Re: Transmit Phase Noise

Rob Sherwood
 

Hi Dale,

I don’t know, but I doubt the type of transistor is significant. The really close-in noise is affected by the cooling fans, an issue that N0QO and I found a year ago.  Elecraft supposedly fixed that with an electrolytic capacitor addition to filter the electrical noise from the fans.  I had to do the same thing with my aftermarket fan cooling kit for the IC-781.  

Rob. NC0B


On Jan 13, 2019, at 4:23 AM, dalej via Groups.Io <dalej2@...> wrote:

Rob,

How about the K3 with the old bipolar transistors?  Is there much difference or none at all?

Dale, K9VUJ



On 12, Jan 2019, at 12:06, Rob Sherwood <rob@...> wrote:

Here is some data I have at both 100 watts and 30 or 35 watts for six rigs.
Different lab, different measuring equipment, different rig samples, so don’t expect absolute correlation with ARRL data.
ARRL lab data only measures phase noise, not composite noise (phase and AM noise).
Data from Contest University presentations of mine.
Note: While the listing are sorted by column 1, the ranking varies with frequency offset.
Rob
NC0B
 
Transmit Composite Noise Rig Comparisons 20 meters
Best at maximum power output, but degrades at lower power levels
 
Rig @ 100 watts                10 kHz offset, dBc/Hz     20 kHz offset, dBc/Hz     100 kHz offset, dBc/Hz
K3S                                         -141                                       n/a                                         -143
IC-7300                                 -130                                       n/a                                         -132
IC-7851                                 -129                                       n/a                                         -138
IC-7610                                 -127                                       -129                                       n/a
TS-890S                                -120                                       -129                                       n/a
FTdx-3000                           -120                                       n/a                                         -121
 
Rig @ 30 watts                   10 kHz offset, dBc/Hz     20 kHz offset, dBc/Hz     100 kHz offset, dBc/Hz
K3S                                         -132                                       n/a                                         -140
IC-7851                                 -123                                       n/a                                         -133
IC-7610                                 -122*                                     -124*                                     n/a
FTdx-3000                           -117                                       n/a                                         -117
TS-890S                                -113*                                     -122*                                     n/a
IC-7300                                 -112                                       n/a                                         -120
 
* = Power level was 35 watts
n/a = data not available
Rev D
 



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