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The 440mhz Slingshot Antenna Project by N9YBP

Here's the details on the antenna I threw together patterned after the 2 Meter Slingshot and scaled for 440mhz..

The Problem:
I had a mag-mount antenna in my attic and could not reach a 440 repeater to my east. 
Even when I went to 35 watts, I still received bad reports.  I needed an antenna with some directivity that I could point east.  I still wanted to hide the antenna in the attic.  I saw the Slingshot antenna project on the Hamuniverse website and wondered if it could be cut
down to 440 Mhz from 2 Meters. I assumed the 2 Meter drawing was for 146 Mhz. 
I added 5 Mhz to the repeater out frequency and came up with an ideal, (input), frequency of 449.300Mhz,  then I simply scaled the elements as follows,
(This is a neat trick below worth remembering.....Editor)

(146/449.3) x 20 = 6.5 inches  (20 refers to original length on
2 meter Slingshot.....Editor)

(146/449.3) x 40 = 13.0 inches  (40 refers to original length on
2 meter Slingshot.....Editor)

I reduced the 4 inch measurement between the horizontal legs to 2 inches.  I have no logical way to describe how I came up with that.  It just looked right on the workbench.
A Parts List:

One (1) Piece of wood, 2" x 4" x 16" long
Two (2) End cap for 1/2" copper pipe
Two (2) 90 degree elbow for 1/2" copper pipe
Two (2) Vertical element cut from 1/2"copper pipe
Two (2) Horizontal element cut from 1/2" copper pipe
Four (4) Clamps to hold horizontal element to 2 x 4



1. I cut the 2 x 4 to the length of 16".  Obviously this is not critical.

2. I cut the elements so that their overall length matched the
dimensions on the drawing.
I do not remember the blank lengths.

3. Solder the horizontal element to the elbow and then the vertical element and then the cap on top of the vertical.

4. Mount the elements to the board using four clamps.  I purchased these clamps at the same place as the pipe, elbows, and caps. 
I had to squeeze the clamps to make them hold the elements to the board.

5. While screwing down the clamps I placed the electrical connections under the innermost screw and made the connections by simply tightening the lugs under the screw.

6. Next I placed the antenna in the attic and ran the coax to the radio room.  I tested the SWR and found it to be 1.25.

I did no adjusting or trimming.  The antenna worked fine "right from the box".
The repeater of choice was easily hit with only ten watts of power.
Signal reports are good. "This antenna was such a success, it kind of put the fun back into ham radio for me. That's it. Hope this helps others. Tom N9YBP


View 2 Meter Slingshot Project here


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