Md116
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Any negative effects with using a GP with a NGP antenna?
NGP antenna question..
- Thread starter Md116
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What band are you asking about? Are you transmitting or just receiving?
Ubbe
Member
The same effect as when any antenna are too close to a metal object. It changes the impedance and screw up the directional pattern. The more gain, and thus narrower directional pattern, the more negative it becomes. A standard 1/4 wave element antenna probably aren't gonna be that much affected that you'll notice it. But NGP antennas are of a different design, probably using an element with a high impedance at the bottom connected to a matching coil and will be extremly sensitive to any nearby objects like ground plane rods.
/Ubbe
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mmckenna
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If you are asking if there are any issues using a No Ground Plane antenna over a ground plane, then the answer is no.
A 1/2 wave antenna will provide 0dB of gain when used without a ground plane. Put it over an ideal ground plane and it will now provide 2.15dB of gain.
The BLM trucks around here are set up that way. Gives them a bit of gain and wide bandwidth.
I run a NGP half wave antenna on my UTV, and it works well. Antenna is mounted off the back of the roll cage. I've used the same antenna on the top of my truck. NMO mount dead center of the cab. Worked well.
Md116
Member
Receiving only, Thanks
Md116
Member
I could have been more specific. The antenna is for receiving and it's a NGP antenna. Was going to mount it using a mobile to base mounting kit for a GP antenna and was wondering if the ground plane would have any negative reception issues.
mmckenna
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No, it won't. In fact, like I said above, it'll change the radiation pattern and give you about 2.15dB gain compared to using it without the ground plane.
Md116
Member
Receiving only at the 150 MHz band
Ubbe
Member
If that's true then the antenna was not designed as a genuine NGP but as a normal GP and removing the ground plane make it loose 2.15dB as the direction beam goes up in the sky.
/Ubbe
mmckenna
I ♥ Ø
No, all the 1/2 wave mobile antennas I have are like that. They are 0dB in free space with a very spherical radiation pattern. Add the ground plane and it flattens out the pattern a bit and increases the gain. The radiation pattern with a ground plane is down towards the horizon, not reflected up.
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