antenna monting question

9

93BLAZER

Explorer
I just bought a FT 8900 and have a Motorola Saber Covertacom for VHF. I will be mounting them this week/end.

I plan to mount the antennas (HV7A) and VHF antennas on a 87 Chevrolet K5 Blazer.

Any suggestions on where to mount them? I was thinking rear bumper but Ive read that's not ideal. Then, I was thinking on the top of the fiberglass shell, but have read through several sources that thats not ideal although, that would seem like the easiest way. I would simply have to drill two holes for both antennas and wire it up... finished. So now Im reading that the ideal place would be right above the cab. I am not a big fan of this mainly because of the headliner. Your thoughts?

What do you think?

Also, should I mount the antennas side by side? If so, how far apart? Or should I mount them on in front of the other? Again, if one in front of the other... how far apart?

Many thanks as usual.
 
Tennmogger

Tennmogger

Explorer
There's some good info on that model antenna here:
http://www.eham.net/reviews/detail/1563 but I know nothing about it from personal use. Every experience I have had with Diamond or Comet antennas has been negative, but I tend to torture antennas.

Obviously some people like that model, some people hate it, but it seems this is not a very robust antenna. Mounting it high and exposed may be asking for breakage.

This type antenna must be mounted on a good ground plane. Fiberglass is out unless you are willing to add ground plane underneath the glass and bond it all together.

Your K5 is metal up front, right? What about mounting the antenna on a lip mount at the back of the hood, center of windshield? That is a lower and protected location and there is ground plane in all directions. Bond the hood to the cab in several places with some good braid. In that location you can watch the damage as it happens LOL. One 'gotcha' in that location is if the hood moves upward then back as it raises.

Bob
WB4ETT
 
xtatik

xtatik

Explorer
You also might look into the Diamond CR8900A. It was designed specifically for that radio, and can be easily modified to be much more robust than the
HV7A.
Also, it has a folding feature and prefers to to be mounted on the side of the vehicle rather than centered on top. If you read the reviews on eham, you'll see lousy remarks from guys who didn't pay attention...using mag mounts or center roof mounting it when the instructions explicitly instruct against either. It has dual setscrews at each connection rather than the single placements found on most.
When I ran the antenna years ago, I covered the traps with adhesive-lined marine grade shrink tube. It helps pad/toughen the traps against impacts (there were many impacts!) and holds all components together tightly. After applying the shrink tube over the entire trap assemblies, I took a single-edge razor and cut access points to the setscrews. It was mounted to a well grounded
K400 mount and the entire mount and antenna lasted at least 10k offroad miles before being sold as a package to another offroader. I don't know it's fate to this day...but I'd bet it's working fine.
 
G

gary in ohio

Explorer
93BLAZER said:
I just bought a FT 8900 and have a Motorola Saber Covertacom for VHF. I will be mounting them this week/end.

I plan to mount the antennas (HV7A) and VHF antennas on a 87 Chevrolet K5 Blazer.

................
Click to expand...

Well that means you need a 10m, 6m, 2 VHF and 1 UHF antenna.
Th HV7A is NOT going to do well off road and in the brush. The very skinny mast and trombone at the top is going to break pretty quick. I would go with the Diamond CR8900A and a Larsen 2/70 antenna if you want to keep the antenna mount to a minimum. If you want the best antennas. then

Get a Larsen NMO 27B for 10m, A Larsen NMO 52C for 6m than 2 larson NMO 2/70 for your VHF/UHF needs. I would use a dual band antenna on the convertacom just to make parts easier.

Were to mount them, Using NMO mounts and mount them on the cab metal roof. You will want as much distance as you can get them but on a k5 thats not much room. middle of the root and you can fish the cables using the overhead dome light hole so the headliner doesnt need to come down.
Use the NMO mounts and drill the "CORRECT" size hole and the installation is easy and water tight. If your unsure about drilling you can often get a 2way radio shop to do it for minimal money.
 
9

93BLAZER

Explorer
Wow! Thanks for the feedback.

So...the bottom line is get rid of HV7A and get a CR8900A and Larsen 2/70 antenna.

