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.
565714 RBN spots between 2025-10-22 00:00 and 23:59 UTC. 163072 spots (28.8%) were from reference skimmers (*). Average spot flow was 393 per minute from 210 active CW skimmers. 316230 spots from 206 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 +1.3 57 1.000001301 3D2AG +0.3 227 1.000000330 5Z4GO +0.4 13 1.000000366 AA0O +1.0 1325 1.000000955 AC0C-1* -0.0 3046 0.999999967 BA4OP -0.1 277 0.999999871 BA6KC -0.1 163 0.999999927 BD4UNT +0.1 223 1.000000080 BD7JNA +0.0 173 1.000000027 BG0AJO* +0.0 253 1.000000024 BG0AJO/0 +0.4 66 1.000000416 BG2TFW -0.4 224 0.999999604 BG4GOV +0.0 7 1.000000000 BH4HKZ -0.5 9 0.999999472 BH4RRG +0.5 120 1.000000509 BH4XDZ -0.1 128 0.999999944 BI4MPH +0.0 80 1.000000045 CT1EYQ -0.4 1389 0.999999602 DD5XX +0.7 2644 1.000000653 DE1LON +0.3 2619 1.000000291 DF1VB* -0.0 2287 0.999999977 DF2CK +0.6 5082 1.000000639 DF7GB* +0.0 2960 1.000000040 DG6FL +0.2 141 1.000000202 DK0TE -0.5 2901 0.999999549 DK3WW* +0.1 3509 1.000000057 DK9IP* +0.1 1889 1.000000070 DK9IP-1* +0.0 2334 1.000000002 DL0LA* -0.0 1230 0.999999990 DL1HWS +0.6 3480 1.000000635 DL1HWS-3 +1.2 2302 1.000001158 DL1HWS-4 +1.5 522 1.000001535 DL8LAS +0.3 3710 1.000000263 DL8TG* -0.0 3272 0.999999998 DM5GG -0.0 3955 0.999999962 DR4W -2.5 3612 0.999997517 DR5X +1.5 2272 1.000001508 EA2CW +0.2 2468 1.000000177 EA2RCF-4* +0.0 1574 1.000000012 EA5WU* -0.0 1716 0.999999988 EA8/DF4UE* -0.0 3983 0.999999957 ES2RR* +0.0 1959 1.000000005 ES5PC* +0.0 4074 1.000000022 F4GOU +5.1 2893 1.000005107 F4VVG +0.2 1607 1.000000162 F6IIT +0.0 17 1.000000000 F8DGY -3.0 2111 0.999997031 G0KTN +0.4 3040 1.000000439 G3AKX -1.3 2749 0.999998744 G3YPP +0.9 112 1.000000933 G4IRN +0.3 4359 1.000000275 G4MKR +0.1 24 1.000000149 G4ZFE +0.7 2969 1.000000722 GI4DOH* -0.1 2670 0.999999937 GX0FRE +0.0 6 1.000000000 HA1VHF +0.1 2931 1.000000104 HA5JI-8* -0.1 2507 0.999999907 HA5PP-2 +1.1 53 1.000001072 HA6PX* -0.1 238 0.999999935 HA8TKS* +0.1 1979 1.000000102 HA8TKS-2* -0.0 195 0.999999978 HB9BXE +0.4 2408 1.000000400 HB9DCO -0.3 1889 0.999999659 HB9GVO +0.7 170 1.000000670 HG0Y +7.5 80 1.000007482 HG8A +0.6 3188 1.000000596 IK3STG +2.6 2505 1.000002553 IK4VET +1.2 3192 1.000001166 IK7YTT* +0.0 2559 1.000000038 IT9GSF* -0.1 3203 0.999999913 IW9GDC -0.5 779 0.999999536 IZ2CPS -2.5 125 0.999997547 JI1HFJ +0.0 37 1.000000017 JJ2VLY -0.4 65 0.999999551 JK1QLQ +0.0 13 1.000000000 JN1ILK -0.6 688 0.999999429 K1RA +0.2 2799 1.000000184 K2PO/7 +0.5 945 1.000000480 K3PA-1* +0.1 2598 1.000000064 K3PA-2 -17.3 291 0.999982692 K4PP* +0.0 1647 1.000000002 K5EM +2.5 1020 1.000002462 K5TR +2.1 2529 1.000002125 K7CO -0.5 1265 0.999999468 K7EK +0.9 418 1.000000867 K9IMM* -0.0 1960 0.999999962 K9LC +0.6 2570 1.000000623 KD2OGR +0.4 1266 1.000000412 KD7EFG +0.4 1055 1.000000400 KH6LC +0.1 128 1.000000056 KL2R -0.7 59 0.999999295 KM3T-2* -0.0 1290 0.999999993 KM3T-5 -0.1 755 0.999999933 KO7SS +0.5 593 1.000000492 KP3CW -0.5 287 0.999999541 KV4TT* +0.0 2294 1.000000025 KW7MM* -0.0 2053 0.999999990 KW7MM/7 +0.5 2143 1.000000508 LA6TPA -1.2 1168 0.999998787 LB9KJ +2.5 971 1.000002483 LU6KK +0.0 5 1.000000000 LU8XW +0.9 30 1.000000871 LZ3CB* -0.0 1981 0.999999988 LZ4AE -1.0 5102 0.999998983 LZ4UX* -0.0 2105 0.999999988 LZ5DI +0.6 2533 1.000000619 LZ7AA +0.8 2008 1.000000768 MM0GPZ -0.4 3531 0.999999594 MM0ZBH +0.2 3777 1.000000186 N2CR +0.2 1329 1.000000205 N2YCH* -0.0 2949 0.999999961 N6TV +0.8 983 1.000000829 N7TUG -0.4 168 0.999999554 N8DXE +1.5 731 1.000001538 N9CO* -0.0 2069 0.999999995 ND7K -0.4 1903 0.999999558 NG7M* -0.1 1441 0.999999925 NN3RP +0.3 661 1.000000253 NT6Q +3.1 1624 1.000003116 NU4F* +0.0 1667 1.000000039 OE3KLU -7.2 23 0.999992758 OE9GHV* -0.0 3524 0.999999956 OH4KA +0.1 128 1.000000093 OH6BG* +0.0 2811 1.000000002 OH8KA -4.8 541 0.999995209 OK1FCJ +0.3 3679 1.000000304 OK1HRA -4.2 2507 0.999995762 ON6ZQ +0.2 2405 1.000000229 OZ1AAB +0.3 1355 1.000000288 OZ1BZS +0.7 625 1.000000654 OZ4ADX +0.2 626 1.000000182 PA5KT-4* -0.1 2885 0.999999935 PE5TT +1.0 2319 1.000000976 PI4CC* +0.2 3482 1.000000153 PY2KNK +2.8 233 1.000002800 PY2PE -3.5 90 0.999996503 R4NCU -0.5 224 0.999999459 RK3TD +0.8 1483 1.000000793 RK3TD-2 +0.7 1838 1.000000655 RN4WA +1.4 249 1.000001421 RU9CZD* +0.0 1184 1.000000008 S50U +0.5 1875 1.000000500 S53A +0.8 3612 1.000000770 S53F -0.5 361 0.999999478 