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Author Topic: CB radio  (Read 3098 times)
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dresda
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« on: June 27, 2015, 12:18:13 AM »

I need to get a CB can somebody tell what to get, will a hand held work ok some only have a range of 4 miles is that ok?
Thanks, Ray.
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Milwaukee Midget
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« Reply #1 on: June 27, 2015, 03:10:08 AM »

Are you racing and possibly need to transmit, or are you just listening in as a spectator?

You'll want the FCC maximum of 4 watts output if you're racing and transmitting - few handhelds provide that.

Walkie Talkies are okay for listening, provided they're frequency agile and can be switched to the frequencies used at Speedweek. 

Cobra, Midland - any old Walmart or truck stop will have CB radios.  Craigslist - easily find one with an antenna for less than $50.00.
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« Reply #2 on: June 27, 2015, 09:03:14 AM »

I've gone through a couple different antennas and finally settled on a Wilson Little Wil...



http://www.amazon.com/Little-Wilson-Magnet-Mount-Antenna/dp/B000I5NQA8

... and do believe that it works better than the others I had.  Not that you have to buy it on Amazon (less here)...

http://www.solidsignal.com/pview.asp?p=305-38&utm_campaign=base&utm_medium=organic&utm_source=google_base&gclid=Cj0KEQjwk7msBRCJj67khY2z_NIBEiQAPTFjv9WZPIYzcMb7Fk7SWY96UDBWj9SZ6J6V2kf7B4csLCwaAsjH8P8HAQ

.... but that is the one I now use,

Sumner
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dw230
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« Reply #3 on: June 27, 2015, 11:15:05 AM »

The rule book does state, 1.L(page 14), that hand held CB are not to be used in the support vehicle.

DW
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1leg
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« Reply #4 on: June 27, 2015, 11:26:34 AM »

I suggest getting the best radio and antenna you can afford. If you need to transmit get a full size mobile unit like a Cobra 25 classic. Donít bother with the weather station models.

Send the radio to a shop that can tune it up. A good shop can adjust the radio for max legal output and it does not require adding any new parts. This is cheap and adds to the performance greatly. Next you will want to get your antenna set-up and the SWR tuned.
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Jerry
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« Reply #5 on: June 27, 2015, 12:30:45 PM »

Just for the sake of the discussion -- a "quality" hand-held unit used with a real antenna mounted on the roof of a vehicle -- will probably work.  No, you're not supposed to use one per the rules -- I'm just trying to explain.

A "basic" CB antenna (any vertical antenna, for that matter) is 1/4 wavelength long and attached to a reflecting surface.  So - something around 96" tall mounted on the roof of the car would be the best-possible.  it'd also be kinda clunky and would hit bridges and trees and so on.  But it'd work well.  The reason you see the "coil" on the bottom (sometimes in the middle, sometimes both) of CB antennas is to trick the radio into thinking it's hooked to a 1/4 wave antenna, and the radio needs to think it's seeing just that.

But -- some of the energy that the transmitter is making -- that 4 watts or whatever - is lost in the coil, and so less of it gets to the (shorter) real antenna.  But then -- the antenna mounted on the roof (or maybe the hood or trunklid) is at least benefiting from the flat ground plane (gotta be a metal truck or roof -- fiberglass won't do it right) will better radiate what power does get through the coil and to the antenna -- so you get some of the "lost" power back, so to speak.

Ergo -- hook your handheld to a decent antenna on the roof and you've got a pretty good chance of things working right.

But there's one drawback that means you can't win that way:  It costs WAY, WAY more to get a quality handheld and a decent antenna - than it does to get a regular $50 Cobra and antenna at the truckstop.  And you won't need to be replacing batteries.
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Jon E. Wennerberg
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« Reply #6 on: June 27, 2015, 12:31:02 PM »

Even with a full 4 watt mobile CB rig and a mag mount antenna like the Wilson if you go down to the far end as a support vehicle you can go beyond your reception range.

As noted if on a crew get a good CB not the cheapest you can find. Do not go cheap on the antenna it is your "ears". Good quality antenna, if mag mount place it near the center of your vehicle roof if you can. The roof provides the "ground plane" that the antenna needs to be effective. More is better. Use large conductor size on your power leads, if you have a choice to make sure you don't have power drop on transmit. Solder all connections on the electrical side and seal with liquid electrical tape.

Get someone experienced in CB/ham radio to help you tune the antenna, to a low SWR (standing wave ratio).
Do not trim the antenna when the car is located close to buildings or over head wires, and make sure if you use a mag mount antenna that it is as far as practical from things like luggage rack cross bars. They will seriously miss-tune the antenna, and make it impossible to get a good SWR tune.

SWR is a measure of how efficient the antenna coax cable transfers power to the antenna and now efficient the antenna can be delivering signal to the radio. Properly tuned the antenna should deliver a SWR at or below 1.2:1, with a proper setup you can get it very near 1:1 which is ideal. Any SWR over 1.5 will seriously impact your ability to pick up weak signals at the far end of the course, or to talk back to the pits and starting line from down course.

