Clean, sturdy, cheap DIY antenna bracket for multiple antennas (ham, CB, etc)
04-28-2013, 06:40 AM
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Clean, sturdy, cheap DIY antenna bracket for multiple antennas (ham, CB, etc)
I installed my CB antenna in the common location, using the factory bolts on the JK's spare tire carrier. I used a DIY bracket that I made from aluminum bar stock. While this location may not be ideal for antenna performance (very little ground plane underneath), it offered a low SWR and would do fine for short-distance communication, which is about all I'd use it for (trail group, etc.) I also like this location because it offers protection to the antennas (and therefore the mounting points); as long as the antennas don't extend far above the roof line, it's highly unlikely that they'll snag on anything when you're driving, so you really don't even need springs at the bases - which would in turn allow enough flex to cause the antenna to strike the rear window when going over large bumps or rough terrain.
This worked fine until I wanted to install a second antenna, for a VHF radio that doubles as a 2 meter ham rig and a police/fire scanner. If I mounted the second antenna on the opposite side of the tire carrier, the two antennas would be too close to one another, which could adversely affect performance, and it also looks silly.
My antenna install goals were then:
- low profile / stealthy
- don't look goofy ("mouse tail" effect)
- won't interfere with trees, limbs, etc. while off-roading
- separated enough to not interfere with each other too much
- rigid mount that allows antenna movement to not stress the mounts or JK
- are easy to install with minimal hacking/drilling into factory parts
I needed a wide, horizontal support to get enough separation between the antennas. The biggest problem here is that the center mounted brake light bracket gets in the way. I thought half-inch, thick walled copper tubing would be a good solution since you could use 45- and 90-degree elbow joints to make just about any shape you wanted, routing it around obstacles. Antennas could be mounted to the tubing using U-clamps and platforms, and coax could even be routed inside the tubing for protection and a clean look. On the downside, soldering the copper components would be a little tedious, and the clamps would look a little ugly.
Flat bar stock would likely not be strong enough, since the antenna could act like a big lever with back & forth movements, especially when the JK accelerates or brakes.
I ended up going with "L" angle aluminum bar stock: light and strong; the L shape resists bending. It's also very easy to cut and drill. I planned for two 12-inch vertical supports, each bolted to an opposite side of the tire carrier, and one 24-inch horizontal bar to support the antennas mounts. Home Depot stocks it in 4-foot lengths, which turned out to be exactly the right length, and cost only $13.27. I also picked up two 3/8-inch by 3/4-inch long hex bolts, two 3/8-inch nuts and two 3/8-inch split lock washers, all zinc. These will bolt the horizontal bar to the two uprights.
I actually went with 11.5-inch uprights (so the remaining horizontal bar was 25 inches), but I think 12-12-24 would also work. In the 11.5 / 11.5 / 25 configuration, installed as shown in the photos, the brackets clear all the body sheet metal. The only interference comes from the ribbing on tire carrier. I got around this by notching those spots in the brackets. This needs to be done in three locations on each upright, and four locations on the horizontal. You could probably avoid having to do this by sandwiching the uprights between the body sheet metal and the tire carrier, but that would require removing the entire tire carrier, and would also put aluminum in contact with the sheet metal, scratching the paint, etc. It also might cause the horizontal bar to be too close to the body sheet metal. So I ended up just putting them on top of the carrier (by 'top' I mean farthest to the rear, not upward), and making notches in the aluminum to clear the ribbing.
When drilling holes in the aluminum bracket for the tire carrier bolts, I found it helpful to make an indentation in the desired spots by using a punch. This keeps the drill bit from wandering as you make the hole.
I also used a smaller bit to make a pilot hole before going with the full-size bit, to help locate the hole better. Locate the hole with enough clearance around it for the washer. Centering the hole left/right on the upright, on one side of the L, allows enough clearance for this. NOTE (and this one got me a couple times) - the left/right center on the "back" side of the 1-inch bracket isn't at the half-inch point, because part of that inch is taken up by the 1/8-inch thickness of bracket itself. That is, on the "front" side of the bracket, the width is 7/8 inch, so the hole is a little offset, as compared to where you'd center it on the "back" side of the bracket.
In short, whenever you are locating centers for holes in the brackets, it's a good idea to do this on the "front" side of the bracket (with one of the lips facing towards you), not on the "back" side. Otherwise you may find the 1/8-inch lip interferes with bolt heads, washers, or antenna mounts. Ask me how I know...
