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Posted: 6/10/2021 1:44:45 PM EDT
Hey guys
I have a short 1/4 wave antenna mounted to the front fender on my F250, and im looking to get a larger or more efficient antenna. Here is the current one  I have a magnetic mount I can try on the roof, but my roof is not flat, it has 6 or 7 good size ridges stamped into it, so my guess it would not be a great ground plane I have a diamondback aluminum bed cover, with a fixed center section, so my thought is to mount it to the aluminum, most likely NMO mount of some sort.  I'm pretty much all 2M, with occasional MURS use, running a KENWOOD TM-D710G with a MARS mod to expand into MURS. Do you guys have a recommendation for a good antenna? I have no experience selecting one. The 1/4 wave was recommendation from the HAM outlet where I picked up the radios about a year ago. |
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Posted: 6/10/2021 2:04:52 PM EDT
[#1]
Those structural ridges in the roof won't make it any less of a ground plane as far as the RF is concerned. Best option would be to punch a hole in or about the center of the rook for an NMO mount.
I've thought about a mount on a metal bed cover, it should work well but it would be a pain if you ever needed to remove the cover for a larger load. |
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Posted: 6/10/2021 2:48:46 PM EDT
[#2]
Center of roof would be best. But it is a whole lot easier to take the third brake light out and mount it just in front of it. Just get in the center and far enough that the hole is flat. Makes the whole install pretty easy.
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Posted: 6/10/2021 5:13:09 PM EDT
[#3]
Unless you are out in the panhandle, you will never notice the difference between a 1/4 wave antenna on the roof and a 5/8 wave antenna on the roof and even then it will only be marginal which your picture appears to have too many trees to say panhandle. A 1/4 wave will also have the best frequency response in terms of working 146 MHz 2m and 154 MHz MURS.
Those SD's are pretty easy for radio installs (done a dozen or so) though. I don't know how the mount will handle the bed liner though...that could cause a seal issue. |
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Posted: 6/10/2021 10:15:50 PM EDT
[#4]
1/4 wave mag mount in the center of the roof with 5" base. MFJ-1402 + MFJ-335BS.
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Posted: 6/10/2021 10:56:41 PM EDT
[#5]
I use a Geotool stake pocket mount. Won't help you much though. I use to use a mount on a steel plate I put on my bed cover.
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Posted: 6/10/2021 11:23:44 PM EDT
[#6]
Drill the hole! Put an NMO in the center of that roof.
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Posted: 6/11/2021 11:01:58 AM EDT
[#7]
I'll most likely wind up doing the roof.
Which antenna would you guys recommend? I'm thinking something like this https://www.eham.net/reviews/view-product?id=3143 I figured if I'm going to do a mobile antenna, might as well go big. Is there anything better that could be tuned to take advantage of MURS better? |
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Posted: 6/11/2021 11:06:42 AM EDT
[#8]
If you want MURS and 2 meters both you will need something low gain and wide bandwidth. Maybe something like this:
https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_196_216&products_id=4286 |
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Posted: 6/11/2021 12:01:45 PM EDT
[#9]
Quote HistoryQuoted: If you want MURS and 2 meters both you will need something low gain and wide bandwidth. Maybe something like this: https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_196_216&products_id=4286 Honestly, I'd just keep the nice broad-band 1/4-wave whip you have and move it to the roof. Run that for your day-to-day stuff and enjoy a little more gain thanks to moving it up there. Then maybe keep a big high-gain dual bander behind the back seat for those times you want a little more performance on the amateur bands. That's exactly what I do. It was mentioned earlier, but it might be worth looking into how that rough bed-liner finish will play into getting a good seal on a through-roof NMO mount. The standard mount expects a clean, smooth surface for the O-ring to seal on, so you might have to clear away some of that bed liner around the mount to get a good seal if you go that route. Otherwise, I swear I've seen some type of through-mount that has a bigger rubber boot on it that might work better on the rough surface, but don't recall where I saw it... |
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Posted: 6/11/2021 1:31:37 PM EDT
[#10]
Just drilled an NMO mount in the roof of my F350 crew cab just forward of center for a 440/GMRS antenna. Also drilled and mounted a Wilson 1000 CB antenna just ahead of the third brake light. Night and day difference vs mag mount with both radios. They are just over 3 feet apart so no interference problems. No regrets. Should have done this YEARS ago.
