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Author Topic: 2 antenna mounting options - which is the lesser of two evils?  (Read 8543 times)
KF6CNP
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« on: September 20, 2011, 02:58:03 PM »

I have been reading through the archives, and konw that I am basically making the best of what is not an ideal mounting situation, but it is one of those cases where I just have to make the best of it.

I am going to install an old TMV-7a into my 2001 Xterra, and am going to ask antenna location advice...  more accurately, which would be the best place.  I am going to buy a Larsen MNO2/70BK based upon my reading here.

Here are my mounting possibilities (can't do a roof NMO):

1.  roof rack bracket for the luggage rack.

2.  one of the L-Bracket type mounts to place antenna on hood lip passenger side - (opposite of the AM/FM antenna)



Which of these would be the best choice as far as the best performance? 

Also, the Larsen NMO cable kits that would attach to the hood mount seem to have RG58 coax - is that small enought to rout throught the hood gap and into the engine compartment, or is there a thinner coax that would do the trich withour being lossy?

Thanks for the help and advice!

Bill
KF6CNP
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KG4NEL
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« Reply #1 on: September 20, 2011, 05:40:43 PM »

I have to ask...why not a roof mount? Cheesy
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KF6CNP
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« Reply #2 on: September 20, 2011, 11:06:56 PM »

I have to ask...why not a roof mount? Cheesy

Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed

The fender mount seems to be a better performing spot (?), and it seems like an easy enough job...   Once I get this decision firmed out, I will be able to order my antenna, the other parts, and get things rolling!  Smiley

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K7RBW
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« Reply #3 on: September 21, 2011, 06:59:45 AM »

In looking at Larsen's mobile antenna mount guide. Any place that is not on the roof suffered about a 2-3 db drop. Even the through-the-glass mount antenna high on the rear window did better than a wired antenna on a fender mount.
http://www.repeater-builder.com/antenna/pdf/larsen-mobile-antenna-mounting-and-designations.pdf
Given that data, you might want to consider a glass-mount antenna or a mag mount.
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HAPLO
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« Reply #4 on: September 21, 2011, 07:39:40 AM »

I have to ask...why not a roof mount? Cheesy

Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed


You must not have been married for very long... Its always better to ask for forgiveness than for permission.  Cheesy
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W0FM
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« Reply #5 on: September 21, 2011, 01:40:32 PM »

"Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed"


Wow.  Does your wife feel that the roof mount won't look as good as the hood seam angle bracket mount?  Has she seen what either mounting style would look like?  Aside from performing in a superior manner, it seems to me that a good NMO roof mounted antenna is far cleaner in appearance to that of an angle bracket hood seam mount.  Heck, even the coax is visible between the mount and the fender on the hood mount.

I'd take her to SEE an example of both.  Or show her on Alan's website:  www.k0bg.com.



73,

Terry, WØFM
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W3LK
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« Reply #6 on: September 21, 2011, 05:40:40 PM »

"Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed"

I'll get flamed for this, but it's happened before ...

It's a 10 year old vehicle?Huh

Who paid for it? Who pays for the insurance? If the answer to both is NOT the wife, then she has no say so, IMHO. ESPECIALLY on a 10-year old vehicle. Smiley
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KF6CNP
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« Reply #7 on: September 21, 2011, 06:34:41 PM »

I have to ask...why not a roof mount? Cheesy

Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed


You must not have been married for very long... Its always better to ask for forgiveness than for permission.  Cheesy

LOL... that is usually my policy, but I figured I would talk to her about it so she wouldn't be concerned with me hanging around that car with power tools...   Grin
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KF6CNP
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« Reply #8 on: September 21, 2011, 06:43:07 PM »

"Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed"


Wow.  Does your wife feel that the roof mount won't look as good as the hood seam angle bracket mount?  Has she seen what either mounting style would look like?  Aside from performing in a superior manner, it seems to me that a good NMO roof mounted antenna is far cleaner in appearance to that of an angle bracket hood seam mount.  Heck, even the coax is visible between the mount and the fender on the hood mount.

I'd take her to SEE an example of both.  Or show her on Alan's website:  www.k0bg.com.
73,

Terry, WØFM


I have looked at and learned a lot from the website...   In fact, your post (along with most of the others) made me take a second look at the situation.

It seems like I could pull the rear dome light (which is in the center at the very back of the car, nearly the rear edge of the roof), and use that as a possible mounting point for an NMO...   it would be within about 4-6 inches of the back of the car, but I imagine it would still be a lot better than the other options, especially referring to the Larsen guide linked in a previous post.

I watched a You Tube video on how to do it, and I think I can handle it... 

I did read that there are a lot of lower-quality NMOs out there - I want a good quality NMO and also need the NMO hole saw drill bit.  Where do you guys recommend I go online for these?


Aside from those two things, I think I am set - it doesn't look like there is anything else necessary to get the install done.  Drill the hole and screw the mount down.  Am I missing something or is it really that easy?    Wink



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KF6CNP
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« Reply #9 on: September 21, 2011, 06:47:10 PM »

"Well, it was part of the negotiation process with my wife in getting the install done...   Lips sealed"

I'll get flamed for this, but it's happened before ...

