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3 element antenna for 2m VHF

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raynerd:
After passing my Foundation Licence only a few weeks ago, I wanted to work SSB on 2m and my roof mounted vertically polorised colinear X200 clearly wasn`t up to the job. I decided to try a homebrew 3 element Yagi, the dimensions and details were all provided by Neil, many thanks:

1. Reflector - 1040.6mm long and fixed at the end of the boom.
2. Diven element - 2 lengths of 475.3 - 10mm gap between them. each individual part of the driven element is insulated from the boom and each other.
3. Director - 842.8mm long and fixed to the boom 737mm from the reflector.

I started of with the parts: 12mm steel rod - 2m length, 12mm steel rod - 1m length, 20mm square ally tubing - 1m length, 20mm dia clear acrylic bar.



I then started on the driven element, making my acrylic insert that would slide into the 12mm tubing and provide a 10mm insulated gap between the two. They needed to be a tight fit so that the driven element would remain rigid as one despite the gap.
 




The insert in one of the sides of the driven element:




Both connected, nice and tight fit and they felt pretty rigid:



Then the driven element was mounted in a box to protect the cables and insulate from the boom:



I then needed to produce some sort of insulating mounts to hold the elements correctly on to the boom. I had some plastic mounting blocks knocking around, so using a 12mm drill I drilled a half circle into a couple of these:





I bolted the elements onto the boom and there it finished - a 3 element Yagi for use on 2m. A brief test portable showed it to work really well but I`ll post more when I have tested again.

HS93:
I used a similar design to use it for fox hunts some years ago they work well,

congatulation on the pass by the way

Peter

G0PAH

Brass_Machine:
Heya Chris,

Fixed some tags in your post so all the pictures would show. Congrats on the pass!

Never got into radios... did help a guy put up a 20' ft antenna in his yard though!

Eric

shoey51:
Congrats on the pass mate.
what did you use as a balun mate :scratch:
job looks good :thumbup:
If you get yourself a copy of the RSGB book it has some great tips there for making antenas :D

73's Graham

andyf:

--- Quote from: craynerd on April 29, 2010, 07:04:27 AM ---I then needed to produce some sort of insulating mounts to hold the elements correctly on to the boom. I had some plastic mounting blocks knocking around, so using a 12mm drill I drilled a half circle into a couple of these:






--- End quote ---

I'm not sure it was necessary to insulate the director and the reflector from the boom, Chris. It's 30 years since I passed the RAE, but I seem to recall that there is a current "null" in their centres.

Andy

PS Have just looked at an old TV Yagi. The directors are connected (both physically and electrically) to the boom by self-tapping screws.

PPS Why are those furniture connectors called "modesty blocks"?

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