K3 frequency accuracy versus displayed precision

[Paul Kirley]

The K3 is capable of displaying frequencies to 1 Hz.  It can
be calibrated to somewhat less than 1 Hz against WWV (method 2).

Because I wanted to see if my K3 serial 1322 was capable of
measuring frequency to its displayed precision, I decided to
attempt the November 11/12 ARRL Frequency Measuring Test.

I warmed up my K3 for about two hours because--even with the
optional TCXO--my K3 drifts almost 0.1 ppm per degree Centigrade
from 25C to 30C, the latter part of its warmup range this time
of year at my QTH.  (0.1 ppm is almost 1 Hz on 40 meters.)

Then I carefully used method 2 to calibrate against 10 MHz WWV,
checking after exiting REF CAL by tuning across WWV on CW with
SPOT activated to see that the beat notes were similar on each
side of zero beat for 1 and 2 Hz off frequency.  (A lack of
similarity indicates that a small tweak of REF CAL is needed.)
Tuning past WWV's carrier on CW with SPOT enabled also provides
practice for the real thing.

When W1AW (and each of the other FMT stations) began its call-up,
I tuned its frequency to be centered in the passband with the DSP
set at 50 Hz bandwidth.  When the long dashes began, I turned on
SPOT and zero-beated against the sidetone with 1 Hz fine tuning.

After recording the result, I moved on to the other frequencies
and stations that had been specified in the ARRL FMT
announcement.  I was able to copy and measure 4 of the 5 tests,
with one station on one frequency being inaudible at my QTH.

Result:  my K3 was within 1 Hz on all 4 readings, that is, its
accuracy matched its displayed precision--after warmup and
careful calibration.

73, Paul W8TM

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[juergen piezo]

Hi Paul

I find the same thing, I have checked the clubs K3's against a rubidium standard that was calibrated to a cesium standard. The K3  is spot on, the only limitation  being  its 1hz calibration step limit for the TCXO. I wonder what use the yet to be released external standard interface will be when we can only  adjust the TCXO  in 1 hz steps.

Its amazing  how far off frequency most stations are when you use a radio thats dead on, the typical average being 40 to 80hz off. The K3 sounds so good on RX these days, its easy  to pick stations that are off frequency by even a few HZ. The radios that I have found to be consistently on frequency are the IC7700 and IC7800.

 The SSB stations that impress me the most for being on frequency are the different Aeronautical control towers. These control towers have such excellent audio quality and they are always spot on frequency. Its a shame  that more ham stations cant sound so professional and clear like these aeronautical SSB stations. I have always wondered what brand of transmitter they use?  The excessive bass and ESSB audio  that we hear so often  just sounds so awful in comparison. Excessive bass and ESSB is just not good audio for SSB use. (I dont want to start a SSB debate!) but ESSB bassy audio sucks in comparison to these commercial SSB stations!

John


--- On Mon, 11/16/09, Paul Kirley <[hidden email]> wrote:

> From: Paul Kirley <[hidden email]>
> Subject: [Elecraft] K3 frequency accuracy versus displayed precision
> To: [hidden email]
> Date: Monday, November 16, 2009, 6:28 PM
> The K3 is capable of displaying
> frequencies to 1 Hz.  It can
> be calibrated to somewhat less than 1 Hz against WWV
> (method 2).
>
> Because I wanted to see if my K3 serial 1322 was capable
> of
> measuring frequency to its displayed precision, I decided
> to
> attempt the November 11/12 ARRL Frequency Measuring Test.
>
> I warmed up my K3 for about two hours because--even with
> the
> optional TCXO--my K3 drifts almost 0.1 ppm per degree
> Centigrade
> from 25C to 30C, the latter part of its warmup range this
> time
> of year at my QTH.  (0.1 ppm is almost 1 Hz on 40
> meters.)
>
> Then I carefully used method 2 to calibrate against 10 MHz
> WWV,
> checking after exiting REF CAL by tuning across WWV on CW
> with
> SPOT activated to see that the beat notes were similar on
> each
> side of zero beat for 1 and 2 Hz off frequency.  (A
> lack of
> similarity indicates that a small tweak of REF CAL is
> needed.)
> Tuning past WWV's carrier on CW with SPOT enabled also
> provides
> practice for the real thing.
>
> When W1AW (and each of the other FMT stations) began its
> call-up,
> I tuned its frequency to be centered in the passband with
> the DSP
> set at 50 Hz bandwidth.  When the long dashes began, I
> turned on
> SPOT and zero-beated against the sidetone with 1 Hz fine
> tuning.
>
> After recording the result, I moved on to the other
> frequencies
> and stations that had been specified in the ARRL FMT
> announcement.  I was able to copy and measure 4 of the
> 5 tests,
> with one station on one frequency being inaudible at my
> QTH.
>
> Result:  my K3 was within 1 Hz on all 4 readings, that
> is, its
> accuracy matched its displayed precision--after warmup and
> careful calibration.
>
> 73, Paul W8TM
>
> ______________________________________________________________
> 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
>

     
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[gm3sek]

Paul Kirley wrote:

>The K3 is capable of displaying frequencies to 1 Hz.  It can
>be calibrated to somewhat less than 1 Hz against WWV (method 2).
>
>Because I wanted to see if my K3 serial 1322 was capable of
>measuring frequency to its displayed precision, I decided to
>attempt the November 11/12 ARRL Frequency Measuring Test.
>
>I warmed up my K3 for about two hours because--even with the
>optional TCXO--my K3 drifts almost 0.1 ppm per degree Centigrade
>from 25C to 30C, the latter part of its warmup range this time
>of year at my QTH.  (0.1 ppm is almost 1 Hz on 40 meters.)
>
>Then I carefully used method 2 to calibrate against 10 MHz WWV,
>checking after exiting REF CAL by tuning across WWV on CW with
>SPOT activated to see that the beat notes were similar on each
>side of zero beat for 1 and 2 Hz off frequency.  (A lack of
>similarity indicates that a small tweak of REF CAL is needed.)
>Tuning past WWV's carrier on CW with SPOT enabled also provides
>practice for the real thing.
>

For anyone who has a reliable 10MHz frequency source (eg locked to GPS),
another calibration method is to compare this reference against the
10.000000MHz CW output from the K3 using an oscilloscope.

The visual display gives much greater certainty than listening to
veeeeery sloooow audio beats.

Switch the 'scope into X-Y mode, connect the 10MHz reference into the X
input, and connect a sniff of RF from the K3 into the Y input. This will
display a slowly rotating Lissajous pattern. Carefully "tune" the REF
CAL setting until the pattern comes almost to a complete stop.

It isn't possible to freeze the pattern completely because REF CAL can
only be adjusted in 1Hz steps at 49.380MHz. Even so, you can very
quickly find the closest possible 1Hz step, so the error at 10MHz will
typically be less than 0.2Hz.

The visual display also gives a very clear indication of frequency
drift.

(Finally, all of these procedures assume that rounding errors in the
internal synthesizer arithmetic are of a much lower order than the
smallest (1Hz) steps in the VFO and REF CAL tuning.)


--

73 from Ian GM3SEK
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[n7ws]

Guys,

I've mentioned this caviet before:

http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451

The way the K3 implements the passband shift, the same signal, with the same VFO setting, will have a different audio beat note if the SHIFT control is changed. *

So your calibrations with your atomic standards are no better than the delta F that takes place when you vary the shift control.

If you want to measure frequency with the K3 BW and SHIFT *always* set to the same values then OK. However, calibrating at 50Hz BW and normalized SHIFT and then changing to SSB bandwidths and declaring that some stations are "on frequency" and others aren't is stretching it.

* I've discussed this with Wayne and it's considered IP.

