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K3 to IC-7800 Comparison?

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Jim Bolit

Re: K3 to IC-7800 Comparison?

Adam,
You are digging a deeper hole...........
JimW6AIM

.

-------- Original message --------
From: Adam Farson <[hidden email]>
Date: 9/14/2015 6:48 PM (GMT-06:00)
To: [hidden email]
Cc: Elecraft List <[hidden email]>
Subject: [Elecraft] K3 to IC-7800 Comparison?

Hi Jim,

To quote:

"If the test is designed to show response of the receiver to a lot of strong
signals such as are present in a contesting or DX pileup environment, or as
are present in a multi-transmitter site, the signal level should be
consistent with that environment, NOT with the design of the receiver."

My explanation of the optimum noise loading point was intended to clarify
the test procedure. As it happens, the optimum noise loading point for an
ADC is also the clipping point, which is the limiting case for a
direct-sampling receiver with an ADC at RF.

I state clearly in my test reports for direct-sampling SDR's that I am
testing NPR just below the clip point. This hard limit dictates the maximum
aggregate signal power at which the receiver can still be expected to
demodulate signals correctly (assuming no attenuation is inserted ahead of
the ADC). I cannot perform the test above ADC clipping, as it will then
yield no usable results. In practice, some attenuation can often be inserted
to extend the upper power limit of the ADC, especially on the lower HF bands
where the band noise level is usually several dB above the receiver's noise
floor.

I have applied noise loading levels as high as -1 to 0 dBm when testing some
direct-sampling SDR receivers. This is equivalent to approx. 1000 contiguous
SSB voice channels, all transmitting simultaneously at S9 + 40 dB each.

In the final analysis, it is up to the radio buyer to decide whether or not
a direct-sampling SDR can handle his chosen operating environment.

73, Adam VA7OJ/AB4OJ

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Wes (N7WS)

Re: K3 to IC-7800 Comparison?

Seems to me that he's just trying to explain himself.

On 9/15/2015 6:04 AM, Jim Bolit wrote:

> Adam,
> You are digging a deeper hole...........
> JimW6AIM
>
> .
>
> -------- Original message --------
> From: Adam Farson <[hidden email]>
> Date: 9/14/2015 6:48 PM (GMT-06:00)
> To: [hidden email]
> Cc: Elecraft List <[hidden email]>
> Subject: [Elecraft] K3 to IC-7800 Comparison?
>
> Hi Jim,
>
>
>
> To quote:
>
>
>
> "If the test is designed to show response of the receiver to a lot of strong
> signals such as are present in a contesting or DX pileup environment, or as
> are present in a multi-transmitter site, the signal level should be
> consistent with that environment, NOT with the design of the receiver."
>
>
>
> My explanation of the optimum noise loading point was intended to clarify
> the test procedure. As it happens, the optimum noise loading point for an
> ADC is also the clipping point, which is the limiting case for a
> direct-sampling receiver with an ADC at RF.
>
>
>
> I state clearly in my test reports for direct-sampling SDR's that I am
> testing NPR just below the clip point. This hard limit dictates the maximum
> aggregate signal power at which the receiver can still be expected to
> demodulate signals correctly (assuming no attenuation is inserted ahead of
> the ADC). I cannot perform the test above ADC clipping, as it will then
> yield no usable results. In practice, some attenuation can often be inserted
> to extend the upper power limit of the ADC, especially on the lower HF bands
> where the band noise level is usually several dB above the receiver's noise
> floor.
>
>
>
> I have applied noise loading levels as high as -1 to 0 dBm when testing some
> direct-sampling SDR receivers. This is equivalent to approx. 1000 contiguous
> SSB voice channels, all transmitting simultaneously at S9 + 40 dB each.
>
>
>
> In the final analysis, it is up to the radio buyer to decide whether or not
> a direct-sampling SDR can handle his chosen operating environment.
>
>
>
> 73, Adam VA7OJ/AB4OJ
>
>
>

Adam Farson

Re: K3 to IC-7800 Comparison?

In reply to this post by Jim Bolit

Hi Jim,

2.7 kHz 5-pole. I have added this information to my chart.

73, Adam VA7OJ/AB4OJ

From: Jim Bolit [mailto:[hidden email]]
Sent: 15-Sep-15 05:13
To: Adam Farson; 'Johnny Siu'
Cc: Elecraft List
Subject: RE: [Elecraft] K3 to IC-7800 Comparison?

Adam,

Please confirm what roofing filter was used for your test on the K3.

Tnx

Jim

W6AIM

.

-------- Original message --------
From: Adam Farson <[hidden email]>
Date: 9/14/2015 3:14 AM (GMT-06:00)
To: 'Johnny Siu' <[hidden email]>
Cc: Elecraft List <[hidden email]>
Subject: Re: [Elecraft] K3 to IC-7800 Comparison?

Hi Johnny,

The K3 with the KSYN3A is in a closely-packed cluster of radios which score highest in the NPR test. Its exact ranking depends on which test frequency is being compared. The differences are very slight, mostly within a couple of dB.

In practice, I regard an NPR value of 80 dB or higher as excellent.

73, Adam VA7OJ/AB4OJ

From: Johnny Siu [mailto:[hidden email]]
Sent: 14-Sep-15 00:54
To: Adam Farson; Elecraft List
Subject: K3 to IC-7800 Comparison?

Hello Adam,

From reading of your NPR chart, could I understand that apart from IC7851, the K3 (with new KSYN3A installed) is the second best in terms of NPR test?

73

Johnny VR2XMC

_____

寄件人︰ Adam Farson <[hidden email]>
收件人︰ Elecraft List <[hidden email]>
傳送日期︰ 2015年09月14日 (週一) 2:51 PM
主題︰ Re: [Elecraft] K3 to IC-7800 Comparison?

For Jim K9YC:

Hi Jim,

Many thanks for the post on my presentations at the club meeting on Saturday
September 5.

To quote:

"There's an important caveat to his work. The NPR measurements require

very sophisticated band-stop filters in his instrumentation setup, and

based on the filters he has been able to source, that limits the

frequency range where he can do his measurements. An example is in the

footnote for the Flex-6700, which has no preselector for the range where

he had to do his measurements, which may have caused that radio to

measure worse than it would on the ham bands."

The instrumentation I use for NPR testing is re-purposed telecom test
equipment, as described in my Web article and also in my article in QEX for
March/April 2015. I rely on the surplus market for the test sets, and also
for the filter pairs (bandstop and bandpass). The bandstop filters typically
have 95 dB stopband attenuation and ~ 3 kHz stopband width.

A number of these filters are on (or near) amateur bands, e.g. 1940, 3886,
5340, 7600 and 11700 kHz. The first filter pair I acquired was on 5340 kHz,
so all the test data in my web article are on this frequency (which is in
the 60m band). The Flex-6700 does not have a preselector for this band, so
the noise loading will hit the front end and the ADC harder. This will
degrade the NPR reading by a few dB, but it will show how the receiver
behaves if heavily loaded on a band for which no preselector is fitted.

As I picked up additional filters, the number of frequencies on which I run
the test has steadily increased. Links to multi-frequency NPR data for
various radios (including the K3 with KSYN3A) are on my website:

http://www.ab4oj.com/test/main.html#NPR <http://www.ab4oj.com/test/main.html#NPR>

It was a pleasure meeting you guys over the Labour Day weekend.

73, Adam VA7OJ/AB4OJ

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Jim Bolit

Re: K3 to IC-7800 Comparison?

In reply to this post by W5GAI

Tnx

Jim
W6AIM

-------- Original message --------
From: Adam Farson <[hidden email]>
Date: 9/15/2015 11:03 AM (GMT-06:00)
To: 'Jim Bolit' <[hidden email]>
Cc: 'Johnny Siu' <[hidden email]>, Elecraft List <[hidden email]>
Subject: RE: [Elecraft] K3 to IC-7800 Comparison?

Hi Jim,

2.7 kHz 5-pole. I have added this information to my chart.

73, Adam VA7OJ/AB4OJ

From: Jim Bolit [mailto:[hidden email]]
Sent: 15-Sep-15 05:13
To: Adam Farson; 'Johnny Siu'
Cc: Elecraft List
Subject: RE: [Elecraft] K3 to IC-7800 Comparison?

Adam,

Please confirm what roofing filter was used for your test on the K3.

Tnx

Jim

W6AIM

.

