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Author Topic: Truck Quad Band Antenna Location  (Read 4628 times)
AK4SK
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« on: May 05, 2012, 08:07:25 PM »

I'm looking at getting a Diamond CR8900A quad band (10, 6, 2, 70) antenna for a Yaesu FT-8900R. It is going to be mounted on a truck and I have no idea where it should be located for best performance. I think it should be as high as possible (on the roof maybe) for 2 m and 70 cm but I'm not sure if that is practical because of how high it is (50"). Also, I don't know what kind of a ground it needs.

Any suggestions would be helpful.

73 AK4SK
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KX0Z
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« Reply #1 on: May 05, 2012, 11:09:30 PM »

Best location would be thruough the roof mount right in the middle of the cab. 
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K5LXP
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« Reply #2 on: May 06, 2012, 06:24:28 AM »

The problem with this antenna is it uses a PO mount, which isn't conducive to sheet metal installs.  You need to pick a location you can fasten a beefy bracket to. 

So you have a conflicting set of requirements.  Pick antennas that can be mounted on the roof for "best performance", or pick a location that will accommodate the mounting requirements of a CR8900.


Mark K5LXP
Albuquerque, NM
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AK4SK
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« Reply #3 on: May 06, 2012, 06:41:47 AM »

The problem with this antenna is it uses a PO mount, which isn't conducive to sheet metal installs.

So, I guess I need to know the difference between a NMO and PO mount. What is the difference?
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K3GM
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« Reply #4 on: May 06, 2012, 08:14:33 AM »

Truck as in pickup?  If so, be very careful about roof mounting if.  A CR8900 is unyielding to overhead obstructions and can easily rip the mount out of the sheet metal.  I went with two antennas, a dual bander, and either a 10m or 6m coil depending which one I wanted to use.  Larsen coils use whips that are very compliant to overhead branches and the like.
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AK4SK
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« Reply #5 on: May 06, 2012, 01:15:24 PM »

Truck as in pickup?  If so, be very careful about roof mounting if.  A CR8900 is unyielding to overhead obstructions and can easily rip the mount out of the sheet metal.  I went with two antennas, a dual bander, and either a 10m or 6m coil depending which one I wanted to use.  Larsen coils use whips that are very compliant to overhead branches and the like.

Yes, pickup. I was wondering about that very thing. Thanks for the info.
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N6AJR
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« Reply #6 on: May 11, 2012, 12:20:19 PM »

In my pickup, I have a total of 8 antennas.  I have 4 through the roof of the cab  ( extended cab 1994 ford  1/2 ton 4wdr) and 4 in the bed rails. For small antennas, ( like 1 or 2 foot tall) I use a greenlee punch and NMO mounts through the roof of the cab. for best transmitting and receiving ability.  In the bed rails  I have 2 larger  antenna on  nmo mounts and a an ATAS 120 and a DK 3 on the other  bed rail. the roof has 1.2g, 220, 900 mhz and 2m/440.

the bed rails have the 2 screwdrivers on on e side, and a 2m and a 2m /440/6m on the other rail.  I also have a ladder rack installed to carry larger antennas and push up poles.

so best signal comes off the roof, but ease of install is bed rails.  and I have in the cab , a 2m/ 2m440/1.2, a 220, a 900MHz, a dedicated 2m FM only and an FT 857.  they work well.
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AK4SK
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« Reply #7 on: May 14, 2012, 07:20:50 AM »

In my pickup, I have a total of 8 antennas.  I have 4 through the roof of the cab  ( extended cab 1994 ford  1/2 ton 4wdr) and 4 in the bed rails. For small antennas, ( like 1 or 2 foot tall) I use a greenlee punch and NMO mounts through the roof of the cab. for best transmitting and receiving ability.  In the bed rails  I have 2 larger  antenna on  nmo mounts and a an ATAS 120 and a DK 3 on the other  bed rail. the roof has 1.2g, 220, 900 mhz and 2m/440.

the bed rails have the 2 screwdrivers on on e side, and a 2m and a 2m /440/6m on the other rail.  I also have a ladder rack installed to carry larger antennas and push up poles.

so best signal comes off the roof, but ease of install is bed rails.  and I have in the cab , a 2m/ 2m440/1.2, a 220, a 900MHz, a dedicated 2m FM only and an FT 857.  they work well.

Wow, thanks.

I still haven't figured it out, what is NMO?
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K1CJS
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« Reply #8 on: May 14, 2012, 08:06:12 AM »

NMO stands for "New MOtorola" mount, an innovative system that distributed the stress of small antennas over a larger area.  Innovative, that is, thirty plus years ago.

To answer your question. I would opt for a mount on a crossbar right behind the cab.  Ground planes for 2 meters and 70 cm would be marginal, but then you probably won't need much with that antenna.  The more centralized location would be better for the ground plane effect for 6 and 10 meters.  

