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Author Topic: C.B. Radios  (Read 3802 times)
Joe Camper
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« Reply #15 on: April 28, 2011, 09:02:14 AM »

Another thing I always do is mount the antenna above the drivers window and then set the tip (height) at 1 inch higher than the highest point on the roof.

Correct me here but there is 1 specific combination of coax and antenna length and it is 15ft of coax and a 3 ft antenna or is it 18 ft coax and 3 ft antenna I forget but thats important too.
« Last Edit: April 28, 2011, 09:06:16 AM by Joe Camper » Logged

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« Reply #16 on: April 28, 2011, 10:45:02 AM »

Thanks Guys... you just added another item for my "to do list".  We've had the bus for 3 years and it came with a CB radio that mostly produced static the few times I turned it on.  Either I wasn't patient enough to listen for chatter or the thing doesn't work.  I think I'll test it by just leaving it on Ch. 19 and see what I get.

Bryan
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Bryan
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« Reply #17 on: April 28, 2011, 03:23:49 PM »

From what I remember, the coax can be any length as long as its divisable by 3.
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Ace Rossi
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Sean
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« Reply #18 on: April 28, 2011, 04:47:29 PM »

Coax length is irrelevant, however the longer the cable the more attenuated the signal will be.  For longer runs, use better cable.

The antenna length must be the wavelength divided by a power of two.  So 1/4, 1/8, 1/16 etc.  Antennas with load coils have different formulas.  Tune the antenna on channel 19, as it is the mid-point of the band.

For best results the entire antenna should be above the roof.  Otherwise the coach itself blocks the signal in some directions.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #19 on: April 28, 2011, 06:28:49 PM »

I found this info pretty informative and easy to understand!



http://www.stu-offroad.com/misc/myth-1.htm
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Ace Rossi
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« Reply #20 on: April 28, 2011, 09:29:40 PM »

  Stuff I remember from the 70's? Boy does this make me feel old...

  The antenna(s) have to be adjusted for wavelength, usually around the middle channel, using a meter that measures the standing wave ratio or SWR. I dont know how much it matters with todays radios, but back in the day if the SWR was too far off it could fry the finals in your radio...no more transmit. So would a pin through a jerks antenna coax.

  Longer antennas work better than shorter antennas, and you want it mounted as high as reasonably possible or practicle. Full length antennas have more physical power, and taller antennas reach out farther and draw in stations from farther away. IIRC the correct antenna length is something like 39 feet, but whatever it was thats what I had on the roof. Smaller antenna's are fractions of that length and IIRC that is what the "base load" in a shorter base loaded antenna is for, to correct the load to mimic the 39' length? At least thats how I remember it.

  The body of the vehicle effects the antenna by creating a "ground plane" that changes shape depending on where the antenna is mounted. The best way to imagine it is to think about a magnetic field. Wherever you place the magnet on the car, you have more magnetic field in the opposing direction. So antennas mounted at the front have more power and reception capability to the rear, antennas at the rear have more power forward, and so on. On a Bus, the best mounting location is likely at the rear with twin antennas as long and tall as you dare. The reason I would mount them near the back is so I could better hear whats going on farther up ahead in the direction im headed. You will still have range to the rear, but not nearly as far as forward. On a Bus with twin rear mounted antennas I would estimate forward range at some 5 times farther than to the rear, possibly farther. Probably farther. With good stuff you may have 20 miles or more range.

  A power mic will boost the modulation of your voice, youll be heard louder and clearer, farther away. But they dont need to be cranked full bore, ask people how you sound

  I wont mention linear amplifiers, but they were around then, and they are around now. Please dont use one. 

  I had a big antenna on our house as a kid with an old tube type Kris 23 channel radio and power mic. This was before the 40 channels came out. By "tuning" the base and load screws on the back of the radio I could tweak it up to around 13 watts, and used to talk regularly with people 3-400 miles away on clear nights, and often much farther. Then that one Christmas of 1978 every bonehead 12 year old and moron got a radio and turned it all into a noisy useless mess almost overnight. The radio started spending more time off than on, and one day I sold the antenna and then the radio and that was that.

  Today, the channels are crystal clear, there is no one out there on any channel other than 19, and even that is very quiet unless your around a lot of truckers. Ive driven for hours flipping through channels and not heard a single peep. Just quiet static. While there is some language around some citoes, generally I see people taking turns and being polite and courteous. Perhaps it could see a resurgence again?

  KAXC9973. 10-10 and on the side.
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Iver
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« Reply #21 on: April 28, 2011, 11:42:31 PM »

Okay, all good information.  Thanks for that.
I guess I'll keep the C.B. and find a spot to mount it.........just in case.
  Thanks,  Iver
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« Reply #22 on: April 29, 2011, 06:40:30 AM »

My old bus had a CB.

It could be on all day in Canada without hearing a word. Or calling with no answer. A lot of truckers have gone to different frequencies, FM?.

It is a little more used in the US. But certainly not an essential thing for me. Especially with the bad language and the useless chatter which gets annoying really quickly. Occasionally, I was able to start a conversation with a trucker following me, me telling him "sorry I am slow, that's as fast as I can go", and the answer would usually be "don't worry, I'm not in a hurry, I'm loaded and couln't get by you anyway". Followed by questions about the bus and "thank you, drive safe" when I was able to let him by.

Travelling with an other bus, you can use a pair of FR walky talkies. They work just as good as CB.

I don't have a CB in the new bus, and I don't miss it.

