The SDR revolution has brought a new element into MW DXing: the use of offsets in signal analysis and pre-identification. In order to use any offset-based tool in JAGUAR, reliable calibration is required.
KALIBRATE is JAGUAR's calibration function. Compared to other SDR software, JAGUAR's calibration method is exceptionally easy, and it does not have to be made before recording. In addition, there is support for the "4th decimal" (a fraction of Hertz) accuracy.
The last fourth decimal is not necessarily always correct: the error margin is +/- 0.5 Hz (or +/- 0.1 Hz in JAGUAR PRO when in the HIRES mode). So if you want to be on the safe side, please use the offsets rounded to the nearest third decimal (the accuracy of one Hertz) in your public offset loggings. Although the fourth decimal can be used when the HIRES mode is activated, logging the fourth decimal requires extra attention and a bit a longer period of time spent in monitoring.
By pressing the "K" key you can calibrate JAGUAR's frequency accuracy, based on the accuracy of the current frequency. You must tune in to a frequency where the station has a known and stable frequency with a sharp carrier peak visible. After the "K" key is pressed, the SPECTOR peak should show the exact .0000 frequency. You can repeat the process if the conditions make the peak to wobble, and it is difficult to get an exact calibration match. The calibration has an error range of 0.0005 kHz so the last fourth decimal is not necessary always correct - but it can be, you cannot be always sure. This is why it is recommended to use only three decimals in official offset loggings.
You can repeat this process any time you see that the calibration is not "spot on". This may be caused due to many things, e.g. a change in the hardware temperature. Calibration can be done either in the LIVE mode, or while listening to any ARCHIVE file (in JAGUAR, calibration can be done also afterwards for old files).
TOOLBAR > K (KALIBRATION) icon 
is red if the calibration is "spot on". JAGUAR can also be calibrated by clicking this icon.
The method of pressing the "K" key requires that you are tuned to the nominal frequency of the station used in calibration. However, most of the JAGUAR PRO users use the FAST CALIBRATION method: you can KALIBRATE your setup being tuned to any frequency and press the "K" key (or click TOOLBAR > K). All what we need is a good solid calibration frequency for your setup. Naturally it must be available at any time you calibrate.
Normally, calibration is done with a station known to be on the exact .0000 frequency. However, if you know that a certain local station always sits on an exact offset frequency, you can use also that offset for calibration.
First, you must define your calibration frequency in SETTINGS > SPECTOR > FAST_CALIBRATE. For example,
FAST_CALIBRATE ............ 828.0000
Now if you press the "K" key (when listening to any frequency!), JAGUAR performs the calibration in the background (the playback control does not jump to 828). Of course, you can go to 828 and check if that was done correctly but if it seems to be "always OK", quite likely you start to trust it and there is no need to check it after pressing "K". When you press "K" in "normal" calibration, JAGUAR prompts a "Do you really want to ..." confirmation box but there is no need for that if you use FAST_CALIBRATE: it does not harm if you press "K" accidentally because calibration is just done one more time using the correct frequency.
In many European setups, 828 is often visible (but not always audible in full daylight) so we in Europe can successfully do this "blind calibration" quite freely. When writing this (March 2021), the following frequencies seem to be stable enough to be used for calibration in Europe: Russia on 828.0000, UK on 1215.0000 (even though some transmitters are listed on 1214.9999), MDA 1413.0000, and UK on 1341.0001.
In JAGUAR PRO you can also keep the CALIBRE applet always visible to monitor the calibration frequency (and calibrate by clicking the applet if needed).
If you trust your calibration frequency (e.g. you have a GPSDO device or there is a good stable calibration frequency available 24x7), you will never need to calibrate manually. Instead, you can let JAGUAR keep the calibration spot on as a continuous background process: define
AUTO_CALIBRATE ............ YES
in SETTINGS > SPECTOR > AUTO_CALIBRATE. This setting takes care of both the standard calibration (with the accuracy of 0.5 Hz) and the HIRES calibration (with the accuracy of 0.1 Hz) for SPECTOR and the spectrum graphs.
Beginning from JAGUAR V7, you can define multiple calibration frequencies for FAST_CALIBRATE (the frequencies must be separated by a comma). If such a list is defined, clicking TOOLBAR > KALIBRATION opens a popup menu and you will need to select the calibration frequency. The currently-used calibration frequency is shown on STATUSBAR.
When you open a new ARCHIVE file, JAGUAR selects the frequency used for calibration as follows:
Note that if you select an alternative calibration frequency from the popup menu for any file, the original frequency in the file header is not updated. So, when you open this file next time, the original "CAL FREQ" in the header is used again for calibration.
LIVE mode/recording can be active while you listen to old ARCHIVE files, and the calibration frequency used in the LIVE mode does not need to be the same as the one used in the ARCHIVE mode.
Beginning from JAGUAR V7, the "live-mode calibration frequency" will be saved in the file header of the recorded file as the default calibration frequency for that file. By default, this frequency is always the first frequency set for FAST_CALIBRATE. This frequency can be overridden with SETTINGS > MESTOR > SET CALFREQ, or by selecting a new live calibration frequency from the TOOLBAR > K popup menu.
If you define only one "SET CALFREQ" row in MESTOR (let's say "SET CALFREQ 1341.0001 AT 2000"), it means that when the recording is saved, 1341.0001 will be saved in the file header, bypassing the frequency value defined for the FAST_CALIBRATE parameter.
In addition, MESTOR allows you to save different day-time/night-time calibration frequencies for the files, see SETTINGS > MESTOR > SET CALFREQ for details.
To summarize: the saved live-calibration frequency (= the first frequency in FAST_CALIBRATE) can be overridden by "SET CALFREQ" in MESTOR. You can still manually set a different live-calibration frequency via the TOOLBAR > K popup menu. This live-calibration frequency is saved to the file header and will be used as the default calibration frequency for this file when played back later in the ARCHIVE mode.