[Elecraft] Any value in using a Microkeyer III with a K3S or K4?

[Jim Brown]

I strongly agree with Joe on this. The only thing I'll take exception is 
that I suspect his estimates of noise levels are wildly optimistic, 
which further supports his observations about sound card dynamic range. 
 From where I sit with neighbors running WSJT-X modes on the same band, 
I look at dynamic range differently.

Consider a local who's 50 dB over S9 on a well calibrated S-meter (yes, 
that's optimistic too). If you accept 5 dB/S-unit (I don't), your lower 
limit is an S2 signal, or S1 at 6dB/S-unit. Few hams have noise levels 
below S5. Depending on band and the direction my antennas are listening, 
my noise level in the Santa Cruz Mountains with nearest neighbors ~400 
ft from my antennas is S1-S2 with my 6M optimally aimed (to the North 
Pole) to reduce noise and S4-5 pointed at either two solar systems in 
those closer houses. While still in a Chicago residentail neighborhood, 
it was a very good day if I got below S6 on HF on very inferior 
antennas. You've got to be in the middle of NOWHERE with a 50dB over S9 
neighbor to need more than a 16-bit sound card.

What you DO want is a much better than average sound card, which is why 
I've looked to the better units designed for the semi-pro audio market. 
One of the qualities of A/D and D/A stages important both to audio pros 
and to hams is their amplitude linearity around their noise floor (and 
very quiet audio stage feeding the A/D converter.

There's also the issue of how the units address differing sample 
rates.WSJT-X works at 16-bits, 48 kHz. If the hardware runs at 96 or 192 
kHz, how good are they at the conversion. And so on.

73, Jim K9YC

On 1/4/2021 5:36 PM, Joe Subich, W4TV wrote:
> 
>> Are you aware of any move afoot to support higher bit levels in 
>  > upcoming versions of popular software?
> 
> I have no insight into the roadmap for most amateur digital software.
> However, I doubt that many developers will expend the effort to do
> 24 bit processing.  The 97 dB (theoretical) - 88 to 90 dB practical
> dynamic range of a well designed sound card is quite adequate for most
> HF purposes.
> 
> The "background noise" in suburban/semi rural areas is on the order of
> -135 dBm (~0.05 uV).  That means a 90 dB dynamic range can handle from
> the background noise to about S9+30 dB.  Using an attenuator or reducing
> the RF gain in the presence of signals above S9+20 dB can extend the
> useful dynamic range by another 20 dB or more.
> 
> The only use case for greater dynamic range would be for SDR purposes
> where a very wide spectrum was being processed simultaneously or for
> extremely "quiet" frequencies (e.g. VHF/UHF with antennas pointed to
> a quiet part of the sky - EME or radio astronomy).  In the VHF/UHF
> case, dynamic range (noise floor) can be improved much more economically
> through the use of low noise preamplifiers (and receiving converters).
> 
> 73,
> 
>     ... Joe, W4TV
> 
> 
> On 2021-01-04 7:34 PM, Courtney Krehbiel wrote:
>> Thank you for your input Joe!  I didn't really think of the software 
>> as impacting the functional resolution of the sound card.  But upon 
>> looking at the block diagram for my Navigator, I can see that's the 
>> case.  Are you aware of any move afoot to support higher bit levels in 
>> upcoming versions of popular software?
>>
>> Thanks again, and 73!
>>
>>    -- Courtney  KD6X
>>
>> -----Original Message-----
>> From: Joe Subich, W4TV <lists at subich.com>
>> Sent: Sunday, January 3, 2021 7:12 PM
>> To: Courtney Krehbiel <courtney at krehbielart.com>
>> Subject: Re: [Elecraft] Any value in using a Microkeyer III with a K3S 
>> or K4?
>>
>>
>> Unless the interface is poorly designed (like some "low price"
>> amateur only devices), the noise floor is generally set by the IF 
>> noise in the transceiver on the higher bands and by the "no signal" 
>> atmospheric noise on the low bands.
>>
>> A 24 bit sound card has the potential to provide greater dynamic range 
>> than the more common 16 bit cards but *only* if the software is 
>> written to take advantage of the "extra bits".  Swapping a 24 bit 
>> sound card for a 16 bit sound card will make no difference on existing 
>> software like MMTTY, FLDIGI/DM780, etc.
>>
>> 73,
>>
>>      ... Joe, W4TV
>>
>>
>> On 2021-01-03 6:50 PM, Courtney Krehbiel wrote:
>>> I have a K3... the best radio I've ever owed in my 50+ year ham 
>>> life.  I'm currently using a US Interface Navigator with it for 
>>> digital modes.  This is now sold as the Time Wave Navigator and has 
>>> worked really well for me for many years.
>>>
>>> My understanding is that the K3S and now the incoming K4's have sound 
>>> cards built-in via the USB port.  So perhaps I won't need the 
>>> Navigator anymore when my K4 eventually arrives.  But my question is 
>>> whether there is still something to be gained using a newer 
>>> transceiver interface with the K3S or K4?  I've been looking at the 
>>> Microkeyer III with its 24 bit audio processing.  Does anyone have 
>>> any hands-on experience with the Microkeyer III with Elecraft 
>>> radios?  I'm particularly interested if it has a lower noise floor or 
>>> other features that might not be found in the stock K3S or K4.
>>>
>>> Thanks for any input or feedback!
>>>
>>>     -- Courtney  KD6X
>>
>>
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