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K4 Observations

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Buck

K4 Observations

The following is offered based on my observations and discussions at the
Elecraft booth. I am *not* an official, or even unofficial, Elecraft
spokesman and stand willing to be corrected.

First, this is going to be another game-changer from Elecraft. The
radio will have outstanding performance figures and an interface to die
for. The screen is beautiful and functions can be controlled from
either buttons or the touch-screen. There is band-stacking on the touch
screen, a nit people have complained about on the K3.

The radio is full SDR as opposed to the analog front end of the K3.
However an option, the K4HD, is a superhet receive function. Like
previous Elecraft radios, this can be added later if you think you need
it. Preliminary is that it will not be necessary unless you operate in
the presence of strong stations (multi-multi).

Another option has a second set of band pass filters and ADC module that
will allow the two receivers to operate on different bands or antennas
(K4D).

The radio contains a Linux computer so all this magic does not require
an external computer except for logging or audio input. The rig will be
addressable locally or over the internet with no additional software. I
saw it operated from an iPad and Android is coming. The iPad screen
looked exactly like the front panel, including the panadapter.

There are multiple USB ports, an Ethernet port, RS232 and an HDMI port
so you can project the front panel, or parts of it, to an external
monitor. The panadapter looks awesome on the external monitor and you
will be able to point and click to QSY the radio.

The prices are targets but I got the impression the final will be very
close. The cost is less than a fully loaded K3s. The kit version will
be cheaper than factory-assembled and ship several months later to allow
time to write the assembly manual. Target for the factory version is
November.

I suspect the K4 will replace the K3 series as K3s sales are sure to
suffer because of product age and competition from the K4. I did not
hear any talk about sun-setting the K3s when the K4 comes out. I am
sure there are many people who will want to buy the basic K3s and
upgrade over time (or not) rather than plunk down $4,000 for the K4.

What does this do to the value of a K3 or K3s? I expect there will be
some coming on the market. Anyone who buys, or retains, a K3 or K3s
will still have one of the finest radios ever made. We are at the point
where the difference among the top 5 or so on Sherwood's charts is a
decibel or two, almost within the margin of error and certainly beyond
the ability of the human ear to discern. So, don't panic. The demand
for the K3 series will be strong for many years to come.

Keep an eye on the website as more information comes from Watsonville.

--
Buck, k4ia
Honor Roll
8BDXCC
EasyWayHamBooks.com
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Grant Youngman-2

Re: K4 Observations

I think your observations are spot on in most respects.

While the basic K4 is certainly going to be a great radio, it will likely NOT have the strong signal handling characteristics of the K3/K3S. There will still be the likelihood of A/D clipping suffered by virtually all 16-bit SDRs in a high-density RF environment. And although there is a second receiver it appears to be more like a Flex “slice” .. sharing front end filters with the main receiver. In that regard, the K4D will be a great advantage for dual receivers in general, or for diversity.

So by the time you get to the K4HD, you will spend a (I would guess) quite a bit more than a K3S for (perhaps improved by a few dB here and there) strong signal performance in the the most demanding conditions.

Lot of tradeoffs to be considered … for sure.

I have far more than the current list price in my existing K3 .. I’ve purchased several new boards for it over the years as various K3 upgrades and the K3S upgrades came out. So the value it has is as a radio, and not a retirement plan.

One way or the other, I’ve set up a K4 piggy bank, in anticipation of the kit version next year … but have no plans at all to part with my K3. It’s too good a radio :-)

