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Showing posts from January 18, 2020

136kHz receiving noise in WSPR window at nights

Darrin KE9NS did release  P-SDR Version  supporting the MCP23017  I/O expander. Big thanks great job! Automatic bandpass selecting / hopping now also works for the "XVTR" bands 2200m and 630m. The Flex1500  needs external Bandfilters for 137 / 475 kHz  i.e. below 482kHz the bandfilter section is bypassed. 2200m and 630m are added as XVTR bands and use the  BNC port XVTX/C for external bandfilters and antenna. in TX the output is about 0dBm over the XVTX/C port The I2C flexwire is connected to MCP23017 I2C i/o expand band switching The MCP23017  external slave address lines: A0=A1=1(Vcc) ,  A2=0 Then 474kHz /630m band    GPIO A0=low  A1=high = 3.2V and 136kHz /2200m band  A0=hi    A1 =low The GPIO are active high in on state so the circuit can be kept very simple. Only output A0 is used To switch the small relays of my dual bandfilter only an TUN o.c. is needed GPIO A0  active high 3.2V  4k7k at the base of o.c. TUN to select band pass filter 2200m


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