My First Attempt At A Mobile Antenna

[HomerBB]

I want efficiency, but do like to have a nice curve, too. In due time I may want to operate some 10 meter, too. So I have no real opposition to obtaining wide-bandedness. My point was to say if I fail to obtain such a goal I am at least within the current operational parameters.
Thanks for the advice everyone.

 

[HomerBB]

Here is a side-by-side photo of the first antenna and the modified version. This clearly illustrates the height difference the new coil accomplished.

 

[Moleculo]

I just saw this project. I like seeing pictures of people "rolling their own" stuff! HomerBB: Thanks for sharing your project and the great pictures with us...check it out; I put it up on the home page

 

[NY739 Mobile]

Looks good but also looks like alot of wind resistance, probably will put alot of stress on the mount and truck body. I played around with copper and short whip combo's myself but finally broke down and spent $20 at radio shack for a 102" ss whip and a 6" spring, mounted it next to the third brake light on the cab of my F350SD and I skip all over the country......and Its not taller than 13'4" off the road so I don't hit every thing in sight ( up here in NY most bridges are not over 13'6"), also my swr's are almost perfect well above and below the normal 40.....just some thoughts....

 

[HomerBB]

I just saw this project. I like seeing pictures of people "rolling their own" stuff! HomerBB: Thanks for sharing your project and the great pictures with us...check it out; I put it up on the home page

Well what can i say to that. I'm flattered that you've found that much to appreciate in my fumbling efforts . . . but, thanks.

 

[HomerBB]

Looks good but also looks like alot of wind resistance, probably will put alot of stress on the mount and truck body. I played around with copper and short whip combo's myself but finally broke down and spent $20 at radio shack for a 102" ss whip and a 6" spring, mounted it next to the third brake light on the cab of my F350SD and I skip all over the country......and Its not taller than 13'4" off the road so I don't hit every thing in sight ( up here in NY most bridges are not over 13'6"), also my swr's are almost perfect well above and below the normal 40.....just some thoughts....

I see and understand what you're saying here. The thing is, I'm doing it less for the science of it, and more for the sheer pleasure. I can get that steel whip at RS for $19.97, but the last one I had I gave away to someone who just wanted to talk through the antenna. I want to play, and learn so I go at it this way.

Thanks for sharing. I'll warn you, however, the next thread I start may just be some other kind of antenna I'm experimenting with just for fun

BTW, my wife thinks I've lost it

 

[NY739 Mobile]

I hear ya.....I too have spent countless hours playing around with diff designs and deffinatlly had fun doing it......nice work...73's

 

[HomerBB]

A wide banded coil also has a lower Q... If he's going to use it on a single band there is no point in optimizing the 2:1 characteristic... it may make sense to make it as efficient as possible for the intended frequency.

I am curious about this statement, Which direction should I take it to acheive either - wide-bandedness vs efficient?

Also,
I have been unable to do much with this thing lately. What would be the benefit of two wraps with the larger diameter it would provide using the same length of aluminum flat bar - 48"?
I haven't made it longer on the bottom, yet, but can if necessary. It is still like the one on the left in the photo, but now has only two wraps. This made the diameter larger and the spacing wider. I know Doc suggested narrowing the spacing between the wraps, too, and he isn't the only one to hint at doing it.
Thoughts?

Thanks,
Homer

 

[Moleculo]

I am curious about this statement, Which direction should I take it to acheive either - wide-bandedness vs efficient?

Also,
I have been unable to do much with this thing lately. What would be the benefit of two wraps with the larger diameter it would provide using the same length of aluminum flat bar - 48"?
I haven't made it longer on the bottom, yet, but can if necessary. It is still like the one on the left in the photo, but now has only two wraps. This made the diameter larger and the spacing wider. I know Doc suggested narrowing the spacing between the wraps, too, and he isn't the only one to hint at doing it.
Thoughts?

Thanks,
Homer

You sort-of have to make a choice between the antenna bandwidth vs. efficiency; they don't necessarily go together. Your other questions deal with coil efficiency, which is going to be difficult to measure without some equipment. You could model it and get some answers, too (I'm lousy at antenna modeling). Generally, a long skinny coil is less efficient than a short, wider one. Sometimes though, you just have to go with what works given your design or structural requirements and call it good enough. If you want to try something different, try making the coil wider with less turns and the spacing between turns closer together. How much power are you planning on running into that antenna?

 

[HomerBB]

I have only 100 watts PEP to put through it.

 

[Torch39]

How does it handle normal driving speeds? Looks like a DXing machine!

 

[HomerBB]

I've driven up to 80 MPH with both antennas. 75 MPH for extended periods of time without any problems.

 

[HomerBB]

In the first of these two photos it shows the antenna on a homebrewed triple magnet mount on the roof. At 55 MPH it came unglued from the roof top. I will have to add more magnets for this one.
The second photo shows a shot of the antenna sporting two wraps on a shorter center insulator. This change I did during my lunch break last night. However, the antenna seemed to suffer some noticeable performance reduction. I will be putting a longer lower shaft on it to see if I regain performance.

 

[crmzendrgone]

This is an awesome thread. I love the visual aspect of the antenna. I wish I could say more about the function and all that but I have no clue about anything radio related. But that is why I am here, to learn.


So my question is what do those coils do and why copper and the list can go on for questions. Guess I should try the search option.

Again I love the looks!!!

 

[HomerBB]

Okay, someone smarter with the terminology than me step up and break it down for him.

As for the copper, it's simple. I like to homebrew antennas for personal use. Because I'm just an ordinary fellow with limited income I look for adequate materials in those places folks like me can afford to shop. I make my antennas from hardware store materials. In the mean time I am learning more about them. This forum is especially helpful in helping me to understand what to do, and what I'm doing.

Thanks for the compliment on the antenna's appearance.