-------- Original message --------
From: Adam Farson <[hidden email]>
Date: 9/14/2015 3:14 AM (GMT-06:00)
To: 'Johnny Siu' <[hidden email]>
Cc: Elecraft List <[hidden email]>
Subject: Re: [Elecraft] K3 to IC-7800 Comparison?

Hi Johnny,

The K3 with the KSYN3A is in a closely-packed cluster of radios which score highest in the NPR test. Its exact ranking depends on which test frequency is being compared. The differences are very slight, mostly within a couple of dB.

In practice, I regard an NPR value of 80 dB or higher as excellent.

73, Adam VA7OJ/AB4OJ

From: Johnny Siu [mailto:[hidden email]]
Sent: 14-Sep-15 00:54
To: Adam Farson; Elecraft List
Subject: K3 to IC-7800 Comparison?

Hello Adam,

From reading of your NPR chart, could I understand that apart from IC7851, the K3 (with new KSYN3A installed) is the second best in terms of NPR test?

73

Johnny VR2XMC

_____

寄件人︰ Adam Farson <[hidden email]>
收件人︰ Elecraft List <[hidden email]>
傳送日期︰ 2015年09月14日 (週一) 2:51 PM
主題︰ Re: [Elecraft] K3 to IC-7800 Comparison?

For Jim K9YC:

Hi Jim,

Many thanks for the post on my presentations at the club meeting on Saturday
September 5.

To quote:

"There's an important caveat to his work. The NPR measurements require

very sophisticated band-stop filters in his instrumentation setup, and

based on the filters he has been able to source, that limits the

frequency range where he can do his measurements. An example is in the

footnote for the Flex-6700, which has no preselector for the range where

he had to do his measurements, which may have caused that radio to

measure worse than it would on the ham bands."

The instrumentation I use for NPR testing is re-purposed telecom test
equipment, as described in my Web article and also in my article in QEX for
March/April 2015. I rely on the surplus market for the test sets, and also
for the filter pairs (bandstop and bandpass). The bandstop filters typically
have 95 dB stopband attenuation and ~ 3 kHz stopband width.

A number of these filters are on (or near) amateur bands, e.g. 1940, 3886,
5340, 7600 and 11700 kHz. The first filter pair I acquired was on 5340 kHz,
so all the test data in my web article are on this frequency (which is in
the 60m band). The Flex-6700 does not have a preselector for this band, so
the noise loading will hit the front end and the ADC harder. This will
degrade the NPR reading by a few dB, but it will show how the receiver
behaves if heavily loaded on a band for which no preselector is fitted.

As I picked up additional filters, the number of frequencies on which I run
the test has steadily increased. Links to multi-frequency NPR data for
various radios (including the K3 with KSYN3A) are on my website:

http://www.ab4oj.com/test/main.html#NPR <http://www.ab4oj.com/test/main.html#NPR>

It was a pleasure meeting you guys over the Labour Day weekend.

73, Adam VA7OJ/AB4OJ

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Jim Brown-10

Re: K3 to IC-7800 Comparison?

In reply to this post by Wes (N7WS)

On Tue,9/15/2015 7:10 AM, Wes (N7WS) wrote:
> Seems to me that he's just trying to explain himself.

Yes, but in doing so, he's making it clear that his work does not
contribute useful information to a ham trying to evaluate the relative
performance of radios in a strong signal environment, AND that's what
the measurement is designed to show -- IF the same level of test signal
is applied to all of the radios.

For me, primarily a contester, secondarily a DXer, the primary factors
in choosing a radio are performance in a strong signal environment, a
clean TX signal, and a very efficient user interface. After hearing Adam
speak, I had hoped that his work would contribute to that process, but
because the level of his excitation varies depending on the shortcomings
of the radio, it fails to provide useful information.

To clarify -- the strong signal performance and dynamic range of SDRs is
limited by the total voltage at the input to the digital system. If
there is no input filtering (i.e., a preselector, bandpass filter, or
hardware attenuator), the digital system sees the broadband spectrum
from whatever antenna drives it. That's everything from DC to daylight
-- AM broadcast, all the other ham bands, shortwave broadcast, all other
users of the spectrum. It is the SUM of all of those signals that
combine to overload the digital system. When that combined signal level
hits digital clip (all bits are digital zero), the radio stops working.