Grant NQ5T
K3 #2091 KX3 #8342

> On May 18, 2019, at 11:09 PM, Buck <[hidden email]> wrote:
>
> The following is offered based on my observations and discussions at the Elecraft booth. I am *not* an official, or even unofficial, Elecraft spokesman and stand willing to be corrected.
>
> First, this is going to be another game-changer from Elecraft. The radio will have outstanding performance figures and an interface to die for. The screen is beautiful and functions can be controlled from either buttons or the touch-screen. There is band-stacking on the touch screen, a nit people have complained about on the K3.
>
> The radio is full SDR as opposed to the analog front end of the K3. However an option, the K4HD, is a superhet receive function. Like previous Elecraft radios, this can be added later if you think you need it. Preliminary is that it will not be necessary unless you operate in the presence of strong stations (multi-multi).
>
> Another option has a second set of band pass filters and ADC module that will allow the two receivers to operate on different bands or antennas (K4D).
>
> The radio contains a Linux computer so all this magic does not require an external computer except for logging or audio input. The rig will be addressable locally or over the internet with no additional software. I saw it operated from an iPad and Android is coming. The iPad screen looked exactly like the front panel, including the panadapter.
>
> There are multiple USB ports, an Ethernet port, RS232 and an HDMI port so you can project the front panel, or parts of it, to an external monitor. The panadapter looks awesome on the external monitor and you will be able to point and click to QSY the radio.
>
> The prices are targets but I got the impression the final will be very close. The cost is less than a fully loaded K3s. The kit version will be cheaper than factory-assembled and ship several months later to allow time to write the assembly manual. Target for the factory version is November.
>
> I suspect the K4 will replace the K3 series as K3s sales are sure to suffer because of product age and competition from the K4. I did not hear any talk about sun-setting the K3s when the K4 comes out. I am sure there are many people who will want to buy the basic K3s and upgrade over time (or not) rather than plunk down $4,000 for the K4.
>
> What does this do to the value of a K3 or K3s? I expect there will be some coming on the market. Anyone who buys, or retains, a K3 or K3s will still have one of the finest radios ever made. We are at the point where the difference among the top 5 or so on Sherwood's charts is a decibel or two, almost within the margin of error and certainly beyond the ability of the human ear to discern. So, don't panic. The demand for the K3 series will be strong for many years to come.
>
> Keep an eye on the website as more information comes from Watsonville.
>
>
> --
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

stengrevics

Re: K4 Observations

In reply to this post by Buck

Buck,

Did you happen to discuss:

1. Noise blanker improvement

2. Improvement in sensitivity

Relative to the K3S?

73,

John
WA1EAZ

Buck

Re: K4 Observations

Sorrily not but, knowing Elecraft and the excellent work they do, I am
sure this radio will be outstanding.

Buck, k4ia
Honor Roll
8BDXCC
EasyWayHamBooks.com

On 5/19/2019 6:58 AM, John Stengrevics wrote:

> Buck,
>
> Did you happen to discuss:
>
> 1. Noise blanker improvement
>
> 2. Improvement in sensitivity
>
> Relative to the K3S?
>
> 73,
>
> John
> WA1EAZ
>
>> On May 18, 2019, at 11:09 PM, Buck <[hidden email]> wrote:
>>
>> The following is offered based on my observations and discussions at the Elecraft booth. I am *not* an official, or even unofficial, Elecraft spokesman and stand willing to be corrected.
>>
>> First, this is going to be another game-changer from Elecraft. The radio will have outstanding performance figures and an interface to die for. The screen is beautiful and functions can be controlled from either buttons or the touch-screen. There is band-stacking on the touch screen, a nit people have complained about on the K3.
>>
>> The radio is full SDR as opposed to the analog front end of the K3. However an option, the K4HD, is a superhet receive function. Like previous Elecraft radios, this can be added later if you think you need it. Preliminary is that it will not be necessary unless you operate in the presence of strong stations (multi-multi).
>>
>> Another option has a second set of band pass filters and ADC module that will allow the two receivers to operate on different bands or antennas (K4D).
>>
>> The radio contains a Linux computer so all this magic does not require an external computer except for logging or audio input. The rig will be addressable locally or over the internet with no additional software. I saw it operated from an iPad and Android is coming. The iPad screen looked exactly like the front panel, including the panadapter.
>>
>> There are multiple USB ports, an Ethernet port, RS232 and an HDMI port so you can project the front panel, or parts of it, to an external monitor. The panadapter looks awesome on the external monitor and you will be able to point and click to QSY the radio.
>>
>> The prices are targets but I got the impression the final will be very close. The cost is less than a fully loaded K3s. The kit version will be cheaper than factory-assembled and ship several months later to allow time to write the assembly manual. Target for the factory version is November.
>>
>> I suspect the K4 will replace the K3 series as K3s sales are sure to suffer because of product age and competition from the K4. I did not hear any talk about sun-setting the K3s when the K4 comes out. I am sure there are many people who will want to buy the basic K3s and upgrade over time (or not) rather than plunk down $4,000 for the K4.
>>
>> What does this do to the value of a K3 or K3s? I expect there will be some coming on the market. Anyone who buys, or retains, a K3 or K3s will still have one of the finest radios ever made. We are at the point where the difference among the top 5 or so on Sherwood's charts is a decibel or two, almost within the margin of error and certainly beyond the ability of the human ear to discern. So, don't panic. The demand for the K3 series will be strong for many years to come.
>>
>> Keep an eye on the website as more information comes from Watsonville.
>>
>>
>> --
>> Buck, k4ia
>> Honor Roll
>> 8BDXCC
>> EasyWayHamBooks.com
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>

