Vehicle & Technical > Discovery
cb antenna ???
mattyme:
--- Quote from: Saffy on April 26, 2010, 20:18:07 ---SWR has nothing to do with how well an antenna transmits or performs, a good SWR just means the antenna load is more closely matched to that of the radio, in this case ~50ohm.
Just to highlight that, a non inductive resistive load of 50ohm (i.e dummy load) with give a near perfect SWR reading yet is a very poor at resonating RF.
My suggestion for a greenlaning/convoy antenna is nothing more than a RF leaky (unshielded) dummy load capable of safely dissipating the heat from ~5watts of power. This can be put on the end of a length of coax and hung/hooked/stuck on suitable location inside the vehicle. The range will vary but should be satisfactory for a few hundred feet line of sight. No worrying about routing cable to outside of vehicle, no worries about tuning, no worries about trees, no worries about mounting and earthing brackets and mounts.
--- End quote ---
well, that went right over my head!! lol i use a k40 whip antenna on a good mag mount. its pretty long but the good mag mount means it needs a hefty clout to knock it over.
sMUDge:
Think about a hand held CB too :-k
That's what I use with a mag-mounted antenna. With the hand held I can just unplug it from the antenna and leave the vehicle with it, in case I need to walk a route before etc :D
Disco Matt:
I never had any trouble with the mag mount being knocked off by trees, even with a full size springer on top and driving trails where the greenery was brushing over the roof. Mine came from Maplin and is about 6" across with a pretty powerful magnet. I know when I took it off to swap to a body mount on the back door (wish I hadn't, it was much better on the roof but I didn't know much about CB then) it required a fair bit of finger strength to persuade the mag mount to let go! :lol:
I am considering a centre-loaded aerial in an effort to improve the performance with my current mount, basically I need to get the coil up above roof level. The 9' whip aerial works fine on this mount but the rigid lower section is just slightly too long for use if trees are likely.
Anyone know if fitting a back door ladder and then bolting a mirror mount to it would work well or be desirable? I suspect it'd be a pain if you ever wanted to use the ladder to get onto a roof rack.
brianb:
--- Quote from: Disco Matt on April 27, 2010, 20:01:12 ---I never had any trouble with the mag mount being knocked off by trees, even with a full size springer on top and driving trails where the greenery was brushing over the roof. Mine came from Maplin and is about 6" across with a pretty powerful magnet. I know when I took it off to swap to a body mount on the back door (wish I hadn't, it was much better on the roof but I didn't know much about CB then) it required a fair bit of finger strength to persuade the mag mount to let go! :lol:
I am considering a centre-loaded aerial in an effort to improve the performance with my current mount, basically I need to get the coil up above roof level. The 9' whip aerial works fine on this mount but the rigid lower section is just slightly too long for use if trees are likely.
Anyone know if fitting a back door ladder and then bolting a mirror mount to it would work well or be desirable? I suspect it'd be a pain if you ever wanted to use the ladder to get onto a roof rack.
--- End quote ---
Easier to get a mount like mine. You take the spare wheel off the back door and slide the mount over the stude that the wheel goes on Then put the spare wheel back on the studes and tighten the nuts. Then put your antenna mount to the aother end of the newly fitted bracket.
I got mine from ebay for £17 ish just had a quick scan and cant see any on at the moment but they do come up often and im sure there are other places that sell them. You can get them for all sorts of 4x4s.
Brian
fordlltwm:
--- Quote from: Saffy on April 26, 2010, 20:18:07 ---SWR has nothing to do with how well an antenna transmits or performs, a good SWR just means the antenna load is more closely matched to that of the radio, in this case ~50ohm.
Just to highlight that, a non inductive resistive load of 50ohm (i.e dummy load) with give a near perfect SWR reading yet is a very poor at resonating RF.
My suggestion for a greenlaning/convoy antenna is nothing more than a RF leaky (unshielded) dummy load capable of safely dissipating the heat from ~5watts of power. This can be put on the end of a length of coax and hung/hooked/stuck on suitable location inside the vehicle. The range will vary but should be satisfactory for a few hundred feet line of sight. No worrying about routing cable to outside of vehicle, no worries about tuning, no worries about trees, no worries about mounting and earthing brackets and mounts.
--- End quote ---
aye, but a crap SWR will total your rig pretty quickly, so you want it idealy under 2:1, nearer 1:1 the better of course.
MW6TLF
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