Member Since: 25 Mar 2009
Location: Eürope
Posts: 137
CB Aerial Location when OZtent is on the racks
Always been told to try and put the mag mount in the centre of the roof. Whether that is true for cd frequency waves who knows.
So thats what I do, just slap a magmount in the centre of the roof when I need it. Easy.
But this time I need to carry my Oztent, I have a mesh basket this goes into. As you can see from the picture it does start getting rather close to the cb. It doesn't touch unless the aerial was to hit something and wobble left to right. But most of the time when I have Oztent basket up there will be on motorways, so shouldn't be hitting too much.
So here's the question. Should I leave it in the centre to get the best ground plane, all be it very close to the metal Oz Tent Basket (which may cause interferance)?
Or
Do away with the 'centre of the roof' rule, and stick the magnount in the corner of the roof or something?
Click image to enlarge
I don't want a 'permanant' mount as during the week the car is used for work and all cb stuff removed.
Cloth is under the mag mount just while I play around with locations.
1st May 2009 9:47 am
Bodsy Site Sponsor
Member Since: 06 Nov 2006
Location: In the Clubhouse
Posts: 21361
Mine's on the rear roof rail. Seems to work well. Depends on the distance you need the CB to work for, if only local distance in convoy, then no real issue Bodsys Brake Bible
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1st May 2009 10:40 am
MacLeod 313
Member Since: 18 Apr 2008
Location: away
Posts: 10723
Get a Uncle Ray Bracket. Pm him "RLD"
or here on the rear left corner
Before fitting into the rails
1st May 2009 10:42 am
MacLeod 313
Member Since: 18 Apr 2008
Location: away
Posts: 10723
Must type faster
1st May 2009 10:43 am
Bodsy Site Sponsor
Member Since: 06 Nov 2006
Location: In the Clubhouse
Posts: 21361
Yup, the Sirio mount is excellent, along with Rays bracket, but the Sirio means yoiu can leave it on & just attach a decent ariel when you need it Bodsys Brake Bible
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1st May 2009 10:53 am
discocuzzy
Member Since: 02 Feb 2008
Location: surrey
Posts: 2752
Ian,
What fitting have you used on the coax itself to attach to the sirio mount?...mines not as compact as that."you cannot teach stupid people to do clever things"
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1st May 2009 9:31 pm
Bushwanderer
Member Since: 27 Nov 2007
Location: Northern Rivers, NSW, Australia
Posts: 2050
In Oz, most antennas for our (477Mhz) UHF CBs are "ground plane independent" meaning positioning on the vehicle isn't critical. Can you get such a unit in the UK?
neVeTaS - My understanding of magnetic mounts is that they are self grounded so it does actually matter where you put it, it's only the fixed mounts which require a ground plate and these are "best" mounted centrally. That does not mean you can't offset them and still get good signal. I've got mine fitted to the floor plate on the roof rack off to one side and have no issues:
Click image to enlarge
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2nd May 2009 7:53 am
NeVeTaS
Member Since: 25 Mar 2009
Location: Eürope
Posts: 137
MrH, very true. I asked the cb shop, he said if you mount it further back you will get better reception backwards, further forward beter reception forward etc.
Everyone seems to have their own opinion
I doubt it makes that much differance unless you are running some serious kit and really going for it 8)
2nd May 2009 10:21 am
Bushwanderer
Member Since: 27 Nov 2007
Location: Northern Rivers, NSW, Australia
Posts: 2050
I hope that you have misremembered what he said.
The further back the antenna, the signal strength will be stronger FORWARD (larger ground plane). And vice versa.
Likewise, if you offset the antenna to one side, the signal strength will be greater to the OPPOSITE side.
Best Wishes,
PeterThe Bearded Dragon
3rd May 2009 3:15 am
NeVeTaS
Member Since: 25 Mar 2009
Location: Eürope
Posts: 137
May of misheard them I guess.
I will do some testing this week
3rd May 2009 8:48 am
PaulP
Member Since: 04 May 2007
Location: Barcelona
Posts: 4317
You must have misheard - it works as Bushwanderer has said
This is only relevant to ground-planed antennas (such as those that are fitted through a hole drilled in the steel roof of the D3) as the ground plane effectively forms part of the receiver - the bigger the antenna/ground-plane, the better the reception from that direction. If you offset the position of the antenna, as he says, the reception will be better on the opposite side.
To be honest this is not very relevant to mag-mount CB antennas. Just stick it where it fits and don't worry too much about it.
As Bodsy says, if the main use is just for convoys then a mag-mount and standard-output CB will be fine and should give you more than enough range once set-up correctly....if you think you need an amp, then maybe you should be looking at 2m radios etc.2006 Discovery 3 TDV6 SE AutoBuckingham Blue 2007 Golf GT DSG
3rd May 2009 9:22 am
TazDaz
Member Since: 07 May 2007
Location: South East Essex
Posts: 2858
Steve - if you're not fitting the aerial via a magmount, (ie fitting it to the rack) an easy way to ensure you have a decent ground plane is to use an artificial ground plane
Not very expensive and a quick 'google' reveals ..
http://www.4x4cb.com/public/menu.cfm?Category=516
Don't waste your money on an artificial ground plane unless you've got a Robin Reliant, they're designed for fibreglass vehicles primarily. Just make sure your aerial mount is well earthed and you've got the SWR as low as possible.
NeVeTaS, as has been said don't worry about the position, unless you're trying to do some serious DXing it's not going to make much differenceThe End
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