S53WW -0.5 3143 0.999999510 S54L* -0.2 3163 0.999999820 SE5E +0.1 3961 1.000000109 SM0TCZ +2.3 576 1.000002328 SM1HEV +0.4 370 1.000000407 SM7IUN +0.1 2614 1.000000086 SQ5J +7.1 2545 1.000007131 SV1CDN +0.4 295 1.000000362 SZ1A -0.5 2492 0.999999490 TF3Y +2.2 1093 1.000002188 TI7W +1.5 1695 1.000001465 UA4CC +14.1 753 1.000014052 UT5R +3.7 24 1.000003749 UT5R-1 +2.2 29 1.000002154 UY2RA -2.9 1015 0.999997122 V51YJ +0.8 9 1.000000792 VA2NM +0.2 660 1.000000227 VE3EID* -0.1 3066 0.999999867 VE6AO -1.3 1137 0.999998750 VE6JY +1.0 1967 1.000000963 VE6WZ* +0.3 1152 1.000000331 VE6WZ-3 -1.3 420 0.999998728 VE7CC -5.1 74 0.999994949 VK2GEL +0.7 200 1.000000725 VK2RH +0.7 55 1.000000749 VK3RASA -1.3 306 0.999998679 VK4CT +0.2 111 1.000000192 VK6ANC -0.0 177 0.999999982 VR2FUN-77 +0.9 1158 1.000000898 VU2CPL +0.3 65 1.000000256 VU2OY +9.4 88 1.000009409 VU2TUM +2.0 506 1.000002027 W1NT-2* +0.1 2725 1.000000055 W1NT-6* +0.1 3561 1.000000061 W2MV -13.0 178 0.999987047 W2NAF +2.0 2468 1.000001959 W2NNN +12.7 2154 1.000012676 W3DAN +1.5 708 1.000001528 W3OA +0.2 1950 1.000000188 W3RGA +0.0 2947 1.000000050 W4AX +6.7 16 1.000006679 W4KAZ -0.8 1486 0.999999170 W6YX +0.5 1774 1.000000479 W8WTS* +0.1 1828 1.000000127 W8WWV -1.6 2262 0.999998408 WA7LNW +2.3 1565 1.000002340 WB6BEE -0.1 673 0.999999939 WC2L +0.5 1517 1.000000483 WC8GOP +12.5 106 1.000012493 WE9V +0.0 1904 1.000000019 WS2C +9.8 1932 1.000009833 WS3W +0.6 203 1.000000632 WT9U +6.3 1507 1.000006268 WV4P +0.3 1837 1.000000332 WX7V/5 +0.0 34 1.000000000 WZ7I +0.7 3261 1.000000676 YO2CK +0.4 2001 1.000000420 YO2KAR +0.4 2047 1.000000377 YO5LD +0.3 2686 1.000000329 ZF1A +9.6 3010 1.000009614 ZL3X +0.2 503 1.000000227 ZS1NN -4.0 66 0.999996013 Last updated 2025-10-23 00:10:52 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 1022 1021 1020 1019 1018 1017 1016 1015 1014 1013 --------------------------------------------------------------------- 3B8GL +1.3 +0.6 +1.1 +0.7 +1.3 +0.5 +0.0 +0.4 +0.0 +0.0 3D2AG +0.3 +0.3 +0.5 +0.6 +0.5 +0.4 +0.4 +2.9 +0.9 5Z4GO +0.4 +0.0 +1.6 +0.9 +0.7 +0.5 +0.7 +0.5 +0.7 7N4XCV +0.0 +0.0 +0.0 +0.0 +0.0 AA0O +1.0 +1.0 +0.9 +0.7 +0.9 +0.7 +0.6 +1.1 +0.8 +0.7 AC0C-1 -0.0 -0.0 +0.0 +0.0 +0.0 +0.0 -0.0 +0.1 -0.0 +0.3 BA4OP -0.1 -0.1 -0.3 +0.0 -0.1 -0.1 -0.2 +0.0 BA6KC -0.1 +0.3 -0.1 -0.1 -0.1 -0.1 -0.1 +0.0 -0.2 +0.0 BD4UNT +0.1 +0.1 +0.3 +0.1 +0.1 +0.0 +0.5 -0.1 +0.2 -0.5 BD7JNA +0.0 +0.1 +0.1 +0.0 -0.1 -0.0 -0.0 +0.1 +0.1 +0.0 BG0AJO +0.0 +0.0 -0.1 -0.0 +0.0 -0.1 -0.0 +0.1 +0.1 +0.0 BG0AJO/0 +0.4 +0.6 +0.0 +0.4 -0.2 +0.4 +0.1 +0.1 +0.1 +1.1 BG2TFW -0.4 -0.9 -1.0 -0.9 -0.6 -0.4 -0.6 -0.2 -0.1 BG4GOV +0.0 +0.2 +0.0 +0.3 -0.6 +0.5 +0.4 +0.6 BH4HKZ -0.5 +0.0 -1.0 -0.1 -0.3 +0.0 BH4RRG +0.5 +0.5 +0.3 +0.3 +0.6 +0.2 +0.3 +0.3 -0.1 +0.0 BH4XDZ -0.1 -0.0 +0.0 +0.1 -0.0 -0.3 -0.0 +0.1 +0.1 -0.2 BI4MPH +0.0 -0.1 +0.2 +0.3 +0.0 +0.1 +0.1 +0.2 +0.0 CT1EYQ -0.4 -0.5 -0.6 -0.7 -0.8 -0.6 -0.4 -0.3 -0.2 -0.1 DD5XX +0.7 +0.6 +0.4 DE1LON +0.3 +0.2 +0.2 +0.2 +0.3 +0.4 +0.4 +0.4 +0.3 +0.5 DE2SAX +0.0 -0.5 +0.0 DF1VB -0.0 -0.0 -0.0 -0.0 +0.1 +0.0 -0.1 -0.1 -0.0 -0.0 DF2CK +0.6 +0.4 +0.1 -0.5 +0.5 +0.7 +0.3 +0.6 +0.2 +0.7 DF7GB +0.0 -0.0 +0.0 +0.0 +0.0 -0.0 +0.1 -0.0 -0.0 +0.0 DG6FL +0.2 +0.4 +0.4 +0.4 +0.0 +0.3 -5.0 -6.5 DK0TE -0.5 -0.3 -0.7 -0.6 -0.5 -0.6 -0.4 -0.3 -0.3 -0.4 DK3WW +0.1 +0.1 -0.4 -0.4 -0.5 -0.1 -0.2 -0.1 -0.2 +0.2 DK8NE -3.1 DK9BT +0.2 DK9IP +0.1 +0.1 +0.0 +0.1 +0.1 -0.1 +0.1 +0.1 +0.1 +0.1 DK9IP-1 +0.0 +0.0 +0.0 +0.1 +0.1 -0.0 +0.0 +0.0 +0.0 -0.1 DL0LA -0.0 -0.1 -0.1 -0.2 -0.1 -0.1 -0.2 +0.0 -0.1 +0.0 DL1EFW -0.4 +0.5 DL1HWS +0.6 +0.6 +0.5 +0.7 +0.9 +0.5 +0.7 +0.6 +0.4 +0.7 DL1HWS-3 +1.2 +1.2 +0.8 +1.2 +1.3 +1.1 +1.3 +1.1 +0.9 +1.0 DL1HWS-4 +1.5 +1.3 +1.0 +1.0 +1.6 +1.7 +1.4 +0.9 +0.9 +0.9 DL5RCN +12.7 +13.0 +13.0 +12.5 +13.0 DL8LAS +0.3 +0.3 +0.2 +0.3 +0.4 +0.4 +0.4 +0.5 +0.2 +0.4 DL8TG -0.0 -0.1 -0.1 +0.0 -0.0 -0.1 -0.2 -0.2 -0.1 -0.0 DM5GG -0.0 +0.6 +0.1 -0.1 +0.2 +0.2 +0.4 +0.7 +0.4 +0.7 DM6EE +0.0 +0.1 +0.0 +0.1 DM7EE +0.6 +0.5 +0.4 +0.6 +0.1 DO4DXA +0.0 +0.0 +0.1 DR4W -2.5 -2.1 -3.0 -2.5 -2.9 -2.6 -2.2 -2.2 -2.1 -1.7 DR5X +1.5 +1.4 +1.1 +1.7 +1.9 +1.6 +1.7 +1.7 +1.7 +1.8 E28AC -1.0 -0.3 -2.1 -1.3 -1.0 -0.8 EA2CW +0.2 -0.2 -0.5 -0.4 -0.5 -0.6 -0.6 -0.4 -0.4 -0.4 EA2RCF-4 +0.0 -0.2 -0.8 -0.5 -0.6 -0.4 -0.5 -0.3 -0.3 -0.5 EA5WU -0.0 -0.1 +0.0 +0.0 EA8/DF4UE -0.0 -0.0 -0.1 -0.1 -0.1 -0.0 -0.1 -0.0 -0.0 -0.0 