Re-edited by N4UJW from an
original article by David Younker
Please note in drawing that elements are bent 90 degrees. Make your bends as needed depending on material used for elements. If you use copper tubing, a 90 degree elbow on each should work fine. If you are comfortable with bending, great, if not, get the hardware store to do it for you!
The completed antenna is bi-directional with a rough figure
8 pattern and is composed of 2, 3/4 wavelength sections of electrical
conduit bent and cut to the lengths in the drawing and supported
as shown on any type of insulating material attached to the mast with
whatever arrangement of bolts, nuts, clamps, etc.
There is a more complicated formula first and then a simple version....take your choice...they both yeild the same result:
11808/freqmhz = 1 wavelength in inches
11808/147.00Mhz = 80.3 inches (using 147.00Mhz)
3/4 wavelength = .75 x 80.3 = 60.2 inches
Simple version formulas:
8856 / freqmhz = 3/4 wavelength section in inches (total element length)
5904 / freqmhz = 1/2 wavelength section in inches
2952 / freqmhz = 1/4 wavelength section in inches
11808/144.200 = 81.88 inches
According to the article, 15 meters is about as low in frequency as it can be used before it becomes very difficult to keep it up due to size and weight! (one element would be about 34.5 feet long according to my Texas Instruments model TI-7140 handheld calculator and the above formulas!) HI!
MODIFICATIONS, COMMENTS AND UPDATES!
Experimentation performed by LA2PJ of Norway taken from his email: (January 23, 2003)
Tonight I have tried a construction from your webpages,
The Slingshot Antenna.
Just soldered two wires to the end of a short length of coax and pinned it to the wall in my shack with small needles to get the correct shape.
The results were amazing! The direction of the wall is in the right direction to a distant repeater here on the west coast of Norway. Using an Alinco handheld with approx 1W, I was able to work through the repeater with full quieting. The distance is 94 kilometers (approx. 55 miles. The reports indicated that they could not notice the difference when I switched between this indoor antenna and a Diamond X-510 vertical on the roof. The SWR was 1.4:1 at 144MHz rising to 1.7:1 at 146 MHz, indicating that the antenna is a bit long.
But then the elements are made of 1mm stranded copper wire. Am thinking of a way to produce the antenna to be used outdoors.
If your offer is still valid, I would like to present this antenna in Norwegian at our web site.
Egil - LA2PJ
(I said yes to his request for adding the project to his site in Norway. Stay tuned here for the link when he gets it up and running for our fellow Norwegian Ham friends to enjoy.)
Editors note: Egil, LA2PJ, is the former Webmaster for the NRRL, the Norway counterpart to our ARRL!
Update from KC2GOA: The two meter slingshot works now that I made some changes. I had to change the spacing between the two elements to 1/2 inch and cut the short lengths to 19 1/4 inches and the long ones down to 39 1/4 inches and I came up with a 1.2 swr at 146.000mhz. 73's KC2GOA.........
[Editors note: The diameter of the elements and the spacing at the center insulator will play an important part in getting the antenna to resonate at your frequency of operation for lowest SWR. Some experimentation may be needed with your particular construction techniques!]
More updates: January 2004
440mhz scaled version by N9YBP CLICK HERE
From the editor: I hope you try this antenna project as is and if you are pleased with the results, please let me know,
and if you have tried any modifications to it and they worked a lot better in performance, please email me with them.
I will be glad to add them to this project with full credit going to you!
EXPERIMENT! EXPERIMENT! EXPERIMENT!
(See latest experiments with this antenna and input from builders next below.
MORE MODS FEBRUARY,
2005 BY ROY:
I constructed this antenna as per
KC2GOA’s latest dimensions. However I added an S0 239 connector between
the two elements for direct connection with coax with a PL259
I mounted the 239 connector on the PVC with a self tapping screw into the GAP between the antenna sides.
I then bolted thru both PVC and copper tubing with brass machine screws and nuts to secure the tubing to the PVC.
To make the connections to the 239
connector, I bore oversized holes into the PVC so that the screw head and
nuts would contact the copper tubing. I bought the brass screws long
enough - 1 ¼” - so that I could put two nuts on them; one to hold it to
the tubing and the other to act as a lug to connect a short piece of bare
#14 copper wire to. I then soldered the other end to the 239 connector. I
repeated that for the other side. This makes it a neat and clean
I use it as my east/west antenna as I already had built the Hentenna antenna that you have on your website for the north/south coverage!
They both work great! If someone wanted to mount this antenna right side up, they would need to put a PVC tee between the sides and point it downward! I used 12” of PVC pipe, but you could use it much longer and add more screws for better support in the vertical position!
73 N9AGT, Roy.
Editors note:Great work Roy! I'm sure there are other ways to attach the coax to the antenna........
an MFJ ANTENNA ANALYZER would help in tuning the antenna, but use what you have.......
keep experimenting and have fun!.......N4UJW
440 mhz Slingshot Scaled version
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