Skimmer frequency accuracy
To be a good RBN citizen a skimmer should have a frequency accuracy of 2ppm or better.
VERY IMPORTANT: 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 yesterday’s RBN data, 00:00 to 23:59 UTC. This means that when making adjustments, changes in calibration will typically not have full impact on the listed data until the second day after the change.
The deviation estimates are based on spots on all active bands (40m and higher) from the respective skimmer. If different hardware is used for the different bands, the deviation number may thus not represent the actual deviation for a particular band. It is a good practice to run a separate instance of RBN Aggregator with a unique SSID for each hardware, (SM7IUN-1, SM7IUN-2, etc.)
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 daily.
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 criteria 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 are 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. Doing so would 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.
if you want to implement an automated calibration of your skimmer you can access the skew data in machine-readable CSV format here https://sm7iun.se/rbnskew.csv
An skimmer calibration automation based on Windows PowerShell can be found here. It scrapes the calibration adjustment from this page and can be configured to update two CW Skimmer Server instances, two RTTY Skimmer Servers, and one CWSL_DIGI instance.
266017 RBN spots between 2025-09-09 00:00 and 23:59 UTC. 77076 spots (29.0%) were from reference skimmers (*). Average spot flow was 185 per minute from 198 active CW skimmers. 128417 spots from 196 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 ------------------------------------- 3B8GL +0.0 5 1.000000000 3D2AG +0.3 81 1.000000264 5Z4GO +0.4 13 1.000000426 7N4XCV +0.6 21 1.000000566 9M2CNC +0.1 60 1.000000092 AA0O +0.5 522 1.000000533 AC0C-1* +0.0 1431 1.000000009 BA4OP -0.5 60 0.999999524 BA6KC -0.0 78 0.999999970 BG0AJO +0.1 86 1.000000083 BG0AJO/0 +0.4 33 1.000000431 BG2TFW +0.2 98 1.000000174 BG4GOV +0.0 7 1.000000000 BH4RRG +0.7 14 1.000000680 BH4XDZ +0.2 29 1.000000246 BI4MPH +0.0 45 1.000000000 CT1EYQ -0.4 838 0.999999646 CX6VM +1.1 242 1.000001115 DD5XX +0.2 414 1.000000207 DE1LON +1.1 1084 1.000001080 DF2CK* +0.1 2278 1.000000069 DF7GB* -0.0 1223 0.999999963 DK0TE +0.4 1157 1.000000376 DK3UA +5.1 28 1.000005096 DK3WW +0.2 1388 1.000000161 DK9IP* +0.2 701 1.000000167 DK9IP-1* +0.1 