[CQ-Contest] TX phase noise - comparing Apples to Apples?

[William Hein]

I am collecting info on tx phase noise on current rigs and am not sure I am interpreting the data correctly.  I am also collecting techniques to mitigate same.  

The Swiss company that makes the ADAT-200A advertises ", the transmit signal is processed by adaptive predistortion, a technique that is used for the first time in amateur radio. This technology stands out due to high efficiency and a remarkably clean transmit spectrum, combined with an exceptionally clear modulation."   But does anyone actually have a ADAT-200A?

Will GPS clock syncing the LO reduce tx phase noise?

Will operating a tx in Class A reduce tx phase noise?  I believe the FTdx5000MP will operate in Class A, not sure about other rigs.  (Not sure Class A applies to CW mode operation.)

Seems like a good idea to leave ALC switched off, true?

The Flex 6000 series, according to a recent newsletter:
"the preliminary specifications provided in the FLEX-6000 Signature Series brochure projected an industry leading phase noise of -147 dBc/Hz at a 10 kHz offset and -152 dBc/Hz at a 100 kHz offset. After detailed phase noise measurements in the lab, lets just say we have a great big smile on our face!"

By way of comparison, here is some info on the K3 vs. other rigs reported by Elecraft's WA6HHQ which I found via Google:

"Here are transmit composite phase noise numbers from the Lab for the K3.
Needless to say, we are pleased with the results. :-) I've also included
some numbers from the ARRL reviews for several late model rigs.

Rig     1kHz    2   10   20   50   100   1M
K3      -110  -119 -136 -140 -143 -144  -150
IC7800  -103  -112 -130 -138 -140 -140  -140
FT2000  -102  -105 -128 -129 -128 -128  -128
ORION 2 -121  -129 -126 -125 -118 -128  -138
OMNI 7  -102  -103 -120 -123 -127 -129  -126"

How to compare apples to apples here?  How does -147 dBc/Hz at 10 kHz offset measure up with the -136 dB @ 10 kHz figure reported for K3 above?  Even thought "dB" appears in both measurements not sure they are using the same reference point or are indeed the same metric at all.

73
Bill

William Hein, AA7XT
ex-AA4XT, NT1Y, AA6TT, KC6EDP

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1st licensed 1969 - WN6NDC

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