just curious

[NY739 Mobile]

I've read many a thread about coil vs. 1/4 and I agree hands down that 1/4 wins every time but .......This might be a really dumb question, but If I don't ask I won't know the answer......
I find that this forum has a vast wealth of knoweledge of antenna theory so ......
Can a mobile antenna get any better than a full 1/4 wave? ( I'm talking about a 108 inches of real whip here, not a coil antenna)
What I mean is this....
I know that a 1/2 and a 5/8 wave out preform a 1/4
I'm also pretty sure that a 22' antenna is not going to fit under many bridges
But could one add a coil or a cap hat to a full 1/4 wave making it a 1/2 or 5/8 wave... and taking into account coil losses... would it still preform better than a 1/4 wave alone or due to the fact that the antenna is only electrictly longer and not physically longer and because the whip would still be the same length would there be no improvement?
or would the coil losses make it even less efficent than a 108" whip alone?
or in the case of the cap hat instead of a coil would the antenna be actually physically longer while remaining the same height vertically and preform better than a standard 1/4 wave?

Just curious...op:

or mabye I allready have the best most perfect antenna I can have on my truck(108" ss whip) and I should just be satisified.....hmmm :headbang

 

[Moleculo]

The biggest problem that you're dealing with when it comes to HF antennas (CB is at the upper end of HF, so it still applies) is that the size of the antenna required is your enemy. Can you do better than a 1/4 wave mobile antenna? Sure...it's done all the time in the VHF/UHF bands by making collinear antennas, which are basically multiple antennas stacked to improve gain. The problem with trying that on HF bands is that the antenna is just too big to make it practical. Can you imagine trying to stack a couple of 11 meter antennas? I just doesn't work while mobile. Most people can't even run a full sized 1/4 wave 11 meter antenna so trying to do something bigger and better is just out of the question.

 

[Kamikaze]

To get gain the antenna needs current maximum points separated in physical space. A 5/8 electrical wavelength coil antenna which is 1/4 wavelength physically long will behave just like a 1/4 physical wave long antenna minus coil losses.

See "method of moments."

 

[W5LZ]

'Gain' amounts to reshaping radiation patterns. Those radiation patterns amount to that specific length of the antenna. And since the length of a -practical- antenna has limits determined by frequency of use, there are definite limits especially for mobiles! 'Scrunching' whatever proposed antenna length into the length of a 1/4 wave in length, means that you wind up with the radiation pattern of a 1/4 wave antenna. Of course there will be some differences, but nothing like what you'd expect in most cases. I'm afraid you can't 'get around' that. Wish it were possible!
- 'Doc

 

[NY739 Mobile]

Thanks for the reply's gentelmen....thats pretty much what I thought........but I had to ask anyway....thanks again