Skimmer frequency accuracy
To be a good RBN citizen a skimmer should have a frequency accuracy of 2ppm or better.
To use the data below to improve the accuracy of your skimmer, multiply the current value of FreqCalibration in your skimmer software’s settings file with the suggested adjustment factor listed below.
The location of the settings files are:
CW Skimmer Server: %appdata%\Afreet\Products\SkimSrv\SkimSrv.ini
CW Skimmer: %appdata%\Afreet\Products\CwSkimmer\CwSkimmer.ini
The data listed below is based on archived RBN data from the previous day, 00:00 to 23:59 UTC. This means that when making adjustments, changes in calibration will not have full impact on the listed data until the second day after the change.
The deviation estimates listed below are based on spots on all active bands (40m and above) from the respective skimmer. If different hardware is used for different bands, the deviation number may thus not represent the actual deviation for a particular band.
A link to the software used to produce the tables can be found at the bottom of this page. It runs as a cron job in an Ubuntu container on my Synology server and uploads to this WordPress website shortly after midnight UTC every night.
The deviation estimation is done in two steps. The first step uses a small number of highly accurate skimmers (called “anchors” in the code, typically GPSDO-controlled skimmers) as reference. The whole estimation process is then repeated one more time but using both the anchors as well as all skimmers determined to be the “good” as reference. The “good” skimmers are those with less than 0.15ppm average deviation from the anchors, producing more than 100 qualifying spots (the qualification criterion of spots are outlined below.)
Repeating the analysis with this this extended set of skimmers as frequency references drastically increases the geographical coverage of the analysis thereby increasing the number of qualifying spots which means a much more reliable deviation estimates for all skimmers. The skimmers used as reference skimmers in the second stage (i.e. both anchors and “good”) are marked with an asterisk in the table below.
When looking at the numbers, keep in mind that the deviations estimated by the algorithm is 100 to 1000 times smaller than the 100Hz resolution of RBN frequency data. The input data is thus extremely “noisy” which inevitably leads to statistical variations. This is also the reason for not including spots under a certain frequency. They will just skew the statistics and cause underestimation of the frequency error.
Due to propagation characteristics, operator behavior (e.g. small QSY), and just statistical variations due to the 100Hz rounding, some skimmers selected as reference skimmers in the first stage may have more than 0.2ppm deviation in the second stage. This is not an error.
If you do not see your skimmer in the list below in spite of it successfully feeding spots to RBN the most likely reason is that it is off in frequency. The analytics discards all spots from skimmers having more than 0.5kHz frequency error.
