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 <li...@subich.com>
Sent: Sunday, January 3, 2021 7:12 PM
To: Courtney Krehbiel <court...@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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