Increasing CB Radio Range (Is Illegal)
 

Well, I see that the latest thread on improving CB radio range has been closed. In researching this post, I came across a website that details the fines the locally-based Love's Corporation had to pay for illegally boosting the output of CB radios. The chances of you getting caught? Probably close to zero, but the FCC is targeting places that do the mod's.

I just want to offer up one more reason why it's really not worth it. RF range is a logarithmic function. If you take a 4-watt CB radio and boost it's output to 32-watts, that is not an eight fold gain (32/4). It is a 9-DB gain. If you then put that into the formula for path loss calculation, you will learn that the theoretical range for a legal CB radio is 2.2 miles. The theoretical range for a 32-watt CB radio is 3.7 miles--a mile and half improvement. That's theoretical. Truth is, that assumes perfect line-of-sight with no intervening path loss components (hills, vehicles, buildings, trees, etc). Real life suggests that boosting your radio from 4 to 32 watts will give about a 1/2 mile improvement--on the highway. On the trail, line-of-sight is usually going to determine whether you're heard, not RF power output.

It's illegal. It increases spurious emissions that cause interference with other devices (most notably broadcast TV, but sometimes even cable TV and telephone service). And it provides NO (ZERO, NADA, ZIP!) improvement to hearing the other guy, unless he also chooses to break the law and modify his radio. At the end of the day, modifying a CB radio to "tweak" it's output is a waste of time and money.

If you want to run the numbers yourself, get out your scientific calculators and visit here ...

http://web.arundale.co.uk/docs/ais/AppNote_UHF_VHF_Calc.pdf

One thing that you CAN do legally is get an aftermarket mic. Astatic makes a transistorized handheld that is fantastic. I think the one I had was a M-575. It uses a battery and has a volume and tone control. Tone control is important as you can tailor the tone of your voice. Highs freq. response tend to get out better than low end bassy ones. Audio, by itself, has a whole lot to do with the "talk" power of your radio.

Also....Upper and lower SSB is a far more productive means of communication than noisy AM. Plus most CBs that have SSB tend to modulate up to about 12 watts on peaks.....and that's from a legal off the shelf radio.

Excellent points, Dave. And, with SSB you can have a narrower passband, which further reduces that noise level. The only downside (well, other than cost): Will your trail buddy have SSB?

I'm thinking about installing one of the sup'ed up cb's in my Toyota Corolla.:wink:

I knew that a tune and peek was illegal, but I didn't realize how little it did for you. I was thinking about it until I read this. good post!:thumbsup:

Yes. The tendency is for people to think that an eight-fold boost in a radio that gets 2 or 3 miles down the highway should give 16 to 24 miles of performance. But, it doesn't work like that.

A small aside: I was fixing the RF cable in my Jeep the other day (just installed a new rear bumper) and while I was trying to do a radio check the CB band must have been open. LOL: This too is illegal, but it's hard to resist the temptation to talk to someone four states away. Anyway, I wasn't hearing the distant stations, but obviously others were, because half a dozen channels had people working them. Actually, they were probably being legal. I would hear them ask, "Where are you?" .... "Tampa? Okay, got to find someone closer to talk to; have a nice day!"

In addition to a better mic, To get the maximum legal range and best reception on any radio or frequency, focus on the details of the antenna installation. A properly installed and tuned antenna is better than twice the power.

Everyone in our local trail group has a tweaked radio. workin out just fine. What's done is done, we're happy.

I Live about 8 miles from the interstate just had a local shop tune my cb before i couldnt talk to anyone on the interstate at all now i dont have a problem talking that far

See....solar cycle 24 is picking up..... Sure wish you were still interested in HAM radio Mark. I bet we'd have some great ragchews. You know it's never too late my friend. I bet you could walk in and pass the General test without studying ....:thumbsup:

There are a variety of factors in the range calculations, so I had to make some assumptions--path loss, antenna height, antenna gain, etc. You can't compare your eight mile experience with the numbers I used. Therefore, unless you ran actual range tests and have before and after data, all you may have proved is you increased your range for your particular circumstances from perhaps 7.2 to 8.3 miles. You really don't know (and neither do I, except to the extent that the range calculations reveal--and they are pretty accurate. I'm familiar with this because every military radio installation I helped engineer and purchase used these equations to determine expected radio range).