Moving on...
With the uprights installed, the raised edge of the carrier causes a gap between the bracket and the carrier. While maybe not necessary, I filled this with thre washers. The entire 'bolt stack' starting at the bolt head is: thick black washer (factory), upright aluminum bracket, three washers (you supply), and lastly the thin black washer (factory). I went with the washers, rather than leaving a gap, because I could tighten down the tire carrier bolts without worrying about flexing the aluminum or forcing it too hard against the tire carrier; instead, the washers share the load. Just select washer thickness appropriately; you want to more or less exactly match the depth of the ribs. In my case this was three washers, I'd guess about 1/16 inch each (I didn't measure).
With the uprights bolted into place, I test-fit the horizontal section, notching it in four places to clear the ribs on the tire carrier. In the following photo, you're standing outside the gate, looking down from the top of the center mounted stop light. You can see the four ribs that the notches will go around.
Then I eyeballed the locations for the two 3/4-inch bolts at the tops of the uprights, marked the spot with a punch, and drilled. You can do this with the uprights in place, but just go slow and put a block of wood behind the drill hole so you don't punch through and drill into the sheet metal on the gate. The block also helps keep the end of the upright from wiggling. The proper way to do this is to remove the uprights and use a drill press, but I went for the quick/dirty method; I was in a rush.
With the top hole drilled into each upright, set the horizontal bracket back on and mark its corresponding holes through the ones in the uprights, and make the holes in the horizontal.
Now bolt the horizontal to the uprights using the 3/4-inch bolts. For a cleaner look I put the head on the outside (rearward) and the lock washer and nuts on the hidden side. To do this you'll probably need to remove or at least loosen the entire bracket from the tire carrier, in order to get enough room to access the "nut" side of the bracket. I removed it entirely, and also used this as an opportunity to paint the entire bracket. Nothing fancy - I didn't even clean it first! - just applied flat black Rustoleum from a rattle can, and barely even let it dry before continuing. I tightened the top two bolts most of the way but left a tiny bit of looseness so I could flex the assembly into the proper orientation when bolting it back onto the carrier, and after tightening the carrier bolts, then did a final tighten on the top two.
Now it's time to drill the holes for the antenna mounts. Since you now have access to only the "back" (1-inch) side of the horizontal bracket, when you center your drill holes you must remember there's a 1/8-inch lip hidden underneath. You must locate the holes so there's enough clearance underneath for not only the retaining nut on the mount, but also the coax connector! The location of the hole will vary from one install to another because we all use different mounts. Most CB antenna mounts use a half-inch hole but my ham antenna connector (a "UHF" barrel connector) was about 5/8 inch diameter. But the coax connector's diameter was about 11/16 inch, and since it has to fit under the bracket, it's what should be used as a guide for locating the hole. You might want to leave a little extra room so you easily screw on the coax connector, so maybe allow for 3/4 inches of clearance underneath the bracket. Bottom line: locate the hole carefully. There will probably be burrs on the underside of the hole; scrape these away with a larger drill bit as they will probably interfere with the antenna mount and could cause the mount to not properly insulate the center conductor from ground.
I found it easiest to route my coax starting inside the vehicle and going to the outside, rather than starting from the antenna mount and going inside, since fishing the cable through the vent under the spare tire was easier to do from the inside out. I was able to do this even with the coax connectors installed on the ends. Pop the large rectangular wire cover off the inside of the tail gate. It is held on with spring clips along the bottom, and a few plastic lips (not clips!) along the top. Just pop the bottom edge out first - not the top, or you will risk breaking the plastic lips/tabs along the top.
There's an approx 1-inch diameter hole exposed now in the sheet metal where you can route your cables into, then move to the outside of the gate and, through one of the rubber vent flaps, use a small needle nose pliers to grab the center conductor of the coax plug, and pull it through. In order to do this I had to cut out one of the thin plastic support strips just behind the flap. This is a tiny piece of flimsy plastic about 3/4 inch long. I assume the purpose of this was to keep the rubber flap from closing too far, but it doesn't look like that would happen even without the support strip. After pulling the connector through, I routed the cables out the large hole in the botto of the carrier - rather than the side holes which would be a shorter distance. I chose the bottom because this keeps the cables from propping the flap open. Connect the cables to the mounts and reattach the spare tire.
