Need some coil advice

[TwstLok]

Hi all. I'm looking to tinker with coils for use with vertical antennas in the ham radio HF spectrum.
I currently have a Butternut HF6V vertical that uses coils for changing resonant frequencies on the various bands.
These coils are 1/4"O.D. aluminum tubing.
I purchased a roll of this stuff in hopes of tinkering with a home-made 40m (7.100mhz) 1/4wave vertical.
I'm wondering if there's an equation (of course there is) for determining how many turns/diameter etc to come up with x-amount of micro henry's inductance.
**Those were the only 'big words' I know for antennas,please dont assume I'm smart! Please use layman's terms when possible in replies**

Is this formula the same no matter what the frequency? For instance, if I want to get 1/8"O.D. tubing to first try my hand at smaller, more manageable antennas, can I use the formula for like the 2m (144-148mhz) band?

I have pretty much the same question for capacitance hats on antennas. How do you know what size to make them for starters just to get you in the ball park of the right frequency??

Thanks for anything.
Sean

 

[SolderingGunslinger]

Here's a link to the ARRL website and a PDF on winding your own air-core inductors.

http://www.arrl.org/tis/info/pdf/9708033.pdf

It has lots of good information on the mechanical end of the winding along with the formula itself.

Good luck with your antenna project. For a shortened 40-M vertical, look in the ARRL antenna book for a 2-meter length antenna with a big capacitive hat.

As far as shortening your VHF antennas, Why? A quarter wave at 2-meters is around 52-CM (20.5-inches) at the bottom of the band, and a little shorter at 147.99 MHz. Even at 6-Meters (50 MHz) a quarter wave is only 1.5-meters (4-Ft, 11-inches). A quite do-able length for most mobile or fixed operation.

Pick up one of the antenna books available from the ARRL or RSGB. I think you'll enjoy them.

73 DE The Old Soldering Gunslinger

 

[TwstLok]

Thanks for the response.
Didn't think of checking the arrl site.
no, I'm not trying to make a "shorter" 2m antenna. What I meant was, if I'm going to practice with coils/antennas, would the formulas be the same for 2m as they would for hf. That way I can tinker with 20" of wire in the house instead of 40' of aluminum tubing outside. Just to mess with to learn the technique a bit.
Build a 2m antenna? Pa-leeze, my lazy butt will march down to HRO and spend too much on a Diamond and call it good!
Thanks for that pdf link, never thought of checking arrl.
Thanks
Sean

 

[SolderingGunslinger]

I haven't home brewed a mobile VHF antenna for some time, however the antenna at my present QTH is a home brew, plumbers-delight J-pole fed Colinear.

Since I am at 8550-Ft (2606-M) AMSL, 6050-Ft (1844-M) above the city of Tucson, the two half-waves aren't really in phase. They are slightly out of phase to give me a little beam tilt and increase my signal in the Valley. I still get Q-5 reports from as far away as Prescott.

From "The Hall of the Mountain King" in the beautiful Santa Catalina Mountains of Southern Arizona, I remain,

The Old Soldering Gunslinger

73