SWR and return loss
What the standing wave ratio means: type in the SWR or forward and reflected power from the wattmeter, and you get reflection coefficient, return loss and mismatch loss.
SWR and return loss
One value is enough, the others follow: either the SWR or forward and reflected power. Mismatch loss means what the mismatch costs you on top in the cable. Where SWR comes from and how to get rid of it is shown in the Smith chart.
How the page calculates
- ฯ = (s โ 1) / (s + 1)
- from power: ฯ = โ(P refl / P fwd), s = (1 + ฯ) / (1 โ ฯ)
- Return loss = โ20 ยท log10(ฯ) dB
- reflected fraction = ฯยฒ
- Mismatch loss = โ10 ยท log10(1 โ ฯยฒ) dB
An SWR of 1.5 reflects 4 % of the power, and the mismatch loss is then about 0.18 dB. How much is missing in the end also depends on the cable, because the reflected wave is attenuated again on the way; the cable loss calculator takes that into account.
Related terms
- SWR
- standing wave ratio, a measure of the match between cable and antenna
- Antenna tuner
- matches the impedance, but doesn't turn a bad antenna into a good one
- Balun
- transition between a balanced antenna and an unbalanced cable