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Posted: 6/11/2021 11:17:22 PM EDT
[#11]
Quote HistoryQuoted: If you want MURS and 2 meters both you will need something low gain and wide bandwidth. Maybe something like this: https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_196_216&products_id=4286 Check out the Larsen NMO150-WB. It's become the standard 5/8 wave solution where needed for the Texas Department of Transportation and the Texas Department of Public Safety due to the wide spread of the VHF side of GATRRS. It's only 2.5 dBd of gain (versus the traditional 3 dBd in a 5/8 wave). |
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Posted: 6/11/2021 11:38:32 PM EDT
[#12]
Quote HistoryQuoted: Check out the Larsen NMO150-WB. It's become the standard 5/8 wave solution where needed for the Texas Department of Transportation and the Texas Department of Public Safety due to the wide spread of the VHF side of GATRRS. It's only 2.5 dBd of gain (versus the traditional 3 dBd in a 5/8 wave). Quote HistoryQuoted: Quoted: If you want MURS and 2 meters both you will need something low gain and wide bandwidth. Maybe something like this: https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_196_216&products_id=4286 Check out the Larsen NMO150-WB. It's become the standard 5/8 wave solution where needed for the Texas Department of Transportation and the Texas Department of Public Safety due to the wide spread of the VHF side of GATRRS. It's only 2.5 dBd of gain (versus the traditional 3 dBd in a 5/8 wave). I have one of those and would recommend them if a gain antenna is truly needed. That said, on a truck roof with that big ground plane I'd just use a 1/4 wave with a spring: https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_195_457_212&products_id=5200 The spring plus larger diameter whip results in more bandwidth. If you really want bandwidth, cut a piece off the base of a low band whip and tune for VHF. |
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Posted: 6/12/2021 2:31:25 PM EDT
[#13]
Quote HistoryQuoted: I have one of those and would recommend them if a gain antenna is truly needed. That said, on a truck roof with that big ground plane I'd just use a 1/4 wave with a spring: https://www.theantennafarm.com/catalog/index.php?main_page=product_info&cPath=191_192_195_457_212&products_id=5200 The spring plus larger diameter whip results in more bandwidth. If you really want bandwidth, cut a piece off the base of a low band whip and tune for VHF. True. I tend to use those heavy duty Motorola wideband antennas (on the old Antenna Specialist design). |
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Posted: 6/12/2021 6:53:30 PM EDT
[#14]
I put a Diamond Dual-Band Mobile Antennas SG7900ANMO on the luggage rack on top of my fiberglass truck cap.
It doesn't need a ground plane and works very well.. i saw a big difference compared to my 1/4 wave mag mount on top of the cab It does hit trees and low bridges though. |
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Posted: 6/14/2021 1:37:59 AM EDT
[#15]
Try this for info. You need to bond all your body panels so that your antenna has something to 'push against'.
k0bg is pretty smart about mobile installations. 
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Posted: 6/14/2021 9:55:49 AM EDT
[#16]
Quote HistoryQuoted: Try this for info. You need to bond all your body panels so that your antenna has something to 'push against'. k0bg is pretty smart about mobile installations. You'll find a Super Duty has adequate enough bonding for VHF/UHF operation. Same is true with most pickups built by GM, (Dodge) Ram, and Ford. Ford's newer aluminum designs can be a bit wonky if you aren't mounting to the cab but everything is bonded adequately. Source: Do it for a living. |
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Posted: 6/14/2021 12:48:55 PM EDT
[#17]
I wouldn't proactively bond a vehicle for vhf/uhf operation. HF is a different story, bond everything.
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Posted: 6/20/2021 9:21:09 PM EDT
[#18]
Quote HistoryQuoted: Ford's newer aluminum designs can be a bit wonky if you aren't mounting to the cab but everything is bonded... Tell me what you know about the aluminum trucks, I just traded in to one. Its a terrific truck (Coyote baby  ) but I have not done any permanent antenna installs yet. I want to put a 2/70 of some kind plus an ATAS on it.
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Posted: 6/21/2021 10:28:24 AM EDT
[#19]
Quote HistoryQuoted: Tell me what you know about the aluminum trucks, I just traded in to one. Its a terrific truck (Coyote baby ) but I have not done any permanent antenna installs yet. I want to put a 2/70 of some kind plus an ATAS on it.Aside from having to have installed a handful of Motorola's in various aluminum Ford's, that's about it. The aluminum roof is a little thicker than other manufacturer's steel roofs granted in the previous generations Ford really cut back on the sheet metal thickness to save weight (which they could have saved a significant amount of weight just by unboxing the frame). |
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Posted: 6/21/2021 11:46:33 AM EDT
[#20]
Quote HistoryQuoted: Center of roof would be best. But it is a whole lot easier to take the third brake light out and mount it just in front of it. Just get in the center and far enough that the hole is flat. Makes the whole install pretty easy. This is the method I used on my F-150. |
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Posted: 6/21/2021 4:09:07 PM EDT
[#21]
My guess is that if the ridges in the roof are less that one tenth wavelength high they are of no consequence.
