In my quest to get up to speed with Amateur Radio (see my previous posts about amplifiers and the such) I need an ATU - or antenna tuning unit. At the moment all I have as an aerial is a length of wire from the upstarts bedroom window down to my study. This in no-way matches the input of my small Software Defined Radio (Acorn G0NQE model). And all I get is tons of loud hissing or, as amateur call it, QRM.
So I looked first into a simple LC matching network. But what values to use.
If you assume their are just restive source and load then:
Xl = sqrt(Rs ( Rs - Rl)
Xc = Rl sqrt(Rs/(Rl - Rs))
For Rs = 50R and Rl = 1000 this would yield:
Xl = j217.9R and Xc = 229R
Now, if the frequency is 3.6MHz, then:
C = 1/(2pi x f x Xc) or 193pF and L = Xl/(2pi x f) or 9.6uH.
That was easy wasn't it?
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