If you have problems getting the antenna to tune due to poor mounting limitations you can add a counterpoise to the ground lead at the antenna cut for just slightly longer than 1/4 wave (about 104 inches) and tape it to the car body. I use the flat ribbon conductor Radio shack sells for speaker wire and get a near perfect SWR with a 102 inch whip mounted on a luggage rack bar to avoid drilling holes in the body.

If you are willing to spend just a bit more to get a CB radio that has a reputation of being reliable and bullet proof look at the Galaxy DX-949 they have been building radios for CB since the 1970's. The radio uses older but very mature and reliable designs (not modern super tiny surface mount components) which means it is repairable and rock reliable. It is bigger than many of the modern radios, but also offers SSB on a 40 channel rig which can talk much farther than standard AM CB.

The course safety announcements will of course be made on AM channel 1 or 10 (usually) but having SSB to your team base could be the difference between being able to talk to them and not if you have problems far from the primary pits and starting line area.

Several of us who go out to Bonneville are HAMs and would be happy to help if you need more personal info on radio choice and mounting. It can be an intimidating subject and sometimes individual constraints like no holes drilled in the car body etc. make it difficult to get a setup which you can really depend on.
« Last Edit: June 27, 2015, 12:33:20 PM by hotrod » Logged

1leg
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« Reply #7 on: June 27, 2015, 01:41:48 PM »

If your into youtube

https://www.youtube.com/channel/UCzPbWdbg4ngKvnbeGIFejZg

http://www.gijoesradioelectronics.com/scripts/prodList.asp?idCategory=161

« Last Edit: June 27, 2015, 01:49:20 PM by 1leg » Logged

Jerry
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« Reply #8 on: June 27, 2015, 04:35:56 PM »

Okay -- I'll offer it up and see if there's any response.  I've got an SWR (Standing Wave Ratio) bridge and I'll put it in the trailer for this year's trips to the salt.  But while it can help tune your antenna - remember that the way to tune is to vary the length of the antenna rod and check the SWR at varying lengths.  And there -- varying the length - is the biggest hassle.

The rods are pretty strong - built to be able to whip around in the wind and get hit by tree limbs and big bugs and birds and so on.  So cutting said whip isn't just a wire-cutter thing.  Now make it more difficult -- because what if the SWR bridge tells you that the rod needs to be longer?  How do you cut something to make it a half-inch longer - or whatever - than it is?  Well, you don't - you do stuff like use alligator clips at the far end of the whip - making it a little bit longer each time.  There's usually some extra whip sunk into the top of the coil, so most likely you won't have to add anything.  But it can happen.

The shorter the whip is - meaning the coil is doing more of the "work" - the smaller the amount of change you'll need to make to change the SWR.  A long antenaa -- say, 54" - might be changed 1/2" at a time.  A 24" whip might need to be adjusted in 1/4" increments.  And a tiny one - 16" or whatever -- might have you making changes of an eighth of an inch at a time.  Baby steps -- or you'll go right past the best point.

Then there's going to be the problem of tuning it to the correct frequency.  Each channel is a different frequency, and each frequency has its correct antenna length.  Most common antennas are set to be best at the middle of the band covered -- and they still work fairly well at the ends.  But if you're trying to peak the system for everything you can get -- tune for best SWR at the frequency you'll be using -- in this case, 1 & 10.  I don't have the frequencies of those channels in front of me - they're in my old Handbook, no doubt - but I'll sooner or later have them and let you know where you'll want to be tuning.

Little stuff, but if you're really anal you'll be trying to do stuff like this.  Have at it - and don't forget to find the SSS pit.  I'll have the SWR bridge there.

73

Jon a/k/a WA8GDW  a/k/a SSS
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Jon E. Wennerberg
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dresda
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« Reply #9 on: June 27, 2015, 05:31:25 PM »

Holy crap guys, it was bad enough building the bike to race and this year, I thought I would just go out and buy a CB  shocked
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Seldom Seen Slim
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« Reply #10 on: June 27, 2015, 05:54:15 PM »

Back to a comment I made earlier:  go to a truckstop and buy a $50 Cobra or something that includes a magnet mount antenna.  Plug it into the cigarette lighter, plunk the antenna on the roof and run the coax cable through the back window - and it'll probably work well enough unless you're going out past the 7 or 8 and then it'll likely be okay.
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Jon E. Wennerberg
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RichFox
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« Reply #11 on: June 27, 2015, 07:11:22 PM »

i don't even know what kind of CB I have. Had it since 2001 when the old one went belly up. Has an antenna that clips on the rain gutter. Works great. That's all I want to know about CBs
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dresda
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« Reply #12 on: June 27, 2015, 07:11:36 PM »

Ok thanks, only plan on running my old triumph over a mile.
Ray.
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« Reply #13 on: June 27, 2015, 08:48:32 PM »

Be sure to use a microphone holder so you don't sit on the mic and render the channel unusable.

   Gary
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« Reply #14 on: June 27, 2015, 10:04:10 PM »

"respect ohms law- support your local electromotive force"
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