Buck

Re: Sensitivity - Was K4 Observations

In reply to this post by stengrevics

Here's a question about sensitivity. We used to say if you could hear
the atmospheric noise, that was enough. Time to reduce RF gain.

New modes hear below the noise and DSP is getting better at removing it.
Does that mean our "old" wisdom is now wrong and sensitivity below the
noise level is useful?

Buck, k4ia
Honor Roll
8BDXCC
EasyWayHamBooks.com

On 5/19/2019 6:58 AM, John Stengrevics wrote:

Wes Stewart-2

Re: Sensitivity - Was K4 Observations

What current modes hear below the noise level?

Wes N7WS

On 5/19/2019 4:42 AM, Buck wrote:

> Here's a question about sensitivity. We used to say if you could hear the
> atmospheric noise, that was enough. Time to reduce RF gain.
>
> New modes hear below the noise and DSP is getting better at removing it. Does
> that mean our "old" wisdom is now wrong and sensitivity below the noise level
> is useful?
>
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com

Ed Muns

Re: Sensitivity - Was K4 Observations

JT65, JT9, FT8.73,Ed W0YK
-------- Original message --------From: Wes <[hidden email]> Date: 5/19/19 07:49 (GMT-06:00) To: [hidden email] Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level?Wes N7WSOn 5/19/2019 4:42 AM, Buck wrote:> Here's a question about sensitivity. We used to say if you could hear the > atmospheric noise, that was enough. Time to reduce RF gain.>> New modes hear below the noise and DSP is getting better at removing it. Does > that mean our "old" wisdom is now wrong and sensitivity below the noise level > is useful?>> Buck, k4ia> Honor Roll> 8BDXCC> EasyWayHamBooks.com______________________________________________________________Elecraft mailing listHome: http://mailman.qth.net/mailman/listinfo/elecraftHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:[hidden email] list hosted by: http://www.qsl.netPlease help support this email list: http://www.qsl.net/donate.html
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Joe Subich, W4TV-4

Re: Sensitivity - Was K4 Observations

In reply to this post by Buck

Buck,

New mode "hear below the noise" in a normal SSB bandwidth even
though they may be as narrow as 16 to 50 Hz (in the case of
JT9 and FT8).

The largest part of the claimed -21 to -27 dB S/N threshold is
based on the difference in noise bandwidth. The actual "filters"
for each of the "tones" are just 1 - 2 Hz wide and there one
still needs to "hear atmospheric noise."

