Posted by
Don Wilhelm-4 on
Dec 31, 2010; 1:53pm
URL: http://elecraft.85.s1.nabble.com/Re-Latest-Sherwood-table-tp5882563p5882658.html
Bob,
I can't think of an easy answer - mainly because many or the parameters
tested are in the realmm of engineering, and as such use engineering
terms to achieve some level of communications clarity.
In short, if you do not develop some understanding of the terms, there
is no easy way and must involve some study.
I would suggest two things - first is to try looking up each of the
parameters on Wikipedia, second, do some study of the Receivers section
in the ARRL Handbook to provide you with some understanding of how the
various parameters work together. If you want to gain a little better
understanding, look at the ARRL Testing procedures (for Receivers) - you
really don't have to read the entire test procedure, usually the Purpose
of each test will provide some insight. You can find the ARRL Test
procedures at
http://www.arrl.org/files/file/Technology/tis/info/pdf/Procedure%20Manual%202010%20with%20page%20breaks.pdfLastly, some parameters will be more important to one type of operation
than others. Exactly which ones relate to your operating tastes and
style will vary. A contester or avid DXer will want good performance in
the narrow spaced dynamic range because he must work in a section of the
band crowded with signals and does not want the stronger ones to
overload the receiver. If your operating style is more of the ragchew
variety, that same parameter may not be important to you since you will
likely QSY if QRM is nearby rather than trying to "stick it out" and
work within the QRM area of the band.
73,
Don W3FPR
On 12/31/2010 7:42 AM, Bob Naumann wrote:
> Is there a non-engineer's guide to the Sherwood table for those of us who
> are not engineers?
>
> In particular, the table is sorted by Narrow Spaced Dynamic Range, and I see
> that the FT5000 is listed first, but the K3 also gets a 101 in that column,
> albeit with a "pf" footnote instead of just an "f".
>
> I decode these footnotes to be "f" = "Measurement was Phase-Noise Limited"
> And "pf" = "Measurement was Phase-Noise Limited" and was "with 200 Hz 5-pole
> filter"
>
> OK - so why is the FT5000 at the top of the list? Why no indication of what
> filter was used in the FT5000?
>
> What is the second sort column for the table? What puts the FT5000 on top?
>
> What does this table really tell us? It seems that both of these receivers
> are pretty close as many of the numbers are similarly different from those
> listed below them.
>
> When a parameter is higher or lower - which is better? I presume that the
> higher the narrow-spaced dynamic range, the better, but what about 100kHz
> blocking (for example). Is higher or lower there better? The K3 is a 140 on
> that one, and the FT5000 is a "lowly" 127. The Down-conversion Kenwood 590
> gets a 144 in this column - is that better or worse than the K3? But, the
> 590 only gets an 88 in the narrow-spaced dynamic range, so I guess that
> means it's much worse?
>
> How does one interpret this data?
>
> 73,
>
> Bob W5OV
>
>
>
>
>
>
>
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of Bil Tippett
> Sent: Friday, December 31, 2010 6:18 AM
> To:
[hidden email]
> Subject: Re: [Elecraft] Latest Sherwood table
>
> > I wonder how such a high performance filter would work in the K3?
> Not that its
> needed in the K3. However in the interest of science, it might be a worthy
> pursuit. It also might push the K3 well ahead of the FT5000 in ultimate
> performance.
>
> Not very well since it's at 70 MHz. ;-) The Inrad filters are
> already better than whatever is in the FT5000 since Sherwood measured
> ultimate rejection in the K3 at 105 dB vs 90 dB for the 5000.
>
> 73, Bill W4ZV
>
>
>
>
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