[Elecraft] K3 External Reference input

[Brendan Minish]

On Fri, 2008-02-22 at 20:24 -0500, Paul Christensen wrote:
> > Is there interest among the group for the necessary parts to input a
> > disciplined 10MHz signal to control frequency?  We all know there is a 
> > place
> > holder on the back panel, but Gary just told me there were no plans.
> 
> I'm really hoping for this option.  I use a Hewlett-Packard 58540A GPSDO for 
> use with my IC-7800.  Long-term accuracy when GPS-locked is typically 1E-12. 
> That's essentially the same accuracy as the atomic cesium beam standards 
> used on board the GPS satellites.

The 7800 has some decimation error issues and can be off from the
standard by up to 0.1Hz 
A simple demo of this is to put main and sub RX on the same signal on
the same antenna and listen in stereo for the slow phasing that goes on
between the 2 receivers, it's horrid and makes it a very poor diversity
receiver. It's due to the IF of the sub RX being separated by 100Khz
this leads to a difference in the decimation errors between the main and
Sub RX. Shame on Icom for getting this so wrong.

I Don't know if decimation errors will limit the accuracy of the K3 when
using an external ref but I would not be surprised if this was the case.
Just because you can attach an external ref does not mean that your
RX/TX is now as accurate as the reference, there are other factors that
may limit overall system accuracy  

My Racal 3702 is on the other hand a true diversity receiver, both
receivers are truly phase locked at all stages to any supplied
reference, external or internal. It's a joy to use for diversity
reception and true diversity reception is a fantastic tool for tropical
band BC dxing 

One other issue is that the 7800 simply replaces it's internal
oscillator  with the external source so that external source needs to
have excellent Phase noise performance if you are to avoid degrading the
performance of the radio. This will be an even bigger issue with the K3
at narrow spacings.   

IF Elecraft get to market with the external ref port I'll probably be
adding it.

I have a collection of GPS locked oscillators, 2 of them are rubidium
based 
I also have a home brew IPv6 stratum 1 NTP server at 
balrog.home.minish.org
If you have IPv6 Internet connectivity try it out and let me know how
you get on  


73 Brendan EI6IZ 

-- 
Don‘t complain. Nobody will understand. Or care. And certainly don‘t try
to fix the situation yourself. It‘s dangerous. Leave it to a highly
untrained, unqualified, expendable professional.