[Elecraft] Re: N6KR's 4 MHz oscillator cal method for the K2

[Wayne Burdick]

Hi Steve,

Steven Gibbs wrote:
> 
> Wayne Burdick wrote:
> > Not if you use my new method, and that's the entire point.
> > No iteration needed.
> 
> But Wayne, step 2 of your method says
> 
> > Now alternately move the K2's internal counter probe between
> > TP1 (VCO) and TP2 (BFO), adjusting C22 in small increments
> > until the kHz and Hz digits at the two test points match as
> > closely as possible."
> 
> That *IS* an iterative method, even though CAL-PLL & CAL-FIL
> are not included in the loop.  

It may be "iterative" in the sense that you're moving the probe back and forth,
but it only takes a few seconds to converge on the matched frequencies,
visually, if the reference is on an exact kHz boundary. "Iteration" in the sense
used earlier means adjusting C22, then running CAL PLL and CAL FIL, then
adjusing C22 again, running CAL PLL and CAL FIL again, etc. This can take a half
an hour. The new method is so much faster and easier that it's an apples/oranges comparison.


> It suffers from CAL-FCTR's
> 10Hz display ambiguity which cannot afford the precision
> needed to ensure MCU oscillator setting within the one part
> in a million which is needed.

10 Hz precision is adequate to hit the +/- 30 Hz target alignment accuracy at 28
MHz, assuming the source signal is at 10 MHz or higher. Those who want better
accuracy can use another method, such as one of yours, or use a known reference
signal in the 28 MHz band rather than one at 10 or 15 MHz.


> > Your objection regarding accuracy of tuning of the reference
> > signal can be addressed in other ways, as noted by other
> > posters.
> 
> You will need to define these in a manner understandable by
> average K2 builders who have been misled by so many scatter-
> brained schemes posted here.

I'd prefer to use a less pejorative word when referring to those who have
volunteered their time to come up with their own methods. Many kit builders are
by nature experimenters, and a big part of the value added by the Elecraft
reflector is that everyone is free to suggest modifications, improvements, or
alignment techniques. We're pretty tolerant of "first-time-designers" around
here  ;)

My objective is to determine whether "average builders" like the new method I've
suggested. If they don't, there's no problem. The method in the printed K2
manual is entirely adequate anyway.


> > But from the standpoint of adjusting C22, this is the only
> > non-iterative adjustment method.
> 
> *Not so*.  My comment gave two *real* non-iterative methods,
> repeated below. Please take time to verify that they are
> straightforward and that they really do *consistently* work
> to the needed accuracy.

My method is not "iterative" in the same sense, and takes only seconds (see above).

I've read through your methods, which are both extremely well document, AND they
work. The problem is that "average builders" don't have access to accurate bench
references or oscilloscopes, and using Spectrogram and a PC to complete
alignement takes a lot longer than simply using the K2's built-in frequency
counter. As the designers of the kits, we have to strive to simplify the
alignment in view of what test gear the average ham possesses.

What I would recommend to builders is that they use the methods from the present
K2 manual, or try my new method, if they'll be happy with 20-30 Hz accuracy on
the highest band. 

If they want better accuracy, they can use my method with a 28 MHz known
reference signal, or use one of your methods. 

tnx
Wayne