With everything buttoned back up, all brackets and coax are completely hidden from the rear view. You can see the brackets from the side but even then they are stealthy, especially when painted black.
Since this is a new configuration, you will need to make sure your antenna is properly tuned. Altering its location or its proximity to nearby metal objects will affect its electrical length, so you really need to use an SWR meter to adjust it. My CB antenna tested at about 1.5:1 SWR, and the ham antenna about 1.7:1. As long as it's under 2:1 I'm happy; that's good enough for the light transmitting and low power that I'm usually running.
This install does has some downsides:
- you can't have the rear window open with the antennas on, because they are too tall
- if close the gate without closing the window first, you risk bending the antennas
- in my install, the rear wiper rubs against the CB antenna very slightly. I rarely use my rear wiper so this doesn't bother me much.
- this isn't an ideal location for antennas in terms of ground plane, because there simply isn't much of a ground plane, which vertical antennas neeed for best performance. However, as long as the SWR is low (under 2.0:1), and power is kept low, and you intend to communicate only short distances, this should be fine. I think the clean and easy install is worth the tradeoff, especially for multiple antennas.
This job was a little sloppy and a learning experience so now that I have a functional setup, I might take my time to do nicer "version 2.0" but the concept is the same.
This worked fine until I wanted to install a second antenna, for a VHF radio that doubles as a 2 meter ham rig and a police/fire scanner. If I mounted the second antenna on the opposite side of the tire carrier, the two antennas would be too close to one another, which could adversely affect performance, and it also looks silly.
My antenna install goals were then:
- low profile / stealthy
- don't look goofy ("mouse tail" effect)
- won't interfere with trees, limbs, etc. while off-roading
- separated enough to not interfere with each other too much
- rigid mount that allows antenna movement to not stress the mounts or JK
- are easy to install with minimal hacking/drilling into factory parts
I needed a wide, horizontal support to get enough separation between the antennas. The biggest problem here is that the center mounted brake light bracket gets in the way. I thought half-inch, thick walled copper tubing would be a good solution since you could use 45- and 90-degree elbow joints to make just about any shape you wanted, routing it around obstacles. Antennas could be mounted to the tubing using U-clamps and platforms, and coax could even be routed inside the tubing for protection and a clean look. On the downside, soldering the copper components would be a little tedious, and the clamps would look a little ugly.
Flat bar stock would likely not be strong enough, since the antenna could act like a big lever with back & forth movements, especially when the JK accelerates or brakes.
I ended up going with "L" angle aluminum bar stock: light and strong; the L shape resists bending. It's also very easy to cut and drill. I planned for two 12-inch vertical supports, each bolted to an opposite side of the tire carrier, and one 24-inch horizontal bar to support the antennas mounts. Home Depot stocks it in 4-foot lengths, which turned out to be exactly the right length, and cost only $13.27. I also picked up two 3/8-inch by 3/4-inch long hex bolts, two 3/8-inch nuts and two 3/8-inch split lock washers, all zinc. These will bolt the horizontal bar to the two uprights.
I actually went with 11.5-inch uprights (so the remaining horizontal bar was 25 inches), but I think 12-12-24 would also work. In the 11.5 / 11.5 / 25 configuration, installed as shown in the photos, the brackets clear all the body sheet metal. The only interference comes from the ribbing on tire carrier. I got around this by notching those spots in the brackets. This needs to be done in three locations on each upright, and four locations on the horizontal. You could probably avoid having to do this by sandwiching the uprights between the body sheet metal and the tire carrier, but that would require removing the entire tire carrier, and would also put aluminum in contact with the sheet metal, scratching the paint, etc. It also might cause the horizontal bar to be too close to the body sheet metal. So I ended up just putting them on top of the carrier (by 'top' I mean farthest to the rear, not upward), and making notches in the aluminum to clear the ribbing.
When drilling holes in the aluminum bracket for the tire carrier bolts, I found it helpful to make an indentation in the desired spots by using a punch. This keeps the drill bit from wandering as you make the hole.
I also used a smaller bit to make a pilot hole before going with the full-size bit, to help locate the hole better. Locate the hole with enough clearance around it for the washer. Centering the hole left/right on the upright, on one side of the L, allows enough clearance for this. NOTE (and this one got me a couple times) - the left/right center on the "back" side of the 1-inch bracket isn't at the half-inch point, because part of that inch is taken up by the 1/8-inch thickness of bracket itself. That is, on the "front" side of the bracket, the width is 7/8 inch, so the hole is a little offset, as compared to where you'd center it on the "back" side of the bracket.