I also need to mount them above the cab. Shucks.... I was really hoping I could mount them on the fiberglass shell. Oh well.

But to move on...

So based on Gary and xtatik's advice I'll pick a CR8900A up in the coming week or so. Since I'll do the majority of my traffic on the 2/70 band, I'll make it a priority to get a Larsen 2/70 antenna first. I see that the antenna itself (the antenna only) sells for about 50 bucks.

I still have a few questions.

What about the mount itself? You mention "NMO Mount" Does that mean magnetic mount? Can you suggest a particular mount? I want a permanent mount.

So I use the CR8900A for the FT8900 and the Larsen 2/70 for the Motorola Saber Convertacom? SO I need two separate antennas?


Shopping List:

1 Diamond CR8900A
1 Larsen 2/70
2 NMO mounts

Is that correct?
 
xtatik

xtatik

Explorer
93BLAZER said:
I also need to mount them above the cab. Shucks.... I was really hoping I could mount them on the fiberglass shell. Oh well.
Click to expand...

Actually, no, not in the case of the CR8900A it likes to be mounted off the side of the vehicle. Off the body and to the side of the shell would probably work/tune just fine. And, you could devise a method to attach the antenna in its folded position as well. I haven't looked into the theory behind this mounting, but Diamond is adamant that this antenna is not to be roof mounted and states so repeatedly and in bold in their mounting instructions.
I would go to the Diamond site and drill down on the 8900 to get to the pdf mounting instructions. You'll see it says the antenna is "optimised for trunk lid mounting and is not recommended for for center roof mounting". I would mount it high on the rear driver-side 1/4 panel region where you could keep an eye on it while wheeling. And, don't forget the adhesive lined heat shrink mod. It really makes a difference in durability and longevity for this and all other trapped mobile antennas.
 
9

93BLAZER

Explorer
I would mount it high on the rear driver-side 1/4 panel region where you could keep an eye on it while wheeling
Click to expand...

That is where I seem to have the most pinstripes/ trail damage. It seems that is the area thats most susceptible and exposed to trail damage.

Anyways... I look into that.

What are your thoughts on a rear bumper mount?
 
G

gary in ohio

Explorer
93BLAZER said:
So based on Gary and xtatik's advice I'll pick a CR8900A up in the coming week or so. Since I'll do the majority of my traffic on the 2/70 band, I'll make it a priority to get a Larsen 2/70 antenna first. I see that the antenna itself (the antenna only) sells for about 50 bucks.

I still have a few questions.

What about the mount itself? You mention "NMO Mount" Does that mean magnetic mount? Can you suggest a particular mount? I want a permanent mount.

So I use the CR8900A for the FT8900 and the Larsen 2/70 for the Motorola Saber Convertacom? SO I need two separate antennas?


Shopping List:

1 Diamond CR8900A
1 Larsen 2/70
2 NMO mounts

Is that correct?
Click to expand...

There are 3 basic types of antenna mounts. NMO, UHF, 3/8 x 24 thread. You will also find some vendor specific.


The antenna mounts are how the antenna connect to the antenna base. UHF looks like a longer version of the connect found on the back of most CB/ham gear and 3/8x24 thread is a screw in thread, typically found on CB and larger ham HF antennas. The NMO is a flat little disk and found on many commercial 2 way radio antennas and is popular with hams using through the roof mounts.

The mount then connect to the body of the vehicle in some way, mag mount, bumper mount, through body hole or a wide variety of ways.



The Diamond CR8900A is a UHF mount antenna and the Larsen is an NMO mount. Your best bet for both are through the body mounts, but a magnetic mount for the larsen is an ok option. The Diamond specially says no mag mounts.

Here are some mounts from diamond http://rffun.com/catalog/hamantm/diamx.html here are some from larsen http://rffun.com/catalog/hamantm/larsenx.html

IN the larsen mount page the NMOK mount would be good for the dual band and the PO-K mount for the diamond antenna would work. Both are through the roof mounts.
 
G

gary in ohio

Explorer
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