what are the difference between single and dual coil mobile antennas . I want to get a new antenna wanna try a coily or a 10k but dont know what make either better from each other??
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dual coil , single coil whats the difference
- Thread starter 2at124
- Start date
dual or single coil
thanks for the replies now i can make a good choice before i buy my ne wantenna i'll keep you informed
thanks for the replies now i can make a good choice before i buy my ne wantenna i'll keep you informed
Both Kale(10K) and Dan(Coily) make a very good antenna. Kale's is a little lighter if that is a concern. Also Kale's is screwed together. Dan's is welded, a little heavier, and the shaft is a little skinnier. I have been running both for several weeks now and the performance of their single coil antenna is about the same. They both offer great customer service. They answer their e mails and are more than willing to answer your questions over the phone. Good luck and let us know how you made out.
2at124 said:
The only differance on the coily double is this,I take a single coil and split it in half :idea: the reason i did this is to get any extra loading and losses out of the longer multiple single wrapped coil section, and this also helps in the tuning.I have found in testing over many years by breaking up the coil into sections the antenna is less lossy,and the reflection was even lower than it already is.I don't add another coil i split mine in half.
And they look cool...Coily :Wavey
There are some theoretical downsides to dual coils to consider:
First some background: On a straight 1/4 wave antenna (no coil) the current is at it's maximum at the base and tapers off to the tip. Whenever you add a coil in the middle, this causes the current to stay pretty close to constant up the antenna, and through the coil, then taper off past the coil. This can be a good thing when done properly.
Not too long ago, I saw a double coil predator 10K modeled. The model showed the current INCREASING through the second coil. It wasn't real clear why that was happening, but it's not necessarily a good thing. A possibility that came to mind was stray capacitance causing circulating currents.
Another thing to think about is that as current passes through a coil, it creates a magnetic field. If you put two coils next to each other, the magnetic fields will interact with each other. This is how a transformer works. Now, these coils are open air, not wound on an iron toroid, but I would think that it's theoretically possible for the second coil to cause the antenna to exhibit step down transformer properties. In this case the second coil would reduce the voltage but cause an increase in current in the second coil which could also explain why the model showed the increased current.
I've attached a couple interesting links on antenna loading design. Maybe someone with a little more experience and knowledge than me can comment on my ideas above.
www.w8ji.com/mobile_and_loaded_antenna.htm
www.w8ji.com/loading_inductors.htm
First some background: On a straight 1/4 wave antenna (no coil) the current is at it's maximum at the base and tapers off to the tip. Whenever you add a coil in the middle, this causes the current to stay pretty close to constant up the antenna, and through the coil, then taper off past the coil. This can be a good thing when done properly.
Not too long ago, I saw a double coil predator 10K modeled. The model showed the current INCREASING through the second coil. It wasn't real clear why that was happening, but it's not necessarily a good thing. A possibility that came to mind was stray capacitance causing circulating currents.
Another thing to think about is that as current passes through a coil, it creates a magnetic field. If you put two coils next to each other, the magnetic fields will interact with each other. This is how a transformer works. Now, these coils are open air, not wound on an iron toroid, but I would think that it's theoretically possible for the second coil to cause the antenna to exhibit step down transformer properties. In this case the second coil would reduce the voltage but cause an increase in current in the second coil which could also explain why the model showed the increased current.
I've attached a couple interesting links on antenna loading design. Maybe someone with a little more experience and knowledge than me can comment on my ideas above.
www.w8ji.com/mobile_and_loaded_antenna.htm
www.w8ji.com/loading_inductors.htm