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.
339716 RBN spots between 2026-07-20 00:00 and 23:59 UTC. 111233 spots (32.7%) were from reference skimmers (*). Average spot flow was 236 per minute from 201 active CW skimmers. 180658 spots from 197 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 ------------------------------------- 5Z4GO +0.2 90 1.000000237 9M2CNC +0.4 98 1.000000371 AA0O +2.0 112 1.000002013 AA4PA +0.5 715 1.000000484 AK6RI-1 -0.1 213 0.999999911 BA4OP -0.1 145 0.999999934 BA6KC +0.0 214 1.000000007 BD4UNT +0.2 91 1.000000165 BD7JNA +0.0 9 1.000000000 BD8CS* -0.0 618 0.999999976 BG2TFW +0.3 53 1.000000283 BG4GOV +0.9 31 1.000000868 BH4RRG +0.1 86 1.000000083 BH4XDZ -0.4 44 0.999999622 BI7JMD +0.5 36 1.000000484 CT1EYQ -0.1 157 0.999999909 CX6VM +4.8 81 1.000004835 DC8YZ +0.4 1514 1.000000440 DE0QPG* -0.1 850 0.999999916 DE1LON* -0.0 1744 0.999999975 DF7GB* -0.0 2138 0.999999992 DG1ELE +0.1 905 1.000000121 DK0KK +0.1 411 1.000000096 DK0TE +0.2 1928 1.000000229 DK3WW* -0.1 2358 0.999999902 DK8NE +0.0 48 1.000000042 DK9IP +0.2 1446 1.000000197 DK9IP-1* +0.1 1796 1.000000074 DL0LA +0.0 74 1.000000001 DL1HWS +0.6 2799 1.000000632 DL1HWS-3 +0.7 1578 1.000000684 DL1HWS-4 +1.3 1073 1.000001316 DL8LAS +0.6 3306 1.000000591 DL8LAS-1 +0.5 2728 1.000000450 DM5GG +0.8 2923 1.000000793 DM6EE +0.2 1271 1.000000204 DO4DXA* +0.1 2544 1.000000119 DR4W -1.8 1285 0.999998166 EA1URA +0.6 834 1.000000644 EA2CW +0.2 47 1.000000210 EA2RCF-4 +1.2 815 1.000001179 EA4RKC +0.2 187 1.000000203 EA5WU* -0.0 1719 0.999999961 EI4HQ* -0.1 2934 0.999999945 ES2RR* -0.0 2745 0.999999976 ES5PC* -0.0 2623 0.999999967 EY8ZE* +0.0 321 1.000000040 F4BPO +1.6 1131 1.000001578 F4GOU +9.3 1349 1.000009329 F5AHD +3.5 297 1.000003501 F6KGL* +0.0 885 1.000000018 G0KTN +0.3 1951 1.000000292 G0TMX -0.3 1186 0.999999680 G4IRN +0.2 2679 1.000000235 G4KCM* -0.0 1148 0.999999962 G4ZFE +0.4 2414 1.000000366 GI4DOH* +0.1 1156 1.000000128 GX0FRE* +0.0 1259 1.000000017 HA1VHF +1.1 1563 1.000001057 HA2NA +0.7 203 1.000000684 HA8TKS* +0.1 1835 1.000000077 HB9BXE* +0.1 1948 1.000000140 HB9DCO -0.1 80 0.999999881 HG8A +0.6 2154 1.000000567 HS0ZGZ +0.3 74 1.000000294 IK3STG +1.1 1012 1.000001131 IK4VET +4.4 2462 1.000004447 