Wes  N7WS

--- On Tue, 11/17/09, juergen piezo <[hidden email]> wrote:

From: juergen piezo <[hidden email]>
Subject: Re: [Elecraft] K3 frequency accuracy versus displayed precision
To: [hidden email]
Date: Tuesday, November 17, 2009, 12:53 AM


Hi Paul

I find the same thing, I have checked the clubs K3's against a rubidium standard that was calibrated to a cesium standard. The K3  is spot on, the only limitation  being  its 1hz calibration step limit for the TCXO. I wonder what use the yet to be released external standard interface will be when we can only  adjust the TCXO  in 1 hz steps.

Its amazing  how far off frequency most stations are when you use a radio thats dead on, the typical average being 40 to 80hz off. The K3 sounds so good on RX these days, its easy  to pick stations that are off frequency by even a few HZ. The radios that I have found to be consistently on frequency are the IC7700 and IC7800.

 The SSB stations that impress me the most for being on frequency are the different Aeronautical control towers. These control towers have such excellent audio quality and they are always spot on frequency. Its a shame  that more ham stations cant sound so professional and clear like these aeronautical SSB stations. I have always wondered what brand of transmitter they use?  The excessive bass and ESSB audio  that we hear so often  just sounds so awful in comparison. Excessive bass and ESSB is just not good audio for SSB use. (I dont want to start a SSB debate!) but ESSB bassy audio sucks in comparison to these commercial SSB stations!

John


--- On Mon, 11/16/09, Paul Kirley <[hidden email]> wrote:

> From: Paul Kirley <[hidden email]>
> Subject: [Elecraft] K3 frequency accuracy versus displayed precision
> To: [hidden email]
> Date: Monday, November 16, 2009, 6:28 PM
> The K3 is capable of displaying
> frequencies to 1 Hz.  It can
> be calibrated to somewhat less than 1 Hz against WWV
> (method 2).
>
> Because I wanted to see if my K3 serial 1322 was capable
> of
> measuring frequency to its displayed precision, I decided
> to
> attempt the November 11/12 ARRL Frequency Measuring Test.
>
> I warmed up my K3 for about two hours because--even with
> the
> optional TCXO--my K3 drifts almost 0.1 ppm per degree
> Centigrade
> from 25C to 30C, the latter part of its warmup range this
> time
> of year at my QTH.  (0.1 ppm is almost 1 Hz on 40
> meters.)
>
> Then I carefully used method 2 to calibrate against 10 MHz
> WWV,
> checking after exiting REF CAL by tuning across WWV on CW
> with
> SPOT activated to see that the beat notes were similar on
> each
> side of zero beat for 1 and 2 Hz off frequency.  (A
> lack of
> similarity indicates that a small tweak of REF CAL is
> needed.)
> Tuning past WWV's carrier on CW with SPOT enabled also
> provides
> practice for the real thing.
>
> When W1AW (and each of the other FMT stations) began its
> call-up,
> I tuned its frequency to be centered in the passband with
> the DSP
> set at 50 Hz bandwidth.  When the long dashes began, I
> turned on
> SPOT and zero-beated against the sidetone with 1 Hz fine
> tuning.
>
> After recording the result, I moved on to the other
> frequencies
> and stations that had been specified in the ARRL FMT
> announcement.  I was able to copy and measure 4 of the
> 5 tests,
> with one station on one frequency being inaudible at my
> QTH.
>
> Result:  my K3 was within 1 Hz on all 4 readings, that
> is, its
> accuracy matched its displayed precision--after warmup and
> careful calibration.
>
> 73, Paul W8TM
>
>

     
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[ab2tc]

Hi,

First time I have heard about this. How much frequency shift are we talking about here? A fraction of a Hz, 10Hz? I have certainly never noticed this, but of course on speech anything less than 10Hz is practically inaudible unless you do a USB/LSB comparison on an AM station.

