Topband: RE: Minimum discernible signal ?

[Marijan Miletic]

Mike, KC1SX wrote:

>But back to Tom's point.  I went through a number of swept test data and
>was surprised to find that my generalization was not true in all cases.
>Here is the 5-kHz data for the rigs I checked:

(In alphabetical order...)

Rig                     BDR          IMD DR
Elecraft K2             126          88
ICOM IC-706 MkII G      86           74
ICOM IC-756             98           67
ICOM IC-756 Pro         104          80
ICOM IC-775DSP          104          77
Kenwood TS-570D         87           72
Ten-Tec Omni 6+         119          86
Yaesu FT-1000MP         111          83
Yaesu FT-1000MP Mark V  106          78

>In the vast majority of cases, the numbers are less than at the 20 kHz
>spacing, but the amount of variation between similarly priced radios was
>unexpected.

>Note that some of the above rigs would experience a _blocking_ response
>from an S9+30 signal that was more than 5 kHz away.

K2 and Omni 6+ are not affected by 5 KHz separation as this signal is still
outside of the first SSB crystal filter.  Variations in the other cases are
dependent on the position of 5 kHz signal in regard to the roofing filter
skirts as seen on ARRL extended reports.  Quality of the second mixer is
otherwise the main culprit.

It would be nice to see log scale for ARRL sweep tests.

73 de Mario, S56A, N1YU




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