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Author Topic: Do I want to Get High  (Read 454 times)
W5MKE
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Posts: 5




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« on: April 22, 2007, 02:38:40 PM »

I want/need to maximize my range.

F-250 4x4 Crew Cab with a headache rack which tops out at about 7" feet.

I figure to mount a Larsen in the middle of the rack with a fold over mount in the rare event I find myself in a situation that I am concerned about head clearance.  This would put the tip of the antenna close to 12" high.

Not knowing anything about planes, waves, and such, I come to you for wisdom.

Is higher better?

W5MKE
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K0BG
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Posts: 9879


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« Reply #1 on: April 22, 2007, 04:56:29 PM »

The range of say a Larsen NMO2/70BK mounted on the roof of the truck, and the left side cowl area isn't worth talking about. Yes, there may be some little bit of difference, but unless you set out to measure it, you'd never know based on day-to-day operation. That said, the center of the roof is best. However, please note there are ribs in the roof, and you need to avoid them.

Alan, KØBG
www.k0bg.com
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WB2THV
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Posts: 16




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« Reply #2 on: April 23, 2007, 09:42:49 AM »

I too have a 4x4 F250 CC. I'm going to put a Larsen w/NMO mount in a 3/4" hole in the middle of the roof. Also running 10-gauge wire from the battery (+ & -)to the inside of the cab to a rigrunner. Right now I have a FT8800R in there with a mag-mount.
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W5MKE
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Posts: 5




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« Reply #3 on: April 23, 2007, 03:51:11 PM »

Sounds like the set up I'm working on.

My concern may not be so much range as it is dropping out of coverage due to gullies and rises.

I'm getting set up for next year's spotting season and while doing ride-alongs this year I have noticed the slight rises and dips on the "flat" South Plains of Texas really come into play, especially on simplex.

I figured if I could get the antenna as high as possible, it would deal with slight elevation changes better.    

Not really being a radio guy, just a guy that uses a radio, I was concerned with grounding, planes, and all those other things that I haven't learned yet.

If it really didn't make much or any difference mounting on the headache rack compared to the roof itself, I was even considering some way of running it up higher if I found myself out in the middle of nowhere.

I'm just trying to wrap my mind around all of this.

Best Regards,
W5MKE

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WB2THV
Member

Posts: 16




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« Reply #4 on: April 23, 2007, 05:14:32 PM »

I think you'll be better off putting the antenna in the middle of the roof instead of the headache rack. It would provide a way better groundplane. And being we have CrewCab's, that's alot of groundplane for 2/440.

I'm going to send away for the Antennex 3/4" hole saw made for mounting NMO connectors. Also sand a bit of the inside where the NMO presses against the inside of the roof.

Once I do it, I'll report back.

See Alan's site for more info.
www.k0bg.com

'73
Bob - WB2THV
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W5MKE
Member

Posts: 5




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« Reply #5 on: April 23, 2007, 07:54:10 PM »

Roof mount it is then.

I'll be looking forward to your report.

MKE
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WB2THV
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Posts: 16




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« Reply #6 on: April 24, 2007, 03:52:38 AM »

OK. Since the warm weather is upon us, I'll be doing it within the next few weeks. Have to spend the first couple of weekends doing "stuff" around the house.

Bob
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WB2THV
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Posts: 16




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« Reply #7 on: April 30, 2007, 05:57:23 AM »

UPDATE:

I plan on doing teh install this coming weekend (weather permitting). Will do along with a friend who is putting an NMO on his Chevy Suburban.

I removed the dome light yesterday to have a look see of what's in store. There is a roof brace where the dome light screws into so it appears the 3/4" hole for the NMO mount will go behind it a few inches. Which is OK. It puts the antenna more in the middle of the CrewCab providing an equal amount of ground plane in all directions.

Stay tuned.

'73
Bob - WB2THV
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WB2THV
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Posts: 16




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« Reply #8 on: May 14, 2007, 10:26:09 AM »

W5MKE:

I posted that I did the install of the NMO and Larsen 2/70 (closed coil) antenna. I went back a few inches from where the dome light is. There is a roof brace there and didn't want to disturb that. Actully that put the 3/4" hole more in the middle of the crewcab so it worked out for the better. Got the Dremel out with the pencil type extension and small grinding wheel. CAREFULLY took off some of the paint on the underside (interior) of the hole so the NMO had GOOD ground contact with the roof. Ran the coax down the passanger side B-pillar making it's way under the dash. Also ran 10gauge Zip-cord (blk/red) directly from the battery to the FT8800. Works FB. Oh and I used an Antennex 3/4" hole saw that worked FB.

Bob
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W5MKE
Member

Posts: 5




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« Reply #9 on: May 22, 2007, 07:15:14 PM »

I pulled my dome off to change a bulb and had took a look.  I had the same thoughts about placement.

Now to get up the nerve to cut a hole in a perfectly good roof.

Couple of other things.

How long did it take?
Where did you mount the unit?  I'm thinking of mounting the radio behind the backseat, passenger side.
Assuming you used the relocation kit, where did you mount the faceplate?

Thanks for sharing.

M
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WB2THV
Member

Posts: 16




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« Reply #10 on: May 23, 2007, 05:57:16 AM »

It took a few hours but like I said my friend and I never did this before. We CAREFULLY took time to measure where to put the mount. You only get one shot at it unless you want to go to a body shop to have a 3/4" hole repaired. We came up with the idea of putting a tight piece of stirng tied to the two "B" pillars and across the roof outside. That gave us a reference point of where the roof brace is located. So we worked off that and went back a few inches to COMPLETELY clear the brace. CAREFULLY drilled a small pilot hole with a Dremel. Did not want to got through the headliner. Next took the Antenex hole saw and went to town. Took the Dremel with the 3ft flex shaft and small grinding wheel to de-bur and to scrap away some paint where the NMO connecter will come into contact with the underside of the roof. DO NOT use the grinder to grind sides of the 3/4" hole. You don't want to make the hole any larger. Fed the coax from the outside to the passanger side B-pillar. Had to drop the headliner on that side so we took off the grab handles and the covers. Also the large nut holding the seatbelt. There's maybe a better/faster way but we NEVER did this before. Fished it to under the dash.

Bought a new Larsen 2/70 (closed coil) antenna. After a coulple of truck washes and few HEAVY rain storms no leaks were found. I also keep an NMO rain cap in the truck.

Of course you can go to a Pro Install shop to have it done if you're not comfortable doing this.

The Ft8800 is mounted under opening to the left of the ash tray (I have a 2003 F250 CC). I have the remote mount kit but I am not using it yet since I sometimes bring the rig into the house. Once I get a newer VHF/UHF permanently in the house, I will remote mount the 8800.
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