This may be a dumb question, but what is the purpose of the dual antenna setup? I always assumed it was for longer range. What would I gain if I added another antenna to my Jeep?

Antennas do not radiate the same level of RF in all directions. If you look at an antenna radiation pattern from overhead (and it's a three dimensional pattern, but we'll just pay attention to two), it has lobes where the signal is stronger and weaker. This pattern is determined by a variety of things, including both the antenna design and the surrounding materials. An antenna on top of a tower is pretty close to perfect because there isn't much material around it. An antenna mounted on your Jeep tailgate, license plate bracket, spare tire, etc, not so perfect. All of that mass of metal will affect the direction that the lobes form--what direction you can talk and hear farthest. Of course, most of this gain in one direction is given up in another direction. So, maybe you can hear people (and they can hear you because this works both directions) on the left side of the Jeep, and not so well on the right side. It should be noted that, in general, the mass of metal of the Jeep will direct most of the energy in that direction--not block it. I know it sounds counterintuitive, but it's RF. In general, you'll have a circular pattern around the Jeep, with a large lobe out towards the front, if your antenna is mounted on top of the spare tire rack. Mount it on the license plate bracket, and that pattern will shirt forwards and out the right, front corner of the vehicle.

So, how, if you're a trucker, can you take advantage of this? Well, for truckers on Interstates, having most of your performance towards the front of the semi, so you can talk to someone further down the highway, is an advantage. It's not so good to be able to talk out to the sides, since most of the time someone you want to talk to is either in front of you or behind you on the highway. So, dual (technically called cophased) antennas work to reshape what is in general a circular pattern (when looked at from the top), to a pattern with large lobes up front and behind. That means you can talk further up and down the highway, but with reduced performance out the sides.

I hope that helps.

What Mark forgot to say tho, is that co-phased (dual) antennas only work properly if they are set at a certain distance between them where they work off each other and resonate properly. Normally, on a small vehicle, you can't achieve that ideal distance. So it's pretty much a waste of time.

Ham vs CB
 

Two weekends ago was my first real use of my 2m ham radio. I was SO impressed I'm seriously considering dumping the CB permanently.

Guys on I-5 were crystal clear at over 50 miles away, but the CB was good up through spitting range (i.e. almost to the Jeep behind me).

I had no idea that ham worked so well.

KJ6DMD

Perfect fellas, that makes perfect sense after the explanation :beer: I have just seen this setup on a few rigs around town and was trying to understand the purpose. Now I know :thumbsup:

You know, I had that in there, in fact. But, I went skulking about for an antenna lobe pattern chart to illustrate what I meant (didn't come up with one before I had an errand to run) and while visiting the Firestik website they say that they have experienced increased gain with antennas as close as four feet:

"32. Some people believe that co-phased antennas must be separated by a minimum of nine (9) feet. We have successfully used co-phase antenna systems with spacing as little as four (4) feet. Space alters the pattern and not always negatively. Each vehicle will be different."

From http://www.firestik.com/Tech_Docs/63Things.htm

So, while I'd always heard what you wrote, Dave, I decided to remove my words saying the same thing. I guess folks can try things out and see what happens. When it comes to RF, it's all FM (frelling magic--I've been watching four seasons of Farscape the past few weeks. LOL).

