I just picked up a CB unit and am confused with all the rhetoric re. types of and locations to mount the antenna. Any suggestions re type, length, etc. to maximize the transmit/receive range would be appreciated.
Thanks.
M.
Thanks.
M.
Best place to locate a CB antenna?
- Thread starter bsa_m21
- Start date
Supposedly, the transmittal range will be farther on the opposite end of the vehicle from where the antenna is mounted, i.e. if you mount it on your front bumper, it will have better transmittal range behind you. Something about using the frame of the vehicle as part of the antenna or something. To that end, the antenna also has to have a good chassis ground. I mounted my Firestik to my metal front bumper, and it grounded out with an almost perfect 1.0 SWR. Firestik has a lot of other mounting options that allow you to achieve good groundplane without direct metal contact though, like you see on the plastic mirrors of big rigs.
I mounted mine to the spare tire carrier and then ran a ground from the mount to a solid ground. I used a firestik with a tunable tip. I dont remember my swr readings, but they were pretty good.
This is the most bizarre statement about antenna placement, and completely wrong at least for the purposes of communication with the vehicles in your group (and not on the other end of the Earth).
Electrically, the best placement for the antenna is the roof of your vehicle; a mag-mount CB antenna works really well on a Discovery's steel roof. Even the potential absence of physical contact between mag-mount base and vehicle body is not that much of a factor because of capacitive coupling of the mag-mount antenna base and the roof.
Roof is however not very practical for other reasons: you want the antenna to be as close to quarter wavelength as possible. A physical-quarter-wave antenna is going to be about ten feet long for CB, and most antennas use some sort of electrical shortening (so the antenna's impedance is matched to that of the transceiver, yet it is physically shorter). In this respect, a 4' Firestik is better than 3' Firestik which is better than 2' Firestik. Even a 2-foot antenna is a lot of mechanical load on the roof and even on the gutter mounts.
That leaves realistically the front bumper or spare tire mount on the rear door. Front bumper is better electrically (even if your reception / transmission will be the weakest in the back of your vehicle); I personally hate seeing a swinging stick in front of me, so my CB antenna is on the spare tire mount.
Firestik antennas have tunable tip - some only require twist of the top, some - unwinding a few coils from the top of the antenna. Out of the box, the SWR is about 2-2.5:1; a well-tuned Firestik antenna can be no more than 1.3:1 across the entire CB band. It is fun to tune the antenna.
I promise I didn't make this up. When I was researching how to mount mine, I came across this on some CB forum somewhere. Not saying that makes it true, and also not saying it's a difference one could really perceive with the limited range that CB's have anyways. I ended up mounting mine on the front because there was a nice convenient spot for it on the ARB.
Edit: I added a photo of the antenna's "radiation pattern" based on where it's placed on the vehicle.
I'm not accusing you of that!
But even a generic statement about CB antenna placement and radiation diagram in a vehicle can hardly be made.
For instance, a Disco is different from a "generic car" by having several conducting body members (roof pillars) nearly parallel to, and almost equal in height to a front bumper-mounted CB antenna. The roof pillars can act as directors or as reflectors (in terms of Yagi antenna), and that changes the directional properties - not very predictably, unless someone actually runs some antenna design software and calculates the radiation pattern.
For that very reason front bumper is a better location (the farther is the active antenna element from the nearest reflector or director, the narrower is the antenna null or radiation peak) than the spare tire bracket.
That brings up another subject I fail to understand, and I have not yet heard anyone to explain convincingly:
- what is the benefit of a VHF/UHF ham radio compared to CB? Let's brush aside the power consideration, and compare 12W PEP allowed for CB in single sideband mode with ~10-20W on VHF.
Wow! A lot of information.
OK, a 4ft Firestik antenna mounted to the rear tire carrier seems to be what I will do.
Anyone know approx how long a coax cable I should order?
Also, without a gauge, is there any way to tune the SWR?
Re CB vs VHF/UHF vs FRS:
CB is 26.965 MHz to 27.405MHz, VHF is 30MHz to 300MHz, UHF above 300Mhz. FRS is 462 to 467Mhz in the UHF range.
Lower frequencies are attenuated less by obstacles, higher frequencies reflect more from obstacles and tend to scatter so less of the signal will survive to directly reach a distant receiver. CB & VHF signal will produce a strong direct signal, whereas a UHF signal will produce a better indirect signal.
I found this link to a pdf that gives a fairly clear description of the benefits/drawbacks of each type. http://cagmain.files.wordpress.com/2015/05/survivalist-radio-communications-ham-vs-cb-vs-frs.pdf
M.
OK, a 4ft Firestik antenna mounted to the rear tire carrier seems to be what I will do.
Anyone know approx how long a coax cable I should order?
Also, without a gauge, is there any way to tune the SWR?
Re CB vs VHF/UHF vs FRS:
CB is 26.965 MHz to 27.405MHz, VHF is 30MHz to 300MHz, UHF above 300Mhz. FRS is 462 to 467Mhz in the UHF range.
Lower frequencies are attenuated less by obstacles, higher frequencies reflect more from obstacles and tend to scatter so less of the signal will survive to directly reach a distant receiver. CB & VHF signal will produce a strong direct signal, whereas a UHF signal will produce a better indirect signal.