Using the standard 10*log(BWn/BWw) equation, one needs to hear
~20-25 dB atmospheric noise (4-5 S units in a K3/K3S) before
reducing the RF gain! This is, however, not really any different
than switching from SSB to CW ... if the "effective" bandwidth
for CW is on the order of 100 Hz a CW signal right at the noise
in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz
wide SSB filter.

73,

... Joe, W4TV

On 2019-05-19 7:42 AM, Buck wrote:

> Here's a question about sensitivity. We used to say if you could hear
> the atmospheric noise, that was enough. Time to reduce RF gain.
>
> New modes hear below the noise and DSP is getting better at removing it.
> Does that mean our "old" wisdom is now wrong and sensitivity below the
> noise level is useful?
>
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com
>

Wes Stewart-2

Re: Sensitivity - Was K4 Observations

In reply to this post by Buck

I feel like I'm gonna be slappin' a tar baby by responding.

Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and
JT9 have been used on HF, but the QSOs are hardly random. If your computer clock
is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those
are bogus.

Wes N7WS

On 5/19/2019 5:58 AM, Ed W0YK wrote:

> JT65, JT9, FT8.
>
> 73,
> Ed W0YK
>
> -------- Original message --------
> From: Wes <[hidden email]>
> Date: 5/19/19 07:49 (GMT-06:00)
> To: [hidden email]
> Subject: Re: [Elecraft] Sensitivity - Was K4 Observations
>
> What current modes hear below the noise level?
>
> Wes N7WS

Joe Subich, W4TV-4

Re: Sensitivity - Was K4 Observations

On 2019-05-19 9:50 AM, Wes wrote:
> FT8 reports negative SNRs number but we both know those are bogus.

All of the modes that quote negative SNRs are doing so by using SNR
in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth
(bandwidth of the final filter whether than be a narrow IF filter,
the "ear-brain" filter or a software [computation] filter).

If one looks at the SNR thresholds of the various Joe Taylor "slow"
modes, 80% of the "negative" SNR can be attributed entirely to the
difference between the occupied bandwidth and the [excess] measurement
bandwidth. The remainder can be attributed to software processing
algorithms that take advantage of the fact that noise is random while
the signal is not - in essence reporting using a "peak noise" level
while actually decoding against a "minimum noise" level (like copying
CW through static crashes - one looses a dit/dah during the crash but
fills that in from the context).

73,

... Joe, W4TV

On 2019-05-19 9:50 AM, Wes wrote:

> I feel like I'm gonna be slappin' a tar baby by responding.
>
> Since we are discussion HF radios, I was assuming HF. I realize
> JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random.
> If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs
> number but we both know those are bogus.
>
> Wes N7WS
>
>
> On 5/19/2019 5:58 AM, Ed W0YK wrote:
>> JT65, JT9, FT8.
>>
>> 73,
>> Ed W0YK
>>
>> -------- Original message --------
>> From: Wes <[hidden email]>
>> Date: 5/19/19 07:49 (GMT-06:00)
>> To: [hidden email]
>> Subject: Re: [Elecraft] Sensitivity - Was K4 Observations
>>
>> What current modes hear below the noise level?
>>
>> Wes N7WS
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

David Woolley (E.L)

Re: K4 Observations

In reply to this post by Buck

Unfortunately, the amateur radio world behaves like popular culture and
hijacks engineering terms and redefines them. Nearly every radio
receiver nowadays is largely an SDR, but the amateur community tends to
use the term in a more restricted sense.

What I think is meant by Full SDR is what, more correctly, would be
described as direct sampling.

However, the really key point is that Elecraft's main skills are with
analogue electronics. To the extent that the K4 has no analogue front
end, it really doesn't benefit from the company's core expertise
(although low phase noise clocks may also be one of their skills).

Personally, I suspect that there is significant analogue processing
before the A/D convertor (the front end) and that is what will give it
any edge it has over the competition.

A/D convertors are essentially commodity items, to the only real input
the Elecraft desginers will have is setting the price point.

