This is a 2-meter, 4-element Yagi that is designed for a “direct connect” feed from coax. The design came from The Antenna Elmer: Beam Lengths
The dimensions I used with calculated performance are below:
2 Meter 4 element beam center frequency 146.52 MHz, 1/2" diameter tubing
Element----------Element Length----------Element spacing from Reflector
Reflector--------------38-1/8"--------------------------*****
Driven-------------------36"-----------------------------24-1/4"
Director 1-------------34-1/2"----------------------------49"
Director 2-------------34-3/8"-------------------------71-1/2"
Freespace ----------- Over ground 30 feet
Gain: 8.43 dbd -------------- 10.34 dbd @ 5 degrees, 13.71 dbd @ 10 degrees
F / B 13.32 db -------------13.60 db at 5 degrees
The antenna is tuned by adjusting the main element’s length when building, but I plan to cut this one down a bit and add some threaded tube to the ends with lock-rings to accomplish field tuning, but it works just fine as-is. I used regular 1.5” SCH 40 PVC for the mast and the tubing came from the ground-plane tubes of a downed CB antenna. The D2 element was cut from 3/8” tubing, the others are ½-inch.
Below are some shots of the elements together and a close-up of the feed:
Below is a shot of the feed detail looking into the mast. The main element is made from two pieces with a nylon dowel in between, and screwed to the feedlines that wrap around to the SO-239 connector. I tightened the screws through the hole for the SO-239 with a ball-Allen wrench, then worked the SO-239 through the hole, where the coax PL-259 connector clamps it tight.
Finally, the SWR and Smith plots:
The antenna is a bit low on the band, but performs GREAT!
The dimensions I used with calculated performance are below:
2 Meter 4 element beam center frequency 146.52 MHz, 1/2" diameter tubing
Element----------Element Length----------Element spacing from Reflector
Reflector--------------38-1/8"--------------------------*****
Driven-------------------36"-----------------------------24-1/4"
Director 1-------------34-1/2"----------------------------49"
Director 2-------------34-3/8"-------------------------71-1/2"
Freespace ----------- Over ground 30 feet
Gain: 8.43 dbd -------------- 10.34 dbd @ 5 degrees, 13.71 dbd @ 10 degrees
F / B 13.32 db -------------13.60 db at 5 degrees
The antenna is tuned by adjusting the main element’s length when building, but I plan to cut this one down a bit and add some threaded tube to the ends with lock-rings to accomplish field tuning, but it works just fine as-is. I used regular 1.5” SCH 40 PVC for the mast and the tubing came from the ground-plane tubes of a downed CB antenna. The D2 element was cut from 3/8” tubing, the others are ½-inch.
Below are some shots of the elements together and a close-up of the feed:
Below is a shot of the feed detail looking into the mast. The main element is made from two pieces with a nylon dowel in between, and screwed to the feedlines that wrap around to the SO-239 connector. I tightened the screws through the hole for the SO-239 with a ball-Allen wrench, then worked the SO-239 through the hole, where the coax PL-259 connector clamps it tight.
Finally, the SWR and Smith plots:
The antenna is a bit low on the band, but performs GREAT!
