Elecraft

[KX3] equalization in DATA-A mode?

Classic

List

Threaded

33 messages Options

Jerry Moore

Re: K3S IMD Questions

Rick,
Check your compression and ALC settings. There's a specific
setup/configuration for proper use AND test. Based on my reading you can
cause a bad signal on ANY transmitter with the comp/alc settings
miss-adjusted.

I'm sure someone here can better address the setup/configuration.
jer

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Rick
Stealey
Sent: Tuesday, September 01, 2015 11:18 AM
To: [hidden email]
Subject: Re: [Elecraft] K3S IMD Questions

I have been playing with a Flex 6300 here in my shack recently. I consider
it a great piece of test equipment for analyzing signals in the shack as
well as on the air. It does everything and more, as a spectrum analyzer,
that my old HP141 analog setup did, except it doesn't have a tracking
generator.
My measurements are not completed and I am still experimenting, but here is
what I've done so far. Phase noise, cw transmitted bandwidth, and 2 tone
IMD tests. My two rigs are a K3/100 and an FT100D (how good, and how bad
can you get!) Using a Flex 6300 as a spectrum analyzer, I fed a greatly
attenuated signal into it, keeping the level just under 0 dbm, and assuming
it is not generating imd of its own, but I haven't quantified that yet.
Phase noise tests - I was interested in seeing if it could display the
RELATIVE benefit of the new synthesizer on my K3, looking at phase noise.
Here are PRELIMINARY RELATIVE results, without numbers, in order of phase
noise level at 2 khz separation:An 8640B signal generator (known to have low
phase noise)The K3 with original synthesizerThe FT100 After I install the
new synthesizer I hope to be able to compare it to the original one.
I verified the FFT spectrum analyzer (Flex 6300) can give an instant view of
transmitted bandwith of the cw signal sending fast dots. MUCH easier and
better than the old analog HP spectrum analyzer which had to sweep extremely
slowly across the band with a narrow filter. With this setup you hold the
key closed, and hit the control-print screen buttons on the keyboard and you
have a beautiful picture ! Ain't technology great?
2-tone IMD measurements -The two tone test of the K3 showed something
interesting, since it has both 10 watt and a 100 watt PAs installed.
Starting with low power and cranking up the power control, you notice, of
course, that the ten watt PA has worse IMD just before the big PA kicks in,
in the 11-12 watt range. Then it is very clean (approximately -40 db for
third order) at its best, and ok in the 30 watt range (where it would be set
to run my 8877 amp) but then gets quite ugly above 65 watts. And I mean in
the -20 db range at 100 watts. IF it was overloading the spectrum analyzer
these tests would be invalid, so I need to verify that. As I said these
tests are preliminary. I need a few more hours.

In my humble opinion, running at full power, 100 watts barefoot, my K3 would
be transmitting an unacceptably sloppy signal. Keeping it in the 65 watt
range or under, or driving an amp would be better, provided your amp is
clean. My 8877 amp is VERY clean. I don't know about a solid state amp.
Some of the ugliest signals I have seen on the bands with the Flex
panadapter in very limited observations have come from Expert 1500 watt amps
(2 examples). The very best was an Anan 100 with a Ten Tec 1500 watt tube
amp. The waterfall was a brick wall - NOTHING whatsoever outside the 3 khz
bandwidth.
Rick K2XT

______________________________________________________________
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]

______________________________________________________________
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]

Bob McGraw - K4TAX

Re: K3S IMD Questions

In reply to this post by Rick Stealey

For a decent Spectrum Analyzer, 9kHz to 1.5 GHz with tracking generator,
check out the Rigol DSA 815-TG. It is available for under $1500 and
free shipping for Amazon Prime members. Not only is it an aide to the
station equipment but it is an excellent piece of test equipment. As
one reviewer stated, "it won't do what the Agilent Spectrum Analyzer
costing some 10X as much will do but for the price, it is an excellent
value".

