NOVELTY - Electrically conductive system comprises a substrate and an electrically conductive track adhered to the substrate where the substrate comprises polyamide-66 and the electrically conductive track is obtained by jet printing, where the substrate is made of a composition consisting of polyamide-66, one other polymer, reinforcing agents, and an additive.    USE - The electrically conductive system is used in an antenna for use in a mobile device. The electrical conductive system is used in the manufacture of electrical circuits or contacts in solar cells, transistors, Organ Light Emitting Diodes (OLED), Flexible Printed Circuits (FPC) and Radio Frequency Identification (RFID) systems (all claimed).    ADVANTAGE - An environment-friendly and low cost method for producing electrically conductive system is provided.    DETAILED DESCRIPTION - Electrically conductive system comprises a substrate and an electrically conductive track adhered to the substrate where the substrate comprises polyamide-66 and the electrically conductive track is obtained by jet printing, where the substrate is made of a composition consisting of (A) 30-100 wt.% of polyamide-66; (B) 0-50 wt.% of one other polymer, where the other polymer may comprise another polyamide in an amount of less than 30 wt.%; (C) 0-60 wt.% of reinforcing agents; and (D) 0-15 wt.% of an additive; where the weight percentages (wt.%) are relative to the total weight of the composition. INDEPENDENT CLAIMS are:    (1) a process for producing an electrically conductive system comprising a substrate and a conductive track adhered to the substrate, by providing a substrate made of a composition above; applying a conductive track precursor on the substrate by a jet printing technique; and sintering the conductive track precursor on the substrate at a temperature of greater than or equal to 150 degrees C so as to obtain a conductive track on the substrate; and    (2) antenna for use in a mobile device, comprising an electrically conductive system above.