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KX2 added to Sherwood's list

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John AE5X

KX2 added to Sherwood's list

I notice that the KX2's narrow dynamic range is tested at a 3 kHz bandwidth. Other radios on Sherwood's list are measured at either 2, 3 and 5 kHz. Doesn't this make direct comparison between various radios (and list order - since they are listed by dynamic range order) invalid?

John AE5X
http://ae5x.blogspot.com/
___________________

>Similar to our lab measurements. (Not bad for a 13 oz radio. If this were 1999, it would have been at >the top of the list :)
>
>
>73,
>Wayne
>N6KR

> On Jul 27, 2017, at 6:11 PM, John AE5X <ae5x at juno.com> wrote:
>
> I haven't seen this mentioned here yet...KX2 receiver specs were added yesterday:
>
> http://www.sherweng.com/table.html

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W0JFR

KX2 added to Sherwood's list

John, N0TA, forwarded this question to me about why I listed the KX2
close-in dynamic range at 3 kHz rather than the more typical 2 kHz.
Some radios have limitations that make a measurement at 2-kHz impossible
or invalid. If a valid measurement cannot be made at 2 kHz, then it is
made at some wider spacing, such as 3, 4 or 5 kHz. Typically if a
measurement cannot be made at 2 kHz, it is because of filter leakage.
When a test is made at 2-KHz, for example, the third-order
intermodulation products are 2-kHz below the lower frequency test tone
and 2-kHz above the higher frequency test tone. If the radio cannot
reject the test tone that is 2-kHz away, then it is impossible to
measure the third-order distortion product.

In the case of the KX2, I could measure the low side distortion product
at 2 kHz with no problem using the standard 500-Hz filter bandwidth. On
the other hand, when measuring the distortion product on the high side,
the filter in the KX2 does not reject the test tone that is 2 kHz away.
Two different KX2 radios were tested, and both showed this identical
anomaly. If one reads the ARRL report on the KX2, you will see that the
reviewer mentioned the filter leakage when tuned above a strong signal.

Here are the odd details on the KX2 filter leakage. If the filter
bandwidth is 500, 400, 300, 200 or 100 Hz, filter leakage makes the
measurement at 2 kHz impossible. On the other hand, if the filter
bandwidth is 550, 450, 350, 250, 150 or 50 Hz, then the measurement can
be made. The League chose to publish a 2-kHz dynamic range in QST even
though the measurement cannot be made on the high side with the
standardized 500-Hz filter bandwidth (or any even bandwidth value).
Note: Both the League and I only publish the LOWER of the two
measurements. Let’s say the low side dynamic range of some radio is 95
dB and the high side is 90 dB. Both the League and I publish the lower
worse-case 90 dB number. In the case of the KX2, I couldn’t pick the
lower of the two readings since no measurement is possible when using
the standard 500-Hz filter.

Since the 2-kHz dynamic range value could not be made with the standard
filter bandwidth at 2 kHz, but could be made at a 3-kHz signal spacing,
I published that data. It may be of interest that the 2-kHz dynamic
range number with the non-standard 450-Hz bandwidth was only 1 dB worse
than the 3-kHz value. The point of listing the 3-kHz value, or any
other radio with a non-2 kHz listing is to point out the radio has a
limitation in its filter performance.

My long form report on the KX2, available in PDF format, goes into
detail about this issue, and has data on the two radios I tested, listed
by serial number.

At this point, Elecraft does not know why the KX2 behaves this way, or
whether there is a possible firmware fix.

Rob Sherwood
NC0B
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wayne burdick

Re: KX2 added to Sherwood's list

Administrator

The cause of this is likely to be straightforward. One of our software engineers is looking into it. Once we have the fix in place, we hope to get a KX2 to Rob for retesting.

A temporary workaround (if needed due to QRM) is to use 450 instead of 500 Hz, etc.

Wayne
N6KR

----
http://www.elecraft.com

> On Aug 1, 2017, at 4:25 AM, John Reilly <[hidden email]> wrote:
>
> John, N0TA, forwarded this question to me about why I listed the KX2 close-in dynamic range at 3 kHz rather than the more typical 2 kHz. Some radios have limitations that make a measurement at 2-kHz impossible or invalid. If a valid measurement cannot be made at 2 kHz, then it is made at some wider spacing, such as 3, 4 or 5 kHz. Typically if a measurement cannot be made at 2 kHz, it is because of filter leakage. When a test is made at 2-KHz, for example, the third-order intermodulation products are 2-kHz below the lower frequency test tone and 2-kHz above the higher frequency test tone. If the radio cannot reject the test tone that is 2-kHz away, then it is impossible to measure the third-order distortion product.
>
> In the case of the KX2, I could measure the low side distortion product at 2 kHz with no problem using the standard 500-Hz filter bandwidth. On the other hand, when measuring the distortion product on the high side, the filter in the KX2 does not reject the test tone that is 2 kHz away. Two different KX2 radios were tested, and both showed this identical anomaly. If one reads the ARRL report on the KX2, you will see that the reviewer mentioned the filter leakage when tuned above a strong signal.
>
> Here are the odd details on the KX2 filter leakage. If the filter bandwidth is 500, 400, 300, 200 or 100 Hz, filter leakage makes the measurement at 2 kHz impossible. On the other hand, if the filter bandwidth is 550, 450, 350, 250, 150 or 50 Hz, then the measurement can be made. The League chose to publish a 2-kHz dynamic range in QST even though the measurement cannot be made on the high side with the standardized 500-Hz filter bandwidth (or any even bandwidth value). Note: Both the League and I only publish the LOWER of the two measurements. Let’s say the low side dynamic range of some radio is 95 dB and the high side is 90 dB. Both the League and I publish the lower worse-case 90 dB number. In the case of the KX2, I couldn’t pick the lower of the two readings since no measurement is possible when using the standard 500-Hz filter.
>
> Since the 2-kHz dynamic range value could not be made with the standard filter bandwidth at 2 kHz, but could be made at a 3-kHz signal spacing, I published that data. It may be of interest that the 2-kHz dynamic range number with the non-standard 450-Hz bandwidth was only 1 dB worse than the 3-kHz value. The point of listing the 3-kHz value, or any other radio with a non-2 kHz listing is to point out the radio has a limitation in its filter performance.
>
> My long form report on the KX2, available in PDF format, goes into detail about this issue, and has data on the two radios I tested, listed by serial number.
>
> At this point, Elecraft does not know why the KX2 behaves this way, or whether there is a possible firmware fix.
>
> Rob Sherwood
> NC0B
> ______________________________________________________________
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w4sc-2

