Re: The Sherwood report

Posted by P.B. Christensen on Dec 02, 2010; 4:52pm
URL: http://elecraft.85.s1.nabble.com/Fwd-New-Sherwood-report-tp5793377p5796698.html

On the Ten Tec Eagle list, Rob Sherwood just posted a very interesting
response to the 2 kHz DR rankings being discussed here.  Apparently, there's
a measurable amount of IMD difference not only between roofing filter
production samples, but the manner in which they're inserted.  For example,
on the Orion II, he gets variations of several dB on close-spaced DR just by
unplugging a filter and reversing it -- something not possible with the K3
since the pin-out isn't symmetrical.  He goes on to discuss why.

Sounds like we could probably take handful of INRAD filters and choose the
best ones that may likely be equal to the FTdx-5K under most, if not all
narrow filter positions in the K3.

On multiple occasions, Rob has stated that once you get up anywhere near
these numbers, a prospective purchaser should be looking at other
performance factors and features.  Probably if you're within the top ten or
so on his list, you would be pretty hard-pressed to notice any differences
when other factors (e.g., the other guy's bandwidth) will mask incremental
improvements to close-spaced DR.

For me, those "other factors" that Rob discusses include low distortion, low
noise AF sections, low TX IMD, and super fast, click-free T/R times.  Right
now, those are the most important factors to me now that basic receiver
performance has advanced so much in the past decade.

Paul, W9AC

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