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[K3] The Way We Rank Receivers (long)

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alorona

[K3] The Way We Rank Receivers (long)

Receivers are always ranked by the "2 kHz third order dynamic range", such as at: http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do we really grasp the meaning of these specs? For instance, the Elecraft K3's (after synthesizer upgrade) number is 103 dB, good enough to be in the top ten. In fact, this number is so strong that very few hams will ever be affected by it. To the best of my knowledge, I have *never* been close to running out of dynamic range. To understand why, let's put "103 dB" into English.

Let's say you're on 20 meter CW, operating at 14.050 MHz. You're listening through your fine Elecraft 500 Hz crystal filter when suddenly, and by incredible coincidence, two equally strong 49 dB over S9 signals begin transmitting at the exact same time, one on 14.052 and the other at 14.054 MHz, exactly 2 kHz and 4 kHz up from where you're listening. With the preamp off (which is totally believeable on 20 meters with a decent antenna) you will just barely hear a "ghost signal" right at the noise level... if you notice it at all. That "ghost" signal is the two-tone, 3rd order intermod product generated in the K3 receiver by those two hugely strong and perfectly placed signals.

Not a very likely scenario, but that's what 103 dB of dynamic range buys you.

I have assumed a noise floor or MDS of -130 dBm because it's a nice round number. If your 20 meter noise floor is higher than this, then the two signals would have to be *even stronger* to hear the intermod come out of the noise.

Even if each of those interferers was *60* dB over S9 -- pegging the S-meter-- the intermod product on 14.050 would still be only S5. Amazing. This kind of performance begs the question, "How much more dynamic range is really needed?" and some (like Rob Sherwood) have said that once you're above 90 dB, you already have enough, at HF at least.

Perhaps it's time to rank receivers by a different measurement, something that affects more of us. Looking through the table at the link above we see another measurement called "2 kHz blocking gain compression" and for the same K3 it is 143 dB. This is a measurement not of two interfering signals, but a single interferer just 2 kHz away. Since there's only one signal, it won't generate a "ghost", but it will reduce the gain of the receiver. ARRL defines this as the signal level that reduces the gain by 1 dB. One dB is really small, something like changing your RF Gain knob from the 3:00 o'clock position to maybe the 2:45 o'clock position. Barely noticeable. Nonetheless, for our K3 the signal required to do this is about +13 dBm, or 20 milliwatts, which is probably near the damage level of the receiver! (I'm quite sure that Wayne has made intercontinental QSOs at 20 mW.) It's a theoretical value that very, very few hams would ever encounter... only the ones living next door to
a guy running a kilowatt. So this measurement is even less relevant to us.

Finally, we notice a measurement called "2 kHz reciprocal mixing dynamic range" -- probably the limiting spec nowadays for top tier receivers. In our example of the single strong signal, way before reducing the gain of the receiver, that signal will have another effect: it will mix with the phase noise of the K3's own local oscillator and deposit that phase noise right onto your desired frequency of 14.050 MHz. As you're listening there, you suddenly notice that the noise floor seems to be rising for no apparent reason. You listen some more, and notice that the noise is following some kind of CW keying. You glance at your panadapter and notice an enormous signal just 2 kHz away on 14.052. So there are two culprits: that strong signal, and the K3 oscillator phase noise. The K3 with upgraded synths has a spec of "-115 dBc", again near the top of the list, which means that a signal 2 kHz away and 115 dB above the noise floor will cause the noise floor to rise by 3 dB. For a K3 n
oise floor of -130 dBm this is -15 dBm, or about 60 dB over S9. The reason I say this is the limiting factor is because the chance of just one 60 dB over S9 signal nearby is greater than *two* of them at the right spacing as in our discussion of 3rd order DR.

For these reasons, we could start ranking receivers by 2 kHz reciprocal mixing dynamic range because reciprocal mixing is far more likely to happen to a larger number of hams. It's not a catastrophic effect, but it's quite noticeable. There's a problem, however, because sampling receivers don't follow the classical reciprocal mixing model. We need a measurement that hasn't been invented yet to compare modern receivers. Maybe we could simulate the worst-case contest by applying thousands of signals and noise to the receiver and seeing how much junk is generated to cover up the signal you're trying to copy at 14.050, something kinda like the noise power ratio test. But in order to compare apples to apples, the exact same test conditions must be used on every receiver, regardless of architecture.

Finally, the general unlikelihood of any of these conditions occurring also convinces me that other ergonomic factors -- not necessarily measureable-- should be considered when choosing a receiver. 'Usability' (whatever that means to you) is underrated. So is 'listenability' -- again, a very subjective term. For instance, I have come to believe that the AGC system in a receiver has everything to do with how it "sounds" and explains why receivers with similar specs can sound so different from each other. This area needs further study.

I hope that this helped turn mere numbers into an actual operating reality.

Al W6LX
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Art Hejduk

Re: [K3] The Way We Rank Receivers (long)

Nice explanation Al. It's nice to know that the K3 ranks high on the
charts, but I agree that 'usability' and 'listenability' are underrated.
Before I purchased my K3, I went to AES in Wickliffe and listened to
several receivers. I liked the sound of the Kenwoods, but I liked the
'modularity' of the Elecraft K3. I was also influenced by my conversations
with Eric and Wayne at Dayton.