73 Bob, K4TAX
K3S s/n 10,163

On 9/1/2015 10:18 AM, Rick Stealey wrote:

> I have been playing with a Flex 6300 here in my shack recently. I consider it a great piece of test equipment for analyzing signals in the shack as well as on the air. It does everything and more, as a spectrum analyzer, that my old HP141 analog setup did, except it doesn't have a tracking generator.
> My measurements are not completed and I am still experimenting, but here is what I've done so far. Phase noise, cw transmitted bandwidth, and 2 tone IMD tests. My two rigs are a K3/100 and an FT100D (how good, and how bad can you get!)
> Using a Flex 6300 as a spectrum analyzer, I fed a greatly attenuated signal into it, keeping the level just under 0 dbm, and assuming it is not generating imd of its own, but I haven't quantified that yet.
> Phase noise tests - I was interested in seeing if it could display the RELATIVE benefit of the new synthesizer on my K3, looking at phase noise. Here are PRELIMINARY RELATIVE results, without numbers, in order of phase noise level at 2 khz separation:An 8640B signal generator (known to have low phase noise)The K3 with original synthesizerThe FT100 After I install the new synthesizer I hope to be able to compare it to the original one.
> I verified the FFT spectrum analyzer (Flex 6300) can give an instant view of transmitted bandwith of the cw signal sending fast dots. MUCH easier and better than the old analog HP spectrum analyzer which had to sweep extremely slowly across the band with a narrow filter. With this setup you hold the key closed, and hit the control-print screen buttons on the keyboard and you have a beautiful picture ! Ain't technology great?
> 2-tone IMD measurements -The two tone test of the K3 showed something interesting, since it has both 10 watt and a 100 watt PAs installed. Starting with low power and cranking up the power control, you notice, of course, that the ten watt PA has worse IMD just before the big PA kicks in, in the 11-12 watt range. Then it is very clean (approximately -40 db for third order) at its best, and ok in the 30 watt range (where it would be set to run my 8877 amp) but then gets quite ugly above 65 watts. And I mean in the -20 db range at 100 watts. IF it was overloading the spectrum analyzer these tests would be invalid, so I need to verify that. As I said these tests are preliminary. I need a few more hours.
>
> In my humble opinion, running at full power, 100 watts barefoot, my K3 would be transmitting an unacceptably sloppy signal. Keeping it in the 65 watt range or under, or driving an amp would be better, provided your amp is clean. My 8877 amp is VERY clean. I don't know about a solid state amp. Some of the ugliest signals I have seen on the bands with the Flex panadapter in very limited observations have come from Expert 1500 watt amps (2 examples). The very best was an Anan 100 with a Ten Tec 1500 watt tube amp. The waterfall was a brick wall - NOTHING whatsoever outside the 3 khz bandwidth.
> Rick K2XT
>
>
>
>
>
> ______________________________________________________________
> 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]
>
>
>

______________________________________________________________
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]

Jim Brown-10

Re: K3S IMD Questions

On Tue,9/1/2015 10:00 AM, Bob McGraw - K4TAX wrote:
> For a decent Spectrum Analyzer, 9kHz to 1.5 GHz with tracking
> generator, check out the Rigol DSA 815-TG.

Hi Bob,

I've got one of these, in addition to a vintage HP 8590D. Specs are
similar, the HP is a bit better, but not a lot. Both are blown away by
some of the best of SDRs, including the K3 with P3/SVGA. While the
P3/SVGA can display only 80 dB, the front end is good for about 100 dB,
the display can be scaled up to view down to that level. Not as good as
the Rigol or HP, but P3/SVGA frequency resolution can go down to 1 Hz
(2048 point FFT for a 2 kHz span), two orders of magnitude better than
the Rigol or HP. Rigol phase noise is specified as -80dBc/Hz at 10 kHz;
the original K3 (with original synth board) was measured by ARRL as
-140dBc/Hz.

Bottom line -- the Rigol and HP are fine for looking at harmonics and
spurs, but useless for looking at occupied bandwidth. Take a look at the
plots in this link, especially slide #8, K3 steady carrier at 25W. I
can't do this with my Rigol or my HP!

http://k9yc.com/P3_Spectrum_Measurements.pdf

73, Jim K9YC

______________________________________________________________
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]

gm3sek

Re: K3S IMD Questions

In reply to this post by Rick Stealey

I found very much the same as Rick did, with a completely different test
setup (SDR-IQ).

The details vary somewhat with frequency and supply voltage but the
three main features reported by Rick remain the same:

>the ten watt PA has worse IMD just before the big PA kicks in, in the
>11-12 watt range.

>Then it is very clean (approximately -40 db for third
>order) at its best, and ok in the 30 watt range (where it would be set
to run
>my 8877 amp)

> but then gets quite ugly above 65 watts. And I mean in the -20 db
range at 100 watts.

My figures confirm those three main features (assuming we're both
reporting 3rd order IMD, "dB below either tone").

The other important feature is that the levels of higher-order IMD do
not fall quickly when tuning away from the main signal. If we had
reported "total occupied bandwidth at -60dBc", those results would not
look pretty at all!

