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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

MCP23017 Ali Express 0.95€  including shipping....

DCF39  near Magdeburg  is direction East
The best signals i have on the west BeverageI
do not know why signals east of me at 137 kHz are stronger on the West Beverage.
Both West and East  have the same length about 300m checked them several times no faults found.

The picture below shows the WSPR 200Hz window as a grey bar
137.400 -- 137.600 kHz
the high peak 80dB  over noise is DCF39
Clearly there is some extra noise peak exactly within the WSPR window
i looks like one of the side bands IMD ? but that noise is only at night time
the window is clear during day when DCF39 is still about the same strength 70-80 dB / noise
I do not know the origin of this noise that reduces receiving s/n with 20dB
it sounds like fast FSK modulation


never the less i can receive here
 last 2 weeks LF reception 136kHz USB dial WSPR
15 spots:
TimestampCallMHzSNRDriftGridPwrReporterRGridkmaz# Spots
 2020-01-09 07:40  K3RWR  0.137527  -29  0  FM18qi  1  PA0O  JO33hg  6279  45  1 
 2020-01-04 07:50  K3MF  0.137406  -28  0  FM19sr  1  PA0O  JO33hg  6162  46  8 
 2020-01-04 07:08  N1BUG  0.137438  -26  0  FN55mf  1  PA0O  JO33hg  5297  52  128 
 2020-01-04 19:08  UA4AAV  0.137522  -22  0  LO21  1  PA0O  JO33hg  2578  290  75 
 2020-01-14 23:34  UA3DJG  0.137572  -18  0  KO95  0.2  PA0O  JO33hg  2089  277  14 
 2020-01-08 22:30  SV8CS  0.137510  -18  0  KM07js  0.1  PA0O  JO33hg  2038  332  1 
 2020-01-06 23:32  EA5DOM  0.137532  -16  0  IM98xn  1  PA0O  JO33hg  1713  15  16 
 2020-01-04 19:12  OE3EMC  0.137441  -27  1  JN78jo  0.001  PA0O  JO33hg  772  315  74 
 2020-01-04 22:20  G8HUH  0.137450  -18  0  IO81mg  0.1  PA0O  JO33hg  688  67  24 
 2020-01-04 19:40  2E0ILY  0.137550  -2  0  IO82qv  0.5  PA0O  JO33hg  619  82  101 
 2020-01-06 05:56  F4GUK  0.137456  -27  0  JN18gt  0.2  PA0O  JO33hg  572  28  2 
 2020-01-15 22:54  LA3EQ  0.137551  -27  0  JO28xj  1  PA0O  JO33hg  571  176  1 
 2020-01-04 18:14  DL7NN  0.137440  -6  0  JO60it  1  PA0O  JO33hg  498  306  356 
 2020-01-04 18:22  G6AVK  0.137582  -22  -1  JO01ho  0.05  PA0O  JO33hg  447  63  31 
 2020-01-07 00:06  DC0DX  0.137426  -12  0  JO31lk  0.1  PA0O  JO33hg  205  354  44


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