IZ2CPS +0.5 545 1.000000518 JA1CCA -0.8 59 0.999999154 JH7CSU1 +1.0 102 1.000001048 JI1HFJ -0.4 61 0.999999559 JK1QLQ +0.0 29 1.000000000 JQ1BVI +0.0 19 1.000000000 K3GMQ* +0.0 1313 1.000000026 K3PA-1 +0.6 1212 1.000000625 K4PP +0.7 485 1.000000661 K5EM +5.4 297 1.000005378 K5KHK -0.1 393 0.999999873 K5TR -0.2 1196 0.999999809 K6FOD +0.4 219 1.000000371 K7CO +2.4 435 1.000002447 K7EK +1.6 298 1.000001551 K7RUT +3.0 233 1.000003038 K9IMM* +0.0 1218 1.000000018 K9LC +0.2 1122 1.000000181 KD7EFG +0.3 445 1.000000301 KG6NFJ +0.0 430 1.000000039 KH6LC +0.1 58 1.000000123 KM08QR +0.3 215 1.000000278 KM3T-2 +0.4 1482 1.000000388 KM3T-3* +0.1 2020 1.000000115 KM3T-5* -0.0 1635 0.999999988 KW7MM +0.5 1215 1.000000461 KW7MM-2 +0.6 1086 1.000000638 KW7MM-3 -3.5 90 0.999996514 KW7MM-4 +15.6 571 1.000015607 LU8XW +0.4 25 1.000000380 LZ3CB* -0.0 1218 0.999999967 LZ4UX* -0.1 886 0.999999935 LZ5DI +3.8 2343 1.000003758 LZ7AA +0.6 1289 1.000000585 M1GEO -3.7 344 0.999996279 MM0ZBH* +0.1 2959 1.000000088 MM9PSY* -0.0 2575 0.999999999 N2CR +0.7 493 1.000000680 N2EPE +0.2 881 1.000000188 N2YCH +4.4 1081 1.000004365 N4HAC* +0.1 700 1.000000084 N6TV +0.7 389 1.000000698 N7VVX -0.0 160 0.999999956 N8DXE +0.7 76 1.000000748 N9CO +0.3 1110 1.000000288 ND7K -0.1 880 0.999999907 NG7M -0.1 118 0.999999866 NN3RP +0.8 26 1.000000820 NU4F* -0.0 616 0.999999989 OH8KA +8.1 342 1.000008075 OK1FCJ +0.2 2444 1.000000194 OK1HRA -4.4 2219 0.999995646 ON6ZQ +0.7 1832 1.000000678 OZ1AAB* +0.1 549 1.000000110 OZ1BZS +0.6 310 1.000000631 PA5KT-4* -0.2 2067 0.999999830 PA5WT +0.0 7 1.000000000 PA8MM +0.3 772 1.000000339 PE5TT +0.9 1452 1.000000859 PI4CC* -0.0 2663 0.999999982 PT2FHC +0.0 143 1.000000017 PY2KNK +2.2 250 1.000002197 PY2PE -0.1 67 0.999999894 R4NCU -0.6 496 0.999999367 RK3TD +0.3 1220 1.000000324 RK3TD-2 +0.8 1275 1.000000838 RN4WA +1.4 1509 1.000001370 RU9CZD* +0.0 1565 1.000000010 S50U +0.5 438 1.000000461 S53A +0.9 2683 1.000000874 S53WW +0.6 2367 1.000000606 S54L +0.6 9 1.000000615 S58W* +0.0 812 1.000000017 SE5E* +0.1 2651 1.000000106 SK6AW* -0.1 1171 0.999999926 SM0TCZ +0.5 60 1.000000514 SM1HEV -0.4 592 0.999999620 SM7IUN* -0.0 1741 0.999999950 SQ5J +8.8 1905 1.000008782 SV1CDN +5.9 12 1.000005944 SZ1A* -0.1 876 