Those measurements were first made about 7 years ago on my original
low-serial K3, and today I made similar measurements on the new K3S. The
10/12W PA is different from the one in the K3 (two TO220 RF power
transistors in the K3S, where the K3 had three). However, the 100W PA is
the original module from my 7-year-old K3, so the IMD performance of
that module may not be representative of current production.

Today, anyone can make 2-tone IMD measurements using a modern SDR and a
little care in setting up the input levels. The K3 itself provides the
2-tone test signal (CONFIG:2TONE On).

If anyone can report comparable results for an all-new K3S/100, that
would be very interesting to see... but don't expect any radical changes
in those three main features reported by Rick.

73 from Ian GM3SEK

>-----Original Message-----
>From: Elecraft [mailto:[hidden email]] On Behalf Of
>Rick Stealey
>Sent: 01 September 2015 16:18
>To: [hidden email]
>Subject: Re: [Elecraft] K3S IMD Questions
>
>I have been playing with a Flex 6300 here in my shack recently. I
consider it
>a great piece of test equipment for analyzing signals in the shack as
well as
>on the air. It does everything and more, as a spectrum analyzer, that
my
>old HP141 analog setup did, except it doesn't have a tracking
generator.
>My measurements are not completed and I am still experimenting, but
>here is what I've done so far. Phase noise, cw transmitted bandwidth,
and
>2 tone IMD tests. My two rigs are a K3/100 and an FT100D (how good,
and
>how bad can you get!)
>Using a Flex 6300 as a spectrum analyzer, I fed a greatly attenuated
signal
>into it, keeping the level just under 0 dbm, and assuming it is not
>generating imd of its own, but I haven't quantified that yet.
>Phase noise tests - I was interested in seeing if it could display the
>RELATIVE benefit of the new synthesizer on my K3, looking at phase
noise.
>Here are PRELIMINARY RELATIVE results, without numbers, in order of
>phase noise level at 2 khz separation:An 8640B signal generator (known
to
>have low phase noise)The K3 with original synthesizerThe FT100 After I
>install the new synthesizer I hope to be able to compare it to the
original
>one.
>I verified the FFT spectrum analyzer (Flex 6300) can give an instant
view of
>transmitted bandwith of the cw signal sending fast dots. MUCH easier
and
>better than the old analog HP spectrum analyzer which had to sweep
>extremely slowly across the band with a narrow filter. With this setup
you
>hold the key closed, and hit the control-print screen buttons on the
>keyboard and you have a beautiful picture ! Ain't technology great?
>2-tone IMD measurements -The two tone test of the K3 showed something
>interesting, since it has both 10 watt and a 100 watt PAs installed.
Starting
>with low power and cranking up the power control, you notice, of
course,
>that the ten watt PA has worse IMD just before the big PA kicks in, in
the
>11-12 watt range. Then it is very clean (approximately -40 db for
third
>order) at its best, and ok in the 30 watt range (where it would be set
to run
>my 8877 amp) but then gets quite ugly above 65 watts. And I mean in
the -
>20 db range at 100 watts. IF it was overloading the spectrum analyzer
>these tests would be invalid, so I need to verify that. As I said
these tests
>are preliminary. I need a few more hours.
>
>In my humble opinion, running at full power, 100 watts barefoot, my K3
>would be transmitting an unacceptably sloppy signal. Keeping it in the
65
>watt range or under, or driving an amp would be better, provided your
amp
>is clean. My 8877 amp is VERY clean. I don't know about a solid state
>amp. Some of the ugliest signals I have seen on the bands with the
Flex

>panadapter in very limited observations have come from Expert 1500 watt
>amps (2 examples). The very best was an Anan 100 with a Ten Tec 1500
>watt tube amp. The waterfall was a brick wall - NOTHING whatsoever
>outside the 3 khz bandwidth.
>Rick K2XT
>
>
>
>
>
>______________________________________________________________
>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]

Rick Stealey

Re: K3S IMD Questions

In reply to this post by Rick Stealey

I re-ran the IMD tests with another PS and put 30 db more attenuation in front of the spectrum analyzer and the K3 now looks good above 65 watts. -30 db IP3 at 100 watts, in fact.
Sorry.
But it's still cleanest down in the 30 watt range.
Rick K2XT