--
David Woolley
Owner K2 06123

On 19/05/2019 04:09, Buck wrote:
> The radio is full SDR as opposed to the analog front end of the K3.
> However an option, the K4HD, is a superhet receive function. Like
> previous Elecraft radios, this can be added later if you think you need
> it. Preliminary is that it will not be necessary unless you operate in
> the presence of strong stations (multi-multi).

______________________________________________________________
Elecraft mailing list
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Tom Azlin W7SUA-2

Re: Sensitivity - Was K4 Observations

In reply to this post by Joe Subich, W4TV-4

More like a "feel good" detection SNR?

I think fldigi uses a few bins either side of the signal to determine
the noise in the SNR measurement. When I narrow my K3 IF bandwidth down
to just the, say Olivia, bandwidth the SNR number climb up to 30 dB high
as the filter cut the noise in the adjacent "noise" bins. If I use a
600-700 Hz filter or wider for a 500 Hz wide Olivia then the SNR
measurements stay the same.

So I have always thought along the lines of your two emails Joe. Plus
long time ago I discovered how I could add FFTs up and a coherent signal
would "climb" out of the random noise. So for a signal with considerable
time per bin measurement you get that gain as well.

So have always thought of the WSJT type negative numbers as bogus.

73, tom w7sua

On 5/19/2019 7:18 AM, Joe Subich, W4TV wrote:

> On 2019-05-19 9:50 AM, Wes wrote:
>> FT8 reports negative SNRs number but we both know those are bogus.
>
> All of the modes that quote negative SNRs are doing so by using SNR
> in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth
> (bandwidth of the final filter whether than be a narrow IF filter,
> the "ear-brain" filter or a software [computation] filter).
>
> If one looks at the SNR thresholds of the various Joe Taylor "slow"
> modes, 80% of the "negative" SNR can be attributed entirely to the
> difference between the occupied bandwidth and the [excess] measurement
> bandwidth. The remainder can be attributed to software processing
> algorithms that take advantage of the fact that noise is random while
> the signal is not - in essence reporting using a "peak noise" level
> while actually decoding against a "minimum noise" level (like copying
> CW through static crashes - one looses a dit/dah during the crash but
> fills that in from the context).
>
> 73,
>
> ... Joe, W4TV
>
>
> On 2019-05-19 9:50 AM, Wes wrote:
>> I feel like I'm gonna be slappin' a tar baby by responding.
>>
>> Since we are discussion HF radios, I was assuming HF. I realize
>> JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly
>> random. If your computer clock is off, sorry, no QSO. FT8 reports
>> negative SNRs number but we both know those are bogus.
>>
>> Wes N7WS
>>
>>
>> On 5/19/2019 5:58 AM, Ed W0YK wrote:
>>> JT65, JT9, FT8.
>>>
>>> 73,
>>> Ed W0YK
>>>
>>> -------- Original message --------
>>> From: Wes <[hidden email]>
>>> Date: 5/19/19 07:49 (GMT-06:00)
>>> To: [hidden email]
>>> Subject: Re: [Elecraft] Sensitivity - Was K4 Observations
>>>
>>> What current modes hear below the noise level?
>>>
>>> Wes N7WS
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

K9MA

Re: Sensitivity - Was K4 Observations

In reply to this post by Joe Subich, W4TV-4

I've often wondered what the effective bandwidth of a good CW operator
was. I've noticed that, unless there's QRM, reducing the receiver
bandwidth really doesn't help, so the limit factor is the "processing".
On the other hand, neither does slowing down below perhaps 15 wpm, as if
the processing just can't make the effective bandwidth any lower.
Perhaps the real advantage of the JT modes is that they can take
advantage of the lower noise bandwidth at very slow speeds, while our
brains can't. It would be interesting to compare the performance at 15 wpm.

73,
Scott K9MA

On 5/19/2019 09:18, Joe Subich, W4TV wrote:

--
Scott K9MA

[hidden email]

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Evert Bakker (PA2KW)

Re: Sensitivity - Was K4 Observations

In reply to this post by Joe Subich, W4TV-4

We all now (i guess) that decoding below the noise floor needs:
Time, timing and repetition..
no formulas needed .....

