[Elecraft] Sherwood Engineering Tests

[Wayne Burdick]

Jim (et al),

The K3's audio has improved due to three factors in the past couple of years:

- a low-noise, low-pass audio filter stage was added to the DSP board, eliminating high-pitched CODEC artifacts

- DSP firmware changes were made to correct AGC linearity and eliminate a CODEC quantization problem

- main MCU firmware was modified to allow the user to select the lower AF cutoff in CW mode (100/200/300 Hz) by adjusting the lower edge of the crystal filters

With the above changes in place, we carefully measured the K3's audio spectra and compared it to other radios with the same type of class-AB final AF amplifier IC (most transceivers fall into this category). They are all virtually identical. 

Rob, too, told us that the audio spectra he measured on a recent K3 (with new synths and the latest DSP and MCU firmware) was significantly improved from the K3 he measured several years ago.

While it is possible to reduce audio IMD products even further, this typically requires a class-A final audio output stage, which would add perhaps 0.5 to 1.0 amps of additional receive-mode current drain (and an associated heatsink). That is inconsistent with the K3's intended usage, which includes excellent power efficiency for portable applications (Field Day/DXpedition/travel). Also, most users would not notice such a subtle change.

73,
Wayne
N6KR


On Feb 24, 2015, at 8:19 AM, jim <jbollit at outlook.com> wrote:

> Wes, 
> 
> I agree, and if you look at a post I made a couple days ago, it states that.
> Sherwood also states his list is sorted on one column and people shud take
> all factors into account when choosing a radio.
> 
> I would NOT recommend a K3 for it's audio.  
> 
> Each person has their needs and should review them carefully.  I would also
> not recommend a Drake R4-C, even though it is in the top quartile.
> 
> I will send you a copy of an earlier post that I made.
> 
> 
> Jim
> W6AIM
> 
> 
> 
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Wes
> (N7WS)
> Sent: Tuesday, February 24, 2015 6:12 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] Sherwood Engineering Tests
> 
> I'm sure there's a point here and I just fail to see what it is.
> 
> Rob has stated many times (look for his videos) that one number does not a
> radio make.  In fact, as best that I know, he doesn't own a K3.
> 
> Wes  N7WS
> 
> On 2/23/2015 11:01 PM, jim wrote:
>> Guys,
>> 
>> Further, pesky, facts on said Real Radio at 
>> http://www.sherweng.com/table.html .
>> 
>> Number two on the list.  That is out of 116 receivers listed on the 
>> Sherwood page.
>> 
>> That puts said Real Radio in the top 3% of the radios Bob Sherwood has 
>> tested for a critical receiver performance parameter.
>> 
>> BTW, you will have to use the "Page Down" button, more than twice, to 
>> even get a hint of the Kenwood 590.  It is number 20 on the list, 
>> putting it in the top 17%
>> 
>> Also, important to note, is the Drake R4-C with the Sherwood roofing 
>> mod, listed at number 28.  The R4-C is *ONLY*
>> 45 (forty five) year old technology and that puts it in the top 23%.  
>> Yep, FORTY FIVE year old technology.  Yep, top 23 %.
>> 
>> Just some further, pesky, facts.........................
>> 
>> Rake
>> 
>> P.S.  BTW, I learned 45 years ago.  This flies in the face of 
>> someone's comment that I never learn.
>> 
>> Ho Hum, another pesky fact.............
>> 
>> 
>> 
>> 
>> 
>> 
> 
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