> From: [hidden email]
> To: [hidden email]
> Date: Tue, 1 Sep 2015 15:18:05 +0000
> Subject: Re: [Elecraft] K3S IMD Questions
>
> I have been playing with a Flex 6300 here in my shack recently. I consider it a great piece of test equipment for analyzing signals in the shack as well as on the air. It does everything and more, as a spectrum analyzer, that my old HP141 analog setup did, except it doesn't have a tracking generator.
> My measurements are not completed and I am still experimenting, but here is what I've done so far. Phase noise, cw transmitted bandwidth, and 2 tone IMD tests. My two rigs are a K3/100 and an FT100D (how good, and how bad can you get!)
> Using a Flex 6300 as a spectrum analyzer, I fed a greatly attenuated signal into it, keeping the level just under 0 dbm, and assuming it is not generating imd of its own, but I haven't quantified that yet.
> Phase noise tests - I was interested in seeing if it could display the RELATIVE benefit of the new synthesizer on my K3, looking at phase noise. Here are PRELIMINARY RELATIVE results, without numbers, in order of phase noise level at 2 khz separation:An 8640B signal generator (known to have low phase noise)The K3 with original synthesizerThe FT100 After I install the new synthesizer I hope to be able to compare it to the original one.
> I verified the FFT spectrum analyzer (Flex 6300) can give an instant view of transmitted bandwith of the cw signal sending fast dots. MUCH easier and better than the old analog HP spectrum analyzer which had to sweep extremely slowly across the band with a narrow filter. With this setup you hold the key closed, and hit the control-print screen buttons on the keyboard and you have a beautiful picture ! Ain't technology great?
> 2-tone IMD measurements -The two tone test of the K3 showed something interesting, since it has both 10 watt and a 100 watt PAs installed. Starting with low power and cranking up the power control, you notice, of course, that the ten watt PA has worse IMD just before the big PA kicks in, in the 11-12 watt range. Then it is very clean (approximately -40 db for third order) at its best, and ok in the 30 watt range (where it would be set to run my 8877 amp) but then gets quite ugly above 65 watts. And I mean in the -20 db range at 100 watts. IF it was overloading the spectrum analyzer these tests would be invalid, so I need to verify that. As I said these tests are preliminary. I need a few more hours.
>
> In my humble opinion, running at full power, 100 watts barefoot, my K3 would be transmitting an unacceptably sloppy signal. Keeping it in the 65 watt range or under, or driving an amp would be better, provided your amp is clean. My 8877 amp is VERY clean. I don't know about a solid state amp. Some of the ugliest signals I have seen on the bands with the Flex panadapter in very limited observations have come from Expert 1500 watt amps (2 examples). The very best was an Anan 100 with a Ten Tec 1500 watt tube amp. The waterfall was a brick wall - NOTHING whatsoever outside the 3 khz bandwidth.
> Rick K2XT
>
>
>
>
>
> ______________________________________________________________
> 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-4

Re: K3S IMD Questions

In reply to this post by gm3sek

Anyone who does such testing should also include in the report(s) the
power supply voltage as seen by the K3S alternate VFO B display.
Lower power supply voltages will have worse IMD than voltages that are
higher.
Running the K3 or K3S with a power supply voltage above 14.3 volts will
improve the IMD substantially.

73,
Don W3FPR

On 9/1/2015 1:44 PM, Ian White wrote:
> I found very much the same as Rick did, with a completely different test
> setup (SDR-IQ).
>
> The details vary somewhat with frequency and supply voltage but the
> three main features reported by Rick remain the same:
>
>

______________________________________________________________
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]

Jim Brown-10

Re: K3S IMD Questions

In reply to this post by gm3sek

On Tue,9/1/2015 10:44 AM, Ian White wrote:
> Today, anyone can make 2-tone IMD measurements using a modern SDR and a
> little care in setting up the input levels. The K3 itself provides the
> 2-tone test signal (CONFIG:2TONE On).

Yes and no. Let's not forget that the response of any measurement is the
combined response of both the measurement system and the device under
test (DUT).

An important test of any spectrum measurement system is its frequency
resolution, which can be tested by its response to a steady unmodulated,
unkeyed carrier. Like slide #8 in

http://k9yc.com/P3_Spectrum_Measurements.pdf

Likewise, we must qualify the dynamic range of the measurement system --
when does it begin to contribute distortion due to its own
non-linearity. This is what K2XT ran into in his tests.

On Tue,9/1/2015 10:54 AM, Don Wilhelm wrote:
> Anyone who does such testing should also include in the report(s) the
> power supply voltage as seen by the K3S alternate VFO B display.
> Lower power supply voltages will have worse IMD than voltages that are
> higher.
> Running the K3 or K3S with a power supply voltage above 14.3 volts
> will improve the IMD substantially.

