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Author Topic: Okay, mount/antenna help...  (Read 3207 times)
KI4ZSZ
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Posts: 22




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« on: April 17, 2011, 11:57:39 AM »

So I have a nice Larsen dual band antenna that has an NMO mount (this is just the whip and base part, not the other part of the mount that connects to coax). And I have a Breedlove Machine stake pocket mount coming (http://bellsouthpwp.net/b/r/breedlove1/page12.html), and I'm having Mr. Breedlove bore out the mounting hole to 3/4" to accomodate the NMO mount (his mounts tend to use an SO-239/PL-259 interface, so this is semi-custom modification). According to his website, the plate with the mounting hole is 1/4" thick. I really wish I knew more about this mounting and connection stuff...it's a bit of a learning process...

I know I need something along this line: http://www.hamradio.com/detail.cfm?pid=H0-000594  but I am unsure which would be the best product to use on this mount, considering the exposure to weather (I do have some coax seal tape, too, that I will be using)

Thanks,

George

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K1CJS
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« Reply #1 on: April 17, 2011, 12:26:56 PM »

Considering that most NMO mounts are made to be installed in sheet metal about 1/16 thick, I think you're going to find that the setup you ordered isn't going to work out.  Why don't you get to Mr. Breedlove and tell him what you want to do--that way he can either make the mount special for you or recommend a way to use that mount in order to accomodate what you already have.
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KI4ZSZ
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« Reply #2 on: April 17, 2011, 12:35:03 PM »

Considering that most NMO mounts are made to be installed in sheet metal about 1/16 thick, I think you're going to find that the setup you ordered isn't going to work out.  Why don't you get to Mr. Breedlove and tell him what you want to do--that way he can either make the mount special for you or recommend a way to use that mount in order to accomodate what you already have.

Already talked to Mr. Breedlove about this, and he said that he doesn't make that style of mount but would bore the size out to whatever size I needed.


Larsen also makes an NMO mount of the same style that will work with material up to 1/2" thick. Would this be a better/workable choice?
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KC7YRA
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Posts: 256




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« Reply #3 on: April 17, 2011, 12:56:35 PM »

Larsen also makes an NMO mount of the same style that will work with material up to 1/2" thick. Would this be a better/workable choice?

That would be way better.  But most of those thicker metal mounts only use a 3/8 inch hole.  SO having the mount drilled out to 3/4 inch will be totally worthless.  There is NO WAY a standard NMO will be able to accommodate metal that thick, and the hole would be too big for the thick mounts.

You should get a hold of Jerry and have him hold off until you know exactly what you are needing.

Brad
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KI4ZSZ
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« Reply #4 on: April 17, 2011, 01:10:56 PM »

Larsen's info on their thick mount says it uses a 3/4" hole. I will ask Mr. Breedlove to hold off on the mount for a couple of days until I can verify.



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K1CJS
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« Reply #5 on: April 17, 2011, 07:11:03 PM »

Yes, that would be best.  Another thing comes to mind, though.  Quite a lot of NMO mounts have the cable come off the mount at a 90 degree offset, not straight down.  Will there be enough room in the stake pocket to accommodate that?  I kind of doubt it.  Any NMO mount that you may look at would have to have the cable come out straight down, not at a 90 degree offset.

Another possible suggestion to solve this would involve mounting a flat plate to the stake pocket mount, extended to a couple or three inches inside the bed of the truck, then bore a hole in that plate to mount the NMO mount.  Not as neat as the way you're trying, and the plate may be in the way a bit, but you could solve a lot of problems that way.
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KI4ZSZ
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« Reply #6 on: April 17, 2011, 07:25:52 PM »

Yes, that would be best.  Another thing comes to mind, though.  Quite a lot of NMO mounts have the cable come off the mount at a 90 degree offset, not straight down.  Will there be enough room in the stake pocket to accommodate that?  I kind of doubt it.  Any NMO mount that you may look at would have to have the cable come out straight down, not at a 90 degree offset.

Another possible suggestion to solve this would involve mounting a flat plate to the stake pocket mount, extended to a couple or three inches inside the bed of the truck, then bore a hole in that plate to mount the NMO mount.  Not as neat as the way you're trying, and the plate may be in the way a bit, but you could solve a lot of problems that way.

Breedloves mount is an offset mount instead of directing the mount straight down into the stakepocket, so it can be mounted under a camper shell, for example, basically accomplishing what you describe (in a nicely machined form that I could not duplicate)...mine will be offset to the inboard side of the bed. Besides that, my stakepockets fortunately also have large tie down holes in the sides, so they would accomodate a 90 deg fitting if I had to go that way.

I ordered the thick mount today from HRO, so I will be able to get eyes and caliper on it to verify the info that larsen sends me.

It'll be nice to finally get this radio I brought 2 years ago installed  Cheesy I've just been dragging my feet while trying to decide on exactly how I wanted to install it and do it right from the beginning instead of slapping crap together in a haphazard fashion...