73,
Art WB8ENE

On Tue, Oct 25, 2016 at 1:21 AM, Al Lorona <[hidden email]> wrote:

> Receivers are always ranked by the "2 kHz third order dynamic range", such
> as at: http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do we
> really grasp the meaning of these specs? For instance, the Elecraft K3's
> (after synthesizer upgrade) number is 103 dB, good enough to be in the top
> ten. In fact, this number is so strong that very few hams will ever be
> affected by it. To the best of my knowledge, I have *never* been close to
> running out of dynamic range. To understand why, let's put "103 dB" into
> English.
>
> Let's say you're on 20 meter CW, operating at 14.050 MHz. You're listening
> through your fine Elecraft 500 Hz crystal filter when suddenly, and by
> incredible coincidence, two equally strong 49 dB over S9 signals begin
> transmitting at the exact same time, one on 14.052 and the other at 14.054
> MHz, exactly 2 kHz and 4 kHz up from where you're listening. With the
> preamp off (which is totally believeable on 20 meters with a decent
> antenna) you will just barely hear a "ghost signal" right at the noise
> level... if you notice it at all. That "ghost" signal is the two-tone, 3rd
> order intermod product generated in the K3 receiver by those two hugely
> strong and perfectly placed signals.
>
> Not a very likely scenario, but that's what 103 dB of dynamic range buys
> you.
>
> I have assumed a noise floor or MDS of -130 dBm because it's a nice round
> number. If your 20 meter noise floor is higher than this, then the two
> signals would have to be *even stronger* to hear the intermod come out of
> the noise.
>
> Even if each of those interferers was *60* dB over S9 -- pegging the
> S-meter-- the intermod product on 14.050 would still be only S5. Amazing.
> This kind of performance begs the question, "How much more dynamic range is
> really needed?" and some (like Rob Sherwood) have said that once you're
> above 90 dB, you already have enough, at HF at least.
>
> Perhaps it's time to rank receivers by a different measurement, something
> that affects more of us. Looking through the table at the link above we see
> another measurement called "2 kHz blocking gain compression" and for the
> same K3 it is 143 dB. This is a measurement not of two interfering signals,
> but a single interferer just 2 kHz away. Since there's only one signal, it
> won't generate a "ghost", but it will reduce the gain of the receiver. ARRL
> defines this as the signal level that reduces the gain by 1 dB. One dB is
> really small, something like changing your RF Gain knob from the 3:00
> o'clock position to maybe the 2:45 o'clock position. Barely noticeable.
> Nonetheless, for our K3 the signal required to do this is about +13 dBm, or
> 20 milliwatts, which is probably near the damage level of the receiver!
> (I'm quite sure that Wayne has made intercontinental QSOs at 20 mW.) It's a
> theoretical value that very, very few hams would ever encounter... only the
> ones living next door to
> a guy running a kilowatt. So this measurement is even less relevant to
> us.
>
> Finally, we notice a measurement called "2 kHz reciprocal mixing dynamic
> range" -- probably the limiting spec nowadays for top tier receivers. In
> our example of the single strong signal, way before reducing the gain of
> the receiver, that signal will have another effect: it will mix with the
> phase noise of the K3's own local oscillator and deposit that phase noise
> right onto your desired frequency of 14.050 MHz. As you're listening there,
> you suddenly notice that the noise floor seems to be rising for no apparent
> reason. You listen some more, and notice that the noise is following some
> kind of CW keying. You glance at your panadapter and notice an enormous
> signal just 2 kHz away on 14.052. So there are two culprits: that strong
> signal, and the K3 oscillator phase noise. The K3 with upgraded synths has
> a spec of "-115 dBc", again near the top of the list, which means that a
> signal 2 kHz away and 115 dB above the noise floor will cause the noise
> floor to rise by 3 dB. For a K3 n
> oise floor of -130 dBm this is -15 dBm, or about 60 dB over S9. The
> reason I say this is the limiting factor is because the chance of just one
> 60 dB over S9 signal nearby is greater than *two* of them at the right
> spacing as in our discussion of 3rd order DR.
>
> For these reasons, we could start ranking receivers by 2 kHz reciprocal
> mixing dynamic range because reciprocal mixing is far more likely to happen
> to a larger number of hams. It's not a catastrophic effect, but it's quite
> noticeable. There's a problem, however, because sampling receivers don't
> follow the classical reciprocal mixing model. We need a measurement that
> hasn't been invented yet to compare modern receivers. Maybe we could
> simulate the worst-case contest by applying thousands of signals and noise
> to the receiver and seeing how much junk is generated to cover up the
> signal you're trying to copy at 14.050, something kinda like the noise
> power ratio test. But in order to compare apples to apples, the exact same
> test conditions must be used on every receiver, regardless of architecture.
>
> Finally, the general unlikelihood of any of these conditions occurring
> also convinces me that other ergonomic factors -- not necessarily
> measureable-- should be considered when choosing a receiver. 'Usability'
> (whatever that means to you) is underrated. So is 'listenability' -- again,
> a very subjective term. For instance, I have come to believe that the AGC
> system in a receiver has everything to do with how it "sounds" and explains
> why receivers with similar specs can sound so different from each other.
> This area needs further study.
>
> I hope that this helped turn mere numbers into an actual operating reality.
>
> Al W6LX
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

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briancom

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

Al,

As a CW op, I consider the 2 KHz away figures interesting not really
relevant.