Yes, the K3 and K3S are a bit cleaner with higher power supply voltage.
K6XX showed this in a presentation to NCCC a few years ago. It's on my
website.

All of my testing has been done with power supply in the range of 12.3 -
12.6V.

73, Jim K9YC
______________________________________________________________
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]

Wes (N7WS)

Re: K3S IMD Questions

In reply to this post by Rick Stealey

As you no doubt know, to check linearity with a SA you drop in 10 dB of front
end attenuation and look to see that everything on the screen drops 10 dB. You
probably also know that the phase noise of the analyzer should be, as a rule of
thumb, 10 dB better than the device you're measuring. The 6300 claims -140dBc
at 10 KHz offset for its reference oscillator. I believe that's more or less
the same number Elecraft claims for the K3 synthesizer.

On 9/1/2015 8:18 AM, Rick Stealey wrote:

> I have been playing with a Flex 6300 here in my shack recently. I consider it a great piece of test equipment for analyzing signals in the shack as well as on the air. It does everything and more, as a spectrum analyzer, that my old HP141 analog setup did, except it doesn't have a tracking generator.
> My measurements are not completed and I am still experimenting, but here is what I've done so far. Phase noise, cw transmitted bandwidth, and 2 tone IMD tests. My two rigs are a K3/100 and an FT100D (how good, and how bad can you get!)
> Using a Flex 6300 as a spectrum analyzer, I fed a greatly attenuated signal into it, keeping the level just under 0 dbm, and assuming it is not generating imd of its own, but I haven't quantified that yet.
> Phase noise tests - I was interested in seeing if it could display the RELATIVE benefit of the new synthesizer on my K3, looking at phase noise. Here are PRELIMINARY RELATIVE results, without numbers, in order of phase noise level at 2 khz separation:An 8640B signal generator (known to have low phase noise)The K3 with original synthesizerThe FT100 After I install the new synthesizer I hope to be able to compare it to the original one.
> I verified the FFT spectrum analyzer (Flex 6300) can give an instant view of transmitted bandwith of the cw signal sending fast dots. MUCH easier and better than the old analog HP spectrum analyzer which had to sweep extremely slowly across the band with a narrow filter. With this setup you hold the key closed, and hit the control-print screen buttons on the keyboard and you have a beautiful picture ! Ain't technology great?
> 2-tone IMD measurements -The two tone test of the K3 showed something interesting, since it has both 10 watt and a 100 watt PAs installed. Starting with low power and cranking up the power control, you notice, of course, that the ten watt PA has worse IMD just before the big PA kicks in, in the 11-12 watt range. Then it is very clean (approximately -40 db for third order) at its best, and ok in the 30 watt range (where it would be set to run my 8877 amp) but then gets quite ugly above 65 watts. And I mean in the -20 db range at 100 watts. IF it was overloading the spectrum analyzer these tests would be invalid, so I need to verify that. As I said these tests are preliminary. I need a few more hours.
>
> In my humble opinion, running at full power, 100 watts barefoot, my K3 would be transmitting an unacceptably sloppy signal. Keeping it in the 65 watt range or under, or driving an amp would be better, provided your amp is clean. My 8877 amp is VERY clean. I don't know about a solid state amp. Some of the ugliest signals I have seen on the bands with the Flex panadapter in very limited observations have come from Expert 1500 watt amps (2 examples). The very best was an Anan 100 with a Ten Tec 1500 watt tube amp. The waterfall was a brick wall - NOTHING whatsoever outside the 3 khz bandwidth.
> Rick K2XT
>
>
>
>
>
> ______________________________________________________________
> 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 [hidden email]
>

Wes (N7WS)

Re: K3S IMD Questions

In reply to this post by Bob McGraw - K4TAX

I would buy one in a heartbeat, but the phase noise performance is abysmal.

On 9/1/2015 10:00 AM, Bob McGraw - K4TAX wrote:

> For a decent Spectrum Analyzer, 9kHz to 1.5 GHz with tracking generator, check
> out the Rigol DSA 815-TG. It is available for under $1500 and free shipping
> for Amazon Prime members. Not only is it an aide to the station equipment but
> it is an excellent piece of test equipment. As one reviewer stated, "it won't
> do what the Agilent Spectrum Analyzer costing some 10X as much will do but for
> the price, it is an excellent value".
>
>
> 73 Bob, K4TAX
> K3S s/n 10,163
>

Rick Stealey

Re: K3S IMD Questions

>
> I would buy one in a heartbeat, but the phase noise performance is abysmal.
>

A general purpose SDR or possibly a 10 watt rig like Anan 10 would do better.
______________________________________________________________
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]

Wes (N7WS)

Re: K3S IMD Questions

Not without decent, and appropriate to the task, software.

