Hi Joe and All,
.
Observing broken symbols in demod64a.f90, using this diagnostics in line 54 to
catch it in r6643:
if(p1.lt.0.0001) print *,j,p1
.
Sometimes, likely after the signal subtraction, first two information message
symbols
getting 0.0(0) values through the whole signal spectrum(all 64 frequencies). In
this case next 3 information symbols
are also broken with very high p1 value due to the low psum value. Probably
some first SYNC symbols
are also affected with this issue.
.
Fortunately, due to the Fortran accuracy, psum value for 0.0 spectrum is equal
10E-6 and there is no
overflow occuring for p1/p2 calculations.
.
I tried to trace this issue down to the roots and saw in decode65a that cx()
array samples from
twkfreq65 coming with 0.0(0) values, have not got enough experience to trace it
down further.
.
Probably some false decodes are caused by this defect, and both decoders BM and
FTRSD should have
sensitivity degradation for some weak signals.
.
Audio file is there: https://cloud.mail.ru/public/FDWa/PUMc3B8yD
.
There is the diagnostics output:
.
1540 -1 0.8 279 # UA3QUP G7OAE R-15
1540 -12 0.5 492 # KK7X DJ0QO JN39
1540 -1 2.3 809 # CQ DH6FAJ JO41
1540 -2 0.6 1019 # N1FF IU2EWY -19
1540 -3 -0.8 1223 # W4IMD DL8DBN JO41
1 0.0000000000000000
2 0.0000000000000000
1540 -19 2.1 1417 # SV1CIF F4FSY -06
1540 -4 0.3 1665 # 4S6NCH 4Z5ML KM72
1540 -1 0.4 1823 # UR6ISV OM2BK -10
1540 -4 0.4 2074 # YV4DHS DF9QV JO32
1540 -1 0.4 2308 # CQ 5P1KZX JO57
1540 -19 0.4 507 # CQ EW6BN DX
1 0.0000000000000000
2 0.0000000000000000
1540 -1 0.4 1040 # CQ IK3FUS JN55
1540 -5 1.2 1221 # W4IMD DM8PV JO60
1 0.0000000000000000
2 0.0000000000000000
1540 -4 0.1 1640 # CQ RW0BT NP39
1540 -15 0.5 1665 # 4S6NCH DL6GD JN37
1540 -6 0.7 1901 # CQ GM4ZET IO86
1 0.0000000000000000
2 0.0000000000000000
1540 -12 1.2 2095 # YV4DHS IW2CXB JN45
.
.
73
Igor UA3DJY
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