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Old 03-28-2013, 01:52 PM   #1
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Any knowledgeable hams?

Better antenna for an Arizona spare tire mounted 2m antenna: 5/8 or 1/2 no ground plane?

My jeep is a soft top, btw.

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Old 03-28-2013, 03:01 PM   #2
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Never use a NGP antenna when the vehicle has a steel tub & frame like the Wrangler does which serves as superb ground plane. NGP antennas are poor performers at best and are only meant for use in installations where no suitable ground plane is available, like on a fiberglass boat.

Just make sure your antenna's mount has a good bare-metal connection to the Jeep so it gets a good RF ground connection so it can turn the Jeep into a good ground plane.

N6TAY

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Old 03-28-2013, 03:27 PM   #3
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Originally Posted by Jerry Bransford View Post
Never use a NGP antenna when the vehicle has a steel tub & frame like the Wrangler does which serves as superb ground plane. NGP antennas are poor performers at best and are only meant for use in installations where no suitable ground plane is available, like on a fiberglass boat.

Just make sure your antenna's mount has a good bare-metal connection to the Jeep so it gets a good RF ground connection so it can turn the Jeep into a good ground plane.

N6TAY
Got it. I did get a signal report that I was full-quieting into the repeater but it was only 10 miles away and I was pushing 65 watts haha I'll stick with the 5/8.
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Old 03-28-2013, 08:48 PM   #4
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There is NOTHING wrong with 1/2 wave antennas. Thousands of owners of dipoles (1/4 wave each side = 1/2 wave), thousands of owners of 1/2 wave mobile antennas will all tell you they WORK !!!!!! There is NOTHING wrong with 1/2 wave antennas. In fact, they work BETTER than 1/4 wave and 5/8 wave antennas when no ground plane is available.

In the case of an installation where the antenna is at the rear or front or anywhere except center of the vehicle, a 1/2 wave antenna will provide BETTER performance in a 360 degree circle. When you mount a 1/4 wave or 5/8 wave antenna on the corner or spare tire mount, the only ground plane that the antenna is going to see, and use, is in the direction of the front of the vehicle. These types of antennas NEED a ground plane in all directions. In the direction where there is no ground plane, your signal is going up, down, and every direction EQUALLY. This might be fine if you want to talk to people 5 miles below you, or an airplane overhead. When the antenna has a ground plane under it in the direction you want your signal to go, almost ALL of your signal is going towards the horizon.

If all of your communications is going to be with stations in front of you (with spare tire mount) or in the direction of left rear to right front or right rear to left front, then by all means, mount a 1/4 wave or 5/8 wave on one of the rear corners. Or, you can mount your antenna as just mentioned and use 65 watts and jam a lot of other users. If you use a 1/2 wave antenna, mounted anywhere on your vehicle, you should have equal radiation and reception in all directions.

In theory, there should only be a maximum of 2dB difference between a 1/2 wave and 5/8 wave mobile antenna. A properly calibrated S meter requires a difference of 6 dB for every 1 S unit. In theory, you will not be able to hear or see the difference.

Speaking of 65 watts, I'm sure you remember some of the material you studied for your test. FCC Part 97.313 Transmitter power standards:

(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

Regards,
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Old 03-28-2013, 09:38 PM   #5
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There is NOTHING wrong with 1/2 wave antennas. Thousands of owners of dipoles (1/4 wave each side = 1/2 wave), thousands of owners of 1/2 wave mobile antennas will all tell you they WORK !!!!!! There is NOTHING wrong with 1/2 wave antennas. In fact, they work BETTER than 1/4 wave and 5/8 wave antennas when no ground plane is available.

In the case of an installation where the antenna is at the rear or front or anywhere except center of the vehicle, a 1/2 wave antenna will provide BETTER performance in a 360 degree circle. When you mount a 1/4 wave or 5/8 wave antenna on the corner or spare tire mount, the only ground plane that the antenna is going to see, and use, is in the direction of the front of the vehicle. These types of antennas NEED a ground plane in all directions. In the direction where there is no ground plane, your signal is going up, down, and every direction EQUALLY. This might be fine if you want to talk to people 5 miles below you, or an airplane overhead. When the antenna has a ground plane under it in the direction you want your signal to go, almost ALL of your signal is going towards the horizon.