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KI4SDY
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Posts: 1452




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« Reply #7 on: April 17, 2011, 10:28:04 PM »

Just think, you could have been using your radio with an inexpensive magnetic mount (MFJ 1729 power gain antenna for $39.95, it gets great reviews on eHam.net) for that two years, instead of waiting to do everything perfect. Sometimes perfection gets in the way of accomplishment!  Wink

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KI4ZSZ
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Posts: 22




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« Reply #8 on: April 17, 2011, 10:37:06 PM »

Just think, you could have been using your radio with an inexpensive magnetic mount (MFJ 1729 power gain antenna for $39.95, it gets great reviews on eHam.net) for that two years, instead of waiting to do everything perfect. Sometimes perfection gets in the way of accomplishment!  Wink



I actually have a magmount (Larsen, brought with the antenna) and I don't really care for it...



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KI4SDY
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« Reply #9 on: April 18, 2011, 12:19:30 AM »

You may not be satisfied with the performance of your dual band antenna mounted low on the truck either. That is not an ideal location for the antenna. If your going to use an NMO mount, why not install it on the roof where it will perform the best?  Grin
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KC7YRA
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Posts: 256




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« Reply #10 on: April 18, 2011, 06:20:19 AM »

Larsen's info on their thick mount says it uses a 3/4" hole. I will ask Mr. Breedlove to hold off on the mount for a couple of days until I can verify.

I had to see for myself, and sure enough!!  I'm liking that.  As long as you are sure your mount area is 1/2 inch thick.  The ones we used to use on large trucks took a 3/8 inch hole and were adjustable for varying thickness.  Since the roof thickness of firetrucks can vary widely, we were constantly having to tweak them. 

Brad
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K1CJS
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« Reply #11 on: April 18, 2011, 12:12:10 PM »

Breedloves mount is an offset mount instead of directing the mount straight down into the stakepocket, so it can be mounted under a camper shell, for example, basically accomplishing what you describe (in a nicely machined form that I could not duplicate)...mine will be offset to the inboard side of the bed. Besides that, my stakepockets fortunately also have large tie down holes in the sides, so they would accomodate a 90 deg fitting if I had to go that way.

Ah, yes.  Another case of open mouth and insert foot.  I wasn't aware that Mr. Breedlove's mount system worked that way.  All of the stake pocket mounts that I've seen actually put the antenna in the middle of the mount--in the stake pocket.  Sorry!  I'm glad it's going to work out for you!  73!
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KI4ZSZ
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Posts: 22




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« Reply #12 on: April 19, 2011, 05:47:01 PM »

Thanks for the warning on the mount stud size. Larsen says 3/4" hole in their directions with the mount, but I checked it out with the calipers, and 5/8" (this is also Breedlove's standard hole size) is apparently the correct hole size for the parts that have to go through the mounting hole. Hmm. I emailed Mr. Breedlove to ship the mount with the standard hole size and will report on my install results (if I have to hog it out, I can do it, but I anticipate no issues).

It would be very nice if makers gave better details on their websites about their products...posting detailed dimensions of their mount and instructions/diagram of assembly would have cleared up a lot of info about the Larsen mount...I can't just run to the nearest ham radio store (which is 3.5 hours away) at the drop of a hat to check something out...

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K3GM
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Posts: 1755




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« Reply #13 on: April 19, 2011, 06:44:32 PM »

Did you mike across the shoulder on the wings?  To the best of my knowledge, a true Larsen NMO mount has a raised, curved shoulder on the wings which contact the underside of sheet metal.  The dimension across those shoulders is precisely .750".  I even checked some cheapo MaxRad NMO mounts which use a nylon washer and they measured .750" as well.  The shoulders or washer fits into the hole and aligns the mount. At .625", the shoulder or washer won't fit.  I've done lots of Motorola style NMO mounts and they all required a .750" diameter hole.  Get ready to hog it, but careful! A Breedlove mount, and the term "hog" aren't usually used in the same sentence. His mounts are almost too pretty to use.
« Last Edit: April 19, 2011, 07:12:44 PM by K3GM » Logged
KI4ZSZ
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Posts: 22




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« Reply #14 on: April 19, 2011, 07:25:54 PM »

Did you mike across the shoulder on the wings?  To the best of my knowledge, a true Larsen NMO mount has a raised, curved shoulder on the wings which contact the underside of sheet metal.  The dimension across those shoulders is precisely .750".  I even checked some cheapo MaxRad NMO mounts which use a nylon washer and they measured .750" as well.  The shoulders or washer fits into the hole and aligns the mount. At .625", the shoulder or washer won't fit.  I've done lots of Motorola style NMO mounts and they all required a .750" diameter hole.  Get ready to hog it, but careful! A Breedlove mount, and the term "hog" aren't usually used in the same sentence. His mounts are almost too pretty to use.

Dang it, you're right. I sent poor Jerry another email to change it back to 3/4". God, he's going to hate me for being so indecisive. I didn't notice the shoulder on the bottom plate, only the shoulder on the stud.

I'll post some good photos of this stuff later. You're right, his work is exquisite,



George
« Last Edit: April 19, 2011, 07:28:32 PM by KI4ZSZ » Logged
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