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How far does a CB radio reach?

BwoncoHowie

C-4 Wizard
Joined
Nov 11, 2002
Messages
3,571
I was able to talk clearly with 5 barefoot watts from orange to westminster over a lot of traffic about 16 mi. I can only assume it was effective because my mobile unit was parked on the top of a hill. Being up on a hill seems to help carry your signal a lot farther than being on the flats of the city. I dont think repeaters came into play on my frequency.
 

Viperwolf1

Contributor
electron whisperer
Joined
Aug 23, 2007
Messages
24,316
BUMPING for an answer not a statement.

Can you explain why my theory is flawed? Also What do you do with your extra coax?

Your theory may work if you were not using coax cable.

Single conductor wire works well at very low frequencies. As the frequency increases the single conductor losses efficiency as it tends to creaye a magnetic field around itself. The energy from that magnetic field induces current into adjacent metal objects and results in a high SWR and significant power loss at the antenna end. The wire acts as a large inductor. Inductors are very good at passing low frequencies and very poor at passing high frequencies.

Coaxial cable is designed to contain the magnetic field generated around the center conductor. The shielding strands are spaced at an even, calculated distance from the center conductor and cover it almost completely. You still have a series inductor effect but it is very controlled by the dimensions of the coax itself. You also have a parallel capacitive effect between the center conductor and the shielding. A capacitor acts oppositte of an inductor, passing low frequencies poorly and high frequencies well. Together, this controlled series inductance and parallel capacitance determine the frequency range (and characteristic impedance, 50 ohms in this example) of the coax and it contains almost all the energy passing through it within that range. Very little loss.

Why does bundling or coiling it not affect the cable? Because almost all the energy is contained inside the cable and there is no magnetic field beyond the shield, power loss can't occur unless the cable is damaged. Bending tightly can damage it.

The best thing to do with excess is to cut it off. Now I know you've heard that you can't cut it but that's a bunch of BS too. Like I said earlier the coaxial cable is nothing more than a series inductor and parallel capacitor. If you cut an inductor you end up with less inductance. If you make the plates of a capacitor smaller (by cutting) you make the capacitance less. But those two impedances are kept proportional which keeps the characteristic impedance the same. The same impedance keeps the same efficiency at the operating frequency. There is also a series resistance component. That means the longer the cable the more resistance it has. That resistance eats power going to the antenna. The shorter the cable the less resistance loss. Make the cable just long enough to be proper routed without sharp bends or other possible damage and use good quality connectors.
 
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Rustytruck

Bronco Guru
Joined
Feb 24, 2002
Messages
10,875
It doesn't matter what radio you have in any disaster you have a limited amount of channels to talk on and as soon as 3,000 people get on the radio no one can talk to anyone. Emergency trumps all etiquette. Get a couple of cans and a string. A CB radio is only for close car to car chatter and hearing the truckers say flash me your boobs or did you see the one in the? Truly reliable communication its not. Stick with your cell phone and a crank charger for the battery. It’s the first system that may be up and running as soon as they figure out how to get power to the cell towers.
 

SurfCityEB66

Contributor
Sr. Member
Joined
Jul 18, 2005
Messages
461
It doesn't matter what radio you have in any disaster you have a limited amount of channels to talk on and as soon as 3,000 people get on the radio no one can talk to anyone. Emergency trumps all etiquette. Get a couple of cans and a string. A CB radio is only for close car to car chatter and hearing the truckers say flash me your boobs or did you see the one in the? Truly reliable communication its not. Stick with your cell phone and a crank charger for the battery. It’s the first system that may be up and running as soon as they figure out how to get power to the cell towers.

x2... I think we need to worry about protection rather than communication in LA area in an event...I would think a satellite phone would be your best bet to communicate...$$$$$$$
 

BoltBuster

Bronco Guru
Joined
Jun 5, 2002
Messages
2,051
At one time you were able to give the radio repair shop guy an extra 20 at the local truck stop to boost them up from stock, of course you look like a red flag to the FCC.
 

Buldozer

Bronco Virtuoso
Joined
Oct 17, 2007
Messages
3,065
Loc.
God's Country
Fire Stik is probably one of the best known antenna manufacturers. ]

This is true, they are very well known and many of them have been sold. Unfortunately they are not very good antennas. A good antenna can make more of a difference than the radio, buy a Wilson unless a 102" steel whip is in your future. Just my $0.02.;)
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
This is true, they are very well known and many of them have been sold. Unfortunately they are not very good antennas. A good antenna can make more of a difference than the radio, buy a Wilson unless a 102" steel whip is in your future. Just my $0.02.;)


Seen wilsons beat the whip! However whips been around forever.......
 

Dave

Contributor
Bronco Guru
Joined
Aug 25, 2006
Messages
2,190
Some of the old rag tag fleet of Boeings that I used to fly had VHF radios that covered the 27MHz range. I built a Heathkit CB radio when I was a kid and remembered that channel 19 was down there somewhere. 27.185 or soemthing like that. We used to talk to the truckers on those late night flights across the country from 35000 feet. I think they put out about 250 watts.

My experience with 5 watt hand helds on the ground is not very good. Seems like I could walk out of range deer hunting.
 

prosys1

Full Member
Joined
Jan 16, 2011
Messages
307
Loc.
Victorville, CA
Thanks again for more info. Dave and everyone else.

The terrain is West Los Angeles; buildings, some small hills, parking structures, the 405 freeway, and traffic... lots of traffic. So it sounds like CB's will be in the near future for family members B-Days. Maybe I'll get a pair and test them out around town.

