CB radio, how embarrasing!!

  • Thread starter Thread starter Smalesy
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Smalesy

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I want to fit a CB radio to my bike, (how embarrassed am I to ask this?? :eek: ).

Before I get the "10/4 rubber duck" thing, it's to be used when I'm helping at sporting events and the unit itself will live in the tank bag.

What I want to know is that I've been advised that the aerial I need should be a full wavelength one (I think that's about 1metre long) and that it needs to be earthed to the chassis of the bike via a metal baseplate.

If I make an aerial mounting plate out of some 400mm x 50mm x 5mm aluminium sheet and sandwich it between the carrier and top box mounting plate, will that suffice? Does the size and material of the metal baseplate make a difference to reception?

Thanks
Steve
 
CB radio operates on the 11 Metre band, so a full wavelength antenna would be 11 Meter in length. But most mobile antenna are a quarter wavelength, therefore for a CB radio that would be 2.75 metre. However this is far to long to mount on a car, let alone a bike, so what is called a loading coil is built into the antenna by the manufacturer. This has the effect of physically shortening the antenna but electrically it is still a quarter wavelength.

The reason that quarter wave antenna are used is that it has the effect of presenting a load of 50 ohm at the base. Nearly all modern radio's have an output that is coaxial and is at 50 ohm. So you would also use 50 ohm coaxial cable to maintain a match through the whole system.

When you consider that any shortwave radio antenna, (and by this I mean frequencies below 30 Mhz) that is mounted on a mobile situation is a compromise. This is because what is called a ground plane of usually the same length of the wavelength is needed for efficient operation.

However it is also worth mentioning that handheld CB radio works reasonably well but over a reduced distance, and these have no groundplane whatsoever!

I think you will find that it will work on a motorcycle but with reduced range compared to a car. I won't go into how to match the system to get what is called a reasonable V.S.W.R.

I have in fact used HAM radio on frequencies of 1.8Mhz - 160 metre band quite successfully when mounted in my car by using a very large loading coil to physically shorted the antenna and use an ATU (antenna tuning unit). But I generally use VHF or UHF for general mobile as it is a lot easier to mount high gain antenna for these frequencies.

So in order to answer you question, yes it does matter where you mount the antenna and you are trying to get at least a quarter length groundplane for it to work efficiently, but I guess your bike is not 2.75 metre in length!

Therefore it will work to a point, but not very effectively. Plus you could end up with a very high V.S.W.R. which could in certain circumstances damage the radio.
 
While out and about last year got talking to a Harley rider, he noticed I had bike to bike set up (autocom and kenwood), asked how it preformed ?
when I said a couple of miles on a good day :mmmm ,he pissed him self laughing :eek
He used cb and reckened 10 to 15 miles was the norm :nenau

Was he talking bollocks ? :nenau
 
No. CB is a lower frequency at higher power, which for various reasons I won't try to explain, means that it travels further. This can be a bit confusing on summer evenings when you try to talk to your mate a mile behind you and some bloody Italian teenager starts asking you "you liiiiiiiiiike to coo ess ell, yes?"
 
Thanks so far for the information. I think I've got a good idea about the length of the aerial.

What I could really do to know is-

Is the size of the metal baseplate that I'm going to mount the aerial on crucial or is the whole bike effectively the groundplane?

Thanks
Steve
 
The whole bike is effectively the groundplane.

Yes on a good day shortwave radio (frequencies below 30Mhz) i.e. CB radio will have a greater range than a license free, flea power UHF bike to bike setup.

I've used VHF radio on a bike and an excess of 30 miles via a base repeater is the norm.
 
Two friends of mine are on Ham radio and claim they get a range of 40 miles Bike to base!!!

Bike to bike maybe less, but it’s almost worth taking the Ham radio test to get range like that
 
I also know of some people who illegally installed some secondhand marine band VHF radio's on bikes for communications to one another and regularly got about 10 or even 15-20 mile range depending on terrain.

The HAM radio test these days is practically not worth the paper it's written on. They almost give them away in packets of corn flakes. :rolleyes:

Not like the days when I had to take a written theory paper and a test on the license conditions and a morse test at a government radio station. :(
 
Blue Sweeper said:
The HAM radio test these days is practically not worth the paper it's written on. They almost give them away in packets of corn flakes. :rolleyes: Not like the days when I had to take a written theory paper and a test on the license conditions and a morse test at a government radio station. :(
Click to expand...

Yeah yeah, blah blah. And driving was a right pain cos you had to have a man walking in front waving a red flag. :D :D
 
Noddy said:
Yeah yeah, blah blah. And driving was a right pain cos you had to have a man walking in front waving a red flag. :D :D
Click to expand...

I did both written and Morse tests too, so please kindly ..-. --- old man :dabone
 
Blimey CB radio, that take's you back does,nt it. All seems abit daft now lots of strange people with stupid names talking bo**ocks to each other all hours of the day! :rolleyes:
 
Trippy said:
Blimey CB radio, that take's you back does,nt it. All seems abit daft now lots of strange people with stupid names talking bo**ocks to each other all hours of the day! :rolleyes:
Click to expand...

And meeting up with complete strangers to eat/drink/dance/engage in motorsports :thumb

It is funny how things come ful circle, mind. When I was yoof with a CB and twin Webbers (none of this fake-4inch-exaust crap then!!!) I had the same handle as I do xx years later. Whaddaya mean "midlife crisis"? :rolleyes:
 
Buy and fit a cheap retractable/telescopic car aerial then "load" it by fitting one of these these
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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