It is, of course, possible for the user to add bandpass filters outboard
to the radio, and many contesters with SO2R and multi-transmitter
stations do so. This would, indeed, significantly reduce the input to
the digital system to inband signals. BUT -- SO2R and multi-transmitter
stations with closely spaced antennas could still overload the digital
system even with that filtering.

And there's still in-band QRM to get you to digital clip -- a ham a
block or two away running power amp, or a mile away with his antenna
pointed at you, and the sum of all the in-band signals during a major
contest. In EU and AS, there are big broadcast signals in parts of the
40M band that are going to sail right through the world's best
preselector or bandpass filter without attenuation.

My neighbor W6DRX (0.3 miles from me and an active contester) and I both
bought K3s as soon as the radio was announced because we realized that
it was the only way we could coexist and remain friends. :)

73, Jim K9YC
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WA2SI

Re: K3 to IC-7800 Comparison?

Wayne and/or Eric,

Please do NOT shut this thread down. There is so much useful and interesting information being shared. Please let the censorship curmudgeons utilize the Del key. Thank you. Take care es...

Vy 73 de Bert
WA2SI

Sent from my android device.
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Wes (N7WS)

Re: K3 to IC-7800 Comparison?

In reply to this post by Jim Brown-10

I was responding to the comment that you "thoughtfully" deleted so you could go
on with your critique.

I know it's hard for some people to believe, but some of us in the unwashed
masses are actually capable of deciding what is "useful" to us in our own
situations.
.

On 9/15/2015 9:50 AM, Jim Brown wrote:

> On Tue,9/15/2015 7:10 AM, Wes (N7WS) wrote:
>> Seems to me that he's just trying to explain himself.
>
> Yes, but in doing so, he's making it clear that his work does not contribute
> useful information to a ham trying to evaluate the relative performance of
> radios in a strong signal environment, AND that's what the measurement is
> designed to show -- IF the same level of test signal is applied to all of the
> radios.
>
> For me, primarily a contester, secondarily a DXer, the primary factors in
> choosing a radio are performance in a strong signal environment, a clean TX
> signal, and a very efficient user interface. After hearing Adam speak, I had
> hoped that his work would contribute to that process, but because the level of
> his excitation varies depending on the shortcomings of the radio, it fails to
> provide useful information.
>
> To clarify -- the strong signal performance and dynamic range of SDRs is
> limited by the total voltage at the input to the digital system. If there is
> no input filtering (i.e., a preselector, bandpass filter, or hardware
> attenuator), the digital system sees the broadband spectrum from whatever
> antenna drives it. That's everything from DC to daylight -- AM broadcast, all
> the other ham bands, shortwave broadcast, all other users of the spectrum. It
> is the SUM of all of those signals that combine to overload the digital
> system. When that combined signal level hits digital clip (all bits are
> digital zero), the radio stops working.
>
> It is, of course, possible for the user to add bandpass filters outboard to
> the radio, and many contesters with SO2R and multi-transmitter stations do so.
> This would, indeed, significantly reduce the input to the digital system to
> inband signals. BUT -- SO2R and multi-transmitter stations with closely spaced
> antennas could still overload the digital system even with that filtering.
>
> And there's still in-band QRM to get you to digital clip -- a ham a block or
> two away running power amp, or a mile away with his antenna pointed at you,
> and the sum of all the in-band signals during a major contest. In EU and AS,
> there are big broadcast signals in parts of the 40M band that are going to
> sail right through the world's best preselector or bandpass filter without
> attenuation.
>
> My neighbor W6DRX (0.3 miles from me and an active contester) and I both
> bought K3s as soon as the radio was announced because we realized that it was
> the only way we could coexist and remain friends. :)
>
> 73, Jim K9YC
> ______________________________________________________________

Guy Olinger K2AV

Re: K3 to IC-7800 Comparison?

In reply to this post by Wes (N7WS)

On Tue, Sep 15, 2015 at 10:10 AM, Wes (N7WS) <[hidden email]> wrote:

> Seems to me that he's just trying to explain himself.
>

And in explaining, he actually highlights the issues that clearly
contradict his position. With all due respect...

