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)

               

               
               

WSPR - Successful

Hello Everyone,

We were successful using the WSPR technology to connect with another Amateur Radio Operator.

Our setup consists of a Raspberry Pi (Single Board Computer) as a transmitter. For more information on how to use Raspberry Pi as WSRP Tx., please Click Here

We are transmitting using our Engineers callsign: VU3PWT at 10.14015MHz.

WSPR Tx. info: VU3PWT MK32 25

MK32 is the grid location and 25 is the power in dBm. Tx. Freq: 10.14015MHz

From the Raspberry Pi we connected to a very small amplifier (350mW) and then to a Low Pass Filter which is then connected to a very good antenna.

Using this setup we connected with VK6ZT, Australia. We will be running this setup for some more days to get more propagation signals and more research.

Few pics of the setup: