Comparing the "textbook" radiation patterns, lowest take-off angle and greatest horizontal range is achieved by a .64 wave radiator, folowed by 5/8 wave, 1/2 wave, and finally 1/4 wave. My question is if a .64 wave antenna, built small enough to actually be used mobile (under 9ft long), would actually outperform a full 1/4 wave antenna in the real world. I know that in certain situations the higher take off angle of the 1/4 wave is actually an advantage, but let's assume we're dealing with basically flat, rural terrain.
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Better(?) mobile antenna
- Thread starter holttimothya
- Start date
B
BOOTY MONSTER
Guest
not gonna happen .
The Ultimate Guide to 11 Meter CB Antennas
"Most fiberglass whip makers are claiming their antennas are 1/2 wave, 3/8 wave, 5/8 wave and 3/4 wave antennas. That sounds very impressive. But is it electrically true? Yes, the makers of these antenna wind the respective length of wire onto the fiberglass antenna but does the radiation pattern benefit from the extra wire length as claimed? In a nutshell, no. The extra length of wire (beyond 102" inches) is coiled so closely together to be able to actually fit on a skinny fiberglass rod that it electrically ends up performing the same as the 1/4 wave antenna. There are some exagerated claims of performance from some companies."
if you make it shorter than a 1/4 wave it's performance will continue to decrease
The Ultimate Guide to 11 Meter CB Antennas
"Most fiberglass whip makers are claiming their antennas are 1/2 wave, 3/8 wave, 5/8 wave and 3/4 wave antennas. That sounds very impressive. But is it electrically true? Yes, the makers of these antenna wind the respective length of wire onto the fiberglass antenna but does the radiation pattern benefit from the extra wire length as claimed? In a nutshell, no. The extra length of wire (beyond 102" inches) is coiled so closely together to be able to actually fit on a skinny fiberglass rod that it electrically ends up performing the same as the 1/4 wave antenna. There are some exagerated claims of performance from some companies."
if you make it shorter than a 1/4 wave it's performance will continue to decrease
When we talk about 1/4WL, 1/2WL, 5/8WL etc we are talking about a physical length, as can be measured with a tape measure, the real world length of something, ANYTHING that doesn't exhibit this real World length can't be a 1/4WL, 1/2WL, 5/8WL etc, it will be a short loaded 1/5WL, 1/6WL, .21 WL etc, don't be taken in by manufacturer hype, like the 5/8WL Firestick, it isn't, and can't be, a 5/8WL antenna 
HTH
HTH
Radiation patterns are based on the actual length of the antenna. Even if it did have an effect on said radiation pattern the required matching system would likely add in enough additional inefficiency that it still wouldn't perform any better. Remember your matching out at least half of the antenna.
The larger any coil (err matching system) is the more inefficient the antenna is. Laws of physics, plain and simple.
I do know they make coils for HAM radio to use a 102" whip on lower frequencies (and thus longer antennas), I don't see why they couldn't be used/modified to test with if you want to give it a try. A 20 meter adapter coil should get you at least close to where you need to be. That being said, if it really made that much of a difference people would be touting and using them already.
The DB
The larger any coil (err matching system) is the more inefficient the antenna is. Laws of physics, plain and simple.
I do know they make coils for HAM radio to use a 102" whip on lower frequencies (and thus longer antennas), I don't see why they couldn't be used/modified to test with if you want to give it a try. A 20 meter adapter coil should get you at least close to where you need to be. That being said, if it really made that much of a difference people would be touting and using them already.
The DB
Booty, I've read it, and everything else signal engineering has published, as well as alot of other texts on antenna theory. I know enough to know there's a whole lot more I don't know! But, I'm not talking about a skinny fiberglass rod, I'm thinking something more substantial. For a rough idea picture a predator with a capacitance hat added.
DB, that's pretty much what I was thinking, that the efficiency losses would cancel out any theoretical improvement. But there's alot of people on here that know alot more than me, so I started the thread. Thanks!
Booty, you've got the general idea. What I'm looking for is a better performing mobile antenna. I use a full 1/4 wave steel whip mounted approximately center of the roof of my s10 blazer. I've bonded everything on the vehicle; hood, doors, body, engine, trans, even the exhaust. I use a static drain at the rear of the vehicle. I don't want to run any more power, sitting with my head a couple feet from an antenna with a kw of power running to it is not my idea of a good time, besides I'm already "outalking my ears." I know any type of loaded antenna is going to be less efficient, I was just wondering if the theoretical improvement in radiation pattern could outweigh the loss in efficiency in the real world. Prehaps the answer lies in a full size whip made of a material that's a better conducter than stainless. Thank you all for your input
Any shortened antenna will not have the radiation pattern of a 'full sized' antenna, no matter what you do except make the thing longer. That radiation pattern is a function of antenna electrical size/length. There's no magic 'cure' for that, it's just plain old physics. That means the physical length of the antenna. If it's shorter than a 1/4 wave, then the pattern will be less than that 1/4 wave.
- 'Doc
- 'Doc
Rude, Antagonistic Posting is not welcome on the forum, debate, even if it gets heated can be tolerated, not everyone has to agree on everything, but when one has a ego that exceeds ones ability to act civil it is over the top.
Thread has been cleaned, back to the O/P subject.
73
Jeff
Thread has been cleaned, back to the O/P subject.
73
Jeff
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Being more conductive the antenna would need to be just as long if not longer than less conductive materials. I believe this is counter productive for what the op is trying to achieve.
The DB
I'm just chasing the proverbial better mousetrap. A full length 1/4 wave is about as good as it gets for a mobile antenna, but seeing some of the things that are done with base verticals makes me wonder if there isn't any way to improve on it.
The only real way to improve on the quarter wave 11 meter antenna is to make it longer. Making it longer than it already is is simply not practical for mobile applications.
I'm curious as to what is being done to base verticals you are looking at. Aside from Sirio antennas, I haven't really seen anything new recently.
The DB