4 Element Vhf Yagi Antenna

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4 Element Vhf Yagi Antenna

Satnam Singh VU2COR


Yagi-Uda antenna commonly known as Yagi antenna, is a directional antenna consisting multiple parallel elements in a line. The driven element or the radiator is a half wave dipole which is connected to the receiver or transmitter with a transmission line. Parasitic element are placed near the driven element with some space in between them.

In this article, we are going to make a simple 4 element yagi antenna for vhf 2m amateur radio band(144-146 Mhz) which can also be used for 70cm band.

Design

Dimensions(cm)

Dimensions

Element

Position (mm)

Length(mm)

Reflector

0

1016

Radiator

260

980

Director 1

470

924

Director 2

985

890

*Element length for 6mm pipe only*

Material needed

1. Aluminum pipe(6mm)
2. Wooden boom (120cm*5cm*3cm)
3. 5 screws to hold the elements
4. 25mm Pvc pipe(5cm)
5. RG58u coaxial cable for making a 5 turn choke
6. Rf connector as per your requirement
7. Wire terminal for feedpoint.
8. SWR meter/Antenna analyzer

*Note:- You can also use pvc pipe as boom*

Tools needed

1. Saw/Cutter for cutting the elements.
2. Hand drill with drill bit as per the diameter of the elements.
3. Soldering iron 
4. Measuring tape
5. Screwdriver 

Construction

Coaxial Choke
1. Mark the element spacing on the boom and drill in the boom.
2. Measure and cut the elements to the length given in the design
(You can cut extra length for driven element  for adjusting SWR)
3. Drill hole at the center point of the elements to hold them in the boom using screw.
Feed Point
4.Place the reflector, director 1 and director 2 in the boom and secure them with the screws.
5.Cut the driven element into two quarter wave elements of 49 cm each. Place both the elements in the boom with a gap of 10-12 mm between them.
6. Make a coaxial choke of 5 turn over a 25mm pvc pipe using 40 cm (not critical) of rg58u cable as shown in the image.
7. Connect/solder wire terminals to center conductor and braid of coax and connect the feedline to the driven element with screws.
8. Connect/solder any rf connector to other end of the feedline as per your choice.
9. Check SWR of the yagi for 2m/70cm band.

 
As per DK7ZB current profile of this yagi, 3 elements are working on 3/2 lambda mode as direction antenna on uhf band. It will show SWR<1,5 from 430- 440 Mhz with 4dBd gain and 7dBd gain on 144 Mhz band.







I am using it for mobile setup as well as for satellite communication and it is giving good results. If you make one, feel free to share your experience with me.

Regards
VU2COR
Satnam Singh 














Comments

  1. Zeky12 September 2020 at 13:19

    Hi. I use same dimensions but antenna design from https://www.iz2uuf.net/wp/index.php/2013/04/06/100g-yagi/
    Reason is antenna is very light and all elements can be put into boom.
    the reason why I used dimensions like yours... I simplified parts, so I dont use choke, but I use very short rg174 with sma connector which is also stowed insid of boom.
    You can se it in action here https://www.instagram.com/p/B7gTLhyJwTj/?igshid=1aalscrs55pdy
    another difference, I use extension section from same pole which I hold in my hand, together with microphone, and my ft1d is hanging on boom with cable
    tie. Left hand is fre for typing log on my asmartphone.so all elements just put in, extend the pole, connect radio and im ready no mast, long coax(more weight)etc
    Regards from 9A3DZK

    ReplyDelete
  2. Unknown22 February 2022 at 13:03

    Hi
    I am Shahi from P U Chandigarh with very similar hobbies, would like to talk to you about all this
    please give me a miss call on 9815612645
    Regards
    Shahijs

    ReplyDelete

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