[Elecraft] Wait For The K4 Direct RF Sampled SDR?

[k3ndm at comcast.net]

I suspected that was the case. I'm a little out of being current, but S/N on some of the devices I remember were not that great as compared to the better sound cards. 16 bits, ideally should allow 96 db dynamic range. However, you are correct, you don't get the full 16 bits. The oversampling and processing does buy you improvement, but you still need to contend with the 16 bits of quantization and the need to put some amplification ahead of the A/D to improve SNR. That gain should negatively impact on dynamic range. I, too, am waiting to see what Sherwood has to say. It should be interesting. 

I do know this. Operating FD last year with a K3 and a KX3 using QRP power and from the same RV. The only problem we had was my KX3 LO being picked up by the K3. I forgot to turn on the isolation amplifier. Other than that, there was no problem. In the chaos of Field Day, the filtering appeared to be superb. 

73, 
Barry 
K3NDM 


----- Original Message -----
From: wb4jfi at knology.net 
To: "Barry LaZar" <k3ndm at comcast.net>, elecraft at mailman.qth.net 
Sent: Thursday, March 14, 2013 5:03:30 PM 
Subject: Re: [Elecraft] Wait For The K4 Direct RF Sampled SDR? 

I love my K3/P3/SVGA and my KX3 as well. I do want to mention that the new 
Flex 6000 series uses a 16-bit A/D, with over 245Ms/s sample clock, much 
better than 100Ms/s. Processing gain is real, and should help the 16-bit 
range somewhat, but 16-bits is not really 16-bits in the real world. Throw 
away at least 1/2 bit, and maybe more. 

It will be very interesting to see what a Flex 6000 series finally does in 
various receive parameters, especially dynamic range. They claim to handle 
a very large dynamic range, even without the various RF filters. 

I can't wait to see the Sherwood report on the 6000 series. 
73, Terry, WB4JFI 


-----Original Message----- 
From: Barry LaZar 
Sent: Wednesday, March 13, 2013 10:13 AM 
To: elecraft at mailman.qth.net 
Subject: Re: [Elecraft] Wait For The K4 Direct RF Sampled SDR? 

I'm sort of curious about what Flex is doing with their new radio. The 
heart of it has to be a very good A/D converter, but the best thing I'm 
aware of is an Analog Devices 16 bit, 100 Msp/s one that ain't exactly 
cheap. To approach the dynamic range in the KX3 and the K3, 16 bits may 
be a might short. 

I, too, believe that direct sampling and high dynamic range is still a 
bit off particularly if you want to be able to afford one. I like the 
magic of my KX3 when used with NaP3 and a 24 bit, ASIO compliant sound 
card. As a practical matter, it serves for the 95% situations. those 
last five will include a lightning storm over my house or someone like 
W3LPL moving next door. 

73, 
Barry 
K3NDM 


On 3/13/2013 9:49 AM, Wayne Burdick wrote: 
> No need to speculate. There is no such project underway at Elecraft. 
> 
> Direct RF-sampling receivers, for all their technology, still lag well 
> behind the K3 in blocking dynamic range, and probably will continue to for 
> years to come. We're quite happy with our superhet architecture. Also, any 
> advancement we make to the K3 will be retrofittable to existing K3s, so 
> your investment is safe. 
> 
> 73, 
> Wayne 
> N6KR 
> 
> 
> On Mar 12, 2013, at 8:04 PM, Bob Schumacher wrote: 
> 
>> Given the advances in direct RF sampled SDRs (currently available QS1R, 
>> soon to be released Flex-6000, etc.), Elecraft must be quietly working on 
>> on an RF sampled K4 SDR. Maybe we will see an anouncement in May at 
>> Dayton? I am wondering if I should take the leap with the Flex or wait 
>> for Elecraft? I suspect that Elecraft will provide a higher value 
>> solution. Any speculation on this point by Elecraft fans? 
>> 
>> Thanks, 
>> 
>> W9DBR 
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