[Elecraft] K4: superhet vs. direct sampling

[WILLIE BABER]

In my experience the value of high-level blocking and low phase noise is in the ability to hear very weak signals next to  strong ones.  When I first got into So2r years ago, I discovered an entire layer of very weak signals when I switched to usingTenTec Omni V and Omni VI; this was related directly to lower phase noise in so2r where the other radio was not a TenTec.  Also, high level blocking allows you to hear those weak ones in S & P that you would otherwise roll right over especially when the band is full of strong signals. If you are not into cw contesting, and in so2r in particular, then what I just said doesn't matter and lots of radios become good radios. I have used nothing in so2r better than 2 x k3, with Omni VI, Orion and Tentec Eagle almost as good.  After those, there is Kenwood ts590s.

The thing is, you cannot notice the signals that you are not hearing if you have two radios that perform equally poor, and especially with respect to phase noise.

73, will, wj9b

CWops #1085
CWA Advisor levels II and III
http://cwops.org/

--------------------------------------------
On Tue, 6/4/19, Wayne Burdick <n6kr at elecraft.com> wrote:

 Subject: [Elecraft] K4: superhet vs. direct sampling
 To: "Elecraft Reflector" <elecraft at mailman.qth.net>
 Date: Tuesday, June 4, 2019, 8:18 PM
 
 The superhet module buys a lot of
 BDR improvement. But also -- a subtlety I've failed to
 mention so far -- the superhet module is intended to
 somewhat improve 2 kHz IMDDR3 *and* make this figure more
 repeatable. 
 
 Q: Say
 what?
 
 A: As Rob Sherwood
 noted many times before finally immortalizing this point in
 his must-read footnotes, A-to-D converters sharing the same
 part number are not all created equal. The long-time
 previous occupant of his Top Spot benefitted from a
 never-corroborated monotonicity in its ADC's LSBs. An
 act of god. The product of a very good day at the silicon
 foundry when, serendipitously, all the bunny suits were
 defect-free, and no one was exhaling molecules of grain
 alcohol or other substances from the night before.
 
 That said, most ops can get by
 without the extra BDR and IMDDR3, because they're not
 situated in the RF equivalent of the Gulf Stream. Hence the
 different K4 models. 
 
 73,
 Wayne
 N6KR
 
 
 >
 On Jun 4, 2019, at 5:10 PM, Lyle Johnson <kk7p4dsp at gmail.com>
 wrote:
 > 
 > Mark,
 > 
 > The "20 dB
 lower than a K3" figure is an estimate for 100 kHz
 Blocking Dynamic Range rather than the 2 kHz Narrow Spaced
 Dynamic Range.
 > 
 >
 The K3 is listed at 140 to 150 dB (depending on model,
 synthesizer, etc) on Sherwood's Receiver Test Data
 page.  The K4 series without the "HD" option are
 estimated to be in the 120 to 130 dB range, typical of other
 direct sampling SDR products (Flex, Apache, Icom, ...).
 > 
 > 73,
 > 
 > Lyle KK7P
 > 
 > On 6/4/19 4:00 PM,
 mark roz via Elecraft wrote:
 >> Before
 putting my money up front for the first run of K4D I need to
 know what is the dynamic range
 >> of
 the K4D RX at 2kHz spacing. K3 is 105 dB and K4D? If it is
 20dB lower than K3 than it would be 85dB-correct?
 
 
 
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