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| -rw-r--r-- | 5.-KrakenSDR-Web-Interface-Controls.md | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/5.-KrakenSDR-Web-Interface-Controls.md b/5.-KrakenSDR-Web-Interface-Controls.md index 0c76ec8..4e2c12b 100644 --- a/5.-KrakenSDR-Web-Interface-Controls.md +++ b/5.-KrakenSDR-Web-Interface-Controls.md @@ -313,7 +313,7 @@ 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 in nanoseconds 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 time differences in nanoseconds here. Please note the differences must be measured relative to channel 0. `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. @@ -327,20 +327,18 @@ If you are using `explicit-time-delay` as the IQ adjustment source, enter the de 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. +If your VNA only provides TDR length measurements, you can easily convert cable delta measurements into time as long as you know the coax cable velocity factor. The formula is as follows, where c is the speed of light at 299792458, and vf is the cable velocity factor. -Example, for cables with velocity factor (vf=0.66), time_delta in nanoseconds is given by: +time_delta_x = ( cable_length_delta / (c * vf) ) * 10^9 -time_delta_x = ( cable_delta / (c * vf) ) * 10^9 - -Real example: +In the example below we have three cables with vf=0.66 with slightly different lengths that we'd like to compensate for. The time_delta in nanoseconds is given by: 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 +cable_length_delta_1 = 2.00130m - 1.99933m = 0.00197m +cable__length_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 |