hard to see feed
but it looks like left and right are fed separately and both right and left attennas are the same.
but it looks like left and right are fed separately and both right and left attennas are the same.
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This is a one of a kind Mobile Antenna
- Thread starter AudioShockwav
- Start date
The engine runs on methanol too. Unless you can drive around with the antennas on, I fail too see how they can call these "Mobiles". Must be nice to have about $100,000 to spend on that nonsense.
Sha Sha's rear engine and AC alternators.
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It looks to me like a pair of three element vertical yagi's fed in phase a half wavelength apart. The driven elements appear to be folded dipoles. The parasitic elements are not parallel to the driven elements, instead angled with their bottoms pointing towards the driven elements. As these elements are parasitic I am not sure if there is a purpose in mind here or simply a design limitation.
That being said, with as much money as these guys typically spend on those vehicles, I highly doubt it would simply be a design limitation as it would be almost just as easy to mount separate brackets that would hold those elements vertical.
The DB
Yes I agree, the V-8 that is mounted in the back of that Van has a lot of $$$ in it, so I doubt that coin was an Issue on the placement of the elements.
I would like to understand what the object of tilting the elements is about.
73
Jeff
I would like to understand this as well. Judging from it's construction there got got to be multikilowatts flowing out of that mobile. Kind of make me wonder what the safe distance would be when he cranks that up.
Might be better off putting wheels and a engine on a microwave and drive that around?
Might be better off putting wheels and a engine on a microwave and drive that around?
Do you mean by climing into a microwave, OR
Climbing into a mobile with that much Rf power floating around?
Climbing into a mobile with that much Rf power floating around?
Let me get this straight, these nibs are spending thousands of dollars and endangering their health all for the thrill of keying over someone. Amazing, people have WAY too much money and way too little intelligence. Got to wonder if they are married and if so have kids and do the kids have clothes and go to school. What a waste...
Lets not Bag on these guys too much, remember this is the CB section.
Some Guys spend 100`s of thousands of $$$ to see who can get down a 1/4 mile faster, and some of them die each year doing so, to each his own.
The guy IN the van is probably better off than the guys standing around the van.
Some of the Op`s line the interior of the vehicle with copper mesh and ground it to the frame to provide ground/shielding....but that is another thread.
My interest is the Antenna setup.
73
Jeff
Some Guys spend 100`s of thousands of $$$ to see who can get down a 1/4 mile faster, and some of them die each year doing so, to each his own.
The guy IN the van is probably better off than the guys standing around the van.
Some of the Op`s line the interior of the vehicle with copper mesh and ground it to the frame to provide ground/shielding....but that is another thread.
My interest is the Antenna setup.
73
Jeff
DB is right on the money. That's two 3 element vertical beams. The driven element is a folded dipole. The good question is why are the director and reflector angled the way they are. There can only be a few reasons for this. My first thought was they are angled to prevent them from arcing to the ground. This guy runs in excess of 50 kw! These pictures were taken at a event in Florida a year or two ago where he proceeded to kick the snot out of all the competition. The folded dipole will not develop a corona arc on its ends because it has no ends for the high voltage RF to discharge in an arc. By angling the outside elements he has gained some ground clearance on them.
Then I remembered he's combining a pair of folded dipoles together that without parasitic elements would have an impedance of about 300 ohms each or 150 ohms together. There are no impedance adjustments on his driven elements. He could have used a pair of T-matches to tap the driven elements at the correct impedance. He could have used different diameter tubing to form each side of the folded dipole, thereby allowing you to adjust impedance by the gapping distance of the folded dipole. I think he decided to pull the bottoms of the parasitic elements in towards the folded dipole in order to cause the impedance of the system to drop closer to 50 ohms. Simply moving the entire reflector and director elements closer to the driven would do the same thing but could reduce gain too.
I've thought about the possibility of some type of mechanical beam tilt taking place and can pretty much rule that out as a possibility. At this wavelength and low height above ground, tilting the elements will not tilt the radiation angle in the far field. The ground is going to reflect this signal back up to the same take off angle as we would have without the elements tilted at this height above ground. Furthermore, both outside elements are tilted at opposing angles and have similar currents on them. Any effect one could have would be cancelled by the other. He's most likely adjusting his SWR by tilting these elements.
Then I remembered he's combining a pair of folded dipoles together that without parasitic elements would have an impedance of about 300 ohms each or 150 ohms together. There are no impedance adjustments on his driven elements. He could have used a pair of T-matches to tap the driven elements at the correct impedance. He could have used different diameter tubing to form each side of the folded dipole, thereby allowing you to adjust impedance by the gapping distance of the folded dipole. I think he decided to pull the bottoms of the parasitic elements in towards the folded dipole in order to cause the impedance of the system to drop closer to 50 ohms. Simply moving the entire reflector and director elements closer to the driven would do the same thing but could reduce gain too.
I've thought about the possibility of some type of mechanical beam tilt taking place and can pretty much rule that out as a possibility. At this wavelength and low height above ground, tilting the elements will not tilt the radiation angle in the far field. The ground is going to reflect this signal back up to the same take off angle as we would have without the elements tilted at this height above ground. Furthermore, both outside elements are tilted at opposing angles and have similar currents on them. Any effect one could have would be cancelled by the other. He's most likely adjusting his SWR by tilting these elements.
Very Good Post Shockwav, thank you for that.
As recently as last year he was still kicking the snot out of the competition so he is doing something right.
While some of us can wonder why guys do this, you have to agree that they are the cutting edge when it comes to running Multi Kilowatt mobile systems....
73
Jeff
I would like to understand this as well. Judging from it's construction there got got to be multikilowatts flowing out of that mobile. Kind of make me wonder what the safe distance would be when he cranks that up.
Might be better off putting wheels and a engine on a microwave and drive that around?
What's the matter....are you scared of a small thing like retina detachment?
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