On 9/1/2015 2:23 PM, Rick Stealey wrote:
>> I would buy one in a heartbeat, but the phase noise performance is abysmal.
>>
> A general purpose SDR or possibly a 10 watt rig like Anan 10 would do better.
>

______________________________________________________________
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]

gm3sek

Re: K3S IMD Questions

In reply to this post by Jim Brown-10

Yesterday, K9YC wrote:
>
>Likewise, we must qualify the dynamic range of the measurement system
--
>when does it begin to contribute distortion due to its own
>non-linearity. This is what K2XT ran into in his tests.
>
That error did not affect my tests. I re-ran the same tests today and
reconfirmed that, across a 60dB range of input levels to the SDR-IQ, the
measured IMD3 levels change by less than 1dBc.

Making further tests at 100W PEP, I measured IMD3 levels close to -30dBc
at 1.9MHz and -27-28dBc at 14.2MHz... but then deteriorating with
frequency towards -20dBc at 28.5MHz.

However, I do confirm Jim's measurements that the IMD3 values at the 50W
level are at least 15-20dB better. When driving a PA at 30-50W, the K3
or K3S will almost never be the limiting factor in determining IMD.

Responding to Don's point: all of these IMD measurements were made at an
indicated supply voltage of 14.5V. Following discussions in this forum
some years ago, the supply voltage had been deliberately increased to
help improve the TX IMD performance.

I must repeat the warning that these measurements were made with a
7-year-old KPA100 module in a new K3S so they may not be representative
of recent examples of either the K3 or an all-new K3S... but in other
respects the trends are clear.

73 from Ian GM3SEK

>-----Original Message-----
>From: Elecraft [mailto:[hidden email]] On Behalf Of
>Jim Brown
>Sent: 01 September 2015 19:28
>To: [hidden email]
>Subject: Re: [Elecraft] K3S IMD Questions
>
>On Tue,9/1/2015 10:44 AM, Ian White wrote:
>> Today, anyone can make 2-tone IMD measurements using a modern SDR
>and a
>> little care in setting up the input levels. The K3 itself provides

the
>> 2-tone test signal (CONFIG:2TONE On).
>
>Yes and no. Let's not forget that the response of any measurement is
the
>combined response of both the measurement system and the device under
>test (DUT).
>
>An important test of any spectrum measurement system is its frequency
>resolution, which can be tested by its response to a steady
unmodulated,
>unkeyed carrier. Like slide #8 in
>
>http://k9yc.com/P3_Spectrum_Measurements.pdf
>
>Likewise, we must qualify the dynamic range of the measurement system
--
>when does it begin to contribute distortion due to its own
>non-linearity. This is what K2XT ran into in his tests.
>
>
>On Tue,9/1/2015 10:54 AM, Don Wilhelm wrote:
>> Anyone who does such testing should also include in the report(s) the
>> power supply voltage as seen by the K3S alternate VFO B display.
>> Lower power supply voltages will have worse IMD than voltages that
are
>> higher.
>> Running the K3 or K3S with a power supply voltage above 14.3 volts
>> will improve the IMD substantially.
>
>Yes, the K3 and K3S are a bit cleaner with higher power supply voltage.
>K6XX showed this in a presentation to NCCC a few years ago. It's on my
>website.
>
>All of my testing has been done with power supply in the range of 12.3
-

>12.6V.
>
>73, Jim K9YC
>______________________________________________________________
>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]

alorona

Re: K3S IMD Questions

In reply to this post by Wes (N7WS)

Exactly right, Wes. The 10 dB rule-of-thumb is a *minimum* and it would be better if the measuring instrument were more than 10 dB better.

I'm not sure that the Flex radio originally mentioned meets that phase noise requirement. If its phase noise is on par with the K3's then it's not suitable for an accurate phase noise measurement. Depending on the numbers, you *might* be able to say "A is better than B," but you couldn't say how much better with any certainty.

Al W6LX

___

> You probably also know that the phase noise of the analyzer should

> be, as a rule of thumb, 10 dB better than the device you're measuring.
______________________________________________________________
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]