In short, whenever you are locating centers for holes in the brackets, it's a good idea to do this on the "front" side of the bracket (with one of the lips facing towards you), not on the "back" side. Otherwise you may find the 1/8-inch lip interferes with bolt heads, washers, or antenna mounts. Ask me how I know...
Moving on...
With the uprights installed, the raised edge of the carrier causes a gap between the bracket and the carrier. While maybe not necessary, I filled this with thre washers. The entire 'bolt stack' starting at the bolt head is: thick black washer (factory), upright aluminum bracket, three washers (you supply), and lastly the thin black washer (factory). I went with the washers, rather than leaving a gap, because I could tighten down the tire carrier bolts without worrying about flexing the aluminum or forcing it too hard against the tire carrier; instead, the washers share the load. Just select washer thickness appropriately; you want to more or less exactly match the depth of the ribs. In my case this was three washers, I'd guess about 1/16 inch each (I didn't measure).
With the uprights bolted into place, I test-fit the horizontal section, notching it in four places to clear the ribs on the tire carrier. In the following photo, you're standing outside the gate, looking down from the top of the center mounted stop light. You can see the four ribs that the notches will go around.
Then I eyeballed the locations for the two 3/4-inch bolts at the tops of the uprights, marked the spot with a punch, and drilled. You can do this with the uprights in place, but just go slow and put a block of wood behind the drill hole so you don't punch through and drill into the sheet metal on the gate. The block also helps keep the end of the upright from wiggling. The proper way to do this is to remove the uprights and use a drill press, but I went for the quick/dirty method; I was in a rush.
With the top hole drilled into each upright, set the horizontal bracket back on and mark its corresponding holes through the ones in the uprights, and make the holes in the horizontal.
Now bolt the horizontal to the uprights using the 3/4-inch bolts. For a cleaner look I put the head on the outside (rearward) and the lock washer and nuts on the hidden side. To do this you'll probably need to remove or at least loosen the entire bracket from the tire carrier, in order to get enough room to access the "nut" side of the bracket. I removed it entirely, and also used this as an opportunity to paint the entire bracket. Nothing fancy - I didn't even clean it first! - just applied flat black Rustoleum from a rattle can, and barely even let it dry before continuing. I tightened the top two bolts most of the way but left a tiny bit of looseness so I could flex the assembly into the proper orientation when bolting it back onto the carrier, and after tightening the carrier bolts, then did a final tighten on the top two.
Now it's time to drill the holes for the antenna mounts. Since you now have access to only the "back" (1-inch) side of the horizontal bracket, when you center your drill holes you must remember there's a 1/8-inch lip hidden underneath. You must locate the holes so there's enough clearance underneath for not only the retaining nut on the mount, but also the coax connector! The location of the hole will vary from one install to another because we all use different mounts. Most CB antenna mounts use a half-inch hole but my ham antenna connector (a "UHF" barrel connector) was about 5/8 inch diameter. But the coax connector's diameter was about 11/16 inch, and since it has to fit under the bracket, it's what should be used as a guide for locating the hole. You might want to leave a little extra room so you easily screw on the coax connector, so maybe allow for 3/4 inches of clearance underneath the bracket. Bottom line: locate the hole carefully. There will probably be burrs on the underside of the hole; scrape these away with a larger drill bit as they will probably interfere with the antenna mount and could cause the mount to not properly insulate the center conductor from ground.
I found it easiest to route my coax starting inside the vehicle and going to the outside, rather than starting from the antenna mount and going inside, since fishing the cable through the vent under the spare tire was easier to do from the inside out. I was able to do this even with the coax connectors installed on the ends. Pop the large rectangular wire cover off the inside of the tail gate. It is held on with spring clips along the bottom, and a few plastic lips (not clips!) along the top. Just pop the bottom edge out first - not the top, or you will risk breaking the plastic lips/tabs along the top.