73's, Evert PA2KW

-----Oorspronkelijk bericht-----
Van: [hidden email] [mailto:[hidden email]] Namens Joe Subich, W4TV
Verzonden: zondag 19 mei 2019 15:29
Aan: [hidden email]
Onderwerp: Re: [Elecraft] Sensitivity - Was K4 Observations

Buck,

New mode "hear below the noise" in a normal SSB bandwidth even though they may be as narrow as 16 to 50 Hz (in the case of
JT9 and FT8).

The largest part of the claimed -21 to -27 dB S/N threshold is based on the difference in noise bandwidth. The actual "filters"
for each of the "tones" are just 1 - 2 Hz wide and there one still needs to "hear atmospheric noise."

Using the standard 10*log(BWn/BWw) equation, one needs to hear
~20-25 dB atmospheric noise (4-5 S units in a K3/K3S) before reducing the RF gain! This is, however, not really any different than switching from SSB to CW ... if the "effective" bandwidth for CW is on the order of 100 Hz a CW signal right at the noise in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz wide SSB filter.

73,

... Joe, W4TV

On 2019-05-19 7:42 AM, Buck wrote:

> Here's a question about sensitivity. We used to say if you could hear
> the atmospheric noise, that was enough. Time to reduce RF gain.
>
> New modes hear below the noise and DSP is getting better at removing it.
> Does that mean our "old" wisdom is now wrong and sensitivity below
> the noise level is useful?
>
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Alan Bloom

Re: K4 Observations

In reply to this post by David Woolley (E.L)

On 5/19/19 7:39 AM, David Woolley wrote:
> Unfortunately, the amateur radio world behaves like popular culture
> and hijacks engineering terms and redefines them. Nearly every radio
> receiver nowadays is largely an SDR, but the amateur community tends
> to use the term in a more restricted sense.
>
> What I think is meant by Full SDR is what, more correctly, would be
> described as direct sampling.

Yes.

>
> However, the really key point is that Elecraft's main skills are with
> analogue electronics. To the extent that the K4 has no analogue front
> end, it really doesn't benefit from the company's core expertise
> (although low phase noise clocks may also be one of their skills).
>
> Personally, I suspect that there is significant analogue processing
> before the A/D convertor (the front end) and that is what will give it
> any edge it has over the competition.
>
> A/D convertors are essentially commodity items, to the only real input
> the Elecraft desginers will have is setting the price point.
>

I disagree with that. It takes a lot of analog expertise to properly
implement a direct-sampling receiver. There are many ways to get it wrong.

Alan N1AL

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Don Wilhelm

Re: K4 Observations

In reply to this post by Buck

John, Buck and all,

Questions of that nature can likely be addressed better Tuesday after
8AM Pacific time. The developers will be back from Dayton by then and
can respond with authority rather than guesses from those who have not
measured those parameters.

In the meantime, we have the photos, specifications and the FAQ page to
refer to, and that is all.

73,
Don W3FPR

On 5/19/2019 7:02 AM, Buck wrote:

> Sorrily not but, knowing Elecraft and the excellent work they do, I am
> sure this radio will be outstanding.
>
> Buck, k4ia
> Honor Roll
> 8BDXCC
> EasyWayHamBooks.com
>
> On 5/19/2019 6:58 AM, John Stengrevics wrote:
>> Buck,
>>
>> Did you happen to discuss:
>>
>> 1. Noise blanker improvement
>>
>> 2. Improvement in sensitivity
>>
>> Relative to the K3S?
>>

Jim Brown-10

Re: Sensitivity - Was K4 Observations

In reply to this post by Joe Subich, W4TV-4

On 5/19/2019 6:28 AM, Joe Subich, W4TV wrote:
> if the "effective" bandwidth
> for CW is on the order of 100 Hz a CW signal right at the noise
> in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz
> wide SSB filter.

