Slim Jim Antennas incorporate an end fed folded half wave dipole and a quarter wave J integrated matching system. Together these elements create an antenna that requires no grounding or ground plane to operate.
Building on the initial design of the slim jim we added traps that allow proper 70cm operation. Without these traps the folded dipole offers little to no resonance on 70cm. The antenna however yields only j-pole gain on 70cm.
Though you may be tempted to insert the antenna into pvc or other plastic pipe. Please understand that even plastic will affect the velocity factor of the antenna. Ultimately this will mean a loss of the precision tune that each antenna is shipped with. We have found that zip tying the antenna as above to a quarter inch fiberglass mast is ok.
The antennas have a reasonable amount of bandwidth offering a great match to the 2 meter band.
With the addition of the traps in the dual band models great resonance is also afforded on the 70cm band.
Many of our customers have used creative mounting methods to suspend their antennas. As long as the antenna has a couple inches of clearance to the solid material you should be fine.
Q: Can this antenna be placed inside of PVC pipe?
A: While you are free to do as you wish with the product it is highly discouraged as the pipe will degrade the tune of the antenna.
Q: Can I seal the bare wire on the ends with liquid tape or other plastic products?
A: While through exhaustive testing we found there is no need to do this. There is also no downside to sealing the exposed wire portions. We do not do it to help keep the antennas as affordable as possible.
Q: Is the notch cut out of the side of the antenna normal?
A: Yes, and if you look at the design outline above you will see why it exists between the radiator and matching section.
Q: Can I hang the antenna upside down or use it horizontally?
A: The antenna can be used in any position. I do not guarantee that the antenna will exhibit the best pattern when upside down however customers have testified that it still works well like this. Horizontal positioning will only yield good results if the antennas on both ends are horizontal. Remember repeaters will always be on vertical antennas. Also in a horizontal plane the antenna will exhibit a pattern much like a dipole not omni-directional as when mounted vertically.
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