4234209 RBN spots between 2023-05-28 00:00 and 23:59 UTC. 817897 spots (19.3%) were from reference skimmers (*). Average spot flow was 2940 per minute from 202 active CW skimmers. 1961928 spots from 201 skimmers qualified for analysis by meeting the following criteria: * Mode of spot is CW. * Also spotted by a reference skimmer within 1000 spots. * Also spotted by a reference skimmer within 10s. * SNR is 3dB or higher. * Frequency is 7000kHz or higher. * Frequency deviation from reference skimmer is 0.5kHz or less. * At least 5 spots from same skimmer in data set. Skimmer [ppm] Spots Adjustment ------------------------------------- 3B8CW +1.0 4211 1.000001005 3D2AG* +0.0 1689 1.000000005 3V8SS -1.9 5357 0.999998077 7N4XCV +1.2 1906 1.000001191 9M2CNC -0.3 5373 0.999999745 AC0C-1 +0.2 18648 1.000000248 BA6KC -0.1 5120 0.999999888 BD4QJP +4.8 8 1.000004754 BD7DT +1.4 9470 1.000001439 BD7JNA +6.8 4482 1.000006777 BD7JNA1 +0.6 5281 1.000000587 BD7LAE -5.3 3364 0.999994748 BD8CS/8* -0.1 10352 0.999999867 BG2TEM -4.9 2299 0.999995052 BG2TFW +7.6 873 1.000007567 BG2UKX +5.1 112 1.000005052 BG4GOV3 +1.0 3817 1.000000999 BG4WOM +1.0 4196 1.000001004 BG8FZU +4.8 3053 1.000004791 BH3BBJ +1.6 3037 1.000001564 BH4DEG +6.1 4677 1.000006061 BH4RRG* -0.1 4671 0.999999935 BH4RRG0 +0.3 2287 1.000000350 BH4RXP +0.5 9055 1.000000521 BH4XDZ* +0.0 4764 1.000000037 BI4RFP +1.5 5566 1.000001492 CT7ANO -4.6 22165 0.999995404 CX7ACH +17.4 370 1.000017381 DC8YZ +0.1 19122 1.000000109 DD5XX* -0.1 11246 0.999999890 DE1LON +1.0 20972 1.000000986 DF2CK +1.7 30219 1.000001668 DF7GB* +0.0 18006 1.000000028 DK0TE +1.0 20927 1.000001031 DK3UA -8.2 4006 0.999991795 DK9IP +0.2 14085 1.000000213 DK9IP-1 +0.2 16476 1.000000182 DL0PF +3.7 8407 1.000003711 DL1AXX* +0.1 13482 1.000000063 DL1HWS -1.8 21309 0.999998158 DL8LAS +1.5 14354 1.000001456 DL8TG* +0.0 18719 1.000000008 DL9GTB -2.8 23318 0.999997151 DM5GG +0.4 19898 1.000000411 DM6EE* +0.0 5917 1.000000006 DM7EE +0.4 15402 1.000000361 DR4W -2.0 20935 0.999998039 E28AC +4.8 2348 1.000004829 EA1RX -6.1 2943 0.999993945 EA1URA -1.8 18808 0.999998153 EA2CW +0.8 14259 1.000000830 EA2RCF-4 +0.4 12705 1.000000374 EA5WU -0.6 3013 0.999999398 ES2RR* -0.0 21722 0.999999998 EY8ZE +0.6 9531 1.000000628 F AHD +8.5 26 1.000008545 F1TRE +0.5 31 1.000000537 F6IIT -0.7 17973 0.999999350 F8DGY -4.1 12396 0.999995871 G0KTN +0.8 20488 1.000000802 G3XBI +0.3 8031 1.000000343 G3YPP +0.2 4728 1.000000190 G4HSO +0.2 22725 1.000000212 G4IRN +0.7 15861 1.000000660 G4ZFE +0.5 21076 1.000000501 GI4DOH* -0.1 3028 0.999999890 GM6DX +0.8 5592 1.000000771 HA1VHF +1.2 13186 1.000001243 HA6PX +0.8 13111 1.000000768 HA8TKS +0.5 18777 1.000000527 HB9BXE* +0.1 10931 1.000000105 HB9DCO* +0.1 16166 1.000000093 HB9RB -2.8 752 0.999997154 HG0Y +2.0 2555 1.000002014 HG5FMV +0.4 500 1.000000378 HG8A +1.9 20935 1.000001934 HS/F8UKP -0.2 3773 0.999999844 IK3STG +7.2 1123 1.000007184 IK4VET +3.8 23026 1.000003772 IV3DXW -3.8 17619 0.999996190 JA4ZRK* -0.0 5963 0.999999975 JG1DLY -0.6 410 0.999999408 JH4UTP +0.7 8161 1.000000715 JH7CSU1 +5.1 7403 1.000005145 JI1HFJ -1.4 1748 0.999998586 JJ2VLY +2.5 6035 1.000002502 JN1ILK +0.8 9880 1.000000808 K1TTT -0.4 8085 0.999999575 K2PO/7 -4.9 4670 0.999995102 K3PA-1* +0.1 9471 1.000000071 K4PP +0.2 8817 1.000000153 K5EM +0.1 3798 1.000000113 K5TR +0.8 7572 1.000000760 K6FOD* +0.1 3773 1.000000089 K7EG +1.4 135 1.000001389 K7EK +1.3 173 1.000001301 K7MJG +0.5 2384 1.000000529 K9IMM* -0.1 13914 0.999999912 K9LC +0.3 10379 1.000000320 KB9AMG +8.0 5066 1.000007950 KC4YVA +5.8 9981 1.000005832 KD2OGR* -0.0 10651 0.999999977 KH6LC +0.4 3395 1.000000391 KL7RA +1.1 4529 1.000001125 KM3T* -0.0 14623 0.999999958 KM3T-2 +1.2 16925 1.000001174 KM3T-3* -0.1 16909 0.999999857 KO7SS +1.2 12873 1.000001175 LA6TPA -1.5 10076 0.999998476 LY2XW +0.6 1661 1.000000612 LZ3CB* -0.0 9635 0.999999981 LZ4AE +3.3 25765 1.000003345 LZ4UX* -0.1 13275 0.999999891 LZ5DI* -0.0 18347 0.999999982 LZ7AA +0.9 16684 1.000000852 M0JYE -5.8 1896 0.999994192 MM0ZBH +1.0 15801 1.000001037 MM3NDH* +0.0 22941 1.000000008 N2QT +2.7 13485 1.000002739 N4ZR +0.3 221 1.000000333 N6TV +0.6 6269 1.000000594 N7TUG +11.2 2530 1.000011202 N9CO* +0.1 14568 1.000000127 ND7K +0.4 2348 1.000000446 NG7M* +0.0 7283 1.000000042 NN3RP +0.4 3865 1.000000401 NR4U -0.7 328 0.999999262 NU6XB* +0.0 4663 1.000000030 NX5M +1.3 631 1.000001294 OE9GHV* -0.0 22577 0.999999963 OG73X +1.1 6258 1.000001130 OH6BG +2.8 22977 1.000002755 OH8KA +1.2 7944 1.000001205 OK1FCJ +0.3 20442 1.000000284 OK4QRO +2.3 19902 1.000002251 ON6ZQ -0.7 2145 0.999999343 OZ4ADX +7.7 3496 1.000007677 PA0MBO +0.7 7139 1.000000698 PA2SQ +0.0 9 1.000000000 PA5KT -0.8 6193 0.999999176 PJ2A* +0.1 7428 1.000000095 PY7ZC -2.6 3268 0.999997395 R6YY +0.2 18405 1.000000162 RK3TD -0.2 19141 0.999999770 RN4WA -8.8 16024 0.999991178 RU9CZD +4.4 16916 1.000004372 S50ARX +3.6 21299 1.000003602 S53A +0.9 26481 1.000000929 S53M +0.6 5538 1.000000578 S53WW +0.3 12222 1.000000297 SE5E +0.4 12612 1.000000368 SM0TCZ -1.3 3891 0.999998712 SM7IUN* +0.1 19389 1.000000073 SQ5J +2.7 17130 1.000002729 SV8RV -0.3 15161 0.999999676 SZ1A -8.5 369 0.999991498 TF3Y +1.6 16696 1.000001615 TF4M -1.4 16357 0.999998641 TI7W +4.7 12041 1.000004730 TZ4AM -2.4 1420 0.999997639 UA0S -0.1 15033 0.999999926 UA4M +5.1 1192 1.000005052 V51YJ +1.6 2570 1.000001613 VE2WU* +0.0 8423 1.000000007 VE6AO -0.6 3472 0.999999396 VE6JY +2.1 8917 1.000002142 VE6WZ +2.3 8146 1.000002325 VE7CC +0.6 4539 1.000000630 VK2GEL +1.8 1688 1.000001802 VK2RH -0.6 1561 0.999999380 VK3RASA -0.7 2106 0.999999267 VK6ANC -2.6 3563 0.999997402 VR2FUN +3.6 8853 1.000003588 VR2FUN-74 +0.8 3923 1.000000849 VU2CPL +1.7 10222 1.000001723 VU2PTT +1.2 3468 1.000001188 VY0ERC +1.3 62 1.000001343 W1NT-2 +0.5 18826 1.000000467 W1NT-6 +0.4 21289 1.000000391 W2LB +6.5 240 1.000006459 W2MV +0.5 2940 1.000000518 W2NAF +1.6 18265 1.000001645 W3LPL -3.1 19669 0.999996881 W3OA +0.3 16793 1.000000348 W3RGA +0.2 17779 1.000000155 W3UA* -0.0 21717 0.999999957 W4AX +3.7 4174 1.000003748 W4KAZ -1.3 11672 0.999998679 W6BB* +0.1 3729 1.000000055 W6YX +0.6 219 1.000000618 W8WTS -1.9 11602 0.999998112 W8WWV -2.0 15944 0.999998032 WA7LNW +0.6 9208 1.000000639 WB6BEE* -0.1 10665 0.999999925 WC2L +0.7 15464 1.000000710 WE9V +0.1 14417 1.000000114 WZ7I* +0.0 18386 1.000000042 YU1EW +0.7 4161 1.000000669 ZL2KS -2.6 3740 0.999997380 ZL3X -2.9 7031 0.999997112 ZL4YL +1.2 2653 1.000001230 Last updated 2023-05-29 00:26:11 UTC
Historical skimmer frequency accuracy
Below you will find historical accuracy data for the past ten days. Do not be concerned over minor daily variations. Since RBN spots only have 100Hz frequency accuracy, the input data is very noisy. Even for a perfectly accurate skimmer, the typical RMS rounding error across all shortwave bands is around 3ppm. This means that for a skimmer with 1000 spots per day the statistical variation is up to 0.2ppm. For skimmers with less than 100 spots per day the statistical variation can be above 2ppm. The content of the table below is based on the historical content of the above table.
