[Elecraft] operating frequency calibration - K1

[Mike Morrow]

sergio wrote:

>i was wondering what people were using (station on the air) to do this..
>i don't know of any signal that is rock solid on the air to use..

Hi Sergio,

It would help if you included your ham call or other indication of location.
(Most of us like to know the callsigns of the hams on the list.)  I know
from earlier posts that you are speaking of the K1, but with three different
Elecraft rigs it will help to state which rig you are building in order to
keep others from assuming the wrong rig.  It would also help to know what
bands you've built into your K1, and what VFO span (80 or 150 kHz) you used,
in order to recommend a signal to use for calibration.

Finding an external broadcast to use to calibrate your K1 will be difficult
because EACH band has to be separately calibrated due to variations in the
frequencies of the hetrodyne crystals on the filter board.  You'll have to
find a suitable signal for each band.

If you can receive 10 MHz WWV, or have other time/frequency standard
stations around 10 MHz in your part of the world, that would be the best.
I'm sure there's a web site that lists most of these standards stations.
That would take care of 30m.

If your VFO span is 150 kHz, most shortwave broadcasters maintain very tight
frequency control on multiples of 5 kHz.  Zero-beat one on 40m and adjust
your display.   That would take care of 40m.

You'll have to find some other stations for the other bands that you have in
your K1.

As another consideration, most would agree that the display should be
calibrated to show the TRANSMITTER frequency, rather than the RECEIVER
frequency.  For example, if you have adjusted RF-C13 for a transmitter
offset of 600 Hz, then the TRANSMIT frequency will be 0.6 kHz LOWER than the
RECEIVE frequency.

Therefore, one of the best calibration methods consists of measuring the K1
transmitter with a frequency counter or listening to the K1 transmitter in
an accurate receiver (in LSB or USB mode) tuned to zero-beat the K1, then
making the K1 display show the same frequency as that shown on the counter
or external receiver.  You have to do this for EACH band your K1 covers.

There is another approach you can take that is just approximate.  The K1
front panel MCU crystal is 4000 kHz nominal, but has been designed to
actually oscillate around 3999.6 kHz.  Harmonics from this oscillator can be
heard just below the ham bands at about 6999.3, 9999.0, 13998.6, and 20997.9
kHz.  You won't be able to use these approximate signals on 30m if you use
the 80 kHz VFO, or on 17m, since the VFO won't tune that low on these bands.
Also, your VFO may not tune low enough to pick up the signal on 15m.  You'll
be calibrating the receive frequency, not the transmit frrequency.

Try to get an accurate external receiver or frequency counter and use that
method, if possible.

73,
Mike / KK5F