How to calculate inductance/capacitance value for L-C matching network

hello all...

i'm want to use L-C matching Network for Automatic Antenna Tuner but i'm confused for value of inductance or value of capacitance, how to determined for that's value? for example, i use an antenna with dimension length 1.5 M with frequency resonant at 50 MHz, my question is for frequency 3 MHz, i need value of inductance how much and for value of capacitance too?

note: my design radio manpack application for HF, 3 MHz - 30 MHz

best regards for your answer

Have you any S11 measurement data for the antenna and what is value of system impedance? Both are needed to be able to calculate a matching network.

yes, i have measurement data, that's data consist of HF , and value of capacitance because antenna is too short for 3 MHz - 30 MHz, but i don't know what i can do from that data?

thank you very much for ur reply, before

If you have needed data, complex antenna impedance and system impedance, just follow instructions at this link http://www.antenna-theory.com/tutorial/smith/chart.php .

Dear SU-4
Hi
An important thing to design matching networks , is knowing , both impedances ( antenna and transmitter out put ) and naturally line impedance , at this range of frequency you can use stubs for matching too .
And another thing is how much si your power ( for high powers and low powers there are different ways ) . and about selecting the values of matching network : what kind of matching , do you decided to use ? there are many many matching networks available .
Best Wishes
Goldsmith

dear Mr. Goldsmith

thank you for reply my topic, my avarage power is 20 watt, and i have used nine toroidal for binary value of inductance, 0.25uH, 0.5uH, 1uH, 2uH, 4uH, 8uH, 16uH, 32uH, and 64uH., and i plan to select L-C matching network, because when i only use L (inductance) there are several gap between range 10 MHz - 15 MHz. my problem i can't to judge or to choose suitable value of capacitor for get best VSWR 1:1.5, i don't know how? please help me, maybe u can give me for schematic automatic tuner antenna whip with length 1.5 M for HF and tell me how to choose suitable value both of capacitor and inductor to get best VSWR

thank you very much goldsmith

Hi again
why not a simple third order filter ( RLC ) at pi arrangement ? if you want i can help you at low order matchers . ( i can attach some pages from some practical book , here .)
Best Wishes
Goldsmith

---------- Post added at 21:50 ---------- Previous post was at 21:49 ----------

By the way , i forgot to mention it again ! you forgot to talk about your impedances ( line /load / out put of amplifier)

There is a block diagram of one here: http://www.vmarsmanuals.co.uk/newsle...es/vra549c.pdf
You just need to transmit a very short RF burst, and during that time perform your algorithm, switching relays until you get the optimum
match. You won't be calculating a value, because you won't know what kind of antenna is connected (or what frequency has been selected by the operator). That's for a conventional ATU; not sure if that is what you want.

hi.
in any matching network, impedance plays major role, so somehow u need to match the impedance at first, that can be done by using coaxial cable wire with accurate impedance and length of the cable can be find by finding lamda for specific rf...... to find da l n C, CANT U USE BASIC FORMULA FOR FUNDAMENTAL FREQUENCY...