I want to know how well a receiver is able to separate a weak signal
from strong signals 50-100 Hz away. It would be interesting to speculate
how such a measurement would be done. Let the RX use whatever analog or
digital tricks it can to achieve the above.

Your idea of simulating a contest with a hundreds of signal injected at
various random frequencies to gauge RX performance has merit.

Have you overlooked the MM, FD and DXpedition RX uses which in fact push
the dynamic range and mixing limits today? There are MM stations which
operate two transmitters on the same band.

73 de Brian/K3KO

On 10/25/2016 5:21 AM, Al Lorona wrote:

> Receivers are always ranked by the "2 kHz third order dynamic range", such as at: http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do we really grasp the meaning of these specs? For instance, the Elecraft K3's (after synthesizer upgrade) number is 103 dB, good enough to be in the top ten. In fact, this number is so strong that very few hams will ever be affected by it. To the best of my knowledge, I have *never* been close to running out of dynamic range. To understand why, let's put "103 dB" into English.
>
> Let's say you're on 20 meter CW, operating at 14.050 MHz. You're listening through your fine Elecraft 500 Hz crystal filter when suddenly, and by incredible coincidence, two equally strong 49 dB over S9 signals begin transmitting at the exact same time, one on 14.052 and the other at 14.054 MHz, exactly 2 kHz and 4 kHz up from where you're listening. With the preamp off (which is totally believeable on 20 meters with a decent antenna) you will just barely hear a "ghost signal" right at the noise level... if you notice it at all. That "ghost" signal is the two-tone, 3rd order intermod product generated in the K3 receiver by those two hugely strong and perfectly placed signals.
>
> Not a very likely scenario, but that's what 103 dB of dynamic range buys you.
>
> I have assumed a noise floor or MDS of -130 dBm because it's a nice round number. If your 20 meter noise floor is higher than this, then the two signals would have to be *even stronger* to hear the intermod come out of the noise.
>
> Even if each of those interferers was *60* dB over S9 -- pegging the S-meter-- the intermod product on 14.050 would still be only S5. Amazing. This kind of performance begs the question, "How much more dynamic range is really needed?" and some (like Rob Sherwood) have said that once you're above 90 dB, you already have enough, at HF at least.
>
> Perhaps it's time to rank receivers by a different measurement, something that affects more of us. Looking through the table at the link above we see another measurement called "2 kHz blocking gain compression" and for the same K3 it is 143 dB. This is a measurement not of two interfering signals, but a single interferer just 2 kHz away. Since there's only one signal, it won't generate a "ghost", but it will reduce the gain of the receiver. ARRL defines this as the signal level that reduces the gain by 1 dB. One dB is really small, something like changing your RF Gain knob from the 3:00 o'clock position to maybe the 2:45 o'clock position. Barely noticeable. Nonetheless, for our K3 the signal required to do this is about +13 dBm, or 20 milliwatts, which is probably near the damage level of the receiver! (I'm quite sure that Wayne has made intercontinental QSOs at 20 mW.) It's a theoretical value that very, very few hams would ever encounter... only the ones living next door

to
> a guy running a kilowatt. So this measurement is even less relevant to us.
>
> Finally, we notice a measurement called "2 kHz reciprocal mixing dynamic range" -- probably the limiting spec nowadays for top tier receivers. In our example of the single strong signal, way before reducing the gain of the receiver, that signal will have another effect: it will mix with the phase noise of the K3's own local oscillator and deposit that phase noise right onto your desired frequency of 14.050 MHz. As you're listening there, you suddenly notice that the noise floor seems to be rising for no apparent reason. You listen some more, and notice that the noise is following some kind of CW keying. You glance at your panadapter and notice an enormous signal just 2 kHz away on 14.052. So there are two culprits: that strong signal, and the K3 oscillator phase noise. The K3 with upgraded synths has a spec of "-115 dBc", again near the top of the list, which means that a signal 2 kHz away and 115 dB above the noise floor will cause the noise floor to rise by 3 dB. For a K3
n