P.S.: Here are some antenna lobe pattern charts to illustrate what I wrote about above. Not for you, Dave, for those who haven't seen one before ...

http://www.vias.org/wirelessnetw/wndw_06_05_05.html

Back when I was much younger (still in high school) and I had my ham license, I lived in Chula Vista (the one south of San Diego, not east of Birmingham). I used a home-built, 16 element Yagi array mounted on my dad's old TV antenna pole--probably about 25 feet up. 10 watt 2-meter rig. And when ducting would occur over the Pacific, I could talk 59 to Lompoc--well over 200 miles. It was pretty cool.

In the Jeep, on CB you should be able to talk a mile or two reliably on the Interstate. On the trail, you should be able to talk to anyone you're running with unless you put some obstacle between the two of you (same problem with 2-meters, BTW). It sounds like you're getting more the lackluster performance typical of handheld FRS radios. I'd say check out your antenna system, and if that checks out, consider moving it. The one advantage of CB over ham is that most Jeepers will have one if they're heading out on trails.

Yeah, I had a Cobra handheld with an external antenna that was about 12". I wasn't able to hear the lead Jeep in most cases unless I was able to see him. I went to my current setup and have no problems picking up the signals even if they are on the other side of the ridge (depending on the distance).

When you get along ridges, knife-edge refraction can come into play and cause a signal that might not normally work to be heard. This is more pronounced on higher frequencies. Like I wrote above: FM. :yup:

Point of fact is I'm getting LESS performance from my CB than when using my handheld. Its almost a sore point for me - how to get that extra 100 ft by working on the antenna versus dropping it into a lake and using a bull horn.

I would say the the ONLY advantage of CB over ham is that most Jeepers have it. Me, I'm sold on ham now.

Ham radio is great stuff. But, roughly how far are you getting with that CB? What was the terrain? Were your trail buddies also having similar difficulty with range? Something sounds amiss when you're talking a hundred feet of improvement. :thinking:

Im just saying i had it tuned...wether or not it helped.......who knows ......but it makes me feel better to think it did:thumbsup:

I think I can send about a mile, but it has to be damn good conditions. Othertimes I get out of the Jeep, walk the 30 ft to my buddy, then slap them in the back of the head for not answering me. I don't understand why nobody wants to go with me twice.:thinking: Damn POS radio.

Well...I'd have to see that for myself. Meaning I would have to be the one holding the field strength meter and seeing the results with my own eyes. Because unless they've found a way to change the laws of physics.......ah...er RF I mean,....lol then I'd have to call BS to that. The only other thing that I can think of is that because of these small antennas, then the optimal distance between them, and still have them both resonate properly, may also grow closer.....that "may" be the case. But if so, I'd really have to see just HOW MUCH "increased gain" they are getting at 4' to be able to justify buying another whole antenna/coax setup. It may be gain that only the most precision instruments may be able to pick up and not a cheap CB. I agree there are variables, and that's one thing that can make dealing with RF such a pain. But from 9' down to 4.....well that's a pretty big leap.

You know for yourself that there are reasons yagi antenna elements, the driven, directors and reflectors, are spaced as they are. There are formulas that dictate this. This is no different.

But I must say that there is one thing where most HAMs do agree, is that it all looks good on paper, but until you put it up and try it you'll never know.

Wow I just learned more about radios in 3 minutes reading this thread than i did in my entire Ham Technician review class. lol, just kidding.

I have a uniden 520xl pro and a the Ultramount bracket connecting inside my license plate bracket. The only problem i ever run into is that people can usually hear me but I can't hear them (mostly if they are in the front or rear of the pack). This usually only happens when i run my 3ft firestik versus the 4ft Firefly which actually reaches above the hardtop. I bought these at the actual firestik shop in Phoenix and they said the 4ft one is better because it's coiled more towards the top of the antenna which will get the signal out above the jeep versus the 3ft firestik. I use the 3ft one in town so that i can pull into the garage without banging anything. Problem is I usually forget to swap it out with the 4ft one when hitting the trails.

