AUDIO FILTER

Audio filter in Jota 40 receiver Testing Mode:

Schematic Diagram:

Greetings Everyone,

               We are Happy to share this experiment result of this audio filter. Basically this is not our original design. Our sincere thanks to our good ham friends OH2NLT and OH7V for this beautiful circuit which is used in JUMA Receiver.

                We constructed this circuit in a general purpose PCB for simplicity and also modified the circuit
                 in input side adding some external capacitors to achieve good performance.Half voltage of the
                 given supply voltage is required to the pin no 3.

                 Our testing process begins in the evening tuning for some time no stations heard.After a break
                 we received a strong station with call sign VU2MBU giving General CQ CQ Hi. At the time with
                 out using the filter we heard a lot of  hissing noise in the background.The audio filter is                                    connected in the audio chain suddenly performance increased.Hissing noise level reduced to very
                 minimum SIGNAL to NOISE Ratio improves by 2.5db that is measurable.

                  All components are locally available in Bangalore market for Less than 50Rs/-

                  After this improvement we tested the audio filter continously for 2:30Hrs with the following
                  stations received in good quality audio with less noise.

                   1.VU2MBU
                   2.VU2PLL
                   3.VU2LSR
                   4.VU2KSJ

         Warm Regards,
         RnD TEAM.(MIPL)