> oise floor of -130 dBm this is -15 dBm, or about 60 dB over S9. The reason I say this is the limiting factor is because the chance of just one 60 dB over S9 signal nearby is greater than *two* of them at the right spacing as in our discussion of 3rd order DR.
>
> For these reasons, we could start ranking receivers by 2 kHz reciprocal mixing dynamic range because reciprocal mixing is far more likely to happen to a larger number of hams. It's not a catastrophic effect, but it's quite noticeable. There's a problem, however, because sampling receivers don't follow the classical reciprocal mixing model. We need a measurement that hasn't been invented yet to compare modern receivers. Maybe we could simulate the worst-case contest by applying thousands of signals and noise to the receiver and seeing how much junk is generated to cover up the signal you're trying to copy at 14.050, something kinda like the noise power ratio test. But in order to compare apples to apples, the exact same test conditions must be used on every receiver, regardless of architecture.
>
> Finally, the general unlikelihood of any of these conditions occurring also convinces me that other ergonomic factors -- not necessarily measureable-- should be considered when choosing a receiver. 'Usability' (whatever that means to you) is underrated. So is 'listenability' -- again, a very subjective term. For instance, I have come to believe that the AGC system in a receiver has everything to do with how it "sounds" and explains why receivers with similar specs can sound so different from each other. This area needs further study.
>
> I hope that this helped turn mere numbers into an actual operating reality.
>
> Al W6LX
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

NJ8M

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

EXCELLENT excellent excellent post...Great summary. The listen ability and
ease of ergonomic operability are the reason I love radios with knobs. This
is what the maestro is trying to do for for the Flex 6XXX radios. There is
just not a better box for both on the market other than the K3, K3s, KX3,
KX2. Seemingly Elecraft has nailed it. Your post only confirms what I
believe all Elecraft owners already know and experience when we hit the
power on switch.

Again you summary is excellent and great reading. Well written and well
thought out and equally well presented.

Strong work.

Vy 73,

Morgan Bailey NJ8M

On Tue, Oct 25, 2016 at 12:21 AM, Al Lorona <[hidden email]> wrote:

Bill Frantz

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by briancom

Before I bought my K3, I discussed the radio with someone in the
booth at Radiofest, a small hamfest held near Monterey, CA.
After I had learned a very little bit about the radio, I had my
wife (KI6SLX), a retired QA engineer for Apple, discuss UI
issues. When she said it seemed OK, I wrote a check.

I like Brian's idea of simulating contest conditions to test
receivers. Such a simulation would need to be reproducible and
good enough that it can't be gamed. For testing CW reception,
perhaps a fixed set of signals modulated through a very linear
SSB modulator would work. That could give at least 2KHz of
signals for the receiver to handle.

The West Valley Amateur Radio Association field day operation
sometimes has 3 signals active on one band (CW, digital, and
SSB). We manage to get by running QRP with K3(S)s, KX3s, K2s and
carefully placed antennas. For CQP, we managed to run two
stations on a band at 100 watts with similar equipment and techniques.

73 Bill AE6JV

On 10/25/16 at 5:45 AM, [hidden email] (brian) wrote:

>I want to know how well a receiver is able to separate a weak
>signal from strong signals 50-100 Hz away. It would be
>interesting to speculate how such a measurement would be done.
>Let the RX use whatever analog or digital tricks it can to
>achieve the above.
>
>Your idea of simulating a contest with a hundreds of signal
>injected at various random frequencies to gauge RX performance
>has merit.
>
>Have you overlooked the MM, FD and DXpedition RX uses which in
>fact push the dynamic range and mixing limits today? There are
>MM stations which operate two transmitters on the same band.

---------------------------------------------------------------------------
Bill Frantz | Re: Computer reliability, performance, and security:
408-356-8506 | The guy who *is* wearing a parachute is
*not* the
www.pwpconsult.com | first to reach the ground. - Terence Kelly

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briancom

Re: [K3] The Way We Rank Receivers (long)

There is another frontier. That is noise/RFI reduction.
The Pandora's box of RFI has been opened and can't be shut at this point.

We need to address the issue of noise reduction and noise blanketing in
some quantitative way to compare various RX's. Right now the
"comparisons" are all innuendo, e.g. "my old xyz rig did a much better
job at noise blanketing power line noise than my new widget." The
recent QST article on the K3S singing the praises (without giving any
data) of its NR and NB capability is another example.

This would be tough since the world of RFI sources is huge. It would
take some real effort to quantify the world of noise sources and their
signatures and then find some algorithms to deal with them. Impossible?
The world of big data isn't so big any more. Such an catalog might be
doable. Algorithms are another issue. My hope is that NR/NB could be
made adaptive to recognize the signature(s) and generate appropriate
algorithms on the fly.

There are a lot of smart people out there who could perhaps address
these issues. Unfortunately commercial interests have to see some
payoff. They haven't as of yet. The fact that AM broadcasters are
being burned by RFI and becoming proactive is a plus.

73 de Brian/K3KO

On 10/25/2016 14:32 PM, Bill Frantz wrote:

> Before I bought my K3, I discussed the radio with someone in the booth
> at Radiofest, a small hamfest held near Monterey, CA. After I had
> learned a very little bit about the radio, I had my wife (KI6SLX), a
> retired QA engineer for Apple, discuss UI issues. When she said it
> seemed OK, I wrote a check.
>
> I like Brian's idea of simulating contest conditions to test receivers.
> Such a simulation would need to be reproducible and good enough that it
> can't be gamed. For testing CW reception, perhaps a fixed set of signals
> modulated through a very linear SSB modulator would work. That could
> give at least 2KHz of signals for the receiver to handle.
>
> The West Valley Amateur Radio Association field day operation sometimes
> has 3 signals active on one band (CW, digital, and SSB). We manage to
> get by running QRP with K3(S)s, KX3s, K2s and carefully placed antennas.
> For CQP, we managed to run two stations on a band at 100 watts with
> similar equipment and techniques.
>
> 73 Bill AE6JV
>
> On 10/25/16 at 5:45 AM, [hidden email] (brian) wrote:
>
>> I want to know how well a receiver is able to separate a weak signal
>> from strong signals 50-100 Hz away. It would be interesting to
>> speculate how such a measurement would be done. Let the RX use
>> whatever analog or digital tricks it can to achieve the above.
>>
>> Your idea of simulating a contest with a hundreds of signal injected
>> at various random frequencies to gauge RX performance has merit.
>>
>> Have you overlooked the MM, FD and DXpedition RX uses which in fact
>> push the dynamic range and mixing limits today? There are MM stations
>> which operate two transmitters on the same band.
>
> ---------------------------------------------------------------------------
> Bill Frantz | Re: Computer reliability, performance, and security:
> 408-356-8506 | The guy who *is* wearing a parachute is *not* the
> www.pwpconsult.com | first to reach the ground. - Terence Kelly
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Don Wilhelm

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by Bill Frantz

All,

While the suggestions of simulating contest conditions for testing may
have merit, I believe the existing tests demonstrate that the low phase
noise of the K3(S) allows you to 'saddle up' closer to an offending
station in a contest or DX Pileup. The 2kHz test results does indicate
that to me.

Just how much improvement is gained for each receiver is open to some
question, and depends on what tools are available and used. Certainly
the K3(S) APF function would be of help with its 30Hz peak, but if
testing is to be conducted using very closely spaced multiple signals,
then it would be necessary to specify which of the interference
abatement tools were used on each receiver. I doubt if Rob Sherwood
would want to buy into that form of testing, there are simply too many
variables in that all receivers do not have the same interference
fighting tools.

A long time ago, I built a receiver based generally on the HBR-16
design, except that it used a double-coupled 85kHz IF instead of the
100kHz IF. I added a Q-multiplier stage at 85kHz, and it was fantastic
at pulling a signal out from the 'mud'. I have no idea about the
dynamic range or the 2kHz test for it, but it was quite capable. The
K3(S) APF provides similar capability to the Q-multiplier of old.

73,
Don W3FPR

On 10/25/2016 10:32 AM, Bill Frantz wrote:
>
> I like Brian's idea of simulating contest conditions to test receivers.
> Such a simulation would need to be reproducible and good enough that it
> can't be gamed. For testing CW reception, perhaps a fixed set of signals
> modulated through a very linear SSB modulator would work. That could
> give at least 2KHz of signals for the receiver to handle.
>
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Bill Frantz

Re: [K3] The Way We Rank Receivers (long)

I assume that Don means a 30Hz wide peak below.

While I have found APF to be good for digging out weak CW
signals near the noise level, I have found a 50-100Hz bandwidth
works better when there are nearby strong signals. (I have the
250Hz crystal filter.) The K3 won't let me narrow the DSP filter
that much with APF on, probably for good reason. Am I missing a
way to use APF in these tight spaced conditions?

73 Bill AE6JV

On 10/25/16 at 8:31 AM, [hidden email] (Don Wilhelm) wrote:

>Just how much improvement is gained for each receiver is open
>to some question, and depends on what tools are available and
>used. Certainly the K3(S) APF function would be of help with
>its 30Hz peak, but if testing is to be conducted using very
>closely spaced multiple signals, then it would be necessary to
>specify which of the interference abatement tools were used on
>each receiver...

-------------------------------------------------------------------------
Bill Frantz | When it comes to the world | Periwinkle
(408)356-8506 | around us, is there any choice | 16345
Englewood Ave
www.pwpconsult.com | but to explore? - Lisa Randall | Los Gatos,
CA 95032

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Edward R Cole

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

Most of this very interesting post is not-relevant to my ham radio
operating (eme on VHF+).
Comments preceded by asterisk * inserted below:

---------------------------------------------------------
Date: Tue, 25 Oct 2016 05:21:20 +0000 (UTC)
From: Al Lorona <[hidden email]>
To: Elecraft Reflector <[hidden email]>
Subject: [Elecraft] [K3] The Way We Rank Receivers (long)

Receivers are always ranked by the "2 kHz third order dynamic range",
such as at:
http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do we
really grasp the meaning of these specs? For instance, the Elecraft
K3's (after synthesizer upgrade) number is 103 dB, good enough to be
in the top ten. In fact, this number is so strong that very few hams
will ever be affected by it. To the best of my knowledge, I have
*never* been close to running out of dynamic range. To understand
why, let's put "103 dB" into English.
===snip
I have assumed a noise floor or MDS of -130 dBm because it's a nice
round number. If your 20 meter noise floor is higher than this, then
the two signals would have to be *even stronger* to hear the intermod
come out of the noise.

