Tr: K3 Ref connector

[Dave, G4AON]

The REF input connector is for an external reference that was mentioned
way back, just like synchronous AM and TCXO additional temperature
compensation to 0.5 ppm, it seems to be getting pushed back by new
add-ons such as the internal 2m transverter card. Elecraft do not
publish a K3 project plan showing roll out dates for items that were in
the original specification, so don't hold your breath waiting for the
REF input board.

73 Dave, G4AON
K3/100 #80
------------------------
What is the connector for, and can I plug a 10MHz reference to it?

Mike Short

AI4NS
______________________________________________________________
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

[David Pratt]

The connector is referred to on page 17 of the latest K3 Owner's Manual
and my K3 rear panel is labelled "REF."

In consequence, I have bought a Racal-Dana 9474 Rubidium Frequency
Standard which is now poised to plug in as soon as the KREF3-EXT is
available, hopefully quite soon.

73

David

In a recent message, Dave G4AON <[hidden email]> wrote ...

>
>The REF input connector is for an external reference that was mentioned
>way back, just like synchronous AM and TCXO additional temperature
>compensation to 0.5 ppm, it seems to be getting pushed back by new
>add-ons such as the internal 2m transverter card. Elecraft do not
>publish a K3 project plan showing roll out dates for items that were in
>the original specification, so don't hold your breath waiting for the
>REF input board.
>
>73 Dave, G4AON
>K3/100 #80
>------------------------
>What is the connector for, and can I plug a 10MHz reference to it?

--
David G4DMP
Leeds, England, UK
------


______________________________________________________________
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

[David Pratt]

In a recent message, Jerry T. Dowell <[hidden email]> wrote ...
>
>Do not hold your breath waiting for it. The last time I talked to Wayne and
>Eric about it, they said that it is not a high priority with them and that
>they are not likely to do it soon because very few users are interested in
>having the feature. I am irritated because that capability is one reason I
>bought the K3 (the spec sheet indicated that it was already installed).

I would have expected priority to have been given to those features
originally announced when the K3 was first launched rather than some of
the other 'goodies' that have since emerged.  When all said and good,
Elecraft already have a 2 metre transverter (XV144) that works perfectly
well with the K3.

73
--
David G4DMP
Leeds, England, UK
------


______________________________________________________________
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

[Brendan Minish]

On Sat, 2009-05-16 at 08:03 +0100, David Pratt wrote:
> The connector is referred to on page 17 of the latest K3 Owner's Manual
> and my K3 rear panel is labelled "REF."
>
> In consequence, I have bought a Racal-Dana 9474 Rubidium Frequency
> Standard which is now poised to plug in as soon as the KREF3-EXT is
> available, hopefully quite soon.

Couple of thoughts here

Unlike the Racal RA3702 I have here; the K3 is incapable of phase
accuracy (RF to audio), or indeed exact frequency accuracy (multiple DDS
LO conversions with ensuing decimation errors, varying offsets for
roofing filter positioning etc)    

As a result phase locking or replacing the internal REF with a highly
stable and accurate external source is not likely to be very useful. The
(better than) 1ppm ref carefully set up and used in a stable temperature
environment is probably approaching the limits of the K3's architecture
with regard to frequency setting accuracy. (although an external ref may
further improve frequency stability. )

The K3 is not alone here, my Icom IC-7800 was often up to 0.25 Hz or so
off frequency when driven with a external GPS disciplined Rubidium
reference source, I suspect that the main cause of this was DDS
Decimation errors but it was also an issue between main and sub making
true diversity a non-runner on the 7800 despite having so called
'matching' main and sub receivers.

Lastly be careful with Rubidium as it's phase noise performance is far
poorer than a good Xtal Reference and this can be a problem at times as
it may degrade the strong signal performance of a High Dynamic range
receiver.

I am a time nut and do make on occasion some interesting measurement on
LF & HF with my RA3702 using my external 10MHz ref but I do not think I
will be adding this external locking feature to the K3 when it is
released.

--
73
Brendan EI6IZ

______________________________________________________________
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

[P.B. Christensen]

> As a result phase locking or replacing the internal REF with a highly
> stable and accurate external source is not likely to be very useful.

Brendan raises an interesting point.  I use an HP 58540A GPS/DO with an
IC-7800 and note some of the same decimation errors that he addresses --  
although my long term accuracy is much better than +/- 0.25 Hz, but
certainly not anywhere near the accuracy offered by the GPS/DO for the
reasons that Brendan stated.  That said, anyone know the maximum accuracy
deviation owing to decimation error when using the K3's architecture?

Although my K3 has the high-stability TCXO option, the long-term accuracy of
the IC-7800 with HP 58540A is still significantly better.  Note that I'm
discussing the long-term stability.  To some extent, Elecraft's forthcoming
TCXO calibration algorithm may better match the characteristics of the TCXO
and offer better long-term stability over that which I'm now measuring.

The importance of this is pretty much relegated to a footnote.  Not many of
us need the extreme levels of accuracy we're discussing, but it's an
interesting exercise to extract the highest degree of frequency accuracy
possible from any transceiver.

Paul, W9AC


______________________________________________________________
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

[n7ws]

--- On Sun, 5/17/09, Brendan Minish <[hidden email]> wrote:

> From: Brendan Minish <[hidden email]>
> Subject: Re: [Elecraft] Tr: K3 Ref connector
> To: "David Pratt" <[hidden email]>
> Cc: [hidden email], "Dave G4AON" <[hidden email]>
> Date: Sunday, May 17, 2009, 6:44 AM
> On Sat, 2009-05-16 at 08:03 +0100,
> David Pratt wrote:
> > The connector is referred to on page 17 of the latest
> K3 Owner's Manual
> > and my K3 rear panel is labelled "REF."
> >
> > In consequence, I have bought a Racal-Dana 9474
> Rubidium Frequency
> > Standard which is now poised to plug in as soon as the
> KREF3-EXT is
> > available, hopefully quite soon.
>
> Couple of thoughts here
>
> Unlike the Racal RA3702 I have here; the K3 is incapable of
> phase
> accuracy (RF to audio), or indeed exact frequency accuracy
> (multiple DDS
> LO conversions with ensuing decimation errors, varying
> offsets for
> roofing filter positioning etc)     

... [show rest of quote]

Correct. I have been able to hear, or more easily see using Spectrum Lab, the change in pitch on a signal while simply changing the DSP bandwidth.

There is a lot of frequency changing going on when the passband is moved and not every oscillator moves at the same rate.

Best have another receiver around for the FMT.

Wes  N7WS


     
______________________________________________________________
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