http://elecraft.85.s1.nabble.com/K3-frequency-accuracy-versus-displayed-precision-tp4016138p4024487.html
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.
> 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
> >
> >
>
>
>
>