Antenna Tuner
Monday, February 14, 2011
Kates Playground In A Strawberry Bikini
Extended and Republished Post
Why use an antenna tuner?
All antennas at a given frequency with an input impedance expressed in R + / - jX, where R is the resistance and reactance is Jx.
If the reactance is inductive + J (the antenna is too long) the sign of J is +
If the reactance is capacitive, the sign of J is -
line feeding the antenna is a transposition R + / - Jx value to a new value based on the impedance, length, and the speed factor of the power line.
With the help of the Smith chart we can see this graphically. Therefore
the antenna connector will have a value of R + / - Jx at a given frequency.
For the transmitter can transfer maximum power to the transmission line, the impedance of the transmission line must match the output impedance of the transmitter.
This impedance is normalized to a value of 50 ohms J 0, all solid state equipment.
So the purpose of an antenna tuner is an impedance matching network, is to convert the complex impedance of the transmission line R + / - Jx a standard impedance of 50 ohms and J 0
Design
The variable capacitors are the type of transmission and must be isolated from the metal cabinet or chassis.
ideal is to use the best equipment possible but it all depends on each particular budget and working conditions shall be submitted to the ATU.
Welds shall be for a personal recommendation to "strong" is cheap tin rf transistors and not really even though we do not use more 100 or 200 watts in the continuous use this unit can be coupled loads varied from about 5 ohm about what it means to a high impedance to RF current environment and over the 800 ohm, the highest measured value for me, what means that according to the impedance that we can merge it high current or high voltage rf in rf in the derivations of the coil or band change key.
That and better working experience and a good welder welding power savings are not adequate and that more expensive then paying for any failure.
the varying capacities and inductance coils or vary according to the material with each, for the adjustment is to use a parser antenna or a good quality wattmeter between the transmitter and antenna tuner with 5 watts or less enough to have some indication on the wattmeter and with the help of an alligator clip to start band by band and always tweaking the settings C1 and C2 to find the point of the coil in which we have zero reflected power at that point we can make a referral to the key bands "the ideal would be a coil variable
So to find the best materials for our project, in terms of the variable capacitors do not recommend the use of capacitor typical old radio reception to valves, better to spend a bit of a good pair of variable capacitors for transmission.
vercion You can download a hard copy of this article here
For if you have questions or comments like the answer in my e-mail: cx2ua@hotmail.com
73 good dx. Paolo
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