If all of your communications is going to be with stations in front of you (with spare tire mount) or in the direction of left rear to right front or right rear to left front, then by all means, mount a 1/4 wave or 5/8 wave on one of the rear corners. Or, you can mount your antenna as just mentioned and use 65 watts and jam a lot of other users. If you use a 1/2 wave antenna, mounted anywhere on your vehicle, you should have equal radiation and reception in all directions.

In theory, there should only be a maximum of 2dB difference between a 1/2 wave and 5/8 wave mobile antenna. A properly calibrated S meter requires a difference of 6 dB for every 1 S unit. In theory, you will not be able to hear or see the difference.

Speaking of 65 watts, I'm sure you remember some of the material you studied for your test. FCC Part 97.313 Transmitter power standards:

(a) An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

Regards,
The "haha" was meant as a "whoops!" kinda thing, I do remember that part but didn't check what output I was using when I called out. And with my tm-281 it's either 25 or 65, I just so happened to be on 65. But thanks for the reminder.

Back to the topic:
So the jeep won't "pull" the signal to the front if a 1/2 NGP antenna is used? It'll radiate a full 360 degrees? (This part I paid no attention to apparently)
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Old 03-28-2013, 09:50 PM   #6
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That is correct. In theory, a 1/2 wave antenna will radiate, and receive, equally in all directions, irregardless of what the antenna is mounted on or whether a ground plane exists. In reality, there might be a tiny bit of increased signal strength in the direction of the ground plane, but should be undetectable without test equipment.

73
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Old 03-28-2013, 09:53 PM   #7
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That is correct. In theory, a 1/2 wave antenna will radiate, and receive, equally in all directions, irregardless of what the antenna is mounted on or whether a ground plane exists. In reality, there might be a tiny bit of increased signal strength in the direction of the ground plane, but should be undetectable without test equipment.

73
Ok. Thanks for the info. I'll try the 1/2 out. Larsen!
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Old 03-29-2013, 11:41 AM   #8
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Quote:
Originally Posted by n6hal View Post
There is NOTHING wrong with 1/2 wave antennas. Thousands of owners of dipoles (1/4 wave each side = 1/2 wave), thousands of owners of 1/2 wave mobile antennas will all tell you they WORK !!!!!! There is NOTHING wrong with 1/2 wave antennas. In fact, they work BETTER than 1/4 wave and 5/8 wave antennas[b/ when no ground plane is available.[/b]
The OP's question wasn't what wavelength antenna works best, it was whether a conventional 5/8 would work better than a 1/2 wave NGP. This isn't about 5/8 vs. 1/2 wave, it was which would make a better antenna... a NGP 1/2 wave or a 5/8. NGP vs a conventional antenna that makes use of his TJ's available ground plane characteristics.

He didn't request a lesson on what wavelength antennas work best... it was really just a NGP vs. a conventional type of antenna question and there is no doubt a NGP type of antenna is not going to work nearly as well on a TJ as a conventional antenna that takes advantage of a groundplane will.

If you take the NGP part out, then it's time to talk about which wavelength antenna will perform best... but he asked about using a NGP antenna which is little better than nothing at all.
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Old 03-29-2013, 11:43 AM   #9
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The OP's question wasn't what wavelength antenna works best, it was whether his 5/8 would work better than his 1/2 wave NGP. This isn't about 5/8 vs. 1/2 wave, it was which would make a better antenna... a NGP 1/2 wave or a 5/8. NGP vs a conventional antenna that makes use of his TJ's available ground plane characteristics.

He didn't request a lesson on what wavelength antennas work best... it was really just a NGP vs. a conventional type of antenna question and there is no doubt a NGP is not going to work as well on a TJ as a conventional antenna that takes advantage of a groundplane will.
So many confusing replies! Haha I'm just gonna leave the 5/8 on until someone tells me they can't hear me well.
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Old 03-29-2013, 11:51 AM   #10
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There is no confusion on the basic fact I have been trying to get across... that a NGP antenna isn't going to work nearly as well as an antenna that makes use of the Jeep as a ground plane. I didn't need to get into an encyclopedic dissertation on antenna theory for the simple answer you appeared to be seeking so I didn't.

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