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Diffstat (limited to '5.-KrakenSDR-Web-Interface-Controls.md')
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1 files changed, 25 insertions, 5 deletions
diff --git a/5.-KrakenSDR-Web-Interface-Controls.md b/5.-KrakenSDR-Web-Interface-Controls.md index 498c92d..0c76ec8 100644 --- a/5.-KrakenSDR-Web-Interface-Controls.md +++ b/5.-KrakenSDR-Web-Interface-Controls.md @@ -313,16 +313,36 @@ How many coherent calibration sync failures are required before recalibration is This provides an option to calibrate the full system by compensating for phase differences in the antenna coax cables. -`explicit-time-delay` - If you've measure time delay with a VNA you can input the differences here. Please note the differences must be measured relative to channel 0. +`explicit-time-delay` - If you've measure time delay with a VNA you can input the differences in nanoseconds here. Please note the differences must be measured relative to channel 0. -`touchtone` - You can output .s1p files for the 5 coax cables in your system, and add them to the _calibration folder. Name them as cable_ch0.s1p, cable_ch1.s1p and so on. You need to ensure that the touchstone file covers the frequency range that you will be using. +`touchtone` - You can output .s1p files from your VNA for the 5 coax cables in your system, and copy them to the _calibration folder. Name them as cable_ch0.s1p, cable_ch1.s1p and so on for each of your five cables used in the system. You need to ensure that the touchstone file covers the frequency range that you will be using. **IQ Adjust Amplitude** -If you have some reason to manually adjust IQ amplitudes, this can be done here. +If you have some reason to manually adjust IQ amplitudes, this can be done here. In most cases this is only used for testing. **IQ Adjust Time Delay** -If you are using `explicit-time-delay` as the IQ adjustment source, enter the delta time differences here. (Relative to the CH0 cable, so delta = CH_0 - CH_X) +If you are using `explicit-time-delay` as the IQ adjustment source, enter the delta time differences in nanoseconds here. (Relative to the CH0 cable, so time_delta_x = CH_0 - CH_X). -**TODO: Show how to calculate time delay from cable length + velocity factor.**
\ No newline at end of file +Remember, these are measurements relative to CH-0, so for the KrakensDR with five channels, there should be four inputs. For the KerberosSDR with four channels, there should be three inputs. + +If your VNA only provides length measurements, you can easily convert cable delta measurements into time as long as you know the coax cable velocity factor. + +Example, for cables with velocity factor (vf=0.66), time_delta in nanoseconds is given by: + +time_delta_x = ( cable_delta / (c * vf) ) * 10^9 + +Real example: + +Cable 0: 2.00130m +Cable 1: 1.99933m +Cable 2: 1.99910m + +cable_delta_1 = 2.00130m - 1.99933m = 0.00197m +cable_delta_1 = 2.00130m - 1.99910m = 0.00220m + +time_delta_1 = (0.00197m / (c * 0.66)) * 10^9 = 0.009956383ns +time_delta_2 = (0.00220m / (c * 0.66)) * 10^9 = 0.011118803ns + +Repeat for Cable 2,3,4 and enter the values of time_delta_1,time_delta_2,time_delta_3,time_delta_4 into the `IQ Adjust Time Delay` box. (Do not add any time units like ns)
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