Personally I have a problem with handicapping or dumbing down measurements
just so they fly under a known weakness of certain classes of SDR. That
turns the measurements into a perverse "radio Special Olympics" designed to
not embarrass handicapped radios. Either the radio can stand the mustard at
the high levels with all the rest of the radios or they can't. An RX
hitting a wall at a given point because there is now A/D clipping, or for
any other reason, is a valid should-be-reported characteristic of the RX.
Put it out there like that. No problem with putting down the number and
adding why. Just don't tell why and then NOT tell the number by burying
that decision in "adjusted" testing parameters.

Not every one has to put up with the kind of signal levels found at
multi/multi contest stations or with the overload from monster HF antennas
or a naval ship-to-shore station with Godzilla transmitters in the area or
other hams effectively next door. Some in common-enough better
circumstances will have an absolute wonderful time with less than a
top-of-the-list radio, even if there is a 10 dB weakness on some
measurement. Put it out there and let people chose. They can read the
numbers for themselves and figure out what they mean for themselves. Then
the sales receipts can inform companies if they need to kick their research
and engineering departments to make some improvements.

People who want the radio with the top specs (whether they actually NEED
that or not is a separate issue) are going to be very suspicious of
dumbed-down measurements. And once the word on dumbing-down is out, it's
out, no recalling.

Just tell it like it is, no pulling of punches. Tough tests are what
improve the craft. For technical reasons, Elecraft is the best thing to
happen to ham radio's radios in quite a while, and that's *all* brands I'm
talking about. Nothing like getting your b*tt whupped in the market place
or high-profile contest arenas to tell you it's time to invest in some
improvements that clearly a very big crowd cares about.

A test designed to make everyone feel good about what they bought is like
T-ball for the tots. T-ball is really great for the little kids. Love to
watch 'em. But the top of the Sherwood list is the major leagues. There are
those that will make the "post-season" and those that will go home. In the
playoffs you make the pitches, you make the plays, you get the hits, or you
go home. No underhand pitches because the batter is hurt and can't swing
hard.

73, Guy

>
> On 9/15/2015 6:04 AM, Jim Bolit wrote:
>
>> Adam,
>> You are digging a deeper hole...........
>> JimW6AIM
>>
>
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Eric Swartz - WA6HHQ

Re: K3 to IC-7800 Comparison?

Administrator

In reply to this post by Jim Bolit

Guys - please keep it civil.

Eric
Moderator etc.
/elecraft.com/

On 9/15/2015 6:04 AM, Jim Bolit wrote:
> Adam,
> You are digging a deeper hole...........
> JimW6AIM
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Re: K3 RX in real world

In reply to this post by Lu Romero - W4LT

I held this for three days deciding whether to send it or not – here ‘tis.

I went from TT Orion - 3 of them at various times - to K3 . I was more than a little concerned by size and Hold/Tap functions etc - I read all the stuff from Sherwood ,keep reading stories here about KSYN3A wonders.

Here is my take - I live in a hot bed of BIG time DXers and contesters - it takes quite a receiver to hold up when they all get going .I need a rig I can use when they are on.

One guy about 4 miles away has K3/ALPHA8410 - and puts a measured 75 millivolts into the K3 ant jack on 160. I can copy and work weak DX with a 2khz split – (250hz 8pole) I kind of know he is there ,(no doubt about it looking at P3) but stuff is copyable. (I can see his carrier on a scope on my antenna input , that’s something like S9+65dB)

Another guy about 2 miles farther away has a bit better TX antenna and is usually within plus/minus 1 dB of the closer guy – but he is painful +/- 15 khz- and 30 dB of external pad does not make it go away. Its NOT my K3 RX. (he DID find an arcing filter last year that was making him +/- 50 khz or worse )

I do really wonder what I would notice with KSYN3As on my main /sub rx - I live in a “field of RF noise” even before the big guns. I DO really like both main and sub rx now truly being fed by same LO.

So I am a happy camper PLUS Elecraft support has been BEYOND superb – I have found no-one to begin to compare. I could go on with a page of my experiences with other vendors.

My K3 “feels” smooth to me – every bit as “smooth” as the Orions were -

Just hope Elecraft lasts longer than I do !!!! Ham for 64 years – the K3 / P3 / KAT500 / KPA500 is such a SWEET combo.