Hmm...zzz...

Chris, how far are you trying to reach?
And in a disaster, given you're location, I think a semi-automatic pistol in the 9mm range would be more useful.......
 

NYLES

Bronco Guru
Joined
Aug 13, 2004
Messages
9,846
If you aint having to upgrade the alt to keep the headlights from dimming when ya key it, you aint got enough!
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
One option for your family Chris, might be simple magnetic mount antennas with hand-held radios. That way they don't have to be mounted all the time and can be carried in the trunk or bed of a truck or under a seat.

The radio should have both internal battery power AND a port for plugging in a charger/power supply and MUST have a removable antenna, so you can swap from it's own antenna for hand-held duties and the car mounted antenna for longer-range reliable communications. Or as reliable as it's capable of getting anyway.

For the antenna, I've found the base-loaded Wilson '1000' with magnetic base a very convenient and all-around good performer. It can be moved from car to car in a pinch, or just carried in the car that you feel is the best to use in an emergency.

Paul
 

whttail101

New Member
Joined
May 7, 2011
Messages
37
Loc.
Mount Vernon, TX
At one time you were able to give the radio repair shop guy an extra 20 at the local truck stop to boost them up from stock, of course you look like a red flag to the FCC.


That is not a thing of the past. I still peak and tune, upgrade, and all the good stuff. Just make sure if you have it done, take it to a shop that is qualified, not a snip and hack shop.

As far as the magnetic antennas go, make sure that it is a no-ground-plane antenna. You will get your best results from a conventional mounted antenna. If you have an antenna that requires a ground plane, which most do, and it is not present, you will not get out more than 2 miles from your ride.

On the antenna subject, yes 102" steel whips are the best for range, especially when setting still. When in motion, the steel whip will loose some of its efficiency, but will still out-perform other mobile antennas. If you go that route, make sure that you have something to insulate the whip from touching any part of your vehicle. At the time it grounds out, you do not have an antenna. That is why you usually see a tennis ball slid over one where it may make contact with the vehicle.


Now for SWR (Standing Wave Ratio). SWR it the ratio between the power being transmitted and the power that is being feed back into the cb radio. Basically, it determines the efficiency of the antenna. The only part of your system that will will affect and can set SWR is the antenna. Your radio and coax both have a 50 ohm impedance. When you are setting the antenna SWR, you are trying to reach as close to a 50 ohm impedance as you can. The problem with high SWR is that all of your transmitted RF power from the radio does not get transmitted out of the antenna. What does not leave the antenna travels back into the radio to the final transistor. When that happens, that power turns into heat, and the more heat built up can burn the transistor (which most people call "blowing the final").

If you do not want to have the added issue of setting SWR, go with a fiberglass stick antenna, such as a Francis or a Firestick, that is non-tunable.
If anyone has questions about setting SWR, shoot me a pm or email and I will be happy to help you out.


It is correct, most stock cbs get about a 5 mile range, give or take, with a properly set up system. After a radio is peaked and tuned, take a Cobra 29 LTD CLassic for instance, it will typically modulate between 25 and 30 watts, depending on how wide open the modulation trim pot is turned to. If it is opened wide, the radio will usually modulate over 100%, which you do not want it to. It is best to have the modulation set between 90 and 100%. At 100% a Cobra 29 will typically modulate right around 25 watts with a clean signal.

10-meter radios are able to be turned up more than most cb radios. You can get 10 meter radios that can be turned up to 400 watts. The reason 10 meter radios are against the the FCC rules, is because they are considered dual purpose radios. They come ready to talk on the 10 meter band (ham), but can be converted to 11 meter band (cb). The conversion is not a difficult or lengthy process if you know what you are doing. Some just have a chip that is moved from 1 set of prongs to another. Other conversions that a resistor cluster that has to be removed. It just depends on the manufacturer.
 

bmc69

Contributor
Bronco Guru
Joined
Jun 11, 2004
Messages
11,851
Great info whttail101!

Interesting timing too. For years I've been running CBs in every truck we use on road or trail...so probably 6 CBs in all. Most of the them are various versions, newer and older, of the ubiquitous Cobra 19 and the one in my primary tow rig is a Cobra 148GTL. And all were just 'slapped in' by me and mated up to whatever antenna looked like it fit the vehicle it was on.


Had a CB tuning ace work on the two street rigs just over a week ago. He made me scrap both existing antennas and he mounted the Wilson of his choice where he wanted it for max ground plane and then tuned them both for opt. SWR.

We rolled with both rigs to an event last weekend. The difference 'after' to 'before' was astounding; not just in range but even more so in voice clarity. So yeah..when one of the CB tech gurus sez an antenna is junk or improperly mounted or.....listen to 'em.;)

This might have been raised before, but I'll raise it again...if you trail ride your rig and expect to do so at organized events like the MEB Roundup...a functional CB is a 'must have'...even if its only a handheld or poorly tuned EBay special you got for 35 bucks with mag-base antenna. Pretty much anything will work at the distances between giude and tail gunner on a trail ride. ;D Managing a group of rigs on difficult trail conditions is a major PITA if most all don't have CB radios.
 

whttail101

New Member
Joined
May 7, 2011
Messages
37
Loc.
Mount Vernon, TX
Thanks bmc69. I will try to help out as much as I can on answering cb related questions and helping people get set up with cb rigs.

I can tell you right off the bat that I know a lot about radios, but there is a lot that I still have to learn. I do not know everything, yet, lol.
 
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