Re: KX2 added to Sherwood's list

A ”temporary” FW fix may be to make the BW settings reside on 50Hz boundary’s every 100Hz i.e. 150,250,,,2150,,, as adjusted. I doubt if the ‘tween settings “00” would be missed.

73 de Ben W4SC.

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Igor Sokolov-2

Re: KX2 added to Sherwood's list

In reply to this post by W0JFR

The problem described below also exists in KX3,

That is why I always adjust bandwidth to 50,150,250, 350 etc Hz.

73, Igor UA9CDC

01.08.2017 16:25, John Reilly пишет:

>
> Here are the odd details on the KX2 filter leakage. If the filter
> bandwidth is 500, 400, 300, 200 or 100 Hz, filter leakage makes the
> measurement at 2 kHz impossible. On the other hand, if the filter
> bandwidth is 550, 450, 350, 250, 150 or 50 Hz, then the measurement
> can be made. The League chose to publish a 2-kHz dynamic range in QST
> even though the measurement cannot be made on the high side with the
> standardized 500-Hz filter bandwidth (or any even bandwidth value).
> Note: Both the League and I only publish the LOWER of the two
> measurements. Let’s say the low side dynamic range of some radio is
> 95 dB and the high side is 90 dB. Both the League and I publish the
> lower worse-case 90 dB number. In the case of the KX2, I couldn’t pick
> the lower of the two readings since no measurement is possible when
> using the standard 500-Hz filter.
>
> Since the 2-kHz dynamic range value could not be made with the
> standard filter bandwidth at 2 kHz, but could be made at a 3-kHz
> signal spacing, I published that data. It may be of interest that the
> 2-kHz dynamic range number with the non-standard 450-Hz bandwidth was
> only 1 dB worse than the 3-kHz value. The point of listing the 3-kHz
> value, or any other radio with a non-2 kHz listing is to point out the
> radio has a limitation in its filter performance.
>
> My long form report on the KX2, available in PDF format, goes into
> detail about this issue, and has data on the two radios I tested,
> listed by serial number.
>
> At this point, Elecraft does not know why the KX2 behaves this way, or
> whether there is a possible firmware fix.
>
> Rob Sherwood
> NC0B
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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K9MA

Re: KX2 added to Sherwood's list

In reply to this post by w4sc-2

Another interesting detail, I think. For the KX3, if I recall
correctly, both the QST review and Sherwood's tests indicated that the
audio image (opposite side of zero beat) wasn't all that far down, like
60 dB, and limited close-in dynamic range. I don't recall any such
qualifications for the KX2, and indeed mine doesn't seem to have an
audible image even on the strongest signals. (Not a scientific test, I
know, but I think I'd hear an image 60 dB down.) If this is so, what is
the difference responsible?

Note that the optional "roofing" filter in the KX3 is really just an
audio filter. While it may improve dynamic range beyond a few kHz, it
has no effect on the image.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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wayne burdick

Re: KX2 added to Sherwood's list

Administrator

We found the problem; turns out to be in the setup command to the DSP, not in the DSP itself. With any luck we'll have it fixed this week in both rigs.

Wayne
N6KR

----
http://www.elecraft.com

> On Aug 1, 2017, at 6:29 PM, K9MA <[hidden email]> wrote:
>
> Another interesting detail, I think. For the KX3, if I recall correctly, both the QST review and Sherwood's tests indicated that the audio image (opposite side of zero beat) wasn't all that far down, like 60 dB, and limited close-in dynamic range. I don't recall any such qualifications for the KX2, and indeed mine doesn't seem to have an audible image even on the strongest signals. (Not a scientific test, I know, but I think I'd hear an image 60 dB down.) If this is so, what is the difference responsible?
>
> Note that the optional "roofing" filter in the KX3 is really just an audio filter. While it may improve dynamic range beyond a few kHz, it has no effect on the image.
>
> 73,
>
> Scott K9MA
>
>
> --
> Scott K9MA
>
> [hidden email]
>
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Dave AD6A

Re: KX2 added to Sherwood's list

In reply to this post by K9MA

Excellent! What great customer service and support - second to none!!

73, Dave AD6A

Sent from my  iPhone 7 Plus

On Aug 1, 2017, at 6:29 PM, K9MA <[hidden email]> wrote:

Another interesting detail, I think. For the KX3, if I recall correctly, both the QST review and Sherwood's tests indicated that the audio image (opposite side of zero beat) wasn't all that far down, like 60 dB, and limited close-in dynamic range. I don't recall any such qualifications for the KX2, and indeed mine doesn't seem to have an audible image even on the strongest signals. (Not a scientific test, I know, but I think I'd hear an image 60 dB down.) If this is so, what is the difference responsible?

Note that the optional "roofing" filter in the KX3 is really just an audio filter. While it may improve dynamic range beyond a few kHz, it has no effect on the image.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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