Why different lengths?

Hello ICL1P,

The Lautus uses magnetics to attenuate high frequency interference from the two worst offenders: FM (VHF) analogue broadcasting centered on 100MHz, and DAB digital broadcasting centered on 200MHz. When attenuated by the Lautus cable the audio is clearer.

They work on the quarter wavelengths of the two frequencies - where the carrier wave is at maximum power. At a calculated distance from the start of the cable the quarter wave of 200MHz exists. This is essentially shorted together by the magnetics and results in a new start of the cable at that point. At the next calculated distance the quarter wave of 100MHz exists and this is essentially shorted out by the next magnetic circuit. Each magnetic circuit forms a radio-frequency-transformer which is how it 'shorts' the conductors together at the frequencies of interest. The shorts do no damage to the audio stages driving them because they are at frequencies far greater than the audio stages can do (if designed properly that is).

The positions of the magnetics are dictated by the quarter wavelengths and 1.5 metres allows placement at the required distance where 0.6m would not. At 1m length positioning is tight to the end of the cable, so 1.5m was chosen as the nearest conventional length allowing for correct positioning.

(We have made one or two for customers which only did 100MHz as an early part of development charging CuSat50 prices)

We decided to limit the maximum length at 3m because after that the effectiveness could be compromised because cable impedance rises with frequency, and interference could be propagated in the remaining length.

(Picture accredited to 'Electronic Products' )

Graham Slee wrote: Hello ICL1P, The Lautus uses magnetics to attenuate high frequency interference from the two worst offenders: FM (VHF) analogue broadcasting centered on 100MHz, and DAB digital broadcasting centered on 200MHz. When attenuated by the Lautus cable the audio is clearer.  .. .. .. ..