73 Hank K7HP

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Jim Brown-10

Re: K3 to IC-7800 Comparison?

In reply to this post by Wes (N7WS)

On Tue,9/15/2015 10:36 AM, Wes (N7WS) wrote:
> I was responding to the comment that you "thoughtfully" deleted so you
> could go on with your critique.

I always try to trim what I'm replying to without losing meaning.

> I know it's hard for some people to believe, but some of us in the
> unwashed masses

You're hardly one of the unwashed masses, Wes. :) As it happens, while
looking for something else, I just came across your excellent piece in
ARRL Antenna Compendium #6 about loss in window line. I'd read and
appreciated it years ago, but didn't remember that it was your work.

> are actually capable of deciding what is "useful" to us in our own
> situations.

Of course. I articulated my priorities so that readers might evaluate my
concern with the strong signal handling issue and user interface. A more
casual operator might place a far lower priority on those factors, and
as a result be quite happy with an SDR.

When I take the time to write an explanation of concepts, it's directed
at those who are less technical, with the intent of helping them develop
a BS filter, or to generally expand their knowledge. Others have done
that for me. A few who come to mind are you, Adam, W4TV, K2AV, N0AX,
W8JI, and Wayne. Only last week, W8JI took the time to go through this
same issue of front end overload in the context of a preamp. Don't
recall whether it was on Tower Talk or Topband.

73, Jim K9YC
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Jim Brown-10

Re: K3 RX in real world

In reply to this post by HP

On Tue,9/15/2015 11:35 AM, Hank P wrote:
> I do really wonder what I would notice with KSYN3As on my main /sub rx - I live in a “field of RF noise” even before the big guns. I DO really like both main and sub rx now truly being fed by same LO.

It won't help a bit when the other guy(s) are dirty, putting trash in
your IF passband (that is, what your BW is set to), but it can help a
lot with strong signals outside that passband.

73, Jim K9YC
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alorona

Analog vs. Digital Front Ends

In reply to this post by Jim Brown-10

Adam Farson's explanation of why the ADC clipping level has to be avoided at all costs is another reason why many people still prefer analog front ends.

Don't proponents of analog audio point out that when an analog channel overloads, it does so "gracefully"? This is especially true of fans of vacuum tube audio. You can actually tolerate some clipping, as long as it doesn't occur that often. All it does is make the audio sound a little raspier every once in a while, but you can still derive relatively uninterrupted pleasure from, say, the Salzburg recital of Grigory Sokolov playing Rameau's 'Les Sauvages'.

This is as opposed to a digital audio system where you can't even tolerate a *single* overload event. Clipping in a digital system is catastrophic and highly disruptive... the audio goes away entirely or becomes so severely distorted that you can't tell if it's Rameau's section in Bb major or the lovely chromatic passage in the turnaround.

Similarly, a receiver with an analog front end degrades gracefully. You might get intermod, but you'll probably still be able to copy because intermod simply sounds like more QRM. It's not a sudden collapse. But an all-digital front end is always in danger of failure in a very disturbing way right when it matters most.

Al W6LX
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Lynn W. Taylor, WB6UUT

Re: Analog vs. Digital Front Ends

Maybe I'm wrong, but if the thing we're testing is supposed to be a
radio, and we want to compare how radios work under conditions we'd
encounter in actual use, it just seems intuitively obvious to the most
casual observer that the tests should be the same.

73 -- Lynn

On 9/15/2015 12:25 PM, Al Lorona wrote:
> Adam Farson's explanation of why the ADC clipping level has to be avoided at all costs is another reason why many people still prefer analog front ends.

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Bill-3

Re: K3 RX in real world

In reply to this post by Jim Brown-10

Real World - that is all that really counts. All the testing and arguing
that has been appearing of late is great, if you are a numbers cruncher
and chart maker. But, to my thinking - the technical performance
differences between the top rigs can only be discerned in a "copper" room.

Real world experience with QRM, QRN, good or poor antennas, band
conditions are all the great equalizers. Reported real world experience
- comparing one rig (A to B) - is of far greater value to me than a list
of numbers.

Lots of explanations why one rig is preferred over another: handles
QRM/QRN better, has more pleasing audio, better/worse ergonomics, more
??? for the money, too many menus, great audio reports, great
keyer/break-in, eye candy, etc.