0.999999896 TF3Y +1.7 1052 1.000001727 TI7W +1.0 1511 1.000001023 UR4RXX +0.3 66 1.000000324 UT5R* +0.1 708 1.000000082 UY2RA -0.4 627 0.999999612 V51YJ +0.5 27 1.000000542 VE4DRK -11.2 289 0.999988830 VE6AO -0.3 418 0.999999722 VE6JY +0.5 82 1.000000522 VE6WZ* -0.3 1095 0.999999719 VE6WZ-3 -0.8 919 0.999999175 VK2RH +0.0 11 1.000000000 VK3RASA -1.2 53 0.999998820 VK6ANC +0.0 49 1.000000000 VU22DX -0.6 33 0.999999424 VU2CPL +0.0 5 1.000000000 VU2OY +0.0 23 1.000000000 VU2PTT -0.9 6 0.999999078 VU2TUM +1.9 138 1.000001850 W1NT-2 +0.7 1491 1.000000696 W1NT-6 +0.7 1733 1.000000695 W2MV +0.5 305 1.000000467 W2NAF +1.3 243 1.000001288 W2NNN +4.4 1158 1.000004434 W3DAN +0.8 75 1.000000759 W3LPL -0.6 280 0.999999415 W3RGA +0.3 397 1.000000348 W3UA* -0.0 1358 0.999999971 W4KAZ +0.5 774 1.000000485 W6YX +0.7 789 1.000000682 W8WTS +0.4 708 1.000000431 W8WWV -1.5 774 0.999998502 WA7LNW +0.7 1088 1.000000697 WB6BEE* -0.1 1472 0.999999911 WC2L +0.4 771 1.000000402 WE9V +0.1 1224 1.000000111 WS2C +9.8 432 1.000009818 WT8P +0.1 270 1.000000089 WT9U* +0.1 574 1.000000146 WW1L +0.0 13 1.000000000 YO2CK -9.6 1647 0.999990361 YO2KAR* -0.2 1506 0.999999839 YO5LD +0.7 1931 1.000000667 ZF1A -5.9 338 0.999994118 ZF9CW -5.5 1511 0.999994486 ZL2KS +0.2 111 1.000000193 ZL3X -1.4 277 0.999998643 ZL4YL +0.3 584 1.000000313 ZS1NN -4.5 26 0.999995461 Last updated 2026-07-21 00:15:31 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 0720 0719 0718 0717 0716 0715 0714 0713 0712 0711 --------------------------------------------------------------------- 5Z4GO +0.2 +0.1 +0.2 +0.1 +0.2 +0.4 +0.6 +0.1 +0.6 +0.5 9M2CNC +0.4 +0.0 +0.7 +0.3 +0.0 +0.2 +0.4 +0.4 +0.5 +0.5 AA0O +2.0 +0.9 +1.9 +1.2 +0.2 +1.5 +1.8 +1.1 +1.8 +2.3 AA4PA +0.5 +0.4 +0.2 +0.2 +0.2 +0.1 +0.1 +0.5 +0.4 +0.6 AC0C-1 -0.0 +0.0 -0.0 -0.0 +0.0 +0.0 +0.1 -0.0 +0.1 AK6RI-1 -0.1 -0.1 +0.1 -0.1 +0.0 +0.6 +0.1 +0.0 -0.1 +0.1 BA4OP -0.1 -0.1 -0.1 -0.2 -0.0 +0.1 -0.2 BA6KC +0.0 -0.0 +0.1 +0.1 -0.6 -0.0 -0.0 +0.2 -0.1 +0.1 BD4UNT +0.2 -0.0 +0.0 -0.1 +0.3 +0.1 +0.2 BD7JNA +0.0 +0.1 +0.1 -0.1 +0.0 -0.0 +0.0 +0.4 -0.0 +0.0 BD8CS -0.0 -0.0 -0.0 +0.0 -0.0 -0.1 +0.0 -0.0 -0.0 -0.0 BG2TFW +0.3 +0.3 +0.5 +0.2 +0.2 +0.1 +0.0 +0.1 +0.5 +0.8 BG4GOV +0.9 +0.0 +0.9 BG7IEJ +6.6 +6.3 +6.5 +7.0 +6.6 +6.9 BH4RRG +0.1 -0.1 +0.3 -0.1 +0.0 -0.0 -0.1 -0.2 -0.1 +0.2 BH4RRG0 +0.1 +0.4 BH4RXP +0.5 BH4XDZ -0.4 +0.2 +0.2 +0.1 +0.2 +0.0 +0.0 +0.0 -0.1 -0.1 BI4MPH +0.0 BI4UYX +0.0 +0.0 +0.0 -0.1 -0.1 BI7JMD +0.5 -0.1 -0.1 +0.0 +0.0 +0.0 +0.0 +0.2 +0.0 -0.0 CT1EYQ -0.1 -0.3 -0.5 -0.1 -0.4 -0.3 CX6VM +4.8 +4.2 +3.6 +1.4 +2.3 +1.5 +1.3 +2.8 +3.1 DC8YZ +0.4 +0.6 +0.4 +0.2 +0.1 +0.2 +0.2 -0.0 +0.5 +0.2 DD0VS -0.4 -0.1 DE0QPG -0.1 +0.4 -0.0 -0.1 -0.1 -0.0 -0.2 DE1LON -0.0 +0.0 -0.0 +0.0 +0.0 -0.1 -0.0 +0.0 +0.0 -0.0 DF7GB -0.0 -0.1 -0.0 +0.0 +0.0 -0.1 -0.0 -0.1 -0.1 -0.0 DG1ELE +0.1 +0.1 +0.1 +0.0 +0.1 -0.2 +0.1 +0.0 -0.1 -0.1 DK0KK +0.1 +0.1 +0.2 +0.1 -0.4 +0.0 +0.1 DK0TE +0.2 +1.4 +1.6 +1.1 +1.0 +0.7 +0.9 +0.8 +1.9 +2.2 DK3WW -0.1 +0.0 +0.1 +0.0 +0.2 +0.1 +0.3 DK8NE +0.0 -0.1 -0.6 +0.6 -0.3 +0.5 +1.1 DK9IP +0.2 +0.1 +0.1 +0.1 +0.2 +0.1 +0.1 +0.1 +0.1 +0.1 DK9IP-1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.2 +0.1 +0.0 +0.1 DL0LA +0.0 -0.1 +0.3 +0.2 +0.2 +0.2 +0.1 +0.2 +0.3 +0.3 DL1EFW +0.6 +0.6 DL1HWS +0.6 +0.6 +0.6 +0.4 +0.4 +0.7 +0.6 +0.6 +0.8 +0.7 DL1HWS-3 +0.7 +0.7 +0.8 +0.5 +0.5 +0.7 +0.6 +0.5 +0.9 +1.0 DL1HWS-4 +1.3 +1.6 +1.6 +1.2 +1.4 +1.3 +1.3 +1.2 +1.6 +1.7 DL5RCN +14.8 DL5RMH +4.6 +4.8 DL8LAS +0.6 +0.6 +0.7 +1.0 +1.6 +2.1 +1.9 +1.7 +1.9 +2.2 DL8LAS-1 +0.5 +0.4 +0.5 +0.6 +0.5 +0.8 +0.8 +0.8 +1.0 +1.1 DL8LAS-3 +5.3 +5.2 +5.3 +5.1 +5.1 +4.3 +4.2 DL8TG -0.2 +0.0 -0.1 -0.0 DM5GG +0.8 +1.1 +1.7 +1.2 +1.2 +1.5 +1.3 +1.6 +1.3 +1.3 DM6EE +0.2 +0.1 +0.1 +0.0 -0.0 DM7EE +0.6 +0.6 DO4DXA +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.0 -0.0 +0.1 DP5G +0.1 +0.0 +0.0 +0.1 DR4W -1.8 -1.9 -2.2 -1.6 -1.6 -1.6 -1.3 -1.5 -2.1 -2.1 E28AC +0.5 +0.5 EA1URA +0.6 +0.7 +0.5 +4.1 +23.7 +24.8 +25.3 +25.5 +24.6 +26.1 EA2CW +0.2 +0.3 +0.2 +0.4 +0.7 +0.5 +0.1 +0.5 +1.2 +0.5 EA2RCF-4 +1.2 +1.3 +1.5 +1.2 +1.1 +1.4 +1.5 +1.5 +1.8 +1.9 EA4RKC +0.2 +0.1 +0.1 +0.2 +0.3 +0.1 +0.2 +0.1 +0.3 +0.3 EA5WU -0.0 -0.0 -0.0 -0.1 -0.0 -0.1 EI4HQ -0.1 -0.0 -0.0 -0.0 +0.0 +0.0 -0.0 -0.0 -0.1 -0.1 ES2RR -0.0 -0.1 -0.0 +0.0 +0.0 -0.0 +0.0 +0.0 -0.1 -0.0 ES5PC -0.0 -0.0 -0.1 -0.0 -0.1 -0.1 -0.1 -0.0 -0.1 -0.1 EU1ST +4.8 EU8RO +0.3 +0.5 EY8ZE +0.0 F4BPO +1.6 +2.1 +2.7 +2.0 +1.7 +3.2 +2.9 +3.6 +2.6 +2.6 F4GOU +9.3 +7.8 +0.1 +0.0 -0.1 +0.4 +0.1 +0.0 +0.3 +0.4 F5AHD +3.5 +4.0 +3.7 +4.3 +3.5 +3.9 +4.4 +4.3 +4.2 F6KGL +0.0 +0.1 +0.1 +0.2 -0.2 +0.0 +0.2 -0.0 +0.2 +0.2 G0KTN +0.3 +0.4 +0.3 +0.2 +0.3 +0.4 +0.5 +0.4 +0.6 +0.5 G0TMX -0.3 -0.9 -0.6 -0.4 -0.3 -0.3 -0.9 -2.3 -1.1 -1.1 G4IRN +0.2 +0.2 +0.3 +0.2 +0.2 +0.2 +0.3 +0.2 +0.5 -0.0 G4KCM -0.0 -0.1 +0.0 -0.1 -0.0 -0.0 -0.2 -0.1 -0.1 -0.0 G4ZFE +0.4 +0.2 +0.4 +0.5 +0.5 +0.8 +0.6 +0.7 +0.8 +1.3 GI4DOH +0.1 +0.1 +0.0 +0.2 +0.4 +0.5 +0.4 +0.5 +0.6 +0.8 GX0FRE +0.0 +0.1 +0.2 +0.1 +0.1 +0.1 +0.1 +0.1 +0.2 +0.2 HA1VHF +1.1 +1.3 +1.4 +1.0 +0.8 +0.9 +1.1 +1.2 +1.4 +1.5 HA2NA +0.7 +0.6 +0.6 +0.2 +0.5 +0.9 +0.7 +1.0 +0.7 +0.5 HA5E +0.3 +0.2 +0.2 HA8TKS +0.1 +0.1 +0.1 +0.0 -0.0 +0.0 +0.0 +0.3 +0.1 +0.1 HB9BXE +0.1 +0.2 +0.2 +0.1 +0.2 +0.1 +0.2 +0.1 +0.1 +0.2 HB9DCO -0.1 -0.1 -0.1 -0.0 -0.0 +0.0 -0.1 -0.1 HG8A +0.6 +0.8 +0.9 +0.5 +0.5 +0.5 +0.5 +0.4 +0.6 +0.6 HS0ZGZ +0.3 +1.0 +0.7 +0.3 -0.1 +0.1 +0.9 +0.2 +0.6 +0.1 IK3STG +1.1 +1.8 +1.6 +1.4 +1.2 +1.2 +0.9 +1.5 +1.6 +1.8 IK4VET +4.4 +4.5 +4.5 +4.7 +4.7 +4.6 +4.6 +4.4 +4.3 +4.6 IK7YTT -0.0 -0.0 -0.0 -0.1 -0.1 +0.0 +0.0 +0.0 IT9GSF -0.1 -0.0 -0.1 -0.1 -0.1 -0.1 IZ2CPS +0.5 +0.4 +0.3 +0.3 +0.3 +0.5 +0.3 +0.2 +0.7 +0.6 JA1CCA -0.8 -1.0 -1.3 -0.8 -0.8 -0.7 -1.2 -1.0 -1.6 -1.6 JE2YCR +0.1 +0.9 JH4UTP +0.6 +0.3 JH7CSU1 +1.0 +1.7 +1.8 +1.1 +1.3 +1.2 +1.0 +0.5 +2.5 +1.8 JI1HFJ -0.4 -2.9 -2.5 -1.3 -0.3 -2.4 -3.8 -0.4 -0.2 JJ2VLY +2.0 +2.0 +1.5 +1.0 +2.6 +1.5 +0.6 +3.5 +2.1 JK1QLQ +0.0 +0.0 +0.4 -0.6 +0.6 +0.0 -0.2 +0.3 JN1ILK +1.4 +0.7 +1.6 +1.3 JO1YYP +1.9 +2.6 +2.9 +3.0 JQ1BVI +0.0 +0.9 +0.0 +0.0 +0.4 +0.6 K1RA-4 +0.3 +0.2 +0.2 +0.3 +0.3 +0.2 +0.3 +0.1 +0.4 K3GMQ +0.0 -0.0 +0.0 -0.1 -0.1 -0.1 -0.0 +0.1 -1.4 +0.0 K3PA-1 +0.6 +0.5 +0.5 +0.4 +0.3 +0.6 +0.5 +0.6 +0.9 +1.0 K3PA-2 +0.0 +0.0 +0.1 K4PP +0.7 +0.6 +0.5 +0.5 +0.5 +0.7 +0.1 +0.7 +1.1 +1.1 K5EM +5.4 +5.2 +5.1 +6.0 +4.7 +5.2 +4.8 +5.0 +4.4 +5.0 K5KHK -0.1 +0.1 +0.0 -0.2 -2.6 -2.5 -9.3 -9.2 K5TR -0.2 -0.2 -0.2 -0.3 +0.3 +0.3 +0.2 -0.0 +0.9 +0.7 K6FOD +0.4 +0.0 +0.1 -0.1 -0.6 -0.1 +0.3 +0.1 +0.1 +0.3 K7CO +2.4 +1.5 +1.0 +1.5 +1.8 +1.7 +1.7 +1.7 +3.4 +2.6 K7EK +1.6 +1.8 +0.5 +1.3 +0.9 +0.9 +0.9 +1.2 -0.5 +2.3 K7RUT +3.0 +3.9 K9IMM +0.0 +0.0 +0.0 +0.2 +0.1 +0.1 +0.1 -0.1 -0.1 +0.1 K9LC +0.2 +0.2 +0.2 +0.2 +0.3 +0.4 +0.4 -0.6 -1.1 -1.2 KC4YVA +0.7 +0.8 +0.8 +0.8 +0.9 +1.1 +1.2 +1.4 KD2M +0.0 KD2OGR +0.0 +0.0 +0.9 +0.5 +0.0 +0.5 +0.5 +0.6 KD7EFG +0.3 +0.4 +0.2 +0.1 +0.1 +0.2 +0.1 +0.3 +0.6 +0.5 KG6NFJ +0.0 -0.1 +0.1 -0.1 -0.3 -0.1 +0.1 +0.1 +0.0 KH6LC +0.1 +0.1 +0.8 -0.5 +0.5 +0.3 +0.0 -0.3 +0.1 +0.4 KK4FL +0.0 KM08QR +0.3 +0.1 -0.1 +0.1 -0.1 -0.2 KM3T-2 +0.4 +0.4 +0.4 +0.3 +0.4 +0.5 +0.3 +0.3 +0.6 +0.7 KM3T-3 +0.1 +0.0 +0.1 -0.0 -0.1 -0.0 -0.0 +0.0 -0.0 -0.2 KM3T-5 -0.0 +0.0 -0.0 -0.0 -0.0 +0.0 +0.0 -0.0 +0.0 +0.0 KW7MM +0.5 +0.5 +0.3 +0.2 +0.4 +0.4 +0.5 +0.6 +0.7 +0.7 KW7MM-2 +0.6 +0.7 +0.4 +0.4 +0.5 +0.7 +0.7 +0.7 +1.0 +1.1 KW7MM-3 -3.5 -1.7 -1.2 -5.4 -3.7 KW7MM-4 +15.6 +15.9 +16.0 +15.6 +15.4 +15.0 +15.8 +15.8 +15.6 +15.9 LB9KJ -14.9 +1.4 +13.8 LU8XW +0.4 +0.3 +0.0 +0.0 +0.4 +0.0 +1.2 +1.1 LY3G +0.6 LZ3CB -0.0 -0.1 +0.0 +0.0 -0.0 -0.1 -0.1 -0.1 -0.0 LZ4AE +1.2 +1.4 LZ4UX -0.1 -0.0 -0.2 -0.0 -0.2 +0.1 +0.0 -0.0 -0.1 -0.2 LZ5DI +3.8 +3.8 +3.9 +4.2 +3.5 +3.2 +3.2 +3.4 +3.3 +3.5 LZ7AA +0.6 +0.6 +0.8 +0.5 +0.7 +0.7 +0.6 +0.8 +1.5 +1.3 M1GEO -3.7 +0.0 -0.1 -0.0 -0.1 -0.1 -0.1 -0.1 MM0ZBH +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.2 +0.2 MM9PSY -0.0 -0.0 -0.0 -0.0 -0.1 +0.0 -0.0 -0.0 -0.0 -0.1 N2CR +0.7 +0.6 +0.5 +0.5 +0.9 +0.5 +0.6 +0.8 +0.9 +1.2 N2EPE +0.2 +0.1 +0.1 +0.1 +0.1 -0.0 +0.1 +0.3 +0.2 +0.2 N2YCH +4.4 +4.3 +3.7 +4.0 +3.6 +3.9 +4.0 +3.9 +3.8 +4.4 N4HAC +0.1 +0.0 +0.1 -0.1 -0.1 +0.1 +0.0 +0.0 N6TV +0.7 +0.7 +0.4 +0.3 +0.5 +0.5 +0.5 +0.4 +0.9 +0.9 N7TUG +0.6 +0.1 +0.3 +1.2 +0.0 +0.3 +1.0 +1.6 +0.9 N7VVX -0.0 -0.0 +0.3 +0.0 -0.2 +0.0 +0.0 -0.1 -0.1 +0.0 N8DXE +0.7 +0.6 +1.7 +1.7 +1.0 +1.4 +1.2 +2.3 N9CO +0.3 +0.3 +0.2 +0.2 +0.0 +0.1 -0.3 -0.2 -0.6 +0.4 ND7K -0.1 -0.1 -0.1 -0.2 -0.3 -0.3 -0.1 -0.2 -0.4 -0.2 NG7M -0.1 +0.2 +0.0 -0.1 -0.3 -0.1 -0.0 -0.1 -0.1 +0.1 NN3RP +0.8 +1.7 +0.0 -0.3 +0.6 +0.7 +0.0 +1.3 +0.9 NU4F -0.0 +0.0 +0.2 +0.0 -0.1 -0.0 +0.1 +0.1 -0.2 +0.1 OE3KLU +0.5 +1.0 +0.7 +0.0 OE9GHV +0.0 +0.0 -0.0 OH4KA +1.6 +1.3 OH6BG +0.2 +0.1 +0.2 +0.3 +0.4 OH8KA +8.1 +8.3 +7.8 +8.0 +8.2 +8.0 +7.9 +8.9 +8.4 +8.0 OK1FCJ +0.2 +0.2 +0.1 OK1HRA -4.4 -4.4 -4.5 -4.3 -4.5 -4.2 -3.9 -4.0 -4.7 -4.5 ON6ZQ +0.7 +0.8 +0.9 +0.9 +0.9 +1.0 +1.0 +1.0 +1.3 +1.2 