Diy Tape Measure Yagi Antenna for Ham Radio

Today we are going to build a Yagi antenna designed for 2 meter and 70 cm ham radio bands. It can be used to communicate with amature radio satellites or to assist in getting into that repeater that is just a little to far away.

I am currently attending Terre Hill Mennonite High School

To build this you will need:

Prerequisites:

• Access to a 3d printer
• A ham radio
• A ham radio license (if you plan to transmit with it)
• SWR meter (recommended but not required)

Components

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• 1x Extrusion 20x20x1000mm
• M5 Hardware (I bought a assortment)
• M5 T-nuts
• Tape measure (to be cut)
• 10 Ft Coax
• 1/4" 20 Heat set inserts (for tripod bracket)
• 22 Gauge wire

Tools Needed

• Tape measure (not to be cut)
• Soldering Iron
• Solder
• 3d printer
• Wire cutter
• Wire stripper
• Electrical tape
• Tin snips
• Sand paper
• Some kind of saw (to cut extrusion if you choose to)

For my dimensions I borrowed from KB9VBR's project. I also used an online calculator. The 2 meter side of my antenna is optimized for 145mhz, and the 70cm side is optimized for 437mhz. Feel free to modify parameters to fit to your design.

This step can be skipped! The extursion will just be 36 in instead a more concise 24.5 in length. By cutting the length at 24.5 1 inch of exturison will be saved on each side.

Using the dimensions you decide upon, cut the elements to the length they need to be. Danger! the cut tape measure can tend to be sharp! Add a piece of tape to the ends to avoid being cut by the sharp tape measure.

Print the parts and remove support materials. Sand parts smooth.

Print

1x Tripod Bracket

2x Driven Element Base

2x Driven Element Clamp

6x Normal Element Base

6x Normal Element Clamp

I placed electrical tape on both sides of the bracket that touches the elements. This provides a rubbery surface for the tape measure to grip against.

Put the hot soldering iron tip into the heat set insert and apply force downward untill the heat set insert slips into place. Allow time to cool before touching or applying pressure. Danger insert will be hot afterward

Begin by placing the Reflector elements one inch from the end of the extrusion. Asseble the antenna to the dimensions you chose building off of the first reflector. For the 2 meter side leave 1 inch between the driven elements. For the 70cm side leave 1/4 in between the driven elements.

First cut the coax at about the midpoint. Next split the center braid and the outer coating. Solder one to each side of the driven element. Connect the elements with piece of 22awg wire. (hairpin match) Tape up connections to tiddy up the build.

This step will not be possible without an swr meter!

It is recommended to do this in an open area!

Swr tuning:

• Chose a frequency in the middle of the band you plan to tune for.
• Call out on that frequency that you will be performing swr testing.
• Connect the antenna to your radio via the swr meter.
• Turn radio on low power mode (if you are using a high power radio) if you are using a ht with only a few watts it is most likely not nesecary. But for maximum safety It can be done.
• Key the radio
• The best reading possible is 1:1
• To lower the swr:
• Raise the frequency on your tranceiver. Call out and key.
• If the swr is better that means your antenna is resonent above your target frequency.
• To lower the resonent frequency, lengthen the elements at the gap of the driven element.

• If the swr is worse that most likely means your antenna is resonent below your target frequency.
• To raise the resonent frequency of your antenna, bring the elements together at the gap in the driven element.

SWR is only critical for transmiting.