[Elecraft] Noise Power Ratio and the K3 with new synthesizer?

[Johnny Siu]

Thanks Joe for the highlights.  Should I pass this to Adam and give him a chance to explain?
73
Johnny VR2XMC
      寄件人︰ "Joe Subich, W4TV" <lists at subich.com>
 收件人︰ elecraft at mailman.qth.net 
 傳送日期︰ 2015年03月13日 (週五) 10:09 AM
 主題︰ Re: [Elecraft] Noise Power Ratio and the K3 with new synthesizer?
   

> Anyway, just let us read both Rob Sherwood and Adam's test data and
> use them as a cross reference to each other.

The issue is that Adam's data is flawed in at least two ways.  The
notch is wider than the SSB filter which means the noise is not being
applied to the product detector or DSP ADC.  Second by reducing the
noise level for DDC receivers, they are not being fairly tested for
the same level of total noise power.  There are also questions about
the effects of roofing filters of different bandwidth - to what degree
do they change the total noise power applied to the entire receiver
chain (including the product detector or DSP ADC)?  Secondly, what are
the effects of AGC ahead of the product detector/DSP ADC and does the
noise power testing really measure dynamic range or is MDS compromised
by the AGC?

With a 3.3 KHz notch, the only way Adam can fairly test receivers is
with a 6 or 15 KHz roofing filter.  If he truly expects to test SSB
performance, the notch width needs to be less than half the width of
the SSB filter.  Secondly, receiver MDS needs to be measured with the
noise present to rule out AGC desensitization.

BTW, Adam's MDS measurements for the two K3s he tested are off by
6 to 9 dB compared to both Sherwood and ARRL Labs while his MDS
values for Icom are within 2 dB of ARRL Labs.  There is something very
unequal about the testing of the K3.

73,

    ... Joe, W4TV


On 2015-03-12 9:26 PM, Johnny Siu wrote:
> Hello Scott,
> I am afraid I do not agree to your comments.  I am a owner of both Icom and entire K-line, I understand what Adam AB4OJ is doing.  Adam knows the design and structure of K3 no worse than any radio expert here (or at least far better than me).
> Anyway, just let us read both Rob Sherwood and Adam's test data and use them as a cross reference to each other.  I don't mind reading articles from different angles.
> While there are many CW guru here, voice mode is still the most popular mode across the HF users.  Some tests under voice mode conditions do give another view.
> I think we just keep our fingers crossed and see what are the results for IC7851 and K3 new synthesizer model perform in both Adam and Sherwood test.
> By the way, both Rob and Adam know each other and do have the chance to communicate.
> 73
> Johnny VR2XMC
>
>        寄件人︰ Scott Manthe <scott.manthe at gmail.com>
>  收件人︰ elecraft at mailman.qth.net
>  傳送日期︰ 2015年03月13日 (週五) 2:08 AM
>  主題︰ Re: [Elecraft] Noise Power Ratio and the K3 with new synthesizer?
>
> I suspect that the "Noise Power Ratio" test was used because that is the
> only test that Adam could use to get his beloved Icom gear near the top
> of the list. Mr. Farson has had a website devoted to Icom gear for many
> years, so I'm not sure if this test could be considered even remotely
> objective.
>
> Here is a NPR tutorial from another source, for those interested and
> technically proficient enough to investigate further.
>
> 73,
> Scott, N9AA
>
>
>
> On 3/12/15 10:53 AM, Chip Stratton wrote:
>> Adam Farson VA7OJ has an article in the current March/April 2015 QEX
>> discussing the use of Noise Power Ratio (NPR) to help define a
>> receiver's performance in a crowded band in a way that might be more
>> illuminating than the simpler two tone tests. Its an interesting
>> discussion which makes some sense, but then I'm not anywhere close to
>> an expert in that field.
>>
>> In any event, he has figures from a number of transceivers, including
>> a couple of K3s which no doubt do not have the new synthesizer. The
>> K3s still performed very well relative the the rest of the field in
>> these tests, though they were slightly behind the IC-7700, IC-7800,
>> and TS-590S.
>>
>> Which of course makes me wonder how the K3 with new synthesizer would
>> perform in this arena?
>>
>> >From a guy with a mild metrology addiction...
>> Chip
>> AE5KA
>>
>
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