Ham Radio News!
Ham Radio Videos!
HF & Shortwave
RFI Tips and
Support The Site
Vhf and Up
The 440mhz Slingshot Antenna Project by
Here's the details on the
antenna I threw together patterned after the 2 Meter Slingshot and scaled
I had a
mag-mount antenna in my attic and could not reach a 440 repeater to my
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
(146/449.3) x 20 = 6.5
inches (20 refers to original length on 2 meter
(146/449.3) x 40 = 13.0 inches (40
refers to original length on 2 meter
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
Two (2) 90 degree elbow for 1/2" copper pipe
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
THE END RESULTS!
Construction: (SEE DRAWING BELOW FOR
1. I cut the 2 x 4
to the length of 16". Obviously this is not critical.
cut the elements so that their overall length matched the
on the drawing.
I do not remember the blank lengths.
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.
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
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
DEUTSCHE GERMAN VERSION BELOW- Sorry, no
View 2 Meter
Hamuniverse.com uses Green Geeks Web