10k.Boy was i wrong!

[Moleculo]

The length of meterials did not change so the actual coil and overall antenna tuned out the same height

Did the amount of space between each turn in the coil change? I'm guessing it did if the shape of the material changed? If the size of the gap changed (narrower, I'm guessing), then the inductance value changed. That would explain why you would have to change the tap, or mess with the shaft length. Just trying to help figure out what's going on...

 

[W5LZ]

Mole',
I think you've hit it. The distance between turns of a coil will make a difference in the total inductance of a coil, so will the coil's diameter. The 'shape' of whatever the coil is make of , round, square, rectangular conductors, will also change the inductance because of the interaction between what makes the coil. Square or rectangular conductor will have more surface area at a 'constant' distance from each other. Round conductors will have a varying distance between the surface areas of the conductor, not much, but some. Two 'round' surfaces versus two 'flat' surfaces, even if the other dimensions are the same between the two (length and diameter of the coil), will mean a difference of inductance between two otherwise simular coils. The 'wider' the flat conductor is compared to the round conductor will mean a larger inductance. That will mean that a shorter coil made up of that 'wide' stuff will have the same inductance as a longer coil made up of round stuff.
The diameter of a coil also comes into play. Assuming the same diameter between two coils, if one uses 'wider' conductor and the other uses round conductor, the 'wider' one will have a smaller diameter. A smaller diameter reduces the total inductance. If the change in surface area between the flat/round stuff is much larger in proportion to the coil's diameter, then the inductance of the whole thing may not be very much, or if the difference is even larger (as in the flat stuff reducing the inside 'hole' in the coil significantly) the inductance may even be ~smaller~ than the round stuff coil. That's a stretch, but still true!
- 'Doc

[I'm getting a headache, more coffee!]

PS - Oh, one last thingy. Don't even think about using a triangular shaped conductor, the sharp points of a turn will make it very easy for it to short between turns. Ought'a make a good 'light show', though...

 

[mrcoily]

The length of meterials did not change so the actual coil and overall antenna tuned out the same height

Did the amount of space between each turn in the coil change? I'm guessing it did if the shape of the material changed? If the size of the gap changed (narrower, I'm guessing), then the inductance value changed. That would explain why you would have to change the tap, or mess with the shaft length. Just trying to help figure out what's going on...

Well i hear you on trying to help :Wavey the spacing really has no affect i trieds all kinds of differant coils,There all dialed in now i tune them all at 1.0.1-1.1.1 and right at 49-50 ohms, i have it all figured out this is all really old stuff.The coils changed alot the old coil was 3" round the new coil 6 " round and flat making the feed point to close, and that's what thru me off ,and thats why i had to move it out to get the reflection out the coil, and feed point. It would not tune out i made several coils,of differant sizes and spacing before i figure out it was reflection off the coil.As far as trying to take a smaller coil and shorter coil with less spacing won't work same thing goes for mobile antennas ,when i build my mobile antennas i have set amounts of coil for certain size antennas..5.5 feet,6.9 feet,8 feet all taking differant length coils,can't just use a fatter meterial and space it closer will not work.

-W5lz-
That will mean that a shorter coil made up of that 'wide' stuff will have the same inductance as a longer coil made up of round stuff. -w5lz-

That won't work have a pile of coils telling me the truth, if the coils are not the same length they will not load up for the band i am tuning for, and if you wanted to use less coil be it flat or round the vertical mast would have to make up for it..as i am using the .64 wave i have to build the correct length coil to get the optimal performance for.64 wave ,,tightening and widening will not make up for that...tried that already for the optimal and right length antenna a certain amount of coil is needed to be used,You will end up changing the over all height and over shoot or under shoot the .64 Changing tap points does not work tried that also..throws off the entire antenna has to be the certain amount my antenna is very touchy on this.spacing has really no affect and to narrow the spacing can give you arcing on high currents.Now i could shorten the antenna to say 5/8 or half wave,But i would have to change the coil length and tap points.I see what your saying about the large flat surface having more area,and that may give you the illussion that all that added flat area would make up for it,but it does not you still need the same amount or you will be making up for it in vertical heights throwing everything off wave..73sss Dan

 

[Moleculo]

Coily, not trying to start an argument, but what Doc and I both posted is well documented. The properties of a coil and how they work are parts of basic electronics theory. They behave the same way whether used inside a radio or used as part of an antenna. Some of the things you said you found in your tests are a direct result of what we're trying to say (maybe you misread what Doc & I posted?). Anyway, here's an interesting read: http://www.w8ji.com/mobile_and_loaded_antenna.htm

 

[mrcoily]

Coily, not trying to start an argument, but what Doc and I both posted is well documented. The properties of a coil and how they work are parts of basic electronics theory. They behave the same way whether used inside a radio or used as part of an antenna. Some of the things you said you found in your tests are a direct result of what we're trying to say (maybe you misread what Doc & I posted?). Anyway, here's an interesting read: http://www.w8ji.com/mobile_and_loaded_antenna.htm

I was looking at it differantly i usually refer to my Antenna manual books on this stuff and all the years of bulding i have done. but that's a good read not that it all works as per text book would like,I try and keep it to basics and i know what works and what won't tune.I see what your getting at in spacing and overall coils sizes.but i know i can't just shorten the coil,respace to change the inductance without also changing alot of other stuff and when i have done just that the antenna itself need to compensate and i don't want that i want a certain height. as i changed the coil and went from 3"x6" to 6"x8" there was a major change in the electrical property of the coil.But Basicly the only thing i really had to adjust was the actual coupling between the coax and the tap point making it longer and that's also probably, where the tune cam back.I See what your getting at i just do it and look at it a bit differantly.

 

[Groundhog KSS-2012]

s

Kale, I have three different shaft length 10k's, 17", 27", and 36". I also have two short coils and three long coils for the 10k's. I have mounted the 10k's in different length and coil configurations just about everywhere and can't get below a 1.3 swr and fairly high reflect. Maybe they don't like my Ford pickemup. I don't know. I also mounted the 102" whip in many different locations with high swr and high reflect, until I mounted it just behind the cab on the driver side bed rail - 1.1 with almost no reflect. I'm not saying your antennas aren't great, they are. They just aint working on my pickup truck...

Just my experience, LoneWolf TN

Another very old thread but, that is exactly where I mount my 102 SS Whip and big barrel spring and also get a 1.1 on 1, and 1.2 on 40.