OZ1AAB +0.1 -0.1 -0.1 -0.2 +0.1 +0.3 -0.3 -0.1 -0.2 -0.1 OZ1BZS +0.6 +0.6 +0.6 +0.3 +0.2 +0.8 +0.5 +0.6 +1.0 +0.9 PA5KT-4 -0.2 -0.3 -0.3 -0.0 +0.2 +0.2 -0.0 -0.3 -0.1 +0.1 PA5WT +0.0 +0.0 +0.0 +0.1 +0.1 PA8MM +0.3 +0.3 +0.3 +0.2 +0.4 +0.6 PD2RPS +5.4 PE5TT +0.9 +0.8 +1.0 +1.0 +1.0 +0.7 +0.6 +0.8 +1.2 +1.2 PI4CC -0.0 -0.0 +0.0 -0.0 +0.0 -0.1 -0.0 -0.0 PT2FHC +0.0 +0.0 +0.1 +0.0 -0.1 -0.2 -0.1 -0.0 +0.1 -0.1 PY2KNK +2.2 +3.2 +3.3 +4.9 +3.7 +3.9 +2.5 +1.0 +2.0 +3.8 PY2PE -0.1 +0.3 +0.2 +0.2 +0.6 -0.1 +0.5 +0.0 +0.4 +0.1 R4NCU -0.6 -0.5 -0.6 -0.2 -0.7 -0.6 -0.3 -0.4 -0.6 -0.8 RK3TD +0.3 +0.1 +0.1 -0.0 +0.1 +0.2 +0.2 +0.3 +0.7 +0.8 RK3TD-2 +0.8 +0.8 +0.9 +0.7 +0.7 +1.0 +0.8 +0.8 +1.1 +1.1 RN4WA +1.4 +1.5 +1.2 +1.1 +0.9 +1.3 +1.6 +1.4 +2.2 +2.2 RU9CZD +0.0 +0.1 +0.1 +0.1 +0.1 -0.1 +0.1 -0.0 -0.0 -0.4 S50U +0.5 +0.7 +0.4 +0.3 +0.4 +0.7 +0.5 +0.7 +0.7 +0.4 S53A +0.9 +0.9 +1.0 +0.6 +0.6 +0.2 -0.3 S53F +0.7 S53WW +0.6 +0.7 +0.7 +0.5 +0.6 +0.7 +0.7 +0.7 +0.9 +0.9 S54L +0.6 +1.5 +1.0 +0.9 +1.3 +1.7 +1.1 +1.7 +0.7 +2.1 S58W +0.0 +0.0 -0.0 -0.1 +0.0 -0.3 -0.1 +0.0 +0.1 -0.3 SA6LKX +0.0 -0.0 -0.1 SE5E +0.1 +0.2 +0.2 +0.1 -0.0 -0.1 +0.0 -0.0 +0.0 -0.1 SK6AW -0.1 -0.0 -0.0 +0.0 -0.0 -0.1 -0.0 -0.3 SM0TCZ +0.5 +0.1 +0.4 +0.4 -0.2 +1.0 +1.2 -0.1 +0.7 +0.6 SM1HEV -0.4 +0.0 +0.2 +0.3 +0.1 +0.3 +0.2 +0.2 +0.0 +0.3 SM7IUN -0.0 -0.1 +0.0 +0.0 +0.0 +0.1 -0.0 +0.0 +0.0 +0.1 SQ5J +8.8 +8.8 +8.7 +8.8 +9.0 +9.2 +9.1 +8.8 +8.6 +8.5 SV1CDN +5.9 +9.9 +10.5 +4.8 +4.8 +4.3 +4.8 +4.1 +4.2 SV1DPJ -0.6 -0.4 -0.9 +0.8 +0.0 SZ1A -0.1 +0.0 +0.0 +0.0 +0.0 -0.2 -0.1 -0.8 -4.0 TF3Y +1.7 +1.8 +1.7 +1.6 +1.0 +1.4 +1.3 +1.2 +1.8 +2.0 TI7W +1.0 +1.1 +1.2 +1.0 +0.9 +1.1 +1.0 +1.0 +1.6 +1.3 UR4RXX +0.3 +0.3 -0.2 +0.0 -0.1 +0.2 +0.3 +0.5 +0.3 UT5R +0.1 +0.1 +0.2 +0.1 +0.1 +0.2 +0.1 +0.0 +0.0 UY2RA -0.4 -0.5 -0.5 +1.8 +35.8 -0.5 -0.4 -0.9 -1.3 -0.9 V51YJ +0.5 +1.5 +1.7 +0.3 +1.1 +0.0 +1.2 +1.2 +1.8 +1.9 VE4DRK -11.2 -10.2 -11.0 -11.3 -11.8 -11.6 -11.2 -13.1 -10.1 VE6AO -0.3 +0.1 -0.1 +0.1 -0.2 -0.4 -0.3 -0.1 -0.6 -0.2 VE6JY +0.5 +0.6 +0.4 +0.8 +0.0 +0.3 +0.3 +0.4 +0.9 +1.0 VE6WZ -0.3 -0.2 -0.4 -0.2 +0.6 -0.1 -0.4 -0.6 -0.0 -0.8 VE6WZ-3 -0.8 -0.6 -0.6 -0.7 -0.3 -1.0 -0.7 -0.6 -1.1 -1.0 VE7CC +1.0 +0.8 +0.9 +0.7 +1.6 +1.5 VK2RH +0.0 +0.0 +0.3 -1.2 +0.0 -1.4 -0.7 -0.1 VK3RASA -1.2 -1.5 -1.0 +0.2 -0.9 -0.8 -0.2 -0.7 -0.5 -1.6 VK3VB -1.4 VK6ANC +0.0 -0.3 -0.0 +0.3 +0.0 -0.2 -0.9 -2.8 -0.5 -1.4 VU22DX -0.6 +0.0 -0.0 +0.0 VU2CPL +0.0 +0.3 +0.3 +0.0 +0.0 +0.0 -0.7 +0.0 -0.1 -0.4 VU2OY +0.0 +1.1 +0.8 +0.7 +0.4 +0.5 +0.6 +0.2 +1.0 +0.7 VU2PTT -0.9 +0.2 +0.0 +0.0 -1.0 +0.0 +0.1 -0.2 VU2TUM +1.9 +1.7 +1.2 +0.3 +0.4 +0.7 +1.2 +0.5 +1.1 +1.2 W1NT-2 +0.7 +0.6 +0.5 +0.6 +0.6 +0.8 +0.7 +0.5 +1.0 +1.0 W1NT-6 +0.7 +0.7 +0.7 +0.8 +0.7 +1.1 +0.8 +0.7 +1.1 +1.2 W2MV +0.5 +0.5 +0.3 +0.2 -0.0 +0.5 +0.2 +0.2 +0.5 +0.5 W2NAF +1.3 +1.6 +0.4 +1.2 +1.2 +1.2 +1.4 +1.5 +2.0 +2.1 W2NNN +4.4 +4.0 +3.2 +5.6 +2.8 +4.3 +4.1 +3.3 +4.0 W3DAN +0.8 +0.8 +1.5 +1.0 +1.2 +1.3 +1.1 +1.7 W3LPL -0.6 -0.7 -0.8 W3RGA +0.3 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 +0.1 W3UA -0.0 +0.0 +0.0 -0.0 -0.0 -0.1 -0.1 +0.0 -0.2 -0.0 W4KAZ +0.5 +0.6 +0.3 +0.4 +0.4 +0.4 +0.3 +0.3 +0.6 +0.6 W6YX +0.7 +0.5 +0.4 +0.4 +0.7 +1.0 +0.9 +0.6 +1.0 +1.1 W8WTS +0.4 +0.5 +0.5 +0.5 +0.6 +0.6 +0.4 +0.6 +1.0 +0.8 W8WWV -1.5 -1.4 -1.6 -1.3 -1.4 -1.7 -1.2 -1.7 -1.9 -2.1 WA7LNW +0.7 +0.5 +0.4 +0.4 +0.7 +0.7 +0.6 +0.7 +1.1 +0.9 WB6BEE -0.1 +0.0 +0.0 +0.0 -0.1 -0.0 -0.0 +0.1 -0.0 -0.0 WC2L +0.4 +0.3 +0.3 +0.5 +0.4 +0.4 +0.3 +0.8 +1.2 +1.2 WE9V +0.1 +0.2 +0.2 +0.0 +0.3 +0.0 +0.1 +0.1 +0.9 -0.1 WS2C +9.8 +9.3 +9.6 +9.6 +10.2 +9.2 WS3W +0.1 +0.0 -0.0 +0.1 +0.0 -0.1 -0.1 +0.0 WT8P +0.1 -0.1 +0.2 -0.1 -0.2 +0.1 +0.2 +0.1 +0.2 +0.3 WT9U +0.1 +0.2 +0.2 -0.1 +0.0 -0.0 -0.1 +0.2 -0.1 +0.6 WW1L +0.0 -0.1 +0.0 -0.1 WX7V/5 +0.2 +0.6 +0.8 +1.0 YO2CK -9.6 -9.1 -7.9 -8.9 -9.5 -9.4 -10.2 -10.2 -9.0 -8.9 YO2KAR -0.2 -0.1 -0.2 -0.2 -0.2 -0.2 +0.0 +0.2 -0.1 +0.0 YO5LD +0.7 +0.7 +0.7 +0.4 +0.5 +0.5 +0.4 +0.3 +0.3 +0.3 ZF1A -5.9 -6.9 -6.3 -5.2 -3.6 -4.3 -6.0 -7.1 ZF9CW -5.5 -5.7 +0.6 +0.8 +0.8 +0.8 +0.8 +1.0 +1.0 ZL2KS +0.2 +0.4 +0.4 +0.2 +0.6 +0.7 +0.3 +1.0 +0.2 -0.6 ZL3X -1.4 -1.0 -0.7 -1.0 -0.7 -0.0 -0.1 -0.5 -1.0 -1.9 ZL4YL +0.3 +0.6 +0.5 +0.4 +0.4 +0.8 +0.4 +0.4 +0.8 +0.6 ZS1NN -4.5 -4.5 -4.8 -5.5 -5.4 -3.8 -2.7 -4.5 -4.7 -5.0 Last updated 2026-07-21 00:15:39 UTC
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 MM9PSY WB6BEE Last updated 2026-07-21 00:15:39 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.