Description
The difference between a J-Pole and a Slim Jim is simple: while both share the same design, the Slim Jim folds another 1/2 wave element over onto itself, turning the single half wave concept of the J-Pole into a double half wave, or ed fed folded dipole antenna. The folded dipole nature of the Slim Jim gives you about 3dbi of extra gain when compared to the standard J-Pole.
Benefits
- Increased gain: compared to a standard J-Pole the Slim Jim has about 6dbi of gain
- Wider Bandwidth: Almost 8MHz of 2:1 bandwidth (double that of the J-Pole antenna)
- More RF energy aimed at the horizon: with a take-off angle of about 7 degrees for the Slim Jim, compared to 20 degrees for the J-Pole
- Compact size: the 2 meter Slim Jim is still only 58 inches tall
- Hear weaker stations: lower noise floor than a wire antenna will help you hear more and capture distant signals better.
Specs
- 58 inches tall, end-fed folded dipole design
- Gain: 6 dbi, 7 degree takeoff angle
- Bandwidth: 5+ Mhz
- Pretuned to 146 MHz: Just connect the coax and transmit
- Heavy duty construction out of 1/2 inch copper tubing
When would I choose a Slim Jim compared to a J-Pole antenna
2 Meter Slim Jim antenna ready for service on W9HDG-10 Winlink Node
Both the Slim Jim and J-Pole are great antennas and I continue to recommend both styles of antennas for different situations. The J-Pole will excel at lower mounting heights, apartments, or limited space locations. It’s 20 degree takeoff angle makes it a great choice for people living in valleys or the base of mountain ranges. It’s even radiation pattern is great for communicating with satellites and the International Space Station.
The Slim Jim likes to be mounted high. My experience with it is that you want to get this antenna up at least 20 or 30 feet for it to really perform. The lower takeoff angle is great for simplex communications with handheld or mobile radios. The low noise floor is perfect for data and packet stations. If you live on the top of a hill, go for the Slim Jim.
Mounting
Click to enlarge image
The 2 meter Slim Jim needs to be isolated from your mast. If you use a non metal mast you should be fine. The antenna does come with a mounting kit that consists of a length of PVC tubing and two hose clamps. You will need two additional clamps to attach the isolator section to the mast.
Mounting instructions for the KB9VBR Slim Jim Antenna.
The [Slim Jim] antennas arrived today. I hooked one up to my transmitter and VSWR meter. I am impressed with the flatness of the antenna over the frequency range. Thank you. – Gerald Marsh
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