There's an approx 1-inch diameter hole exposed now in the sheet metal where you can route your cables into, then move to the outside of the gate and, through one of the rubber vent flaps, use a small needle nose pliers to grab the center conductor of the coax plug, and pull it through. In order to do this I had to cut out one of the thin plastic support strips just behind the flap. This is a tiny piece of flimsy plastic about 3/4 inch long. I assume the purpose of this was to keep the rubber flap from closing too far, but it doesn't look like that would happen even without the support strip. After pulling the connector through, I routed the cables out the large hole in the botto of the carrier - rather than the side holes which would be a shorter distance. I chose the bottom because this keeps the cables from propping the flap open. Connect the cables to the mounts and reattach the spare tire.
With everything buttoned back up, all brackets and coax are completely hidden from the rear view. You can see the brackets from the side but even then they are stealthy, especially when painted black.
Since this is a new configuration, you will need to make sure your antenna is properly tuned. Altering its location or its proximity to nearby metal objects will affect its electrical length, so you really need to use an SWR meter to adjust it. My CB antenna tested at about 1.5:1 SWR, and the ham antenna about 1.7:1. As long as it's under 2:1 I'm happy; that's good enough for the light transmitting and low power that I'm usually running.
This install does has some downsides:
- you can't have the rear window open with the antennas on, because they are too tall
- if close the gate without closing the window first, you risk bending the antennas
- in my install, the rear wiper rubs against the CB antenna very slightly. I rarely use my rear wiper so this doesn't bother me much.
- this isn't an ideal location for antennas in terms of ground plane, because there simply isn't much of a ground plane, which vertical antennas neeed for best performance. However, as long as the SWR is low (under 2.0:1), and power is kept low, and you intend to communicate only short distances, this should be fine. I think the clean and easy install is worth the tradeoff, especially for multiple antennas.
This job was a little sloppy and a learning experience so now that I have a functional setup, I might take my time to do nicer "version 2.0" but the concept is the same.
Last edited by mostlystock; 04-19-2014 at 04:02 AM. Reason: Fixing broken image links
04-19-2014, 04:07 AM
#4
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I've been yakking on both ham and CB with this setup and it works great.
05-01-2019, 02:15 PM
#5
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I have a cowl mount for mine. 2014 Rubicon JKU. I ran the cable from the antenna through the firewall and up the pillar. My CB is mounted above the rearview mirror. The issue I'm having is putting the male connection on the end of the cable. I had to take the original connection off to get the cable through the firewall. I havent found much luck putting a new connection on the cable. I tried a few different connectors (some that needed soldered and some that didnt)...probably operator error. But I'm getting there. Haha. Anybody had the same issue? Any tips or tricks or suggestions for connections would be great. Thanks!
05-01-2019, 02:40 PM
#6
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The issue I'm having is putting the male connection on the end of the cable. I had to take the original connection off to get the cable through the firewall. I havent found much luck putting a new connection on the cable. I tried a few different connectors (some that needed soldered and some that didnt)
While the male connector has a standard size pin and teeth that mate to the female connector on the CB, there are several sizes of adapters that screw into the connector to accommodate different thicknesses of cables. You need to use the right adapter for your cable. Somewhere along the length of your cable there should be markings telling what type of cable it is - what do you find? It'll be something like "RG-58", "RG-8X", "RG-59" or similar. From there, you can figure out what adapter you need.
Properly preparing the cable end for the connector is important. There are specific lengths recommended for cutting back the jacket, the woven ground shield, and the foam insulator. These are all detailed out in publications such as the ARRL Handbook for Radio Amateurs but instructions/diagrams can certainly be found online too. Following those guidelines will save you lots of trouble, as well as possible short circuits (and damage to your CB).
A soldered connection will be more reliable than a crimp connection. If you have access to a decent soldering iron (a station type that can heat to 600-700 deg F, not one of the $30 pencil types) and soldering skills, I'd go that route. If you know a ham radio operator or electronics geek, they might be a great resource, and could even do the job for you.
You could bring a sample of the cable to a truck stop shop and probably find the right connector.
Good luck with the project. Terminating the cables is a pain but is absolutely doable, a common task, you just need to get the right parts & setup.
Once things are installed it's strongly advisable to use an ohm meter to make sure there's no short between antenna hot and ground. Disconnect the antenna from the CB and measure ohms from the cable connector's shield to center pin, you want to see high resistance. If it goes to zero ohms you have a short (bad).
Also strongly advisable to measure the SWR during transmit (requires an SWR meter) after finishing the install. You want something around 2:1 or less (1:1 is ideal but rarely achievable). Maybe 3:1 at most.
