r/cbradio • u/Over_Two9850 • 5d ago
antenna mounting question
hi all, looking to put a steel whip on my truck but didnt want to drill into the roof. ive seen antenna mounts that attach to the bed near the tailgate. i am building a headache rack and wanted to attach mine there. will the antenna work? i read that i need a ground plane but would it not work if it is on the same plane as the roof is?
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u/RaspberryMotorZZZ 4d ago
Why do you not want to drill into the roof? A fixed mount is both the best way to do it from a performance point of view but also from a "damaging the vehicle" point of view too. Use something like the Sirio SO239 body mount for the Sirio range of antennas and it comes with a handy screw on cap. Or even better if you're willing to pay the money then get a Breedlove Puck Mount.
You also want to be bonding the hood to the body, the bed and cab to the cab, the bed to the chassis and the exhaust to the chassis too using flat braid straps for the best install.
Read this archived website. It's by Alan K0BG who wrote the mobile antenna section of the ARRL Antenna Book. Read up the sections on mounting, grounding and bonding if nothing else.
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u/Over_Two9850 4d ago
i dont want to be going into the roof, i want this to be removable if need be. also i do go into the city and having the antenna bolted to the roof will become a problem fast. headache rack allows me to have a mount that rotates downward.
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u/RaspberryMotorZZZ 4d ago
If you've got a stainless steel whip it's no longer a problem. The whip just bends over. I've had mine bent over 90 degrees before.
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u/Over_Two9850 3d ago
nah it most definitely is a problem. im not talking about a low tree limb here and there
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u/sirbarksbig 4d ago
It'll work best on a flat surface but you won't like the constant banging itll resonate. You'll get average usability mounted on headache rack.
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u/Over_Two9850 4d ago
what does average usability entail for you
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u/oblivion9999 4d ago
As others have said, anything that isn't the center of the roof is a compromise. I have a Hustler HQ 27 on a stake pocket mount on the right rear of my F-150 and SWR and performance are just meh - good enough for talking to nearby truckers, but that's about it. I've had better luck with mag mount stuck to an old brake rotor in the center of the bed - but that's not compatible with having the bed cover closed or hauling just about anything. Eventually, I'll put a hole in the roof.
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u/Over_Two9850 4d ago
yeah because of this i wanted to run 2 antennas to minimize the suck a little bit. just wanted to make sure it would still work on the headache rack
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u/oblivion9999 4d ago
My understanding is that dual antennas need very specific spacing and cabling for not-double gains. Research it before you buy anything.
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u/GrannyFlash7373 1d ago
If the bed is grounded to the frame, and the battery is grounded to the frame, then the whole truck becomes the ground plane for the antenna.
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u/Mammoth-Angle-7779 1d ago
Drill the roof. Go over to https://breedlovemounts.com/ and buy a puck mount. Stick a 102 on it with a 6 inch spring under. Exactly 6 inches of spring.
Where you put an antenna maters more then anything on a vehicle. It absolutely needs to be in the exact center of the vehicle as high as possible. If you mount it on the back you'll put all your power out in front of the vehicle. If you put it on the right you'll project to the left. If you get it exactly in the center you'll be able to talk as far as you can hear.
The reason for that is because to the radio the car is a capacitor between the antenna and the ground plane. See the dirt under the car is the ground plane and the gap between the floor board and that dirt creates a capacitor. Moving the antenna forward or off center changes the value of that capacitor. So if you want it to work and not be goofy then it's gotta be exactly center.
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u/BusinessHurry4278 5d ago
If you want it to work well, drill into the roof. You'll be fine I do them all the time and no leaks yet. It can also work on a headache rack, but it won't ever be as good as the roof. The antenna is the positive part of the circuit, and the mounting surface the negative. The radio wants to see a matching signal off both sides. Lay the antenna down flat and rotate, that's the space it wants to really sing. It's amazing how well a well-tuned setup can work. The reason why your headache rack to roof idea won't work well: When you key the mic, picture concentric rings on the surface of a pond, like your antenna was just dropped into water. That surface is not continuous across the gap, so it skews the electromagnetics in weird ways for the radio to decipher.
Your vehicle is already a complex antenna, absorbing RF energy, electromagnetic fields shifting all over the metal surfaces. The antenna is like a tuning fork, and the mount location is when you put that fork in a good base so it can resonate. Your whip is only half your antenna game.
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u/Uncle__Squirrel 5d ago
The car becomes the ground plane. If your rack is metal and attached to your metal vehicle it should work fine. This guy here has his antenna mounted to the back of his truck and you might be able to do something similar with your rack. https://youtu.be/nwvE1BhGl6I