| Author |
Message |
    
Barracuda
| | Posted on Monday, April 14, 2003 - 8:10 am: | 
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For any of the Techs out there (or anyone else)
I have a question regarding mobile antenna configurations. Let me pose a hypothetical question. I have a Jeep G'Cherokee which currently has a 102" SS Whip at the drivers rear corner. What would be the effect of putting another 102" whip at the front, but have it grounded rather than driven. From my meager understanding of antennas I would suspect this would begin to act as a 2 element beam? If so, what would the expected change in performance be over the single driven whip and would anything change further if I added another driven and/or grounded whip?
Just some mental musings. Thanks in advance for the input.
Barracuda
By the way I'm sure such a setup would look silly as heck! |
Tech833
| | Posted on Monday, April 14, 2003 - 10:51 am: |
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You need both of the antennas to be over neutral ground plane and they both need that ground plane distributed evenly in order to work properly. That means, your side mounted whips will not work as a beam.
HOWEVER, introducing an element into the field of your driven element will have an effect on it. Exactly what effect is not entirely predictable. Make sure your 'reflector' element is at least 5% longer than your driven element. Or, if it is a director, it be 5% shorter.
Lastly, unless you can rotate it somehow, what good is a mobile beam? |
Barracuda
| | Posted on Monday, April 14, 2003 - 11:05 am: |
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Thanks Tech833,
I was not actually going to try this. As I said before it was just a thought. As for turning it, true while your driving it would be tough, but stationary you could point any way you wanted. Gives new meaning to "steerable beam" no?
Barracuda |
Tech671
| | Posted on Tuesday, April 15, 2003 - 6:12 am: |
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Driven antenna at rear would need the "director" at front to be isolated. Driven at front would need the "reflector" at rear grounded. Spacing and antenna length will be the key to swr and gain. Directors should be 5%(+/-) shorter and reflectors 5% longer. |
Tech833
| | Posted on Tuesday, April 15, 2003 - 10:24 am: |
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Barracuda,
I remember seeing a 4 element quad on a mast mounted above a van. It was not in motion at the time. The quad would only stick up about 13 feet until raised. It seems that some folding elements could be implememnted which would make assembly easier and quicker.
I know a fellow who likes to travel to hilltops and DX on some VHF ham frequency. The mobile setup includes BIG antennas. I suppose it is becoming a hobby for some. Enjoy! (I'll be home with a warm cup of coco). |
Barracuda
| | Posted on Tuesday, April 15, 2003 - 1:08 pm: |
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Thanks guys,
Tech671,
Just so I'm clear, when you say the director is isolated that means that it is neither driven or connected to the common ground of the driven antenna/radio?
Tech833,
I guess some of us aren't blessed with altitude for our antennas. Meaning we either live at low altitudes (I live at < 20' above sea level)and/or are restricted by community on antenna size and height (I live in a cooperative community of closely spaced homes under the landing flight path of JFK Int'l airport). It's just easier to move the shack sometimes. Though I wouldn't mind doing it from home with a cup of coco.
Thanks again guys. I learn a lot from you and it's appreciated.
Barracuda |
Tech671
| | Posted on Wednesday, April 16, 2003 - 5:58 am: |
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>when you say the director is isolated that means that it is neither driven or connected to the common ground of the driven antenna/radio?
Correct. |
Allagator
| | Posted on Monday, April 28, 2003 - 10:16 pm: |
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Hey Barracuda !!! I run a VR 9000 in my camero witha wilson 1000 on the trunk and a francis 51/2 rite dead center of the car !! and it works like a beem if you point it foward it will talk a long way just dont try to talk behind you !!!!!
hope this helps !!!!!!!!
Allagator |
Barracuda
| | Posted on Tuesday, April 29, 2003 - 12:23 am: |
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Thanks Allagator,
I actually saw another post of yours the other day that described your set-up. Very interesting.
I'm still not sure if I'll attempt anything like this or what I'd do if I did.
73, Barracuda |
Red_ranger
New member
Username: Red_ranger
Post Number: 2
Registered: 11-2004
| | Posted on Thursday, December 09, 2004 - 11:04 pm: |
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phased array for kenworth 900? would this work for 10-11 meter? 2 mirror mount w/centered cab guard antenna. |
Tech808
Moderator
Username: Tech808
Post Number: 4261
Registered: 8-2002
| | Posted on Thursday, December 09, 2004 - 11:29 pm: |
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Red_ranger,
You can talk anywhere in the world with a GOOD SINGLE or DUAL antennas mirror mounted on your KW.
We have over a million miles in OTR Driving and DXed Every Single Night.
Do you need a big radio and big power? NO
Do you need a GOOD Single Antenna or a GOOD set of Dual Antennas? YES
When the conditions are right you will be able to talk anywhere in the world that Mother Nature / conditions allows you to.
The Only 2 radios we used were a Cobra 29 and our 2970DX.
Lon
Tech808
CEF808
N9OSN
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Keithinatlanta
Advanced Member
Username: Keithinatlanta
Post Number: 877
Registered: 3-2003
| | Posted on Saturday, June 19, 2010 - 5:26 pm: |
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Hi guys. I remember a friend of mine in Denver back in early 70's, drove a full size station wagon. He bought a "Beam" for his station wagon. It looked almost just like the luggage rack up on top of a car or station wagon. But it worked pretty good for him. And he always ran those Cobra Radios with am and ssb. He was rich in my eyes, because he had SSB and I did not. 
Keith in Atlanta
CEF 150 |