AB2TC - Knut

Wes Stewart wrote

Guys,

I've mentioned this caviet before:

http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451

The way the K3 implements the passband shift, the same signal, with the same VFO setting, will have a different audio beat note if the SHIFT control is changed. *

<snip>

[wayne burdick]

Here are the technical details regarding the K3's VFO tuning accuracy:

The K3's PLL synthesizer is phase locked to its 49.38 MHz reference  
via a DDS chip used as a precision divider. The DDS output is in the  
3.6 MHz range, with a step size of 0.184 Hz (49.38 MHz DDS clock  
divided by 2^28 DDS word size).

Taking the 8.215 MHz 1st IF into account (added to the VCO on 160-10  
m, subtracted from the VCO on 6 m), this translates to a VCO step size  
of about 0.5 Hz on 160 m, 1 Hz on 20 m, and 2 Hz on 6 m. Other bands  
are between these values.

Example:  At RF=14 MHz, the VCO is running at around 22 MHz. The ratio  
between 22 and 3.6 is about 6, and 6 * 0.184 = about 1 Hz. This is the  
worst-case DDS-related tuning error on 20 m.

If REF CAL (in the CONFIG menu) is not set to the exact frequency of  
the reference oscillator, there will be a small additional offset on  
all bands that is proportional to the operating frequency.

In diversity mode (main/sub VFOs and filter bandwidths set  
identically), the DDS chips on the two synthesizers are set to exactly  
the same tuning word, and the VCO outputs are at exactly the same  
frequency. The two synths are phase-locked to the same signal, so  
there is never any beat note between the two. This is critical for  
diversity use, and is lacking in some other transceivers with a sub  
receiver.

73,
Wayne
N6KR


On Nov 17, 2009, at 10:05 AM, ab2tc wrote:

>
> Hi,
>
> First time I have heard about this. How much frequency shift are we  
> talking
> about here? A fraction of a Hz, 10Hz? I have certainly never noticed  
> this,
> but of course on speech anything less than 10Hz is practically  
> inaudible
> unless you do a USB/LSB comparison on an AM station.
>
> AB2TC - Knut
>
>
>
> Wes Stewart wrote:
>>
>> Guys,
>>
>> I've mentioned this caviet before:
>>
>> http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451
>>
>> The way the K3 implements the passband shift, the same signal, with  
>> the
>> same VFO setting, will have a different audio beat note if the SHIFT
>> control is changed. *
>>
>> <snip>
>>
>
> --
> View this message in context: http://n2.nabble.com/K3-frequency-accuracy-versus-displayed-precision-tp4016138p4020213.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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[juergen piezo]

Hi Wes

I am measuring the TX carrier frequency through an attenuator then to the frequency counter which is locked to the Rubidium.  However, I dont know how this figures into what you are saying,  but our club K3's are spot on.

Since there is possibility of improving the  accuracy the external reference will be a waste of  money and time for most us.

John

--- On Tue, 11/17/09, Wes Stewart <[hidden email]> wrote:

> From: Wes Stewart <[hidden email]>
> Subject: Re: [Elecraft] K3 frequency accuracy versus displayed precision
> To: [hidden email], "juergen piezo" <[hidden email]>
> Date: Tuesday, November 17, 2009, 6:15 AM
> Guys,
>
> I've mentioned this caviet before:
>
> http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451
>
> The way the K3 implements the passband shift, the same
> signal, with the same VFO setting, will have a different
> audio beat note if the SHIFT control is changed. *
>
> So your calibrations with your atomic standards are no
> better than the delta F that takes place when you vary the
> shift control.
>
> If you want to measure frequency with the K3 BW and SHIFT
> *always* set to the same values then OK. However,
> calibrating at 50Hz BW and normalized SHIFT and then
> changing to SSB bandwidths and declaring that some stations
> are "on frequency" and others aren't is
> stretching it.
>
> * I've discussed this
> with Wayne and it's considered IP.
>
> Wes 
>  N7WS
>
> --- On Tue, 11/17/09, juergen piezo
> <[hidden email]> wrote:
>
> From: juergen piezo <[hidden email]>
> Subject: Re: [Elecraft] K3 frequency accuracy versus
> displayed precision
> To: [hidden email]
> Date: Tuesday, November 17, 2009, 12:53 AM
>
>
> Hi Paul
>
> I find the same thing, I have checked the clubs K3's
> against a rubidium standard that was calibrated to a cesium
> standard. The K3  is spot on, the only limitation 
> being  its 1hz calibration step limit for the TCXO. I
> wonder what use the yet to be released external standard
> interface will be when we can only  adjust the
> TCXO  in 1 hz steps.
>
> Its amazing  how far off frequency most stations are
> when you use a radio thats dead on, the typical average
> being 40 to 80hz off. The
>  K3 sounds so good on RX these days, its easy  to pick
> stations that are off frequency by even a few HZ. The radios
> that I have found to be consistently on frequency are the
> IC7700 and IC7800.
>
>  The SSB stations that impress me the most for being on
> frequency are the different Aeronautical control towers.
> These control towers have such excellent audio quality and
> they are always spot on frequency. Its a shame  that
> more ham stations cant sound so professional and clear like
> these aeronautical SSB stations. I have always wondered what
> brand of transmitter they use?  The excessive bass and
> ESSB audio  that we hear so often  just sounds so
> awful in comparison. Excessive bass and ESSB is just not
> good audio for SSB use. (I dont want to start a SSB debate!)
> but ESSB bassy audio sucks in comparison to these commercial
> SSB stations!
>
> John
>
>
> --- On Mon, 11/16/09, Paul Kirley <[hidden email]> wrote:
>
> > From: Paul Kirley <[hidden email]>
> > Subject: [Elecraft] K3 frequency accuracy versus
> displayed precision
> > To: [hidden email]
> > Date: Monday, November 16, 2009, 6:28 PM
> > The K3 is capable of displaying
> > frequencies to 1 Hz.  It can
> > be calibrated to somewhat less than 1 Hz against WWV
> > (method 2).
> >
> > Because I wanted to see if my K3 serial 1322 was
> capable
> > of
> > measuring frequency to its displayed precision, I
> decided
> > to
> > attempt the November 11/12 ARRL Frequency Measuring
> Test.
> >
> > I warmed up my K3 for about two hours because--even
> with
> > the
> > optional
>  TCXO--my K3 drifts almost 0.1 ppm per degree
> > Centigrade
> > from 25C to 30C, the latter part of its warmup range
> this
> > time
> > of year at my QTH.  (0.1 ppm is almost 1 Hz on
> 40
> > meters.)
> >
> > Then I carefully used method 2 to calibrate against 10
> MHz
> > WWV,
> > checking after exiting REF CAL by tuning across WWV on
> CW
> > with
> > SPOT activated to see that the beat notes were similar
> on
> > each
> > side of zero beat for 1 and 2 Hz off frequency. 
> (A
> > lack of
> > similarity indicates that a small tweak of REF CAL is
> > needed.)
> > Tuning past WWV's carrier on CW with SPOT enabled
> also
> > provides
> > practice for the real thing.
> >
> > When W1AW (and each of the other FMT stations) began
> its
> > call-up,
> > I tuned its frequency to be centered in the passband
> with
> > the DSP
> > set at 50 Hz bandwidth.  When the
>  long dashes began, I
> > turned on
> > SPOT and zero-beated against the sidetone with 1 Hz
> fine
> > tuning.
> >
> > After recording the result, I moved on to the other
> > frequencies
> > and stations that had been specified in the ARRL FMT
> > announcement.  I was able to copy and measure 4
> of the
> > 5 tests,
> > with one station on one frequency being inaudible at
> my
> > QTH.
> >
> > Result:  my K3 was within 1 Hz on all 4 readings,
> that
> > is, its
> > accuracy matched its displayed precision--after warmup
> and
> > careful calibration.
> >
> > 73, Paul W8TM
> >
> >
>
>
>
>      

     
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[juergen piezo]

Hi Wayne

If 2 X K3's can be phased locked ON TX and then combined with a Hybrid combiner, it should be possible to substantially reduce the TX IMD. This is a feature that the R&S Series 4100 DSP transmitters use to improve TX IMD  performance. They do the same with their 1KW PA's combining  and phase locking the amplifiers  with powers upto 4kw of output.

