Slim Jim (J Integrated Match J-Pole) is probably the most easiest and powerful 2 meter antenna to build provided you have the exact measurement and material to build it.
This how to will show you how to build a 2 meter slim jim antenna from ordinary insulated copper wire commonly used for carrying AC (alternate current) electricity in your household.
Slim Jim construction basic
I am not only going show you the measurement of slim jim antenna for specific frequency, but I’m going to show you how to calculate slim jim antenna by your own using the basic formula below.
The figure above shows that the longest side of slim jim is 3/4 wavelength long and the shorter side of the slim jim consist of 1/2 wavelength and 1/4 wavelength long seperated by a gap.
The feedline (coax cable) is normally connected 1/20 wavelength from the bottom of the slim jim antenna with the center conductor connected to the longest side and the shield/braid is connected to the shorter side.
Building the Slim Jim antenna
This guide assume you want to build a slim jim antenna that centered on 146MHz.
Calculation
The formula for calculating wavelength in metric system is 300/(freq MHz)
Using the formula from the figure, we have :
300/146 = 2.055 M
Wavelength = 205.5 cm
Wavelength x copper wire velocity factor = 205.5 cm x 0.94
= 193.17 cm
3/4 wavelength = 193.17 x 0.75
= 144.88 cm (57″)
1/2 wavelength = 193.17 x 0.5
= 96.585 cm (38″)
1/4 wavelength minus gap = 193.17 x 0.25 – 2.6 cm
= 45.69 cm (18″)
Coax tap = 193.17 x 1/20
= 9.6 cm (3 3/4″)
Building Materials
- 3/4″ diameter PVC (20mm) – 6 feet (180 cm)
- ordinary insulated copper wire for carrying altenate current (AC) – 11 feet (3.40 meter)
- Cable ties
Tools
- Soldering iron
- Glue gun
- Somthing to make a hole on PVC pipe
Wire Slim Jim Building Steps
- First take the PVC pile and measure it according to the 3/4 wavelength formula above (144.88 cm).
- Make two holes at the opposite side of the pipe. This hole is used for putting the copper wire through the pipe. Repeat this step 144.88 cm away from the top hole. Both of these holes will hold the copper wire.
- Insert the wire through the hole until both end reaches each other on one side of the PVC pipe. Then measure the length of the wire and cut the wire on that side so the setup resembles the figure above.
- Cut the wire insulation (but leave the wire uncut) 1/20 wavelength away (9.6 cm) from the bottom of the PVC pipe, again refer the figure above.
- Solder the center of the coax cable at the longest side of the slim jim (3/4 wavelength part) and the braid/shield at the shorted part of the antenna.
- Test the antenna using SWR meter to ensure that its SWR is at minimum or within acceptable level.
- There you go, you’ve build yourself your own 2 meter Omnidirectional Slim Jim antenna for less than USD2 (RM 6.00)
2 Meter Wire Slim Jim Antenna in action
Hafiz, saya nak tanya sikit. Sesuai atau tidak kita gunakan dawai aluminium yang dikupas dari kabel elektrik hitam yang bekal letrik ke rumah. Setiap urat dawai tu lebih kurang sebesar lidi.
Thank you for this idea i will try to build.
thanks for this idea i’ll try to make it on my very own
hi,
i homebrew this one. its very good .simple electrical wire using this antenna.i assambled one.now i am going on air to contect vu2tcd reapeter in south india.
tnx 73’s de vu3dng
october 17th 2010at 8;00am
what about the formula of the element spacing or the space between 3/4 wavelenght and opposite? thus it seriously matters? coz im planning to build an uhf slim jim using bronze rods and i will not be using the pvc pipe…….. 73’s
willywilly, the spacing is around 3/4″ because I use 3/4″ PVC pipe. Hope that help you
– 9W2WTF
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Hi, Had nothing to do and I’ve heard about this antenna so I decided to build one, changed the frequency to 145.750 Mhz, took me about 1 hour to build it, most of the time went to find my drill, tested to our repeater which is approx. 41 km away from me and only 10W, height to feeding point about 2,5m from the ground, worked perfectly, full signal strength from the repeater.
And all building materials in the scrap box so the cost was nill,
73 de SM2WGV/Esa
This is a good design, It handles the 65 Watts power my radio puts out; I think it should handle more but I could not test it for more output power.
I made 2 of these. Both are a little modified but I kept to the basic design.
The first one is modified to be a 2m/70cm dual band and the other one is 2m mono-band as per design as described.
I made the second one specifically for on the road mobile use in a fiberglass body RV which has little to no ground-plane available so a conventional 2m mobile antenna would have several difficult issues to overcome (if even possible).
The main difference from the design on the mobile use one I built is the ~ 300 Ohm string of #43 Ferrite beads at the antenna’s feed-point; otherwise it is mostly identical.
My minimal write-up of what I did for that is @:
https://forums.qrz.com/index.php?threads/home-brew-2m-mobile-antenna-for-fiberglass-body-rv.525089/
Thanks for your write up
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