[SECC] Matching T Vertical for 160 meters

[Bill Coleman]

On Jul 18, 2007, at 8:36 AM, KC4HW wrote:
> Take a look at this link:  http://www.epanorama.net/documents/ 
> wiring/coaxcable.html  it
> contains information regarding coaxial cable.  The chart displays  
> sort of screwy, but pay
> particular attention to the capacitance/ft values of the different  
> coax.  Notice that RG213 has
> a 30.8pf/ft value.  This would be approximately 71.5 feet to equal  
> 2200pf.

One thing to consider is that any length of coax doesn't just act as  
a capacitor, it also acts as a transmission line, and that will have  
an effect on the resulting capacitance.

W8JI wrote about this on his page on coaxial traps:
http://www.w8ji.com/traps.htm
"Coaxial capacitors are really open stubs, and should be treated that  
way once they are more than a few degrees long."

71.5 feet of coax is about 96 degrees on 1.850 MHz, so this probably  
isn't a good way to get 2200 pF.

> For the inductor, I would try to find a wrecked Butternut veritical  
> and use those coils.
>
> However, here is an article that I found on physical construction  
> of inductors that I thought
> was very interesting...   http://www.arrl.org/tis/info/pdf/9708033.pdf

If you look on the internet, you can find a number of useful web  
pages that have electronic calculators.

For example, if you can measure the antenna impedance, you can figure  
out an L-network to match it: http://www.daycounter.com/Calculators/L- 
Matching-Network-Calculator.phtml

If you want to design an air-wound coil, here's an inductance  
calculator:
http://www.technick.net/public/code/cp_dpage.php? 
aiocp_dp=util_inductance_calculator


Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901