*I wonder where in the world one sees a 20m noise floor that low when
antenna is connected? Only when I lived off the grid running on
battery power did I see S0 noise on my radio (3.9-KHz with TS180S
from a dipole). I doubt that radio had a noise floor that low, but
maybe. I see S3/5 noise on my K3 connected to triband yagi, preamp
off. That is probably about -110 to -100 dBm noise floor. My SDR-IQ
is very good at 28-MHz and displays -132 dBm without an antenna
connected (190-KHz bandwidth). But connecting an antenna raises that
instantly.
===snip
Perhaps it's time to rank receivers by a different measurement,
something that affects more of us. Looking through the table at the
link above we see another measurement called "2 kHz blocking gain
compression" and for the same K3 it is 143 dB. This is a measurement
not of two interfering signals, but a single interferer just 2 kHz away.

*I can only think of two instances seeing such a strong adjacent signal:
1) At 310-KHz a GPS-reference station is locate less than a mile
away and I measure it at -30 dBm on my inverted-L (tuned to 490-KHz)
with SDR-IQ.
2) I once measured a high power pager running 158.100 100-foot away
from my company's 161.325 repeater showing 1/4w on the Bird power
meter installed on the repeater antenna whenever the pager
transmitted (repeater was turned off). That would be +23
dBm. Amazingly the repeater Rx survived this (due to duplexer and
helicoil prefilter). IMD mixing of the 158.1+161.325 produced a
horrendous signal on 156.450 (which interfered marine ch.9).
Both examples extremely unlikely to occur for HF hams.
===snip
Finally, we notice a measurement called "2 kHz reciprocal mixing
dynamic range" -- probably the limiting spec nowadays for top tier
receivers. In our example of the single strong signal, way before
reducing the gain of the receiver, that signal will have another
effect: it will mix with the phase noise of the K3's own local
oscillator and deposit that phase noise right onto your desired
frequency of 14.050 MHz.

*this has application for me. The occurrence of a high power signal
off frequency mixing with the phase noise of my eme Rx. This is one
of the reasons driving a goal for extremely low LO phase noise in eme
systems. This is one of the major selling points for me to purchase
my K3 and upgrade synthesizers.

===snipped the rest (though very interesting proposal)

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Bill Frantz

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

OK, I can't resist. I turned on my KX3 at about 0018z on Oct 26.
It was set up for 20M PSK tuned to 14.070 with a DSP bandwidth
of 2.5KHz. I showed one bar (S1) of S meter with occasional
flashing of the second bar (S3). The preamp was off and it was
in DATA A mode. The antenna is a 2 element wire beam at about 20
feet. There were no obvious signals on the PX3 -- the band was closed.

I am at the family house in Peterborough NH, about 1.5 miles
from the village and some 500-1000 feet from the nearest other
houses. We do have some CFL and LED bulbs in the house, some of
which are turned on.

73 Bill AE6JV

On 10/25/16 at 2:43 PM, [hidden email] (Walter Underwood) wrote:

>Good point. Looking at the photo of my KX3 on top of Mount
>Willson in Henry Coe, I see two bars on the S-meter on 20
>meters. That is miles from Silicon Valley. It was quiet and
>lovely, I could hear everybody. The filters were wide open,
>preamp on, and NR off. Zoom in and you can see for yourself.

---------------------------------------------------------------------------
Bill Frantz |"After all, if the conventional wisdom was
working, the
408-356-8506 | rate of systems being compromised would be
going down,
www.pwpconsult.com | wouldn't it?" -- Marcus Ranum

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David Woolley (E.L)

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by briancom

The main commercial interests in subjective audio noise reduction,
particularly for speech, are probably the hearing aid industry.

It is subjective because noise reduction only really removes noise that
isn't interfering. That is still useful, as whilst the human brain can
also do that, it gets tired in the process.

On 25/10/16 16:13, brian wrote:

> This would be tough since the world of RFI sources is huge. It would
> take some real effort to quantify the world of noise sources and their
> signatures and then find some algorithms to deal with them. Impossible?
> The world of big data isn't so big any more. Such an catalog might be
> doable. Algorithms are another issue. My hope is that NR/NB could be
> made adaptive to recognize the signature(s) and generate appropriate
> algorithms on the fly.
>
> There are a lot of smart people out there who could perhaps address
> these issues. Unfortunately commercial interests have to see some
> payoff. They haven't as of yet. The fact that AM broadcasters are
> being burned by RFI and becoming proactive is a plus.

Lewis Phelps

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

Al, thanks for a very informative and helpful discussion. This sort of posting is what makes the Elecraft listserv so valuable.

