[Elecraft] FW: Sherwood Engineering Tests

[k3ndm at comcast.net]

I'm old enough to remember that the most important characteristic of a receiver was sensitivity. Nothing else seemed to matter. Some receivers of the time had 2 RF amplifiers to make sure that they won the sensitivity battle. And, what would happened when a strong signal, not necessarily S9, would appear, bad things happened to your radio. At this point I won't define the date. 

This lunacy was being looked at by a number engineers, to include Dr. Ulrich Rhode, W2 something. I forget his call. He said in a series of papers in professional journals and Ham Radio Magazine that sensitivity was not the most important parameter at the time. It would turn out to be LO noise sidebands and dynamic range. That still holds today, and now, IMHO, ultimate rejection should be added. All of this is shown in Sherwood's data. What this all means is that all of the receiver parameters must be looked at to decide what makes a great radio. I suggest a review of some of Rhode's papers. His writings make extremely interesting reading as it addresses this discussion directly. 

73, 
Barry 
K3NDM 


----- Original Message -----

From: "Wayne Burdick" <n6kr at elecraft.com> 
To: "Chester Alderman" <aldermant at windstream.net> 
Cc: "Elecraft Reflector" <Elecraft at mailman.qth.net> 
Sent: Tuesday, February 24, 2015 4:57:23 PM 
Subject: Re: [Elecraft] FW: Sherwood Engineering Tests 

Just to complete the point about this: The K3 tested probably didn't have its S-meter calibration ("RX gain cal") completed before we sent it to Rob, an oversight on our part. This procedure is fully automated by the K3 Utility program, and definitely would have corrected the sensitivity threshold issue Rob observed. 

73, 
Wayne 
N6KR 


On Feb 24, 2015, at 1:54 PM, Wayne Burdick <n6kr at elecraft.com> wrote: 

> Some on this list are still mistaking this column of Sherwood's chart as *receiver sensitivity*. I believe it is a measurement of AGC threshold. The K3's receiver sensitivity (MDS) is excellent by any measure; see the "noise floor" column. (Side-note: It's interesting that the preamp-off sensitivity of the tested K3 was -136 dBm, while that of the Flex 6700 was -118 dBm -- an 18-dB difference. One would have to leave the preamp ON much more often with the '6700. As Sherwood noted, this maximizes the '6700's dynamic range, but you'd also be hitting the A/D that much harder.) 
> 
> 73, 
> Wayne 
> N6KR 
> 
> 
> 
> On Feb 24, 2015, at 12:24 PM, "Chester Alderman" <aldermant at windstream.net> wrote: 
> 
>> 
>> 
>> _____________________________________________ 
>> From: Chester Alderman [mailto:aldermant at windstream.net] 
>> Sent: Tuesday, February 24, 2015 1:59 PM 
>> To: 'Yngvi (TF3Y)' 
>> Cc: 'Elecraft Reflector' 
>> Subject: RE: [Elecraft] Sherwood Engineering Tests 
>> 
>> 
>> Hi Yvgvi, 
>> 
>> I wonder, given atmospheric noise levels, if that is really going to be 
>> noticed by the operator. I seriously doubt It would be noticed in a contest? 
>> 
>> 73, 
>> Tom - W4BQF 
>> 
>> 
>> -----Original Message----- 
>> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Yngvi 
>> (TF3Y) 
>> Sent: Tuesday, February 24, 2015 1:26 PM 
>> To: elecraft at mailman.qth.net <mailto:elecraft at mailman.qth.net> 
>> Subject: Re: [Elecraft] Sherwood Engineering Tests 
>> 
>> These are interesting stats. 
>> 
>> One thing I noticed was the apparent loss in sensitivity as measured by 
>> Sherwood. This is probably not a big issue for most these days with the ever 
>> increasing noise levels but for the few in silent locations, incl. 
>> some DXpeditions this might be an issue. 
>> 
>> Any comments on this? 
>> 
>> 73, Yngvi TF3Y 
>> http://www.tf3y.net 
>> 
>> 
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