Ham Hints -
RFI Tips and
The 450 OHM Ladder Line Slim
By KE4NU - Alan Wilson,
Want to homebrew an antenna for 2M? Want
something that actually works well? Want to get it up and running in
an hour or less? Enter the slim jim variation on the jpole.
After researching the internet for easy antennas to build I
came across an article or two referring to a slim jim antenna.
Unfortunately, they were constructed out of copper tubing or
aluminum tubing which was too expensive and I didn't have any laying
around the shop. I also saw one using tv twin lead. Well, I didn't
have that either but I did have quite a bit of 450 ladder line
laying around. So, I decided to adapt the tv
twinlead project to mine using ladder line.
Construction (Refer to
1. Measure out and cut about 59
or 60 inches of ladder line.
2. Strip both ends (top and
bottom) about an 1/2 to 3/4 inch and bend each toward the
center so they will overlap each other.
3. After you overlap
the wire, measure the entire length of the antenna. Your shooting
for 58 inches total length after stripping and overlapping the
4. After achieving your 58 inches (give or take a half
inch), solder both ends.
5. Determine which end has the solid
plastic closest to end and put a hole through it so you'll have some
way of hanging the antenna. (cable tie)
6. On the opposite
end (bottom end), measure up 19 inches from the actual bottom (where
wires are overlapped), and cut out a 1 inch gap of 1 wire from one
side only leaving the gap. You should end up with a very thin slim
rectangle from top to bottom with a 1 inch gap starting at 19 inchs
up from the bottom on one side only.
7. Have an rg58 or rg8x
pigtail made with a pl259 on one end and shield and center wire
tinned with solder on the other end.
8. Measure up about 4
inches from the bottom and remove the insulation from each side of
the Slim Jim antenna using the 4 inch measurement as your
center point and remove the insulation about 2 inches up and
down from the 4 inch mark to give you access to the conductors
on each side of the antenna for swr tuning.
Connect center conductor to the long side and shield to short side
in a temporary fashion. (I used crimp connectors bent on the end of
the pigtail which would connect around the each wire of the antenna
10. Check your swr with an inline meter or
built in to your radio. I used the former (inline swr
meter), with an ht. Slide the pigtail up or down for your best
swr and solder in place.
11. Using 2 or 3 plastic cable ties,
wrap them around the antenna and pigtail so they will be parallel
and snug and to reduce strain on the soldered
Your done, hang it and talk!
I used a commercial jpole to compare the
450 ohm slim jim with. I hung each antenna on a hook using a plastic
cable tie at 10 ft using same length and type feed line and exciter
at same power level.
I could hear normally marginal signals an
average of 2 S units stronger on the slim jim and I could work into
repeaters that I could barely hear on the jpole.
Conclusion: I don't care what certain people
publish about the slim jim not being any better than a standard
jpole. It DOES make a difference on transmit and
I used neither ferrite beads, nor a
homemade coaxial balun to keep the coax from radiating. You may
use either one you like if needed.
Now, go make something
homemade. Lemonade would be nice on a hot day!
73 Alan - KE4NU email@example.com