Rattus' Next Nasty Question

[physis]

I got to thinkin' that I might build a simple AM radio reciever. Nothing fancy.

I have a meter with inductance and capacitance but I have no idea where it is.

The frequency I'm interested in is slightly demanding antenna wise. Because I want to go after the fundamental frequency of the shumann resonance, 7.8 Hz. The only real problem is that I have nowhere to put a 12,000 mile long antenna.

So I'll need to use an inductor to get the length I need electrically. No big deal, if I know the capacitance of the antenna.

I want to use a 2 meter mono-pole.

With no test equipment, how am I going to calculate the capacitance of the antenna element?

 

[physis]

Re: Rattus' Next Nasty Question

Oops. This is supposed to be in engineering. I think I missed.

 

[rattus]

Re: Rattus' Next Nasty Question

Sam, first find your glasses so you can click on the right category; then find your LC meter.

 

[physis]

Re: Rattus' Next Nasty Question

Chicken.

 

[steve66]

Re: Rattus' Next Nasty Question

Sam:

You need a smith chart. It's been a while, so I don't think I can help much.

Smith Chart examples

Good luck.

Steve

 

[physis]

Re: Rattus' Next Nasty Question

I'm not familiar with Smith charts, (one of the draw backs of an incomplete formal education) this looks like a very cool tool.

Unfortunately, they've made it clear on the front page that their charts are copyrighted and reproduction isn't permitted, so I wont post one.

 

[rattus]

Re: Rattus' Next Nasty Question

Sam, Smith charts provide a graphical solution to xmission line and antenna problems. I doubt that anyone uses them anymore. They hurt my head just to look at them.

 

[physis]

Re: Rattus' Next Nasty Question

I've been looking at these Smith charts. Reportedly there not very difficult to understand.

I'm not so sure. I feel like I'm learning ac circuits all over again. After studying them a bit I hope it wont seem so intimidating.

I'm using this site right now and it seems rather informative.

This is very elightening to me Steve, thanks.

 

[physis]

Re: Rattus' Next Nasty Question

You snuck in on me while I was typing Rattus.

In school, you shouldn't use your calculator until you're able to work without it.

I think the same logic might apply here.

A pc and some cheap software can completely remove the need for these charts.

Except for one thing.

You wont understand it.

Edit: Well, that may not be completely true, I think I can understand the math without the charts.

[ May 02, 2005, 06:07 PM: Message edited by: physis ]

 

[physis]

Re: Rattus' Next Nasty Question

And Rattus, a lot of this stuff hurts my head anymore.

 

[steve66]

Re: Rattus' Next Nasty Question

I doubt that anyone uses them anymore.

I'm sure you can find computer programs that do all the work for you. But Physis has a good point about not using a calculator until you learn basic math. I don't think you could you could use an computer program very effectively until you learn some of the basics.

They hurt my head just to look at them.

In school they actually taught us the basics with raw equations first. Now that was a headache. After that, the smith chart seemed like a godsend.

Steve