Lew N6LEW

> On Oct 24, 2016, at 10:21 PM, Al Lorona <[hidden email]> wrote:
>
> Receivers are always ranked by the "2 kHz third order dynamic range", such as at: http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do we really grasp the meaning of these specs? For instance, the Elecraft K3's (after synthesizer upgrade) number is 103 dB, good enough to be in the top ten. In fact, this number is so strong that very few hams will ever be affected by it. To the best of my knowledge, I have *never* been close to running out of dynamic range. To understand why, let's put "103 dB" into English.
>
> Let's say you're on 20 meter CW, operating at 14.050 MHz. You're listening through your fine Elecraft 500 Hz crystal filter when suddenly, and by incredible coincidence, two equally strong 49 dB over S9 signals begin transmitting at the exact same time, one on 14.052 and the other at 14.054 MHz, exactly 2 kHz and 4 kHz up from where you're listening. With the preamp off (which is totally believeable on 20 meters with a decent antenna) you will just barely hear a "ghost signal" right at the noise level... if you notice it at all. That "ghost" signal is the two-tone, 3rd order intermod product generated in the K3 receiver by those two hugely strong and perfectly placed signals.
>
> Not a very likely scenario, but that's what 103 dB of dynamic range buys you.
>
> I have assumed a noise floor or MDS of -130 dBm because it's a nice round number. If your 20 meter noise floor is higher than this, then the two signals would have to be *even stronger* to hear the intermod come out of the noise.
>
> Even if each of those interferers was *60* dB over S9 -- pegging the S-meter-- the intermod product on 14.050 would still be only S5. Amazing. This kind of performance begs the question, "How much more dynamic range is really needed?" and some (like Rob Sherwood) have said that once you're above 90 dB, you already have enough, at HF at least.
>
> Perhaps it's time to rank receivers by a different measurement, something that affects more of us. Looking through the table at the link above we see another measurement called "2 kHz blocking gain compression" and for the same K3 it is 143 dB. This is a measurement not of two interfering signals, but a single interferer just 2 kHz away. Since there's only one signal, it won't generate a "ghost", but it will reduce the gain of the receiver. ARRL defines this as the signal level that reduces the gain by 1 dB. One dB is really small, something like changing your RF Gain knob from the 3:00 o'clock position to maybe the 2:45 o'clock position. Barely noticeable. Nonetheless, for our K3 the signal required to do this is about +13 dBm, or 20 milliwatts, which is probably near the damage level of the receiver! (I'm quite sure that Wayne has made intercontinental QSOs at 20 mW.) It's a theoretical value that very, very few hams would ever encounter... only the ones living next door

Gary Gregory-2

Re: [K3] The Way We Rank Receivers (long)

What he said....
Has got me rethinking my approach somewhat.
I still believe I have the optimum transceiver (k3) available given I will
never rely on software to control my dx chasing.
Gary

On Oct 28, 2016 05:55, "Lewis Phelps" <[hidden email]> wrote:

Al, thanks for a very informative and helpful discussion. This sort of
posting is what makes the Elecraft listserv so valuable.

Lew N6LEW

> On Oct 24, 2016, at 10:21 PM, Al Lorona <[hidden email]> wrote:
>
> Receivers are always ranked by the "2 kHz third order dynamic range",
such as at: http://www.remeeus.eu/hamradio/pa1hr/productreview.pdf but do
we really grasp the meaning of these specs? For instance, the Elecraft K3's
(after synthesizer upgrade) number is 103 dB, good enough to be in the top
ten. In fact, this number is so strong that very few hams will ever be
affected by it. To the best of my knowledge, I have *never* been close to
running out of dynamic range. To understand why, let's put "103 dB" into
English.
>
> Let's say you're on 20 meter CW, operating at 14.050 MHz. You're
listening through your fine Elecraft 500 Hz crystal filter when suddenly,
and by incredible coincidence, two equally strong 49 dB over S9 signals
begin transmitting at the exact same time, one on 14.052 and the other at
14.054 MHz, exactly 2 kHz and 4 kHz up from where you're listening. With
the preamp off (which is totally believeable on 20 meters with a decent
antenna) you will just barely hear a "ghost signal" right at the noise
level... if you notice it at all. That "ghost" signal is the two-tone, 3rd
order intermod product generated in the K3 receiver by those two hugely
strong and perfectly placed signals.
>
> Not a very likely scenario, but that's what 103 dB of dynamic range buys
you.
>
> I have assumed a noise floor or MDS of -130 dBm because it's a nice round
number. If your 20 meter noise floor is higher than this, then the two
signals would have to be *even stronger* to hear the intermod come out of
the noise.
>
> Even if each of those interferers was *60* dB over S9 -- pegging the
S-meter-- the intermod product on 14.050 would still be only S5. Amazing.
This kind of performance begs the question, "How much more dynamic range is
really needed?" and some (like Rob Sherwood) have said that once you're
above 90 dB, you already have enough, at HF at least.
>
> Perhaps it's time to rank receivers by a different measurement, something
that affects more of us. Looking through the table at the link above we see
another measurement called "2 kHz blocking gain compression" and for the
same K3 it is 143 dB. This is a measurement not of two interfering signals,
but a single interferer just 2 kHz away. Since there's only one signal, it
won't generate a "ghost", but it will reduce the gain of the receiver. ARRL
defines this as the signal level that reduces the gain by 1 dB. One dB is
really small, something like changing your RF Gain knob from the 3:00
o'clock position to maybe the 2:45 o'clock position. Barely noticeable.
Nonetheless, for our K3 the signal required to do this is about +13 dBm, or
20 milliwatts, which is probably near the damage level of the receiver!
(I'm quite sure that Wayne has made intercontinental QSOs at 20 mW.) It's a
theoretical value that very, very few hams would ever encounter... only the
ones living next door
to
> a guy running a kilowatt. So this measurement is even less relevant to
us.
>
> Finally, we notice a measurement called "2 kHz reciprocal mixing dynamic
range" -- probably the limiting spec nowadays for top tier receivers. In
our example of the single strong signal, way before reducing the gain of
the receiver, that signal will have another effect: it will mix with the
phase noise of the K3's own local oscillator and deposit that phase noise
right onto your desired frequency of 14.050 MHz. As you're listening there,
you suddenly notice that the noise floor seems to be rising for no apparent
reason. You listen some more, and notice that the noise is following some
kind of CW keying. You glance at your panadapter and notice an enormous
signal just 2 kHz away on 14.052. So there are two culprits: that strong
signal, and the K3 oscillator phase noise. The K3 with upgraded synths has
a spec of "-115 dBc", again near the top of the list, which means that a
signal 2 kHz away and 115 dB above the noise floor will cause the noise
floor to rise by 3 dB. For a K3
n
> oise floor of -130 dBm this is -15 dBm, or about 60 dB over S9. The
reason I say this is the limiting factor is because the chance of just one
60 dB over S9 signal nearby is greater than *two* of them at the right
spacing as in our discussion of 3rd order DR.
>
> For these reasons, we could start ranking receivers by 2 kHz reciprocal
mixing dynamic range because reciprocal mixing is far more likely to happen
to a larger number of hams. It's not a catastrophic effect, but it's quite
noticeable. There's a problem, however, because sampling receivers don't
follow the classical reciprocal mixing model. We need a measurement that
hasn't been invented yet to compare modern receivers. Maybe we could
simulate the worst-case contest by applying thousands of signals and noise
to the receiver and seeing how much junk is generated to cover up the
signal you're trying to copy at 14.050, something kinda like the noise
power ratio test. But in order to compare apples to apples, the exact same
test conditions must be used on every receiver, regardless of architecture.
>
> Finally, the general unlikelihood of any of these conditions occurring
also convinces me that other ergonomic factors -- not necessarily
measureable-- should be considered when choosing a receiver. 'Usability'
(whatever that means to you) is underrated. So is 'listenability' -- again,
a very subjective term. For instance, I have come to believe that the AGC
system in a receiver has everything to do with how it "sounds" and explains
why receivers with similar specs can sound so different from each other.
This area needs further study.
>
> I hope that this helped turn mere numbers into an actual operating
reality.

