开云体育

Yesterday morning, idly running FT8 on my QMX when there was a CQ from New Caledonia, and ATNO for me.
The signal to noise was 0 to -5.? That's from half way round the world!? Tried calling but nothing so got the 7300 going and made the QSO, using about 90W. Cheating, I know but it was an ATNO.
The 7300 gave the S/N as -16 to -18.? Ran both at once in Rx and it was consistent, QMX -3 to -5, 7300 -17.? Similar antennas (EFHW and doublet side by side).

I'm not complaining but wondering why there should be such a difference, the 7300 is working nicely and this difference doesn't seem to be consistent,? I might try analysing the ALL.TXT files for the two systems to see if I can see what's happening.

Chris, G5CTH

On 02/09/2023 07:40, Chris wrote:

The 7300 gave the S/N as -16 to -18.? Ran both at once in Rx and it was consistent, QMX -3 to -5, 7300 -17.? Similar antennas (EFHW and doublet side by side).

Chris,

Maybe the QMX is simply better.
But I would carry out an extended test simultaneously on one antenna with a splitter.
I've done that many times using WSPR. Even then I find results are not conclusive. When I try on different antennas it can get even more confusing.

73 Alan G4ZFQ

My totally uninformed guess is that it might come down to being an advantage of the Tayloe mixer used in the QMX over the RF sampling ADC used in the 7300.