For most intents and purposes on the trail though, the cb setup i have works fine. It's not "tweaked" but I'm able to hear just about everyone and they can hear me. For talking the long distances I have the Ham radio but most jeepers here in Vegas don't have one. The group I used to run with in Phoenix almost all had Ham radios. It was awesome! We'd talk on Simplex after splitting up after a trail run and we'd just keep on talking for miles and miles almost until we were at home. Even on the trail in rough terrain these ham radios have incredible ranges versus the CB.

Glad I didn't throw away my hooker amp

I picked up a cheap Uniden 520XL and a 3' Firestik II, with good line of sight I transmit and receive people 15-20 miles away clearly.
That's a little more than 2.5 miles??

I've been running peaked radios for years and I also run amps that will push 1500 watts ! But the first thing that needs to be altered is your charging system to run these amps! From voltage regulators and high output alternators to 2 or more high output batteries just to maintain peak power! It's a very complex thing to do! And can really mess with your electronics in a jeep! I would leave that to the suburbans and big rigs on the road! Lol
In my jeep I run a power adjusted cobra 29 that dead keys at 2 watts and swings to 28 watts perfect for talking up to 5+miles NO PROBLEM with no amp and a Wilson tunable fire stick whip! And I live in the northeast where buildings and trees and roads and all kinds of communication sources block signals! So out in the open my radio will talk for miles

Gmrs
 

GMRS radios work fairly good too and solve the license issue of the Ham (as you license the radio essentially). Even a cheap camping store pair of these handhelds work great on the trail. Much better than some of the better CB setups I have had in fact. Plus for the cost, you can have 7 or 10 of them laying around and just pass them out to the other members on the trail ride with a fresh set of batteries. Also, you can invest in a surplus VHF mobile radio and have it programmed to LEGALLY use on GMRS and Ham frequencies. This is a great solution if you are so inclinded. The GMRS handheld idea works great too because if for some reason somebody has to get out of the rig and walk, you simply take the radio with you...also prevents theft and vandilism...

Many are just buying Galaxy 10 meter ham radios and doing a simple 2 minute mod that opens it up to get down to the cb band. A few of those 10 meter radios are 100+ watts out of the box. Simple way to get lots of cb power.

I highly disagree with this.....Run numbers all you wantWhen I took a President grant from 4 watts to 16 then with a 1000 watt Kikcer I talked to other countrys....in fact from Chicago to Germany,and Buenos aires...The hieght of your antenna has a lot to do with it and perfect SWR'S sure helps...Also a good modulated MIc...I have a Silver Eagle Works great

:crazyeyes::crazyeyes::crazyeyes::crazyeyes::naw:: naw::naw::naw:

:doh::doh::doh::doh::gak::gak::gak::gak::sad2::sad 2::sad2::sad2::beer::beer::beer::beer:

it's not hard ..yOUR CB has a freq range of 26.695 mhz to 27.405 mhz..welll when you have 26.000 all the way up to 28.000 mhz your signal goes ON AND ON AND ON This was done 30 years ago when my freind was stationed in Germany

Guess he didn't get it Don......lol.......:naw::naw::naw:

Whatever just letting others know..seeing you two Know every thing

The propagation characteristics of of 26mhz and 28mhz are not dramatically different and are limited by the same primary factor: solar conditions.

I've been down the road with the "tweaked" CB units years back. Had a hacked-up Galaxy before I learned about ham radio. Once I became aware I sold the spurious-emission box (Galaxy). Then I started to buy quality radios that could significantly outperform the Galaxy with a fraction of the power, no spurious emissions and full legality.

If distant communication is your intrest, that's really the direction you should consider.

Thanks for your advice,the point I was making is that The formula used is crap you can talk much greater distances than the formula allows,
No distant comms is not my goal , Thanks .

You can talk at a "much" greater distance using just 4 watts, and a good antenna (which is legal). The ARRL Handbook has loads of information on numerous antenna configurations.