This estimate correlates well with my own that FT8 can work about 10 dB
deeper into the noise than CW with good radios and very good operators
on both ends. I've worked a lot of both modes.

On 5/19/2019 6:50 AM, Wes wrote:
> FT8 reports negative SNRs number but we both know those are bogus.

Not if you read the definitions within the WSJT-X docs. Joe has done
that, and correctly interprets the numbers.

73, Jim K9YC

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Elecraft mailing list

Re: Sensitivity - Was K4 Observations

In reply to this post by Buck

Regarding W0YK/Ed’s comment –

The 8-ary FSK of FT-8 may be buried in the ambient noise at my/your/somebody’s QTH. Like LPI communications, knowing where to look in frequency and time allows the decoder to combine noisy samples and recover the original; in the case of FT-8, a 63 bit message. Your receiver does not hear the 63 bits, just the symbols used in statistically recreating the 63 bits.

The real issue with sensitivity or receiver NF is making sure that the receiver is a weak contributor to the overall noise power entering the detection process which is generally dominated by ambient noise. Most of the radios in the top Sherwood top 10 are weak contributors in most locations, even in the CCIR-defined quiet rural environments.

73 Bob R – N7WY

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Joe Subich, W4TV-4

Re: Sensitivity - Was K4 Observations

In reply to this post by Tom Azlin W7SUA-2

There is one place that digital modes (like those by Joe Taylor and
associates) can improve the decoded SNR beyond simply reducing the
detection bandwidth. If the modulation/encoding supports N states
but the encoding only uses M of those states, the decoding software
can make use of the "sparse constellation" to recognize states that
are impacted by noise and select the "closest" valid state.

This "coding gain" can improve the overall SNR beyond that provided
simply by the "matched" (or optimal) noise bandwidth. However, with
all amateur modes (CW to FT8 & FT4) the majority of the SNR improvement
over SSB (or AM) is simply due to the use of optimal bandwidth to
reduce extraneous noise in the detector bandwidth. Even with SSB,
properly tailoring the IF bandwidth will make several dB difference
in the detected SNR. For example, a 2 KHz bandwidth (500 - 2500 Hz)
can provide significant improvement over a 2.8 KHz bandwidth (200 -
3000 Hz) under noisy conditions.

73,

... Joe, W4TV

On 2019-05-19 11:19 AM, Tom Azlin W7SUA wrote:

> More like a "feel good" detection SNR?
>
> I think fldigi uses a few bins either side of the signal to determine
> the noise in the SNR measurement. When I narrow my K3 IF bandwidth down
> to just the, say Olivia, bandwidth the SNR number climb up to 30 dB high
> as the filter cut the noise in the adjacent "noise" bins. If I use a
> 600-700 Hz filter or wider for a 500 Hz wide Olivia then the SNR
> measurements stay the same.
>
> So I have always thought along the lines of your two emails Joe. Plus
> long time ago I discovered how I could add FFTs up and a coherent signal
> would "climb" out of the random noise. So for a signal with considerable
> time per bin measurement you get that gain as well.
>
> So have always thought of the WSJT type negative numbers as bogus.
>
> 73, tom w7sua
>
> On 5/19/2019 7:18 AM, Joe Subich, W4TV wrote:
>> On 2019-05-19 9:50 AM, Wes wrote:
>>> FT8 reports negative SNRs number but we both know those are bogus.
>>
>> All of the modes that quote negative SNRs are doing so by using SNR
>> in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth
>> (bandwidth of the final filter whether than be a narrow IF filter,
>> the "ear-brain" filter or a software [computation] filter).
>>
>> If one looks at the SNR thresholds of the various Joe Taylor "slow"
>> modes, 80% of the "negative" SNR can be attributed entirely to the
>> difference between the occupied bandwidth and the [excess] measurement
>> bandwidth. The remainder can be attributed to software processing
>> algorithms that take advantage of the fact that noise is random while
>> the signal is not - in essence reporting using a "peak noise" level
>> while actually decoding against a "minimum noise" level (like copying
>> CW through static crashes - one looses a dit/dah during the crash but
>> fills that in from the context).
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>> On 2019-05-19 9:50 AM, Wes wrote:
>>> I feel like I'm gonna be slappin' a tar baby by responding.
>>>
>>> Since we are discussion HF radios, I was assuming HF. I realize
>>> JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly
>>> random. If your computer clock is off, sorry, no QSO. FT8 reports
>>> negative SNRs number but we both know those are bogus.
>>>
>>> Wes N7WS
>>>
>>>
>>> On 5/19/2019 5:58 AM, Ed W0YK wrote:
>>>> JT65, JT9, FT8.
>>>>
>>>> 73,
>>>> Ed W0YK
>>>>
>>>> -------- Original message --------
>>>> From: Wes <[hidden email]>
>>>> Date: 5/19/19 07:49 (GMT-06:00)
>>>> To: [hidden email]
>>>> Subject: Re: [Elecraft] Sensitivity - Was K4 Observations
>>>>
>>>> What current modes hear below the noise level?
>>>>
>>>> Wes N7WS
>>>
>>> ______________________________________________________________
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> ______________________________________________________________
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Edward R Cole