JC
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JC
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« Reply #23 on: April 29, 2011, 10:33:08 AM »

I've used CB radios for many years and continue to do so. Most of the truckers, up here, have gone to vhf radios, which aren't as affected by atmospheric conditions and generally have longer range. These vhf setups cost considerably more than CB, but if you make your living driving, it's worth the extra cost.....Bill
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boxcarOkie
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« Reply #24 on: April 29, 2011, 12:50:48 PM »

Gawd, finally!  Artvonne logs in with something that makes sense. 

"Artvonne:  The antenna(s) have to be adjusted for wavelength, usually around the middle channel, using a meter that measures the standing wave ratio or SWR. I dont know how much it matters with todays radios, but back in the day if the SWR was too far off it could fry the finals in your radio...no more transmit. So would a pin through a jerks antenna coax."


Where all this "measuring this and measuring that, and checking the girth of the what-you-ma-call-it" came from I don't know. 

Check the SWR and then hit the road. 

We used to carry ours (radio's) in a briefcase, with a 500 watt Palomar right next to it, the antenna was welded to a pair of vice-grips which we clamped to the top of the mirror post on the pass. side on an old Fruitliner or KW and run 3500 miles and never missed a lick.

We never measured squat and it worked just fine.  Shot skip with it one night from Clovis New Mexico to the West Everglades of Florida.  Whatever you guys are smoking, I want some for the weekend. 

BCO
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TomC
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« Reply #25 on: April 30, 2011, 08:38:27 AM »

Most of the Interstates still have the old road running parallel near by.  As Sean said, with the CB, you can hear of warnings of traffic jams and get off the main road onto the old road and just simply go around.  When I was driving truck, I did that many times-strangely not many others did it-I guess it is the old sheep mentality.  Always have a CB-sometimes cell phones don't work and can get through with the CB-so much so it could save your life (especially in winter).  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #26 on: April 30, 2011, 01:47:13 PM »

We used to carry ours (radio's) in a briefcase, with a 500 watt Palomar right next to it, the antenna was welded to a pair of vice-grips which we clamped to the top of the mirror post on the pass. side on an old Fruitliner or KW and run 3500 miles and never missed a lick.

BCO


  I dont know where length of coax came in either, I think once an antenna is SWR'ed to a particular radio, coax length wouldnt have much effect unless it was significant, but I dont know. I know we hooked up more than a few without checking anything and dont recall blowing up any radios, but I did check SWR whenever I had a "good" radio, I think it helps to have it matched if nothing else. One thing I remember, is a good antenna will always make a bad radio look good, and a good radio isnt any better than a bad radio if you have a bad antenna. Once again, get the tallest antennas you can live with, and put them up as high as your comfortable with. Most OTR trucks have them up where they just clear freeway overpasses. But they also have them up front, and with that long trailer most of their radio power is behind them. On a Bus, if they were mounted in back and set to clear 11-12 feet, or at least as tall as your AC's, you should be good.

 
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luvrbus
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« Reply #27 on: April 30, 2011, 01:59:58 PM »

I can hear all the BS I need with a walkie talkie type CB why do all the plumbing for dash unit lol
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« Reply #28 on: April 30, 2011, 02:01:09 PM »

  I decided to go do a lil reading to refresh some brain cells, and found the following.

  Cool Trimming the length of my coax will lower my SWR.

Wrong. Trimming the length of your coax will trick your SWR meter and you in to believing your SWR is lower. SWR is the ratio of the impedance of your coax to the impedance of the antenna. Standard CB coax is rated at 50 ohms. It has a 50 ohm impedance regardless of whether it is 3 feet long or 1000 feet long. To get a Standing Wave Ration of "1 : 1" both the antenna and the coax must have an impedance of 50 ohms. If the antenna has an impedance of 100 ohms and the coax has an impedance of 50 ohms then your SWR is 2:1, or put another way the impedance of the antenna is twice the impedance of the coax. Likewise an antenna impedance of 25 ohms and a coax impedance of 50 ohms is STILL a 2:1 SWR because the coax impedance is twice the impedance of the antenna.

Changing the length of the coax will neither change the impedance of the coax, nor will it change the impedance of the antenna. It will trick your SWR meter in to a false reading.. In reality the impedance mismatch between the antenna and the coax will remain, and so will the accompanying power loss. It does not matter whether you have a Bird SWR meter or a Radio Shack SWR meter. SWR meters are not perfect, and they can be fooled.

If you can change the SWR reading on your SWR meter by changing the length of the coax then you can be sure of only one thing. You do not have a 1:1 impedance match between your antenna and your coax.

Signal Engineering has a more detailed explanation of coax and various CB myths on-line at

  http://www.signalengineering.com/ultimate/coax_basics.html

 
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bobofthenorth
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« Reply #29 on: April 30, 2011, 03:06:06 PM »

Ours came with a CB installed.  We never run with it on for all the reasons already mentioned - foul mouth truckers, constant banal chatter, white noise, among others.  If we come over a hill and see a parking lot ahead of us I may turn it on to see what is happening.  Sometimes that helps - often the truckers are just as clueless as we are, just more vocally so.  As far as missing traffic jams goes, I couldn't be bothered.  We've got the kitchen and the couch along for the ride.  If we get stuck on the road we can pull over, make lunch and wait it out, which we have done on occasion.  L.A. is another matter altogether but I don't think the CB is going to get me through there without hassles either.

If the bus came with a CB I wouldn't bother pulling it out but if ours ever quits working I sure won't replace it.  Not a prayer I'd install one.
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R.J.(Bob) Evans
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