[Elecraft] Soon to be owner

[Ron D'Eau Claire]

The phase-locked loop (PLL) design in the K2 is a bit unusual. It's =
actually
a combination of a PLL and a VXO (variable frequency crystal =
oscillator).
The VXO acts as the reference frequency for the PLL. The PLL handles big
frequency steps and the VXO is electrically tuned to set the precise
frequency in between the larger steps.  That unusual design plays a big =
role
in the superb "quietness" of the receiver compared to other synthesized
rigs. The Elecraft PLL generates far less noise than conventional PLL
designs.

However, it does require that the reference oscillator for the PLL be
variable in order to tune to a specific frequency. That makes it pretty
tough to use a fixed external frequency standard unless it could be =
adjusted
too, and if you use a variable external reference oscillator you no =
longer
have the system locked to the GPS signal. You might design an external =
PLL
to produce the right signal to replace the VXO in the K2 that is =
controlled
by the GPS signal, but the end result would probably compromise the K2's
noise figure with more phase jitter in the L.O. signal.=20

In any case it's anything but a "simple" project.=20

Like all good designs, the K2 is a lot of compromises. In this case they
went for superior low noise receiver performance instead of using a =
noisier
full PLL system like most of the other rigs on the market today. Then =
they
worked hard on stabilizing the PLL reference oscillator to ensure that =
it
was solid enough for digital modes.=20

So, from where I sit, the INability to lock the K2 to an external source
like the GPS signal is a feature, not a shortcoming <G>

Ron AC7AC

=20

-----Original Message-----
I appreciate this reflector / board, it looks like a great group of =
folks
here. If I would like to see Elecraft do one thing, it would be to add a =
PLL
option ie; where the rig could be locked to an external 10mhz. signal =
via
GPS......on the digital modes & using for a VHF/UHF IF, it would be
perfect.....the new Icom 7800 will have the feature..(envy). I don't =
think
it would be har to add??? CT1DMK mades a PLL board but I don't know the =
osc.
range it will work with or the LO of the K2....

                Hope to be on the air soon with a K2....

                                    Brian w3eme