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Author Topic: Recommend to me please- HF antenna on my minibus.  (Read 9556 times)
4Z5PM
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« on: September 28, 2005, 06:37:15 PM »

Recommend to me please- as it is possible to install HF antenna on my minibus.
The unique explanatory - the roof is made of plastic!
http://www.qrz.co.il/images/gallery/4z5pm_b31009889.jpg

Thanks!
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K0BG
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« Reply #1 on: September 29, 2005, 05:08:22 AM »

On vans and mini buses, the most efficient location is the front of the vehicle. Depending on how efficient you wish your antenna to be, determines what antenna you buy, and how you mount it. There are too many variables to discuss here. However, if you visit my web site, you'll find most of the information you need to make an intelligent choice.

Alan, KØBG
www.k0bg.com
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W7PHEONIX
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« Reply #2 on: September 29, 2005, 01:16:00 PM »

I don't agree.  No surprise there.  I would mount it on the back of the van.  If you do put it on the front, you risk not seeing someone or something in front of the van.  It appears that you are not in the U.S.  Over here, you'd have a hard time defending yourself in a lawsuit or criminal case with an antenna mounted in the field of vision.  

I recommend a fairly long antenna and mount it on the back of the van.  I would use the sides of the van for the groundplane.  That has always worked for me in over 40 years of active operation.

I would not recommend a so-called antenna tuner (they don't tune antennas).  A resonant antenna would be far superior.  Ham Sticks are really poor radiators.  There are lots of other choices.  

Don't believe most of what you read on the net.  There are a lot of experts who write a lot of nonsense.  

Most of all, be careful and have fun operating mobile.
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4Z5PM
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« Reply #3 on: September 29, 2005, 02:51:35 PM »

All greetings and thanks for answers!

To: K0BG,
Has visited your site, all very professionally and beautifully!

For me is available antenna AH-2b and AH-4 antenna tuner, antenna mount it is intended for installation in front of the car (or behind) on a hook which it is intended for transportation of the car.
For the clear reason to install antenna it is possible only in front, problem- the tuner should be near to the antenna, and the opportunity to install a tuner near to the antenna is not present.
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4Z5PM
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« Reply #4 on: September 29, 2005, 03:02:47 PM »

It is possible to use a variant used K0BG by its car- but do not forget about height of the machine and plus the antenna (~2.5m), all contain will give almost ~ five meters of height, it is not so good. HI!
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AA4PB
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« Reply #5 on: September 29, 2005, 04:55:17 PM »

Actually when a tuner is mounted directly at the base of the whip it does indeed "tune" the antenna by inserting the necessary inductance. It's exactly the same thing as using a base loading coil.
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4Z5PM
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« Reply #6 on: September 29, 2005, 07:02:50 PM »

To: AA4PB,

Quite right, but unfortunately near a whip there is no opportunity to install a tuner.

Question to K0BG,

What material is used at manufacturing mobile antenna, it is tube or rod?

TNX.
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KE4DM
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« Reply #7 on: September 30, 2005, 03:53:54 AM »

Actually, I've always felt that the best end of the vehicle to mount the antenna on is the one furthest from the engine. Spark plugs wires are terrific little noise generators! Many years ago I ran 75 meters in a VW Beetle with a Swantenna mounted on the front bumper.  With a front engine vehicle, I'd look for mounting locations on the rear.
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AC2RC
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« Reply #8 on: September 30, 2005, 04:45:39 AM »

There was an interesting mount of an antenna [SGC website] on a tonneau cover made of fiberglass .The antenna was in the center of the cover. The ground plane consisted of  3" wide strips of copper glued to the underside of the cover going radially out from the center and the copper was in turn connected to the vehicles frame. This would do for any nonmetallic panel....Rear mounted antennas on a SUV or van has a problem of pattern.We did some tests with a rear mount on a suburban. As he went home his signal went up and down depending on direction. Putting the antenna on the roof changed it to a consistant signal regardless of travel direction.
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K0BG
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« Reply #9 on: September 30, 2005, 06:19:51 AM »

On my web site is a fairly new article called Installs. In that article are several examples of how and where to mount an auto-coupler. One is mounted behind a license plate holder at the front of a vehicle. If the coupler is outside of the vehicle, it really doesn't matter is the lead is even a foot long. You just have to make sure it is routed so you do not get any arcing. The RF voltage can be as high as 10KV, perhaps more, so caution is necessary. Further, make sure the ground is robust. When you read the article, look for my installation and the large ground.

When you mount a whip on the back of a van or SUV, there is a large amount of coupling to the body. Depending on frequency and the distance from the body, it is not uncommon to measure 20pF or more. Remembering the capacitance of the antenna is about 20pF to 45pF depending on frequency and length, a simple calculation will tell you why this isn't the best place to mount it.

The aforementioned is one of two misconceptions that just won't go away. The other is that front mounting increases the amount of RFI from the ignition system. This is also false. No matter where you mount an antenna on a vehicle, you have to do a fair amount of noise abatement if you want good results.

Alan, KØBG
www.k0bg.com
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K0BG
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« Reply #10 on: September 30, 2005, 06:28:24 AM »

I'm sorry, I didn't answer the question about the mast.

It is a Texas Bug Catcher, but it could be made home brew. Here is a good reference on building your own: http://www.qsl.net/k5lxp/mobile/HFMast/HFMast.html

The whip is a shortened CB whip.

Your comment about overall length is valid. It all depends on where you live. Out here in the wild southwest, 16 feet won't get you into too much trouble. Try this back east and your antenna won't last long. The nominal maximum is 11 feet, so a bumper-mounted antenna would have to be about 9 feet in length. I have used a full quarter wave on 20 meters (17 feet long or so), but is was made a little different, and most hams wouldn't put up with.

Alan, KØBG

www.k0bg.com
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4Z5PM
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« Reply #11 on: September 30, 2005, 07:04:03 PM »

All Thanks!!

To K0BG,

I think to use a variant which you used in the car, or to install 3/8x24 mount in an aperture (orifice) for the car radioreceiver antenna, in a forward part of the bus on the right parties of a "wing" (possible to see on a picture, a link on which in the first message).
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4Z5PM
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« Reply #12 on: September 30, 2005, 07:15:24 PM »

P.S. In a place of an aperture not big angle (~12-degrees) which it is necessary to compensate!
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