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Suv models

The DB

Sr. Member
Aug 14, 2011
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St. Louis, MO
About a year ago I converted the 102" whip +6" riser I was using for CB on my SUV into a ham antenna by adding a remote autotuner right at the feed point. Thus far I've made contacts on 20 through 80 meters.

Today I remade my SUV model for 4nec2. I had to remake it as I lost all of the models I had not to long ago. This version of the model was designed to be use-able as los as the 80 meters band when modeling, which is new for me as with previous vehicle models I made had trouble even at 40 meters.

As I was curious what the modeling software would show for this layout, I modeled my SUV on several ham bands.

Here is the vertical pattern, the front of the SUV is to the right.

suv1.jpg


And the horizontal pattern. On these models, up is the front of the vehicle.

suv2.jpg


Most of these models are showing lower gain towards the front of the vehicle, I haven't noticed this, but I haven't really been paying attention for something like this either. With where the antenna is most people would expect their to be more gain towards the front as the antenna is almost to the back of the vehicle on the roof... I guess at some point I will have to test this with a field strength meter to verify the weaker signal towards the front...

I've also made a small pickup model based on the Ford Ranger, although I haven't really played with that much yet...


The DB
 
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Marconi

Usually if I can hear em' I can talk to em'.
Oct 23, 2005
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Houston
DB, regarding your SUV model that covers several bands, what do you attribute this effect to...in reversing the maximum radiation pattern to the rear?

Doesn't this defy logic? My experience with an 11 meter whip on the rear of my PU trucks never worked that way.

I'm sure most of my old Eznec mobile models with the antenna mounted at or near the rear of the auto, also showed a typical response to the front.

About a year ago I converted the 102" whip +6" riser I was using for CB on my SUV into a ham antenna by adding a remote autotuner right at the feed point. Thus far I've made contacts on 20 through 80 meters.

This sounds to me like you did not realize your new real world setup was primarily radiating off the back. I would have been amazed at such results.

Are you suggesting that the auto-tuner, located at the feed point, is causing this shift in the RF pattern to the rear?
 

The DB

Sr. Member
Aug 14, 2011
1,988
1,469
193
St. Louis, MO
DB, regarding your SUV model that covers several bands, what do you attribute this effect to...in reversing the maximum radiation pattern to the rear?

Doesn't this defy logic? My experience with an 11 meter whip on the rear of my PU trucks never worked that way.

I'm sure most of my old Eznec mobile models with the antenna mounted at or near the rear of the auto, also showed a typical response to the front.

This sounds to me like you did not realize your new real world setup was primarily radiating off the back. I would have been amazed at such results.

Are you suggesting that the auto-tuner, located at the feed point, is causing this shift in the RF pattern to the rear?

At 10 meters and CB frequencies the patterns are close to omni directional. I think, as far as the model is concerned, that lower frequencies having the rear directional patterns are caused by the rear roof supports having more current than the other roof supports. This actually surprised me so I want to try and verify it with a field strength meter to confirm if the pattern is actually accurate to some degree.

I don't think the autotuner has anything to do with the patterns, I don't see how, in this case, it would.


The DB
 

Marconi

Usually if I can hear em' I can talk to em'.
Oct 23, 2005
7,064
2,073
343
Houston
I don't think the autotuner has anything to do with the patterns, I don't see how, in this case, it would.

The DB
I don't think so either, but Bob recently talked about his A/P problem having something to do with his tuner being in line.

I figure you had to use the auto-tuner when you changed frequencies. How did you do that with the models?

The field strength meter might give some clues. However, I don't see how you could have missed the difference driving around and testing the idea last year when you setup your SUV with this multiband 1/4 wave.
 

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