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TxFire
Administrator
Joined: 19 Aug 2005
Posts: 2848
Location: Cedar Creek Lake, Texas
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 Posted: Wed 13-Aug-2008 00:23 Post subject: Antenna Mounting Question |
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OK...in the picture below, I put a circle and arrow to the, well...what I call the "lip" of the bed at the front....ya'll call it what you want and laugh at me!!   Is it ok to mount an antenna there?? On some trucks...I have seen that be a good 1.25" wide...my Dodge was close to 1.5" in the middle. I have also seen a few people mount there antenna there...and when I say antenna, I am referring to a VHF hi-band 5/8 whip, base load type antenna.
My question, is this OK to do?? I hear most people saying that any antenna needs a good ground plane and etc etc...this has a good ground...but I don't think a good ground "plane" so to speak. Local radio guy here suggests a good 12" to 18" around the base of any antenna...UNLESS you use a No-Ground Plane type antenna.
Any truth to this?? I am considering mounting my antenna here on my next truck instead of going through the roof...which it seems the roof is best....but I hate drilling there!!
Give me some tips on this....because I have had several other people asking me this same question!! Thanks!!
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huntinggamo
Regular
Joined: 06 Jul 2008
Posts: 51
Location: Denver, Colorado
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| Posted: Wed 13-Aug-2008 02:45 Post subject: |
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| i've seen it done but i believe it greatly reduces the efectivness. if i were u i would go on the roof with a low profile style antena. just my .02 cents |
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60a
Regular
Joined: 11 Jan 2006
Posts: 196
Location: Columbus, OH
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| Posted: Wed 13-Aug-2008 05:24 Post subject: |
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| I'd personally be afraid of all that rf coming through that back window before the ground plane. I'm not sure how many watts you are pushing but that should also be a consideration. Combined with ground plane I'd also say mount it on the roof. I know it's not the prettiest but it will give you the best performance results and at least put some shielding between you and that RF. |
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QualityLights
Frequent Poster
Joined: 23 Sep 2007
Posts: 1477
Location: Port Jervis, NY
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| Posted: Wed 13-Aug-2008 06:04 Post subject: Re: |
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| 60a wrote: |
| I'd personally be afraid of all that rf coming through that back window before the ground plane. I'm not sure how many watts you are pushing but that should also be a consideration. Combined with ground plane I'd also say mount it on the roof. I know it's not the prettiest but it will give you the best performance results and at least put some shielding between you and that RF. |
+1 RF is a major consideration when it is a mobile unit, be it 15 watts or more at that distance. As for the ground plane, your radio guy is telling you the truth. On a VHF antenna you would want, at a minimum, 12" around the antenna. Ideally, you would want the antenna in the center of your roof AND as high on the vehicle as you can get it. Remember, height is might! The higher the antenna, the better the reception, both TX and RX.
I have found one method that seems to work very well on pick-ups and that is to mount the antenna towards the rear of the cab over the 3rd. brake light. Remove the light from the rook, see just how far forward you can go and drill your 3/4" hole for an NMO mount. The nice thing about doing it this way is that you don't have to drop the headliner when you drill the hole and fishing the wire is extremely easy. You can run it right out the bottom of the housing into the cab, tuck it up under the trim molding or the edge of the headliner until you reach the rubber gasket for the door. From there, just pull down the gasket, tuck the wire wither up over the door and then down behind the A pillar plastic or down the B pillar behind the plastic and then under the sill plate. Once that is done, just put the rubber back in place. The whole process shouldn't take you but 10 minutes or so. |
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EVS1
Regular
Joined: 25 Dec 2005
Posts: 939
Location: West Virginia
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| Posted: Wed 13-Aug-2008 07:40 Post subject: |
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The radio guy told you what he did for a reason, or for several reasons.
Since he's the radio guy, I would pay attention to what he says. |
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TxFire
Administrator
Joined: 19 Aug 2005
Posts: 2848
Location: Cedar Creek Lake, Texas
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| Posted: Wed 13-Aug-2008 10:24 Post subject: Re: |
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| EVS1 wrote: |
The radio guy told you what he did for a reason, or for several reasons.
Since he's the radio guy, I would pay attention to what he says. |
if you met him....you would understand why I asked!! |
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Robert W.
Regular
Joined: 27 May 2008
Posts: 713
Location: Hartford, CT
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| Posted: Wed 13-Aug-2008 10:46 Post subject: Re: |
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| TxFire wrote: |
| EVS1 wrote: |
The radio guy told you what he did for a reason, or for several reasons.
Since he's the radio guy, I would pay attention to what he says. |
if you met him....you would understand why I asked!! |
I know what you mean, but he is right in this case. Keep clearance if you do base loaded antennas. That mounting location is a possibility if you do an elevated feed antenna though, yet I have not found them for VHF yet, I have found them for UHF and 800MHz though, I think it is because of the wavelength.
I personally hate being suggested this, because I don't like drilling in roofs, but how about a low profile roof mount, such as a Phantom Antenna. The don't have a great reputation around here, but I have had no problems whatsoever if they are mounted correctly, have enough power, and you are not too far from the nearest repeater. We have one on an engine mounted 3" away from the HVAC unit on the top with a CDM1250, and on talk around, I can hear them fine from about 10 miles away, with heavy woods and a mountain separating the apparatus and my receive point.
There is never anything wrong with a hood channel mount an a 3dbi gain antenna. Granted the whip is long, but your reception and transmit abilities are amazing. |
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Model 12
New member
Joined: 03 Jan 2008
Posts: 6
Location: Milwaukee Metro
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| Posted: Wed 13-Aug-2008 10:56 Post subject: |
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Do not mount an antenna there...too close to the cab for RF exposure and the performance will be less than desireable. Your radio guy is absolutely correct about needed a proper ground plane, in this case 18" because it's VHF highband. If you mount a 1/4w on the roof, it will have it's proper ground plane and work better than a 5/8w on the bed rail.
Mount something on the roof, or worse case on an "L" bracket on a front fender. I'd stick with the roof first if at all possible. |
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LFD-Mike
Frequent Poster
Joined: 20 Aug 2005
Posts: 1872
Location: Metro Milwaukee, WI
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| Posted: Wed 13-Aug-2008 16:02 Post subject: |
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Don't mount it there- it will work but the propagation will be less than optimal, and biased to the rear of the vehicle
In a very real sense, the entire vehicle is going to be the ground plane- all of the body parts are electrically at the same potential |
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mhpf15
Regular
Joined: 17 Mar 2008
Posts: 85
Location: Fulton,MS
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| Posted: Wed 13-Aug-2008 17:34 Post subject: |
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 3/4 inch hole saw in the ROOF!!! I love drillin a hole in a vehicle!!! not only does it look good, it works a lot better that the L brackets too. |
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