Skimmer 0528 0527 0526 0525 0524 0523 0522 0521 0520 0519 --------------------------------------------------------------------- 3B8CW +1.0 +1.0 +1.0 +0.6 +1.2 +0.6 +1.6 +0.8 +1.0 +0.5 3D2AG +0.0 -0.1 +0.0 -0.1 +0.0 +0.0 +0.0 -0.3 -0.1 +0.0 3V8SS -1.9 -2.0 -2.1 -1.8 -1.7 -1.1 -1.1 -2.0 -1.8 -2.0 4X6FB +0.4 5B/HA5PP +1.7 +1.2 7N4XCV +1.2 +1.5 +0.1 9M2CNC -0.3 -0.0 -0.2 -0.2 +0.0 +0.1 +0.2 +0.5 +0.1 AC0C-1 +0.2 +0.3 +0.2 +0.2 +0.3 +0.2 +0.2 +0.1 +0.2 +0.0 BA6KC -0.1 -0.0 +0.0 -0.1 -0.0 -0.3 -21.8 +1.1 -2.4 +0.2 BA6KC1 -0.1 -0.9 +1.4 +0.9 BD0AH +0.4 +0.4 +1.0 BD4QJP +4.8 +1.5 +3.7 BD7DT +1.4 +2.0 +1.0 +0.7 -1.0 -1.6 -2.8 +0.4 -0.3 +0.2 BD7JNA1 +0.6 +0.4 +0.6 BD7JNA +6.8 +6.7 +3.7 -6.9 -1.2 +0.6 +0.2 BD7LAE -5.3 -5.3 -6.5 -6.8 BD8CS -0.2 -0.2 -0.0 +0.1 -0.1 +0.0 +0.1 -0.0 BD8CS/8 -0.1 -0.1 -0.0 BG2TEM -4.9 -5.0 -5.8 -7.0 BG2TFW +7.6 +7.4 +6.8 +5.5 +5.8 +5.8 +6.8 BG2UKX +5.1 +8.6 BG4GOV3 +1.0 +1.1 +0.2 -0.2 +0.2 -0.8 -2.9 +3.0 -1.6 +0.7 BG4WOM +1.0 +0.2 -0.0 -0.4 +0.0 -0.0 +0.6 +0.7 +0.4 BG8FZU +4.8 +4.3 +4.9 +3.5 +3.9 +5.1 +3.7 +5.2 +4.6 BH3BBJ +1.6 +1.3 +1.5 BH4DEG +6.1 +5.8 +5.3 +5.8 +4.4 +5.0 +4.1 +5.2 +5.3 +5.0 BH4RRG0 +0.3 +0.5 +0.3 +0.2 +0.2 +0.3 +0.1 +0.7 +0.8 +0.3 BH4RRG -0.1 +0.1 -0.1 -0.2 +0.0 -0.0 +0.0 -0.3 +0.2 -0.1 BH4RXP +0.5 +0.6 +0.3 +0.2 +0.3 +0.4 +0.3 +0.4 +0.8 +0.2 BH4XDZ +0.0 +0.1 +0.4 -0.0 +0.1 -0.2 +0.0 -0.1 +0.7 +0.9 BH4XDZ-1 -0.1 +0.2 +0.3 +0.1 -0.3 +0.8 +0.6 +0.2 BI4RFP +1.5 +1.4 +1.1 +1.7 +0.9 +0.9 +0.5 +1.5 +1.7 +0.4 CT7ANO -4.6 -4.5 -4.9 CX6VM -3.8 -3.3 -3.6 -4.7 -4.7 -5.1 -4.4 -3.3 CX7ACH +17.4 +17.5 DC8YZ +0.1 -0.1 +0.1 +0.1 +0.1 +0.1 +0.0 +0.0 +0.1 +0.1 DD5XX -0.1 -0.3 +0.1 -0.3 -0.2 -0.0 +0.2 +0.0 +0.1 -0.3 DE1LON +1.0 +0.8 +0.6 +0.3 +0.3 +0.5 +0.7 +0.4 +0.5 +0.3 DF1DN -6.3 -6.5 -5.9 -8.0 -4.5 -9.0 -6.0 DF2CK +1.7 +1.7 +1.2 +0.9 +1.0 +1.1 +1.2 +1.2 +1.3 +0.8 DF7GB +0.0 -0.0 -0.1 +0.0 -0.0 -0.0 -0.1 -0.1 -0.0 -0.1 DG8NCY +0.0 DJ2BC -0.3 -0.5 -0.5 -0.4 DK0TE +1.0 +1.0 +0.7 +0.6 +0.5 +0.6 +0.8 +0.7 +0.8 +0.5 DK3UA -8.2 -7.9 DK8NE -2.0 DK9IP +0.2 +0.2 +0.2 +0.1 +0.1 +0.1 +0.3 +0.1 +0.1 +0.1 DK9IP-1 +0.2 +0.2 +0.2 +0.0 +0.0 +0.1 +0.2 +0.1 +0.1 +0.0 DL0PF +3.7 +3.0 +3.9 +4.4 +4.4 +4.8 +5.2 +3.5 +3.3 +3.0 DL1AXX +0.1 +0.2 DL1HWS -1.8 -1.5 -1.2 +0.3 +0.3 +0.3 +0.4 +0.3 +0.4 +0.2 DL8LAS +1.5 +1.3 +0.9 +0.8 +0.8 +0.9 +1.1 +1.0 +1.1 +0.8 DL8TG +0.0 +0.1 -0.0 +0.0 -0.0 -0.0 +0.0 -0.0 +0.0 -0.1 DL9GTB -2.8 -3.0 -0.5 -0.0 +0.3 +0.2 DM5GG +0.4 +0.4 +0.3 +0.2 +0.2 +0.3 +0.7 +0.6 +0.8 +0.5 DM6EE +0.0 +0.1 +0.0 +0.0 -0.0 +0.1 -0.1 +0.0 +0.1 +0.0 DM7EE +0.4 +0.4 +0.2 DO4DXA -0.4 -0.2 -0.2 -0.2 -0.2 -0.2 DR4W -2.0 -2.5 -2.4 -2.7 -2.6 -1.3 -0.6 -1.6 -2.1 -3.1 E28AC +4.8 +4.5 +5.0 +5.6 +4.8 +4.6 +4.9 +3.7 EA1RX -6.1 -7.8 -7.8 -8.5 -8.3 -7.2 -6.9 -6.9 -7.2 -7.5 EA1URA -1.8 -1.5 -0.6 -0.2 -0.0 -0.1 +0.2 +0.2 +0.1 +0.3 EA2CW +0.8 +0.6 +0.2 +0.1 +0.1 +0.2 +0.1 +0.1 -0.1 -0.0 EA2RCF-4 +0.4 +0.2 +0.1 -0.1 -0.0 -0.0 -0.0 -0.1 +0.1 -0.0 EA5WU -0.6 -0.5 -1.1 -0.3 +0.0 +0.2 +0.1 +0.1 +0.3 +0.2 ES2RR -0.0 +0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.0 ET3AA +10.1 EY8ZE +0.6 +0.6 +0.4 +0.4 +0.6 +0.4 +0.7 +0.5 +0.4 +0.4 F1TRE +0.5 F4VSQ +4.5 +4.3 +4.2 F4VVG +0.0 +0.1 +0.2 F6IIT -0.7 -0.8 -0.8 -0.9 -1.0 -0.6 -0.5 -1.2 -1.1 -1.5 F8DGY -4.1 -4.4 -4.5 -4.5 -4.9 -4.5 -4.2 -4.7 -4.9 -5.4 F AHD AHD G0KTN +0.8 +0.7 +0.6 +0.3 +0.5 +0.4 +0.5 +0.5 +0.6 +0.4 G0TMX +0.2 G3XBI +0.3 +0.3 +0.3 +0.0 +0.2 +0.3 +0.5 +0.0 G3YPP +0.2 +0.2 +0.2 +0.2 -0.1 +0.1 +0.2 +0.1 +0.1 +0.0 G4AON +0.6 G4HSO +0.2 +0.0 +0.1 -0.3 -0.3 -0.1 -0.0 -0.5 -0.2 -0.2 G4IRN +0.7 +0.8 +0.4 +0.4 +0.4 +0.5 +0.6 +0.6 +0.5 G4ZFE +0.5 +0.5 +0.4 +0.3 +0.3 +0.3 +0.3 +0.1 +0.4 +0.3 GI4DOH -0.1 +0.1 +0.1 -0.0 -0.1 +0.0 -0.2 -0.0 +0.0 +0.2 GM6DX +0.8 +0.7 +0.6 +0.7 +0.4 +0.7 +0.6 +0.7 +0.9 +0.5 HA1VHF +1.2 +3.8 +0.8 +0.6 +0.5 +0.4 +0.4 +0.1 -0.0 -0.3 HA6PX +0.8 +3.2 +5.0 +4.1 +4.6 +5.1 +3.4 +4.5 +3.8 +1.5 HA8TKS +0.5 +0.5 +0.2 +0.3 +0.3 +0.3 +0.3 +0.3 +0.4 +0.2 HB9BXE +0.1 +0.0 +0.0 -0.1 -0.1 -0.0 +0.0 -0.1 -0.0 +0.0 HB9DCO +0.1 +0.2 +0.1 -0.0 -0.1 +0.2 -0.2 +0.1 -0.0 +0.1 HB9RB -2.8 +0.5 +0.8 HG0Y +2.0 +2.2 +1.4 HG5FMV +0.4 +0.2 +0.2 +0.6 +0.2 +0.3 +0.3 HG8A +1.9 +2.1 +1.7 +1.3 +1.4 +1.0 +1.3 +0.8 +0.9 +0.5 HS/F8UKP -0.2 +0.0 +0.1 +0.5 -0.2 -0.1 -0.4 +0.0 -0.0 +0.2 IK3STG +7.2 +7.3 +6.5 +7.2 +7.0 +7.2 +7.2 +6.5 +6.7 +6.9 IK4VET +3.8 +3.8 +3.2 +2.8 +1.8 +1.5 +1.5 IV3DXW -3.8 -2.0 JA4ZRK -0.0 +0.2 -0.1 +0.0 +0.0 +0.0 +0.3 -0.1 -0.1 +0.0 JG1DLY -0.6 -0.8 JH4UTP +0.7 +0.8 +0.3 +0.3 +0.0 +0.3 +0.6 +0.8 JH7CSU1 +5.1 +5.2 +4.4 +5.1 +4.9 +5.5 +5.5 +4.9 +4.9 +4.0 JI1HFJ -1.4 -1.9 -3.0 +1.3 -4.2 -2.2 -3.8 -2.8 -3.1 -6.0 JJ2VLY +2.5 +2.5 +1.0 +1.0 +0.6 +0.7 +0.5 +3.0 +1.5 +1.0 JN1ILK +0.8 +0.7 -0.0 +0.1 +0.7 -0.5 +0.3 +0.9 +0.6 +0.2 K1TTT -0.4 -0.4 -0.4 -0.3 -0.1 -0.3 -0.5 -0.2 +0.0 -0.2 K2PO/7 -4.9 -4.4 -4.9 -5.9 -4.4 -6.8 -5.0 -6.5 -4.8 -4.8 K3PA-1 +0.1 +0.2 +0.1 +0.1 +0.1 -0.1 +0.0 -0.0 +0.0 +0.1 K4PP +0.2 +0.2 +0.0 -0.1 -0.1 -0.0 -0.1 -0.0 -0.2 -0.0 K5EM +0.1 +0.2 K5TR +0.8 +0.7 +0.4 +1.1 +0.3 +0.6 +0.4 +0.7 +0.5 +0.5 K6FOD +0.1 +0.1 +0.0 +0.1 +0.2 +0.2 +0.0 +0.3 +0.1 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Anchor skimmers
The below skimmers use external frequency references and are confirmed to have continuous, high accuracy. Their accuracy is also confirmed against each other on a daily basis.
DF7GB ES2RR KM3T LZ3CB LZ4UX MM3NDH OE9GHV WB6BEE Last updated 2023-05-29 00:27:33 UTC
It is the owners of these skimmers who make this web page possible. Thank you.
To get good geographic coverage and a good size dataset, a two-step method is used for the analysis shown above. Since the second step also relies on spots from skimmers with slightly lower accuracy the displayed error for the anchor skimmers may not always be 0.0, even though they are perfectly accurate.
Software
The software powering this page can be found on github.