> That's a far ways from -89 dB that you
> quote.
The ARRL review in the April 2008 issue of the K3/10 showed reciprocal
mixing as -95 dBc at 2 kHz spacing.
The ARRL review in the Jan 2009 issue of the K3/100 showed reciprocal
mixing as -86 dBc at 2 kHz spacing.
This is the same lab. Dunno about same test equipment.
73 de dave
ab9ca/4
On 2/13/15 10:29 PM, Joe Subich, W4TV wrote:
On 2015-02-13 10:08 PM, Chortek Bob via Elecraft wrote:
The new synthesizer has essential the SAME IMDDR 106 or 103
depending on the filter bandwidth.
Incorrect! You are comparing measurements by different labs with
different test equipment and procedures.
Sherwood measured 104 dB w/200 Hz filter and 96 dB w/400 Hz filter
for the old Synth vs. 106 and 103 for new synth. That's 2 to 7 dB
improvement depending on filter bandwidth. Since the synthesizer
is about 6dBc/Hz better than the old synthesizer, the first order
estimation is that the improvement in narrow spaced IMDDR3 is due
to the decrease in phase noise.
So, my question: is the real import of all this that the new
synthesizer will give the K3 an IMDDR which is NOT limited to 86
dbs by Reciprocal Mixing so we will now get the FULL benefit of a
IMDDR of 106/103?If so, that 20 db improvement is huge.
One would need to look into the way in which ARRL measures Reciprocal
Mixing to understand exactly what that "Spec" is telling you and what
improvement one might find. It is safe to expect the reduction in
phase noise to directly impact both narrow spaced IMDDR3 and Reciprocal
Mixing.
BTW, I just reviewed the original ARRL review of the K3 (April 2008)
and their Reciprocal Mixing numbers were -116 dBc @20 KHz, -106 dBc
@ 5 KHz and -95dBc at 2 KHz. That's a far ways from -89 dB that you
quote. Assuming a 6 dBc/Hz noise improvement in the new synthesizer,
you can make the numbers -122, -112, -101 which would be a significant
improvement.
73,
... Joe, W4TV
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