Antennenlaengen

Length calculation of shorted (low impedance on TRX) feeder wire

To the Charts: 50 Ohm 100 Ohm 150 Ohm 240 Ohm 300 Ohm 450 Ohm 600 Ohm 750 Ohm 1000 Ohm back

While looking these curves always remember: To the right it goes to the input aerial of the antenna and to the left to the transceiver. From the curves one is able nicely read that with an shorted/low impedance feeder wire on TRX to Lambda/4 feeder wire length becomes the high impedance on the antenna. We must connect the antenna where the right impedance is given - ascertained from the Chart "HF tensions in a wire" with the dipole the value sometimes 2 take the right length and then to the TRX to come thus low impedance as possible. Then the blind shares and the optimum adaptation will worked with the symmetrical tuner.

Dear hamoperator, for the generally consideration of reaktance for a shorted feeder wire is following formula generally applicable:

Zr = Zo * tan(180 * l/Lambda) for degrease or Zr = Zo * tan(pi * l/Lambda) for radianten calculation

Wether degrease or radiant calculation you must switch it on your pocket calculator. Zr is the reactance from the load, Zo the input impedance of the wire, l the length or wire an lambda the wave length (300/frequency in mc)

Now a special case - resonance length:

For lambda/4 and uneven more of that takes effect: Zo² = Za * Ze ====> parallel resonance circuit

Zo is the wire impedance, Za the output load (also Zr reactance matching) and Ze the impedance of input load.

For lambda/2 and even more takes effect: Ze = Za ====> serial resonance circuit