[Elecraft] RE: K1 Receiver OPF Calibration

[Morrow, Michael A.]

MArtin wrote:

> When doing the K1 receiver alignment, I noticed a ref to an
> internally generated signal (K1 manual p41 under operating=20
> freq calibration). I think there is a birdie off the lower
> band edge is this what is being referred to, if so where does
> it come from, is it accurate and should I use it?

Martin,

It's already been pointed out that the birdie comes from the
K1 front panel MCU 4 MHz crystal oscillation.  I think typically
K1 MCU oscillators actually oscillate (by design) at around
3999.5 kHz.  Divide that by four (999.875), then multiply by the
nearest "MHz" of the band edge, and you'll get a more exact
value of the frequency of the band-edge birdie.  Thus:

Band     Exact Birdie Frequency         Proper K1 Zero-Beat Display
                                        (With 0.8 kHz Offset)
  7        6999.1                              6998.3
 10        9998.8 (Requires 150 kHz            9998.0     =20
                  VFO option to tune=20
                  to it.)
 14       13998.3                             13997.5
 18       17997.8 (Unusable.  K1 won't           ---
                  tune to it.)
 21       20997.4                             20996.6

Most people calibrate their K1 display to show transmitter frequency,
not receiver frequency.  There will be an offset between those two
frequencies as explained in the manual for transmitter CW offset
adjustment.  Typically many choose a 800 Hz offset (the transmitter
will be 0.8 kHz lower than the receiver frequency).  So if your receiver
is zero-beat to a frequency of, say 6999.1 kHz, you'd want to calibrate
the display to show 0.8 kHz below 6999.1 kHz (6998.3) in order to have
the display show the *transmitter* frequency.  That's what is shown in
the right-most column above.

It is a very thoughtful part of the K1 design that the MCU crystal=20
oscillates on purpose a little below the nominal 4.0 MHz crystal
frequency.  Otherwise, this band-edge birdie could always show up=20
just *inside* the ham band.

73,
Mike / KK5F