well. They can be made from any 1/8 inch metal rods. Cut them to the EXACT size!

I used stainless steel welding rods which are available at a hardware store.

At UHF frequencies even 1/8 inch difference in length will make the antenna perform differently.

Element Lengths:

Reflector Loop:		28"		Number 12 copper, soldered closed loop
Driven Loop:		26.625"		Number 12 copper, feed point at bottom
Director 1:		11.7500"		1/8" Stainless welding rod
Director 2:		11.6875"		1/8" Stainless welding rod
Director 3:		11.6250"		1/8" Stainless welding rod
Director 4:		11.5625"		1/8" Stainless welding rod
Director 5:		11.5000"		1/8" Stainless welding rod
Director 6:		11.4375"		1/8" Stainless welding rod

Element Spacing:

End of Boom-R:		5.00"
R-DE:		7.00"
DE-D1:		5.25"
D1-D2:		11.00"
D2-D3:		5.85"
D3-D4:		8.73"
D4-D5:		8.73"
D5-D6:		8.73"
D6-End of Boom:		0.75"

Notes:		Total boom length approximately 61" long
		Boom width is 1/2" where elements go through
		Boom height can be anything from 1" to 2" tall
		Reflector & driven element support must be an insulator
		Small capacitance tabs, 1/2" x 1/2" could be added to driven element for tuning
		Tabs added 1/2 way between upper & lower support structure of loop on both sides

Credit for this information goes to n2kbk