Put your quarter wave in the center of the roof and try it out before you get a "bigger" antenna. Where you have it is one of the shittiest places to put an antenna on a vehicle, and proves just how poor something can be and still work. (sort of) |
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Posted: 6/21/2021 9:02:35 PM EDT
[#22]
So I ordered a Larsen NMO150-WB and a 5.5in HD magnet for the center of roof.
Said 2-3 weeks for delivery I'll drill a hole just forward of the brake light and give the 1/4 wave a shot there. If it works well, I guess I can always put the larger 5/8 wave antenna there. This was an incremental leap, because I started with the shortie on the fender, and I just attached the HT to it while in the truck. It worked AMAZINGLY better. Then I decided to splurge and get the truck an actual radio, and thet worked even better still. I'm still playing with placement and getting everything tucked away. Is there any long term concerns about putting the body and the head in the overhead console? I'm in TX, and we hit over 100 for a while in the summers, and it gets to 130-150 interior temps |
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Posted: 6/21/2021 10:25:12 PM EDT
[#23]
Back in the 70s I ran around in a VW Beetle (a real one, not these new ones) with an SO-239 in the center of the roof and a quarter wave stainless steel tube soldered into a PL-259 as an antenna.
There was a screw run into the top to keep the rain out and a turned teflon piece to fill the space in the SO-239. Everyone made fun of me, but it worked as well as any of the 5/8 antennas, and I could actually drive in and out of my garage with it. This was back in the days when you were regarded as some kind of asshole if you didn't have a 5/8 on your vehicle. I just laughed right back at them. |
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Posted: 6/22/2021 1:48:55 AM EDT
[#24]
Quote HistoryQuoted: Everyone made fun of me, but it worked as well as any of the 5/8 antennas, and I could actually drive in and out of my garage with it. I lived in western Oregon for a long time, where the terrain had many hills, valleys, washes, canyons and so on. Back in the day the old Larsen 5/8 wave had almost 100% market share but in some of the deep and twisting valleys the low radiation angle of a 5/8 could not escape the line of sight in the horizontal plane. A 1/4 wave would often reach out better due to the broader vertical beamwidth. But the 5/8 had places where it was the most viable game too. For example there were places in central Oregon from which you could reach coastal or Willamette valley stations with a ~6000 ft. mountain range in the way. These paths used knife edge diffraction and they were pretty reliable but it took a little extra power density to go the ~150 air mile distance. You could use 25W and a 5/8 wave or maybe 200W with a 1/4 wave. Of course that was the good old days. Now the noise floor almost everywhere is considerably higher and it's harder to achieve symmetry with very weak and distant signals on FM. |
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Posted: 6/22/2021 8:54:34 AM EDT
[#25]
We in this part of New England have oodles of repeaters, so we don't have much trouble finding one, and our terrain isn't that difficult.
My view was (and is) "It's a radio, not magic, sometimes it works and sometimes it doesn't." Repeaters are not for DXing. |
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Posted: 6/22/2021 2:26:06 PM EDT
[#26]
Quote HistoryQuoted: So I ordered a Larsen NMO150-WB and a 5.5in HD magnet for the center of roof. Said 2-3 weeks for delivery I'll drill a hole just forward of the brake light and give the 1/4 wave a shot there. If it works well, I guess I can always put the larger 5/8 wave antenna there. This was an incremental leap, because I started with the shortie on the fender, and I just attached the HT to it while in the truck. It worked AMAZINGLY better. Then I decided to splurge and get the truck an actual radio, and thet worked even better still. I'm still playing with placement and getting everything tucked away. Is there any long term concerns about putting the body and the head in the overhead console? I'm in TX, and we hit over 100 for a while in the summers, and it gets to 130-150 interior temps Somewhere I have an old picture I took in the summer of 2013 in Lubbock. The temp gauge on my Trailblazer was reporting 113 degrees. The temp sensor in the Yaesu FT-2900 on the dash was reporting 174. Worked without issue. It's pretty common to install radio bodies in areas where they get minimal airflow. For example, in my pickup the body is mounted under the back seat. In my Cherokee the body is mounted under the back seat. They do just fine. Keep in mind, in police cruisers its common place to install radio bodies in the trunk and they don't typically die from heat. In many cruisers where dash mount radios are used, they are typically always mounted in a console that lacks airflow as well. |
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