It's a 10 year old vehicle?Huh

Who paid for it? Who pays for the insurance? If the answer to both is NOT the wife, then she has no say so, IMHO. ESPECIALLY on a 10-year old vehicle. Smiley

I know it is a 10-year old car and all, but I still talk to her about these kinds of things.  It doesn't matter to me who paid for what, I look at it as me respecting her enough to talk to her about it.  (But we both paid for the car and both pay the insurance on it as we do with our second car).  And if I started getting into a whover paid for it gets to make the decisions debate with her, I would surely lose...   I am a teacher, and she is an RN...    She wins.   Grin Grin Grin

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HAPLO
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« Reply #10 on: September 21, 2011, 09:25:13 PM »

It seems like I could pull the rear dome light (which is in the center at the very back of the car, nearly the rear edge of the roof), and use that as a possible mounting point for an NMO...   it would be within about 4-6 inches of the back of the car, but I imagine it would still be a lot better than the other options, especially referring to the Larsen guide linked in a previous post.

I watched a You Tube video on how to do it, and I think I can handle it... 

I did read that there are a lot of lower-quality NMOs out there - I want a good quality NMO and also need the NMO hole saw drill bit.  Where do you guys recommend I go online for these?
Aside from those two things, I think I am set - it doesn't look like there is anything else necessary to get the install done.  Drill the hole and screw the mount down.  Am I missing something or is it really that easy?    Wink


I assume you watched a white F150 on YouTube do this? Don't put it way in the back. I think K0BG even has it somewhere on his site, that dead center of the roof provides the best ground plane.

I've done this to my truck, and its pretty easy. My headliner had 4 screws on one side that I undid, and it allowed me to get a hand in there and fish the wire. I didn't have to take off the entire headliner.

As far as the hole goes, I bought a metal hole-saw from Lowes for $8.00 or so for my drill. The roof did require a little bit of filing though to clean up the burrs around the edges, which an "NMO panel punch" might not require.

I've heard nothing but good things about Larsen's antennas and NMO mounts, so that is what I went with.

As far as it being that easy, yeah, once you get over the mental aspect of "I'm putting a hole in my vehicle on purpose", its simple to do.  Smiley You may want to rough up the underside of the mount a bit (the inside part of your vehicle, not the outside paint) so you have a good ground connection.

Good luck,
H.
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KF6CNP
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« Reply #11 on: September 21, 2011, 10:58:01 PM »


I assume you watched a white F150 on YouTube do this? Don't put it way in the back. I think K0BG even has it somewhere on his site, that dead center of the roof provides the best ground plane.

I've done this to my truck, and its pretty easy. My headliner had 4 screws on one side that I undid, and it allowed me to get a hand in there and fish the wire. I didn't have to take off the entire headliner.

As far as the hole goes, I bought a metal hole-saw from Lowes for $8.00 or so for my drill. The roof did require a little bit of filing though to clean up the burrs around the edges, which an "NMO panel punch" might not require.

I've heard nothing but good things about Larsen's antennas and NMO mounts, so that is what I went with.

As far as it being that easy, yeah, once you get over the mental aspect of "I'm putting a hole in my vehicle on purpose", its simple to do.  Smiley You may want to rough up the underside of the mount a bit (the inside part of your vehicle, not the outside paint) so you have a good ground connection.

Good luck,
H.

Thanks!  The PDF from Larsen had a good chart showing losses at different antenna positions with different mounts.  They give center of the roof 0.0, with the fender mount at around -2.8 (just from memory, not looking at it right now).  A mag mount on a back corner of the roof was -0.2...  I would assume that an NMO in the same rear position but towards the center would at least do that well?  That being said, I will go as far forward as I reasonably can, and in any case still should be able to do better than the other two options I had originally posted...   Does that gel with conventional logic?

Then I get to try my hand at soldering the PL259 to the other end after I get it routed under the passenger seat...   Hopefully I can do that on the first or second try...  LOL!

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N3IDG
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« Reply #12 on: September 22, 2011, 05:27:54 AM »

I pay 75 dollars to have the headliner dropped hole drilled nmo mount installed coax run to my choice of location and end installed parts&labor included. I put a L bracket on the fender for a second antenna cost 18 for bracket 22 for mount and coax plus the hr and a half of my time to put it together. The roof mount with a 1/4 wave will out perform the fender mount by a HUGE amount even putting a gain on the fender will not equal a quarter wave on the roof.  IMHO a quarter wave mag mount on the roof is better then a gain on the fender.
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KI4SDY
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« Reply #13 on: September 22, 2011, 07:36:24 AM »

Since you concerned about getting into trouble with the boss drilling holes in the car, why don't you try the MFJ-1729 VHF/UHF Power Gain Magnetic Antenna first? For $39.95 you will save a lot of time and money. It is a favorite here in my area and it has very high ratings on eHam.net. In addition to being a black low profile antenna, you have the option to move it around on the vehicle for best performance, utility and appearance.  Grin  
« Last Edit: September 22, 2011, 05:32:28 PM by KI4SDY » Logged
VA3WXM
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« Reply #14 on: September 22, 2011, 10:51:54 AM »

I've drilled nine NMO holes over four vehicles (both hers and mine) and wouldn't do it any other way.
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