879 1.000000084 DL0LA* +0.0 346 1.000000014 DL0PF +11.0 1824 1.000011032 DL1HWS +0.4 1417 1.000000431 DL1HWS-3 +0.0 5 1.000000000 DL1HWS-4 +0.9 123 1.000000942 DL8LAS +3.2 1300 1.000003235 DM5GG +0.6 1348 1.000000626 DM6EE* +0.1 854 1.000000070 DO4DXA* +0.0 1233 1.000000019 DR4W -0.9 1298 0.999999091 E28AC -2.8 28 0.999997196 EA2CW -0.2 1051 0.999999835 EA2RCF-4* -0.1 643 0.999999892 EA8/DF4UE* -0.1 1831 0.999999928 ES2RR* -0.1 1308 0.999999939 ES5PC* -0.1 1607 0.999999878 F4GOU +6.3 1134 1.000006270 G0KTN +0.3 1141 1.000000300 G4IRN* +0.2 1594 1.000000174 G4ZFE +0.7 1142 1.000000667 GI4DOH* +0.0 608 1.000000012 GX0FRE +0.3 533 1.000000303 HA1VHF +0.7 1391 1.000000691 HA5JI-8 -0.7 973 0.999999262 HA8TKS +0.2 715 1.000000189 HA8TKS-2 +0.0 37 1.000000000 HB9BXE* -0.0 316 1.000000000 HB9DCO -0.2 1017 0.999999777 HB9GVO +0.7 49 1.000000726 HG0Y +7.8 251 1.000007811 HG8A +2.1 1179 1.000002132 IK3STG +1.0 952 1.000000979 IK7YTT -6.9 1506 0.999993057 IT9GSF* -0.0 1885 0.999999993 IW9GDC -0.2 421 0.999999762 JH7CSU1 +1.3 68 1.000001329 JI1HFJ +0.0 14 1.000000003 JK1QLQ +0.0 15 1.000000000 JN1ILK -0.2 248 0.999999837 K1RA +0.2 980 1.000000190 K2PO/7 +0.4 411 1.000000439 K3PA-1* +0.0 1252 1.000000028 K3PA-2 -17.4 15 0.999982602 K4PP* +0.0 690 1.000000034 K5EM +2.1 512 1.000002125 K5TR +2.0 961 1.000002042 K6FOD +0.0 611 1.000000007 K7CO +0.6 694 1.000000645 K7EK -0.6 138 0.999999429 K7RUT -0.2 655 0.999999750 K9IMM* -0.0 942 0.999999968 K9LC +0.4 1164 1.000000431 KC4YVA -4.6 295 0.999995414 KD2OGR +0.0 8 1.000000000 KD7EFG +0.2 451 1.000000247 KH6LC +0.2 85 1.000000168 KL2R +0.0 11 1.000000000 KM3T-2* +0.1 977 1.000000120 KM3T-3* +0.0 1296 1.000000022 KM3T-5* +0.0 882 1.000000027 KO7SS +0.6 362 1.000000632 KP2RUM -0.3 83 0.999999676 KP3CW -0.6 522 0.999999376 KV4TT* +0.0 1078 1.000000024 KW7MM* +0.0 1094 1.000000032 KW7MM/7 +0.8 41 1.000000751 LA6TPA -0.1 345 0.999999892 LA7GIA +0.1 175 1.000000120 LB9KJ +0.1 139 1.000000051 LU8XW +0.0 31 1.000000000 LY3G +1.1 24 1.000001120 LZ3CB -0.0 995 1.000000000 LZ4UX* -0.1 818 0.999999916 LZ5DI +2.5 194 1.000002521 LZ7AA +0.6 781 1.000000590 M0ORD -1.1 1566 0.999998877 MM0GPZ* -0.1 1019 0.999999898 MM0ZBH* -0.1 1396 0.999999925 N2CR +0.2 524 1.000000239 N2YCH +0.4 1471 1.000000370 N6TV +0.7 519 1.000000668 N7TUG +0.1 59 1.000000121 N8DXE +1.1 53 1.000001071 N9CO +0.0 772 1.000000043 ND7K -0.1 689 0.999999911 NG7M* +0.0 627 1.000000019 NT6Q +3.1 837 1.000003113 NU4F* -0.0 825 0.999999970 OE9GHV +0.0 411 1.000000023 OG66X +0.0 17 1.000000000 OH4KA -0.0 246 0.999999953 OH6BG +0.2 1169 1.000000155 OH8KA +3.7 67 1.000003666 OK1FCJ* +0.2 1535 1.000000197 OK1HRA -3.8 1131 0.999996211 ON6ZQ +0.6 810 1.000000635 OZ1AAB +0.2 416 1.000000165 OZ1BZS +0.0 27 1.000000000 OZ4ADX +0.2 294 1.000000170 PA5KT-4 -0.2 849 0.999999785 PA8MM +0.3 647 1.000000305 PE5TT +0.7 739 1.000000746 PI4CC +0.3 1435 1.000000282 PY2KNK +3.0 238 1.000003048 PY2PE -1.1 102 0.999998882 R4NCU -0.4 142 0.999999649 RK3TD -0.2 107 0.999999757 RK3TD-2 +0.2 861 1.000000170 RN4WA +1.7 722 1.000001731 RU9CZD* -0.0 449 0.999999967 S50U +0.2 706 1.000000200 S53A +0.6 1307 1.000000623 S53WW +0.2 1198 1.000000245 S54L +0.3 1189 1.000000344 SE5E* -0.1 1593 0.999999926 SM7IUN +0.1 370 1.000000071 SQ5J +8.0 1139 1.000008018 SV1CDN +0.1 143 1.000000100 SZ1A -0.6 1092 0.999999406 TF3Y +1.2 732 1.000001222 TI7W +0.7 1280 1.000000746 UT5R-1 +3.8 100 1.000003796 UY2RA -0.8 950 0.999999204 V51YJ +1.0 90 1.000001047 VE3EID +0.1 1591 1.000000128 VE6JY +2.9 988 1.000002886 VE6WZ -0.4 1211 0.999999578 VE6WZ-3 -1.3 717 0.999998668 VE7CC +0.2 379 1.000000188 VK2GEL +0.9 93 1.000000920 VK2RH +0.5 30 1.000000475 VK3RASA -1.4 82 0.999998609 VK6ANC -0.5 58 0.999999495 VR2FUN-77 +0.8 447 1.000000756 VU2CDP +18.3 26 1.000018289 VU2CPL -0.0 49 0.999999960 VU2OY +10.9 69 1.000010930 VU2TUM +1.3 163 1.000001297 W1NT-2* -0.0 1271 0.999999974 W1NT-6* -0.0 1675 0.999999959 W2LB +1.4 207 1.000001442 W2MV +0.3 109 1.000000261 W2NAF +1.0 1100 1.000001045 W2NNN +13.3 765 1.000013320 W3DAN +1.8 55 1.000001808 W3OA* +0.1 1170 1.000000123 W3RGA* -0.2 1305 0.999999798 W4AX +6.9 11 1.000006906 W4KAZ* -0.2 750 0.999999761 W6YX +0.4 940 1.000000431 W8WTS +0.3 609 1.000000292 W8WWV -1.2 979 0.999998807 WA7LNW* +0.0 1271 1.000000047 WB6BEE +0.0 503 1.000000039 WC2L +0.1 1003 1.000000103 WC8GOP +13.4 24 1.000013437 WE9V -0.2 1283 0.999999800 WS2C +9.7 874 1.000009678 WS3W +0.6 417 1.000000586 WT9U +6.6 587 1.000006624 WV4P +0.2 777 1.000000176 WX7V/5 +0.8 44 1.000000772 WZ7I +0.5 1576 1.000000536 YO2CK +0.2 983 1.000000180 YO2KAR +0.2 570 1.000000223 YO5LD +0.4 729 1.000000393 ZL2KS -2.3 17 0.999997745 ZL3X +0.1 259 1.000000127 ZS1NN -4.0 56 0.999996033 Last updated 2025-09-10 00:10:25 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 0909 0908 0907 0906 0905 0904 0903 0902 0901 0831 --------------------------------------------------------------------- 3B8GL +0.0 +0.1 +0.0 +0.7 +0.2 +0.5 3D2AG +0.3 +0.5 +0.0 +0.4 +0.3 +0.1 +0.1 +0.3 +0.6 +0.1 5Z4GO +0.4 +1.1 +0.0 +0.5 +0.6 +0.9 +0.0 +1.4 +0.0 7N4XCV +0.6 +0.0 +0.2 +0.6 +0.4 +0.6 +1.1 +2.1 +0.9 9M2CNC +0.1 +0.4 +0.1 +0.5 +0.2 +0.2 +0.6 +0.1 +0.1 +0.7 AA0O +0.5 +0.7 +0.6 +1.0 +0.5 +0.6 +0.9 +0.8 +0.6 +0.5 AC0C-1 +0.0 -0.1 -0.1 -0.1 -0.0 -0.1 +0.1 -0.3 -0.0 +0.0 BA4OP -0.5 +0.0 +0.2 -0.2 +0.0 -0.2 +0.0 +0.2 -0.1 -0.2 BA6KC -0.0 -0.4 +0.1 -0.2 -0.1 -0.1 -0.1 +0.3 -0.2 -0.0 BD7JNA +0.0 BG0AJO/0 +0.4 +0.0 +0.0 +0.0 +0.4 +0.0 +0.1 -0.2 +0.1 -0.1 BG0AJO +0.1 +0.5 +0.0 +0.4 +0.4 +0.5 +0.2 +0.8 +0.7 +0.7 BG2TFW +0.2 +0.4 +0.0 +0.4 +0.3 +0.1 +0.2 +0.6 +0.2 +0.3 BG4GOV +0.0 +0.0 +0.6 +0.1 +0.5 +0.0 +0.0 +0.0 +1.0 +0.3 BH4RRG00 +0.0 BH4RRG +0.7 +0.0 +0.0 +0.2 +0.2 +0.4 +0.0 +0.3 BH4XDZ +0.2 +0.0 +0.0 -0.2 +0.1 +0.1 +0.0 +0.1 +0.3 -0.1 BI4MPH +0.0 +0.2 +0.3 +0.3 +0.0 BI4UYX +0.0 +0.0 CT1EYQ -0.4 -0.1 -0.1 -0.1 -0.2 -0.0 -0.1 -0.2 -0.2 -0.1 CT7ANO +8.5 CX6VM +1.1 +0.4 +0.6 +0.8 +1.3 +2.2 +2.1 +2.3 +2.6 DD5XX +0.2 +0.5 +0.6 +0.3 +0.4 +0.5 +0.4 +0.4 +0.4 +0.2 DE1LON +1.1 +1.3 +1.3 +1.2 +1.1 +1.1 +1.1 +1.1 +1.5 +1.1 DE2SAX +0.5 +1.4 +1.4 +0.8 +1.3 +2.3 +0.9 +1.8 +1.5 DF2CK +0.1 +0.2 +0.2 +0.2 +0.1 +0.1 +0.0 +0.0 +0.0 +0.0 DF7GB -0.0 -0.1 -0.0 -0.1 +0.0 -0.1 +0.0 -0.0 +0.0 +0.0 DK0TE +0.4 +0.6 +0.5 +0.5 +0.5 +0.4 +0.4 +0.4 +0.6 +0.5 DK3UA +5.1 +4.8 +4.0 +0.7 +0.3 +0.7 DK3WW +0.2 +0.2 +0.0 +0.2 +0.1 +0.1 +0.2 +0.1 +0.1 +0.1 DK8NE +1.0 DK9IP +0.2 +0.2 +0.0 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 DK9IP-1 +0.1 +0.2 -0.0 +0.1 +0.1 +0.0 +0.1 +0.0 +0.1 +0.0 DL0LA +0.0 -0.1 -0.1 -0.1 +0.1 -0.0 -0.1 +0.0 -0.0 -0.1 DL0PF +11.0 +11.1 +13.4 +12.0 +11.7 +11.9 +11.5 +11.8 +11.7 +11.4 DL1HWS +0.4 +0.6 +0.6 +0.7 +0.6 +0.4 +0.5 +0.5 +0.6 +0.5 DL1HWS-3 +0.0 +3.3 +0.0 +0.6 +0.6 +0.6 +0.6 DL1HWS-4 +0.9 +0.9 +0.7 +0.4 +0.6 +0.5 +0.4 +0.6 +0.6 +0.7 DL5RCN +14.3 +13.0 +13.4 +13.1 DL8LAS-1 +3.0 +3.1 +2.9 +3.1 +3.0 +2.7 DL8LAS +3.2 +2.9 +0.5 +0.8 +0.6 +0.6 +0.7 +0.4 +0.8 +2.0 DL8TG -0.1 -0.0 -0.0 -0.1 -0.0 -0.1 -0.1 DL9GTB +0.1 +0.2 DM5GG +0.6 +0.8 +0.6 +0.7 +0.7 +0.6 +0.6 +0.7 +0.7 +0.6 DM6EE +0.1 -0.1 +0.0 -0.1 -0.1 -0.1 -0.0 -0.1 DM7EE +0.4 +0.5 DO4DXA +0.0 -0.0 -0.0 -0.1 -0.0 +0.0 -0.1 -0.1 -0.0 -0.0 DR4W -0.9 +0.2 -1.4 -1.0 -2.1 -1.3 -1.1 -1.6 E28AC -2.8 -3.1 -0.6 -3.6 -2.5 -2.2 -2.4 -2.1 -2.0 -2.3 EA2CW -0.2 -0.3 -0.0 -0.1 -0.1 -0.2 -0.1 -0.2 -0.3 -0.2 EA2RCF-4 -0.1 +0.1 +0.1 -0.1 -0.1 -0.1 -0.0 -0.2 -0.2 -0.0 EA5RQ/A +0.2 EA5WU -0.1 +0.1 -0.1 -0.1 +0.0 -0.0 +0.0 EA8/DF4UE -0.1 -0.1 -0.3 -0.6 -0.6 -1.3 -1.4 -1.5 -0.4 ES2RR -0.1 -0.0 -0.0 -0.1 -0.0 +0.0 -0.0 -0.2 -0.1 -0.0 ES5PC -0.1 -0.1 -0.0 +0.0 -0.0 -0.0 -0.0 -0.0 -0.0 -0.1 ET3AA -12.5 F4GOU +6.3 +6.1 +6.3 +5.9 +5.8 +5.4 +5.4 +5.0 +6.1 +6.3 F4VVG +0.1 +0.0 +0.0 +0.0 +0.0 -0.0 +0.1 +0.1 G0KTN +0.3 +0.6 +0.3 +0.5 +0.5 +0.3 +0.4 +0.3 +0.4 +0.4 G0TMX +0.5 G3YPP -1.4 +0.9 +0.4 +0.9 +0.9 +0.8 +0.7 G4IRN +0.2 +0.2 -0.4 -6.0 +0.2 +0.2 +0.2 +0.2 +0.2 +0.2 G4MKR +0.2 +0.3 G4ZFE +0.7 +1.2 +0.7 +0.9 +0.6 +0.7 +0.8 +0.7 +0.8 +0.6 GI4DOH +0.0 +0.2 +0.1 +0.2 +0.2 +0.2 +0.1 +0.3 -0.1 -0.3 GX0FRE +0.3 +0.3 +0.2 +0.2 +0.2 +0.1 +0.2 +0.2 +0.2 HA1VHF +0.7 +0.9 +0.7 +0.9 +0.8 +0.7 +0.7 +0.5 +0.7 +0.4 HA5JI-8 -0.7 -0.4 -1.2 -1.1 -0.8 -0.8 -0.7 -0.1 -0.4 -0.8 HA5PP +0.0 +0.2 HA5PP-2 +2.0 -0.1 HA5PP-3 -0.4 HA6PX +0.2 -0.0 -0.1 +0.0 -0.0 -0.1 +0.0 -0.0 -0.1 HA8TKS +0.2 +0.1 +0.1 +0.2 +0.1 +0.2 +0.2 +0.2 +0.2 +0.2 HA8TKS-2 +0.0 +0.0 +0.1 -0.0 -0.1 +0.1 -0.1 +0.0 -0.1 -0.3 HB9BXE -0.0 +0.2 +0.2 +0.2 +0.3 +0.3 +0.1 +0.2 +0.3 +0.2 HB9DCO -0.2 -0.2 -0.0 -0.1 -0.3 -0.6 -0.3 -0.3 -0.2 -0.4 HB9GVO +0.7 +0.8 +1.7 +1.0 +0.5 +1.1 +1.0 +0.2 +0.7 HG0Y +7.8 +8.4 +8.0 +8.5 +8.1 +7.9 +7.9 +7.8 HG8A +2.1 +2.9 +3.1 +3.4 +3.4 +2.6 +2.3 +2.8 +3.0 +2.9 IK3STG +1.0 +1.6 +1.3 +1.5 +1.3 +1.3 +1.2 +1.0 +1.5 +1.3 IK7YTT -6.9 -5.4 -6.7 -5.9 -6.2 -6.9 -6.3 -5.9 -5.5 -5.9 IT9GSF -0.0 +0.0 -0.0 +0.1 +0.0 -0.0 +0.0 -0.0 +0.0 +0.0 IU0MVD -6.0 IV3DXW -1.4 IW9GDC -0.2 -0.4 -0.3 -0.4 -0.3 -0.4 -0.2 -0.3 -0.4 -0.4 JH7CSU1 +1.3 +1.5 +1.0 +1.8 +1.0 +1.6 +1.5 +1.1 +1.8 +1.4 JI1HFJ +0.0 -1.7 -2.8 +1.4 +0.5 -3.0 -3.1 -0.9 +0.6 -0.6 JJ2VLY +2.7 +1.9 +2.3 +1.6 +1.5 +2.3 +2.2 JK1QLQ +0.0 +0.0 +0.0 +0.3 +0.0 +0.2 +0.0 +0.0 +0.4 JN1ILK -0.2 -0.2 -0.2 -0.7 -0.4 -0.2 -0.2 +0.1 -0.5 -0.2 K1RA +0.2 +0.3 +0.3 +1.3 +0.9 +0.4 +0.6 +0.4 +0.4 +0.3 K2PO/7 +0.4 +0.7 +0.7 +1.1 +0.6 +0.6 +1.0 +0.7 +0.6 +0.4 K3PA-1 +0.0 +0.0 +0.0 -0.1 +0.1 -0.0 -0.1 -0.1 +0.1 -0.0 K3PA-2 -17.4 -16.8 -17.2 -17.2 -16.4 -17.0 -17.1 -17.0 -15.5 K4PP +0.0 +0.2 +0.1 +0.2 +0.2 +0.1 +0.2 +0.2 +0.1 +0.2 K5EM +2.1 +2.1 +2.5 +3.2 +2.9 +2.4 +2.5 +2.4 +3.1 +4.0 K5TR +2.0 +1.1 +1.2 +2.3 +2.0 +1.7 +1.5 +0.7 +0.8 +0.9 K6FOD +0.0 +0.0 +0.1 +0.1 +0.2 +0.1 +0.1 +0.2 +0.1 +0.1 K7CO +0.6 +0.8 +0.5 +1.2 +1.0 +0.8 +1.2 +1.2 +0.6 +0.5 K7EK -0.6 +0.1 -1.0 -1.0 +1.2 -0.6 -0.6 -0.2 -0.1 +1.4 K7RUT -0.2 -0.2 -0.2 -0.3 +0.1 -0.1 -0.1 -0.2 -0.7 K9IMM -0.0 -0.0 -0.0 -0.0 +0.2 -0.0 -0.1 +0.0 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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-5 LZ3CB LZ4UX OE9GHV WB6BEE Last updated 2025-09-10 00:10:31 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.