I am no expert in area, so I am not entirely sure if it is as simple as they indicate. It would however  prove very interesting if this could be achieved with two K3's?  A  good reason to buy more K3's!  

Is phase locking 2   K3's transmitters possible?

John

--- On Tue, 11/17/09, Wayne Burdick <[hidden email]> wrote:

> From: Wayne Burdick <[hidden email]>
> Subject: Re: [Elecraft] K3 frequency accuracy versus displayed precision
> To: "ab2tc" <[hidden email]>
> Cc: [hidden email]
> Date: Tuesday, November 17, 2009, 2:04 PM
> Here are the technical details
> regarding the K3's VFO tuning accuracy:
>
> The K3's PLL synthesizer is phase locked to its 49.38 MHz
> reference 
> via a DDS chip used as a precision divider. The DDS output
> is in the 
> 3.6 MHz range, with a step size of 0.184 Hz (49.38 MHz DDS
> clock 
> divided by 2^28 DDS word size).
>
> Taking the 8.215 MHz 1st IF into account (added to the VCO
> on 160-10 
> m, subtracted from the VCO on 6 m), this translates to a
> VCO step size 
> of about 0.5 Hz on 160 m, 1 Hz on 20 m, and 2 Hz on 6 m.
> Other bands 
> are between these values.
>
> Example:  At RF=14 MHz, the VCO is running at around
> 22 MHz. The ratio 
> between 22 and 3.6 is about 6, and 6 * 0.184 = about 1 Hz.
> This is the 
> worst-case DDS-related tuning error on 20 m.
>
> If REF CAL (in the CONFIG menu) is not set to the exact
> frequency of 
> the reference oscillator, there will be a small additional
> offset on 
> all bands that is proportional to the operating frequency.
>
> In diversity mode (main/sub VFOs and filter bandwidths
> set 
> identically), the DDS chips on the two synthesizers are set
> to exactly 
> the same tuning word, and the VCO outputs are at exactly
> the same 
> frequency. The two synths are phase-locked to the same
> signal, so 
> there is never any beat note between the two. This is
> critical for 
> diversity use, and is lacking in some other transceivers
> with a sub 
> receiver.
>
> 73,
> Wayne
> N6KR
>
>
> On Nov 17, 2009, at 10:05 AM, ab2tc wrote:
>
> >
> > Hi,
> >
> > First time I have heard about this. How much frequency
> shift are we 
> > talking
> > about here? A fraction of a Hz, 10Hz? I have certainly
> never noticed 
> > this,
> > but of course on speech anything less than 10Hz is
> practically 
> > inaudible
> > unless you do a USB/LSB comparison on an AM station.
> >
> > AB2TC - Knut
> >
> >
> >
> > Wes Stewart wrote:
> >>
> >> Guys,
> >>
> >> I've mentioned this caviet before:
> >>
> >> http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451
> >>
> >> The way the K3 implements the passband shift, the
> same signal, with 
> >> the
> >> same VFO setting, will have a different audio beat
> note if the SHIFT
> >> control is changed. *
> >>
> >> <snip>
> >>
> >
> > --
> > View this message in context: http://n2.nabble.com/K3-frequency-accuracy-versus-displayed-precision-tp4016138p4020213.html
> > Sent from the Elecraft mailing list archive at
> Nabble.com.
> >
> ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:[hidden email]
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