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Author Topic: K2BJ style antenna mount  (Read 551 times)
N2HBZ
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Posts: 7




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« on: January 25, 2006, 10:08:32 AM »

I want to go mobile in my 2005 XTerra (a rather tall vehicle at 75").  I've read that getting the antenna up high makes a huge difference, so I want to do what K2BJ did, i.e. replace factory roof rail bolts, sandwich in steel mounting plate, ground inside roof, and mount rig  at roof to new bolts, grounding rig and antenna at same point.

http://www.k2bj.com/K2BJ/blazer/k2bj-m_1.htm

A couple of questions:

1) K2BJ says that grounding the rig and antenna at the same point improves efficiency and reduces RFI ingress.  I wanted to get an idea as to how much of a difference this makes vs. mounting the rig in an alternate location, like under the seat.

2) K2BJ uses K400 on this mounting bracket to allow the antennas to fold down.  Then I thought, why not extend the bracket across the roof, bolted and grounded on both sides.  Holes could be cut in the bracket to mount antennas - maybe even construct it so that it can flip over to get antennas out of the way.  Since there would be a few inches of clearance between the bracket and the roof, I was concerned that this may cause problems (capacitance to ground, i.e vehicle body).  Is it OK that the antenna is mounted a foot or more from the grounding bolts?  What do you guys think?

N2HBZ
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K0BG
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« Reply #1 on: January 25, 2006, 04:15:14 PM »

First of all, Brian doesn't like to drill holes. At least he hasn't in the last couple of installs he has done. Secondly, an ATAS is about as minimal of an antenna as you can buy. If you're serious about mobile, this is one antenna to stay away from.

There is a ton of info on my web site if you take your time to wade through it. Afterwards, if you have questions, I'll do my best to answer them.

Alan, KØBG
www.k0bg.com
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N2HBZ
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« Reply #2 on: January 25, 2006, 05:56:45 PM »

Alan,

I am a big fan of your site and have read through most of the material.  As a matter of fact, I carry print outs and read them on my way to work. Thanks for being the eElmer to us all Smiley

I was not considering the ATAS-120, but one of the smaller screwdriver antennas like the Little Tarheel II, the Sidekick, or the ATAS-killer from Hi-Q.  I should have made that clear.

When I read about Brian's installation it sounded pretty good since the hole is hidden.  It seems to me that there is a good ground since it is bolted through the roof - isn't it as good as a NMO roof mount w.r.t. RF ground?  Antenna choice being constant (let's say Little Tarheel II) would his installation perform worse than a ball mount up as high as possible?

I have read that whatever efficiency is gained by using a full size screwdriver is mitigated by mounting it either too close to the body or too low (like a trailer hitch mount); that's why I am trying to get a smaller antenna up higher on the vehicle.  Is this the right thing to do in my case?

You mention that SUVs in general are not ideal for mobile HF, but if you have a better suggestion for the XTerra I would certainly love to hear from you.  How about an AH-2b bumper mounted (I already own the AH-4 and the IC-706MkIIG which I was considering selling)?  Can I use those nice big roof rails for anything antenna related?

If you want to contact me my email addres is my call at masari dot com.

Thanks for your help!
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N2HBZ
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« Reply #3 on: January 26, 2006, 08:35:26 AM »

How is what K9GPS did different (with respect to RF ground) different from what K2BJ did?  
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