well I pondered the same question so I went and seen an expert, he is a coast guard volunteer and mans all the radios, 

he is also a gme outlet, which I tend to think is the best, I have a secondhand gme 3220 (bought off ebay for $100) in little blue with a 2.5 mtr aerial off the bumper ( I might add that is off the ground measurement, the actual aerial is only about 1m - 1.5m in height) 

I asked him the same question "which aerial for me" his answer was simple "height is might" so he sold me a fibreglass whip, supposedly the right one for me, which I may add works a treat 

having said that, the same can be achieved with a little rubber one mouted on the gutter (wont snap and you have the same height anyway) I didnt want to run the cable up to the gutter so I mounted mine on the bar,
 
whichever one you choose I think you are better off going and seeing a gme man and buying a "matched" aerial for your setup, they are not that dear, mine cost $50, 

they go a lot higher than that once they incorporate spring bases, heavy fibreglass rod  and suchlike I've been told that the little rubber one on the roof is fine as it is basically only "line of sight" communication except when it comes to repeaters which I know nothing about

-- Edited by dave06 at 11:28, 2009-01-25

It all depends on what you think you want to get out of your set . If traveling in convoy and board but short distance transmission is all that's required then a 3 db gain will do the trick if you want distance and narrow directional transmission then you may want to move up to the 6 or maybe 9 dB gain range . Obviously the terrain you are traveling in will determine the range, unless you can achieve some atmospheric skip, but that's not a reliable method of communications if you're in the do do and need help .

There's an interesting article in the latest edition of Caravan and Motorhome which may help you decide on your first setup . Please don't take that as an endorsement of the mag or it's contents

If the one you fit works leave it alone . Never fix or change anything if it's working .

Have seen a few rigs with a number of sticks that you can switch from incab position from one to the other as the terrain determines.

dave06 wrote:

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go and grab some info from a gme supplier and do it right the first time, but dont fall into the trap of big bold and ugly, you dont need a thumping big thing, you only need a little one on the roof and as wombat says, dont buggarise around with it, once it's there and working, go on to the next job!!!

we had an electrical contractor on a construction job with us, he had a great swag of aerials hanging off all over his car, a few of our boys had a laugh and placed a bit of pvc in amongst them, he didnt notice the extra one for three days

I had a feller talking to me from hawai once, dont know how but he reckons it was an inversion layer or something I just say WOT THE?????

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That's the skip I mentioned,  happens a lot in the tropics and in antarctic  all depends on the atmospheric conditions, can come and go without any warning.  It can also work in reverse,  on some clear days the range can be much less than the manual states  especially if there's a lot of particulate matter in the air or traveling over high yeild minerial deposits. .  If you want real distance communication then Sat Phone or Sat link radios  are the only way to go , but bring your  cheque  book with you, not cheap   

 

just one other thing that I neglected to mention, my whip aerial is a 6db job, I asked the expert is that what I need for my travels and he said it will suit me just fine, don't know much more about the decibel side of things I always thought that a decibel was a measure of sound????

one thing with the old cb's, if they didnt hear what you said then you could walk over and tell them what it was you were speaking about, had one in the seventies, a megaphone worked just as well

breaker, breaker, good buddy, got your ears on, come back

-- Edited by dave06 at 11:05, 2009-01-29