Re: Sensitivity - Was K4 Observations

In reply to this post by Buck

As Joe-W4TV nicely explained, digital modes excel due to occupying
less bandwidth which also reduces noise bandwidth. There is some
"high-tech" coding that adds to the overall sensitivity of the
modes. CW eme operators are said to be able to reduce bandwidth "in
their heads" to 50-Hz. When I ran CW eme, I found setting my radio
to 100 to 200 Hz worked best for me. 50-Hz DSP filter caused too
much ringing for me to discern the CW note.

Radio sensitivity requirements are mostly set by band noise whose
minimum is established by "celestial" (or sky noise). Such noise is
commonly characterized as applicable sky noise temperature (in
Kevin). Tsky (144-MHz) is thought to be about 250K. At 432 that
lowers to 70K and above 1000 MHz approx 10K.

Receiver sensitivity is tied to noise figure (which also can be
thought of as a temperature (Trx).

Overall receiving sensitivity Te = Tsky + Trx + Tant

The last factor, Tant mostly refers to how much noise the antenna
sees. Earth at 70F is 290K. So if your antenna sidelobes see the
earth, that adds to minimum sensitivity one can achieve. A typical
144-MHz eme receiving system noise temp: Te = 250K + 70K + 29K =
349K. Trx=70 is roughly a noise figure of 0.5 dB.

As one goes higher in frequency, sky noise is less so one wants the
receiver to be less, to improve overall sensitivity.

But as one goes lower in frequency sky noise rises a lot. Tsky
(50-MHz) is roughly 2000K and Tsky (28-MHz) is 5000K (or more).
Making a HF receiver super low noise (low noise figure and thus more
sensitive) is severely limited by Tsky (which is in 10,000K to 100,000K).

And note that I did not add any factor for human generated noise
sources. Te = Tsky + Trx + Tant + Tman-made

Sensitivity is measured in signal power which is related to system
noise temperature b the formula: Pn = KTB.
K is Botlzmanns constant. T is Te derived above. And B is detection
bandwidth in Hz.

If noise power, Pn is in terms of dBm, then Pn = -198.6 + 10Log(Te) + 10Log(B)

SNR = Ps - Pn, where Ps is signal power in dBm. SNR=0 is at the
noise level (where Ps = Pn).

K3 (with PR6) is spec at Pn = -143 dBm at B=500,000 Hz which is very
sensitive. That level would only make a difference on 10m or 6m due
to lower sky noise.

73, Ed - KL7UW
http://www.kl7uw.com
Dubus-NA Business mail:
[hidden email]

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