[hpsdr] K3 vs HPSDR

[N4IS]

Hi Roger

Thank you for sharing this information bout large FFT size. I'm very active
on 160m, weak signals on top band has another aspect to see weak signals on
the waterfall, 160m has QRN, lots of them.

WinRad waterfall is almost insensitive to QRN and I can see weak signals way
before I can hear them, I also try with HDSDR and it almost the same.
SDRMAXV is a better receiver then WinRad or HDSDR but I can't see the weak
signals, I changed everything I could and It is hard to see a weak signal.

I just got Hermes and soon I will be using PowerSDR, My project also
includes transverter up to 10 GHz.

My question is what is different on WinRad to be almost immune to QRN, When
the QRN peaks there is no much change on the water fall, with other programs
there are several bars very intense that makes impossible to spot a weak
signal.

Back on the RX comparison, I have one K3 to compare with the IC7800 for six
month, the IC7800 is much quiet and I can hear better weak signals. However
I have a QS1R , same basic hardware of Mercury and now I have Hermes to use
as well, The DDC SDR does not have phase noise and can hear any very weak
signal close to s9+40 db signal, 
 
The DDC is better the my IC7800 and K3 without any thoughts. Several times I
was able to copy weak signal on DDC that was not detectable on the IC7800,
like 4U1WRC simples on 1819, all Europe and US calling at the same
frequency, also 4W6A, 7O6T , 9M0L,  was clear on the DDC several minutes
before I could copy on the IC7800, no strong signals nearby this time.

All radios with Local oscillator and mixers have phase noise and they are
limited by phase noise, the beautiful number published about receivers has a
small note , limited by phase noise,  this can be translated as only
possible on lab not useful for real operation with the antennas connected to
the receiver. There is no comparison at all between a DDC and a analog radio
with mixer and LO.

Regards
Jose Carlos
N4IS





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