Don't forget bonding the body together--look at www.K0BG.com for a great site and advice about mounting antennas.
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AK4SK
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« Reply #9 on: May 14, 2012, 08:17:16 AM »

NMO stands for "New MOtorola" mount, an innovative system that distributed the stress of small antennas over a larger area.  Innovative, that is, thirty plus years ago.

To answer your question. I would opt for a mount on a crossbar right behind the cab.  Ground planes for 2 meters and 70 cm would be marginal, but then you probably won't need much with that antenna.  The more centralized location would be better for the ground plane effect for 6 and 10 meters.  

Don't forget bonding the body together--look at www.K0BG.com for a great site and advice about mounting antennas.

Thanks. I'm not sure if I can use the crossbar or not because I have a toolbox. While the toolbox doesn't cover the crossbar I think the lid may hit the antenna when it is opened. I'll have to double check to be sure.
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K1CJS
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« Reply #10 on: May 14, 2012, 05:04:52 PM »

Thanks. I'm not sure if I can use the crossbar or not because I have a toolbox. While the toolbox doesn't cover the crossbar I think the lid may hit the antenna when it is opened. I'll have to double check to be sure.

That may be even better if the toolbox is a good solid metal one.  If it is, try attaching an antenna bracket made to clamp onto a mirror directly to the center front (the back as you're looking at it from the pickup bed) of the toolbox itself.  You can even modify or fabricate a mount plate to have the toolbox top avoid hitting the antenna, or put a rubber bumper on the mount plate and have the toolbox top hit that.  A rubber bungee strap can be used to keep the box top open.  

A metal toolbox can stand the flexing better than the roof panel even if it is thin metal--just reinforce it on the inside with a metal plate.  It may even work if the toolbox is plastic with the metal plate inside it, and in that case, you may not have to worry too much about the toolbox top hitting the antenna.  Again, don't forget to bond the toolbox and/or the plate inside it to the truck bed, and the bed to the cab.  
« Last Edit: May 14, 2012, 05:10:49 PM by K1CJS » Logged
K3GM
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« Reply #11 on: May 15, 2012, 07:32:27 AM »

If you haven't actually physically held one of these antenna, you really need to.  It will help you appreciate the weight and flexure of this brute.  Diamond indicates that it is not recommended for center roof mounting, but doesn't say why.  Once you hold one you'll understand.  I agree with 'CJS.  if it's mounted on a bracket, it should be low enough to clear overhead obstacles, and if not, only it will be damaged.  If you cannot fabricate one, there is a least one brand of generic stainless steel, right angle, NMO mount available.
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AK4SK
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« Reply #12 on: May 16, 2012, 09:38:23 AM »

Thanks. I'm not sure if I can use the crossbar or not because I have a toolbox. While the toolbox doesn't cover the crossbar I think the lid may hit the antenna when it is opened. I'll have to double check to be sure.

That may be even better if the toolbox is a good solid metal one.  If it is, try attaching an antenna bracket made to clamp onto a mirror directly to the center front (the back as you're looking at it from the pickup bed) of the toolbox itself.  You can even modify or fabricate a mount plate to have the toolbox top avoid hitting the antenna, or put a rubber bumper on the mount plate and have the toolbox top hit that.  A rubber bungee strap can be used to keep the box top open.  

A metal toolbox can stand the flexing better than the roof panel even if it is thin metal--just reinforce it on the inside with a metal plate.  It may even work if the toolbox is plastic with the metal plate inside it, and in that case, you may not have to worry too much about the toolbox top hitting the antenna.  Again, don't forget to bond the toolbox and/or the plate inside it to the truck bed, and the bed to the cab.  

Maybe I don't completely understand what you're describing but I don't see how I'll be able to open the tool box with the antenna mounted as you are suggesting.
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K1CJS
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« Reply #13 on: May 17, 2012, 03:56:43 AM »

Maybe I don't completely understand what you're describing but I don't see how I'll be able to open the tool box with the antenna mounted as you are suggesting.

If you stop and think about it, it's simple.  How deep is the lid?  Usually it isn't as deep as the space between the top of it and the back of the cab.  Fabricate an 'L' bracket so that it is long enough that you can drill a hole to mount the antenna that will be clear of the open lid.  Mount the bracket below the lid hinge on the toolbox, so when the lid is opened, it can open fully but will not hit the antenna or the bracket. 

Say the lid is 2 inches deep.  You'll have to have a couple of inches more to mount the antenna, so make the bracket at least 4 inches long so that it has area beyond the open lid, and enough room to drill the hole beyond the open lid to allow for the mounting of the antenna.

You may have to play with the toolbox mount position on the truck rails to get the needed clearance, but that usually isn't a big deal.  Just redrill the mounting holes for the toolbox.
« Last Edit: May 17, 2012, 04:01:42 AM by K1CJS » Logged
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