>
> Al W6LX
> ______________________________________________________________
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>
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>

Lew Phelps N6LEW
Pasadena, CA DM04wd
Elecraft K3-10 / KXV144 / XV432
Yaesu FT-7800
[hidden email]
www.n6lew.us

Generalized Law of Entropy: Sooner or later, everything that has been put
together will fall apart.

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Edward R Cole

Re: [K3] The Way We Rank Receivers (long)

In reply to this post by alorona

Walter,

Have to chuckle - "ask what one thought would be rhetorical question"
and some one gives you an answer!

Well, if you can get away from modern civilization and run without ac
power low noise conditions can be found.
My KX3 is out mounted in my truck so don't have it to test. I did
turn on my K3 connected to triband yagi and am seeing S5 noise
"floor" where there are no signals (preamp off). Checking 6m I also
see S5 but this is pointed at a local noise source and with ext
Gasfet preamp on. If I turn the 6-element yagi 90-degrees the noise
level drops to as low as S3 with preamp on (K3 needs some kind of
preamp when using 6m). I also have the PR6-10 which I use on HF or
6m if I turn on DIGOUT-1 which energizes the PR6-10 and disconnects
the ext preamp. It shows about one s-unit lower noise due to less
gain than the Gasfet.

But with "two bars" if you actually measured noise power it would
probably still be about -120 dBm or higher. Still on HF that is *quiet*.

73, Ed - KL7UW

From: Walter Underwood <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] [K3] The Way We Rank Receivers (long)

> On Oct 25, 2016, at 2:31 PM, Edward R Cole <[hidden email]> wrote:
>
> I wonder where in the world one sees a 20m noise floor that low
when antenna is connected? Only when I lived off the grid running on
battery power did I see S0 noise on my radio (3.9-KHz with TS180S
from a dipole).

Good point. Looking at the photo of my KX3 on top of Mount Willson in
Henry Coe, I see two bars on the S-meter on 20 meters. That is miles
from Silicon Valley. It was quiet and lovely, I could hear everybody.
The filters were wide open, preamp on, and NR off. Zoom in and you
can see for yourself.

https://www.flickr.com/photos/walter_underwood/17417496311/in/album-72157652448882921/
<https://www.flickr.com/photos/walter_underwood/17417496311/in/album-72157652448882921/>

wunder
K6WRU
Walter Underwood
CM87wj
http://observer.wunderwood.org/ (my blog)

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

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Tony Estep

Re: [K3] The Way We Rank Receivers (long)

On Thu, Oct 27, 2016 at 8:31 PM, Walter Underwood <[hidden email]>
wrote:

> ...S2 noise was silent, even on a wilderness peak....
>
===========
Nothing new. John Keats noted this in 1816, when he and his fellow SOTA ops:
"...looked at each other in wild surmise,
Silent upon a peak in Darien."

Tony KT0NY
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