Of course, all that said - it would be a very hard sell to get me away
from my K3-Line. But, it would be interesting reading never-the-less.

Bill W2BLC K3-Line
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Jim Bolit

Re: K3 to IC-7800 Comparison?

In reply to this post by W5GAI

Yes, but many can be misled with "official looking" information that has cover statements buried in the content.
Anyone who publishes information of this nature should be prepared to have it critiqued by their peers.
Based on this mail string, it is clear there are numbers and methodologies that are in conflict, raising questions by peers.
Jim
W6AIM
.

-------- Original message --------
From: "Wes (N7WS)" <[hidden email]>
Date: 9/15/2015 12:37 PM (GMT-06:00)
To: [hidden email]
Subject: Re: [Elecraft] K3 to IC-7800 Comparison?

I was responding to the comment that you "thoughtfully" deleted so you could go
on with your critique.

I know it's hard for some people to believe, but some of us in the unwashed
masses are actually capable of deciding what is "useful" to us in our own
situations.
.

On 9/15/2015 9:50 AM, Jim Brown wrote:

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Joe Subich, W4TV-4

Re: Analog vs. Digital Front Ends

In reply to this post by Lynn W. Taylor, WB6UUT

On 9/15/2015 3:39 PM, Lynn W. Taylor, WB6UUT wrote:
> Maybe I'm wrong, but if the thing we're testing is supposed to be a
> radio, and we want to compare how radios work under conditions we'd
> encounter in actual use, it just seems intuitively obvious to the most
> casual observer that the tests should be the same.
>
> 73 -- Lynn

Therein lies the rub ... direct digital conversion SDR devices have
their best performance (best sensitivity) at (composite) signal levels
just below the clip (overflow) point of the ADC in use. However, at
that point they can not withstand any overload. If one decreases the
input signal (e.g., turns off the preamplifier) to provide headroom or
avoid ADC overflow, the sensitivity (MDS) suffers in direct proportion
to the decrease in signal level.

ARRL's review of the Flex-6700 and Flex-6300 shows this inescapable
fact of nature (law of physics) very clearly. AB4OJ's noise power
ratio testing hides the fact by not providing MDS values under each
test condition *and* fails to indicate that even with *no preamplifier*
the total noise signal is more than 10 dB *less* that that used for
testing with traditional superhetrodyne or downcoversion DSP designs.

73,

... Joe, W4TV
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Tony Estep

Re: Analog vs. Digital Front Ends

On Tue, Sep 15, 2015 at 3:36 PM, Joe Subich, W4TV <[hidden email]> wrote:

> ....noise power ratio testing hides the fact by not providing MDS values
> under each
> test condition *and* fails to indicate that even with *no preamplifier*
> the total noise signal is more than 10 dB *less*...

=========
I take this to mean that the test results are not comparable across radios,
and the SDRs are 10db worse than they show up on the comparison chart. If
this is true, it ain't good.

Tony KT0NY
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Jim Brown-10

Re: K3 RX in real world

In reply to this post by Bill-3

On Tue,9/15/2015 1:29 PM, Bill wrote:
> the technical performance differences between the top rigs can only be
> discerned in a "copper" room.

That is definitely not true. Digging weak ones out in a big contest, or
with a close by ham neighbor, will tell you right away. An inferior
dirty radio a few miles away driving a power amp will make your life
miserable.

73, Jim K9YC
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Hisashi T Fujinaka

Re: K3 RX in real world

On Tue, 15 Sep 2015, Jim Brown wrote:

> On Tue,9/15/2015 1:29 PM, Bill wrote:
>> the technical performance differences between the top rigs can only be
>> discerned in a "copper" room.
>
> That is definitely not true. Digging weak ones out in a big contest, or with
> a close by ham neighbor, will tell you right away. An inferior dirty radio a
> few miles away driving a power amp will make your life miserable.

Exactly. Get on during CQWW. I could hear interesting transmitter widths
from people half a continent away and interesting effects in my receiver
as well (mostly noise blanker effects). I heard this all just on my
dipole with no hams close by. Actually, K7VIT is 5 miles away but I can
hardly hear him.

--
Hisashi T Fujinaka - [hidden email]
BSEE + BSChem + BAEnglish + MSCS + $2.50 = coffee
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