[Elecraft] K3 External Reference input

[Paul Christensen]

> 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.

Most GPSDOs are not known for their ultra-high phase noise performance. 
Still, the SC-cut OCXOs as used in the HP Z3801A, HP Z3816A, and HP 58540A 
units are typically -145 dBc/Hz @ 1kHz offset.  On the used market, expect 
to pay USD $300-$800.  However, there is one relatively new, compact GPSDO 
from Jackson Labs that has hit the market and offers excellent phase noise 
performance for a GPSDO.:

http://www.jackson-labs.com/docs/Fury_Flyer.pdf

Even better phase noise performance (e.g., -165 dBc/Hz @ 1 kHz) can be had 
through the use of non-GPS-disciplined OCXOs.  For example, Wenzel makes 
highly accurate OCXOs with phase noise specs that are typically 0-15 dB 
better than the GPSDO types.

http://www.wenzel.com/pdffiles1/Oscillators/Comp.pdf

With either of these types, one simply connects the output of the OCXO to 
the 10MHz reference input on the transceiver with one cable.  The OCXO is 
powered from a low-voltage DC power source.  Although the K3 may not be 
capable of resolving to 1E-12 accuracy, you can be rest assured that when 
using either of these oscillator types that your signal will be the new 
frequency standard on the bands.

Paul, W9AC