I found this link to a pdf that gives a fairly clear description of the benefits/drawbacks of each type. http://cagmain.files.wordpress.com/2015/05/survivalist-radio-communications-ham-vs-cb-vs-frs.pdf
M.
That's an interesting link - and I tend to believe their communication range estimates; outside of high-power options (you either need 100W-capable ham shortwave transceiver, which is expensive, or 100W-capable CB SSB unit which is illegal), 12W PEP SSB CB has the longest range.
There are some other considerations. Most VHF/UHF antennas are more-directional than a CB antenna; it affords a longer range on flat ground, but when your group is on very uneven terrain and with considerable elevation difference, it is a detriment rather than benefit.
Sound quality: built-in speakers in CB units are uniformly better than in small-formfactor HAM transceivers. When the link is solid, FM on VHF/UHF results in better sound quality, but quality degrades more rapidly than AM or SSB.
To answer your question: you will likely have to cut the cable and either solder on the connectors, or splice it in the middle. IIRC, the total length from the top of the windshield, under the floor, and into the rear door, was about 20 ft. I'd get a longer cable, chop it, thread from both ends, cut and splice.
This is what I used. A 4 ft firestick on a medium spring https://www.rightchannelradios.com/...-cb-antennas/products/firestik-cb-antenna-kit 18ft is just a tad long for where I mounted my CB. I just took a more indirect way to get the back door in order to use up the excess.
I actually used an "S" shaped hood mount, and located along the front fender and hood line. I'm using a 6 ft. Firestick (no, I do not have little antenna syndrom); I'll post pics in the morning. It seems to be working fine for my needs.
Mike
Mike
VHF/UHF hams have a robust repeater network and thus do not need as much power.
What was said above about antenna placement is true, no BS. In a perfect world (no such thing) the ideal location would be directly centered on the vehicle mounted to metal... ideal being for best omnidirectional radiation and reception. Since this is not a perfect world you have to choose which compromise to make. With the antenna mounted at one end of the vehicle the direction of the most metal will be favored. In a close group situation that may not be noticeable to the average user.
The worst thing you can do for range is to buy a full wave antenna and tie the end down to the other bumper making an arc. That is handy for traveling but in actual use you are literally shooting yourself in the foot.
What was said above about antenna placement is true, no BS. In a perfect world (no such thing) the ideal location would be directly centered on the vehicle mounted to metal... ideal being for best omnidirectional radiation and reception. Since this is not a perfect world you have to choose which compromise to make. With the antenna mounted at one end of the vehicle the direction of the most metal will be favored. In a close group situation that may not be noticeable to the average user.
The worst thing you can do for range is to buy a full wave antenna and tie the end down to the other bumper making an arc. That is handy for traveling but in actual use you are literally shooting yourself in the foot.
True to some extent.
This is a map of repeaters in Nevada. Not one covers the area where we've spent nearly a week, neither the area where we've been two years ago.
I used to have a K40 base load whip antenna mounted up high on the roof rack. I could hear things nobody else was getting which is real tough in the mountains. No signals travel well in the hills. The only draw back was it would whip around side to side going over obstacles and actually hit the sides of the truck. It was a little too flexible.
Then I went with one like this mount;
https://www.rightchannelradios.com/...ounts/products/chevy-gmc-hood-mount-1999-2001
It look factory, uses one of the fender mount bolts and I used a self tapping screw for the other. I put a stainless steel antenna with a tuneable tip on it and it works great. It is mounted on the driver side, matches the radio antenna on the other side location and looks good. Just went though the firewall right there with the wire and into the CB. I ran a little extra line in case I ever want to change things, but I don't.
Then I went with one like this mount;
https://www.rightchannelradios.com/...ounts/products/chevy-gmc-hood-mount-1999-2001
It look factory, uses one of the fender mount bolts and I used a self tapping screw for the other. I put a stainless steel antenna with a tuneable tip on it and it works great. It is mounted on the driver side, matches the radio antenna on the other side location and looks good. Just went though the firewall right there with the wire and into the CB. I ran a little extra line in case I ever want to change things, but I don't.
Since when did Peter become an admin? And when did dweb start having admins? ( disclaimer: Peter is more than qualified to be an admin). #nailinthedwebcoffin
If/when I get around to putting another radio on another vehicle, I think Ham is the way to go. When I did the CB, I didn't realize how short the range really was. Of course, the downside of Ham is there's not as many people with one.
I also vote rear spare tire carrier.
I used longer mounting bolts on the passenger side, and flipped the head inside the door. This way I could tighten the carrier to the door, then use a second lock nut to mount a vertical mast to the same mounting bolts. I used copper plumbing pipe, with a wooden dowel epoxied inside for stiffness and a copper cap soldered on top. This positioned the antennae mount about 6-7 inches above the carrier, which allowed a 4-foot Firestik antenna to clear the SD roof rack. I also used a quick release mount withe HD spring.
I used longer mounting bolts on the passenger side, and flipped the head inside the door. This way I could tighten the carrier to the door, then use a second lock nut to mount a vertical mast to the same mounting bolts. I used copper plumbing pipe, with a wooden dowel epoxied inside for stiffness and a copper cap soldered on top. This positioned the antennae mount about 6-7 inches above the carrier, which allowed a 4-foot Firestik antenna to clear the SD roof rack. I also used a quick release mount withe HD spring.