ES2RR +0.0 -0.1 -0.0 +0.0 +0.1 -0.0 -0.1 -0.1 +0.0 -0.0 ES5PC +0.0 -0.0 -0.1 +0.0 -0.0 -0.0 -0.1 +0.0 -0.0 -0.1 ET3AA -12.0 F4GOU +5.1 +5.1 +4.8 +5.6 +5.4 +4.8 +4.8 F4VVG +0.2 +0.1 +0.1 +0.2 +0.3 +0.2 +0.2 +0.1 +0.1 +0.3 F5AHD +0.8 F6IIT +0.0 +0.0 -1.8 F6KGL +0.2 +0.2 +0.2 +0.2 +0.2 +0.2 +0.0 +0.2 F8DGY -3.0 -3.6 -4.1 -3.9 G0KTN +0.4 +0.4 +0.3 +0.4 +0.5 +0.3 +0.2 +0.3 +0.2 +0.2 G0TMX +0.3 G3AKX -1.3 -0.6 -0.7 G3BJ +0.3 G3YPP +0.9 +0.7 +0.5 +0.6 +0.8 +1.4 G4AON +0.8 G4HSO -0.6 -0.6 +0.2 +0.5 -0.5 -0.1 -0.3 -0.4 -0.6 G4IRN +0.3 +0.2 +0.2 +0.3 +0.3 +0.2 +0.1 +0.2 +0.2 +0.2 G4MKR +0.1 +0.0 +0.5 +0.1 +0.3 +0.0 G4ZFE +0.7 +0.6 +0.6 +0.7 +0.8 +0.6 +0.6 +0.6 +0.5 +0.6 GI4DOH -0.1 -0.0 -0.1 -0.1 -0.0 -0.0 -0.2 -0.1 -0.1 -0.5 GX0FRE +0.0 +0.1 +0.0 +0.2 +0.3 +0.2 +0.0 +0.1 +0.2 HA1VHF +0.1 +0.1 -0.1 +0.1 +0.2 +0.2 +0.3 +0.4 +0.2 +0.2 HA/5B4ASI +2.6 HA5JI-8 -0.1 +0.1 -0.5 +0.0 -0.3 -0.3 -0.2 -0.4 -0.1 -0.3 HA5PP -0.4 -0.4 -0.5 -1.7 -1.2 -0.4 -0.0 HA5PP-2 +1.1 +3.8 +0.7 -1.5 HA6PX -0.1 -0.1 -0.2 +0.2 -0.0 +0.0 -0.0 +0.0 +0.0 -0.1 HA8TKS +0.1 +0.1 -0.1 +0.2 +0.2 +0.2 +0.2 +0.2 +0.1 +0.2 HA8TKS-2 -0.0 +0.0 +0.2 -0.1 +0.0 -0.1 +0.1 HB9BXE +0.4 +0.3 +0.3 +0.3 +0.3 +0.3 +0.4 +0.3 +0.1 +0.2 HB9DCO -0.3 -0.3 -0.4 -0.6 -0.4 -0.4 -0.4 -0.3 -0.2 -0.4 HB9GVO +0.7 +0.5 +1.3 +1.0 +1.4 +0.9 +1.6 +1.2 +1.5 +0.7 HG0Y +7.5 +7.2 +7.2 +7.3 +7.5 +7.4 +7.6 +7.6 HG8A +0.6 +0.2 +0.1 +0.4 +0.1 +0.3 +0.6 +0.6 +0.4 +0.5 IK3STG +2.6 +2.3 +2.0 +2.2 +2.6 +2.2 +2.3 +2.1 +1.6 +1.9 IK4VET +1.2 +1.1 +1.2 +1.6 +1.7 +1.8 +1.8 +2.2 +2.1 +2.5 IK7YTT +0.0 -0.0 -0.0 +0.0 +0.0 -0.0 +0.0 +0.0 -0.0 -0.0 IT9GSF -0.1 -0.1 -0.0 +0.1 IW9GDC -0.5 -0.6 -0.6 -1.0 -0.8 -0.6 -0.5 -0.5 -0.3 -0.7 IZ2CPS -2.5 -2.5 -2.4 +0.0 +1.3 +1.1 +1.1 +0.9 +0.7 +1.1 JG1DLY -0.2 JH7CSU1 +1.6 +1.5 +2.0 +1.7 +1.0 +1.4 +1.1 +1.6 +1.3 JI1HFJ +0.0 +0.5 +1.3 +0.5 +1.0 -2.7 +0.7 -2.9 +1.2 -1.1 JJ2VLY -0.4 +0.4 +1.1 +1.7 +2.0 +1.5 +1.4 +0.9 +1.0 JK1QLQ +0.0 +0.5 +0.0 +0.8 -0.3 -0.1 +0.0 +0.5 +0.0 +0.0 JN1ILK -0.6 -0.5 -0.4 +0.0 -0.1 +0.1 -0.1 +0.2 -0.1 +0.1 K1RA +0.2 -0.0 +0.3 +0.5 +0.4 +0.1 +0.2 +0.8 +0.2 +0.3 K2PO/7 +0.5 +0.4 +0.3 +0.6 +0.5 +0.5 +0.6 +0.6 +0.4 +0.5 K3PA-1 +0.1 +0.1 +0.0 +0.1 +0.0 +0.1 +0.1 +0.2 +0.0 +0.1 K3PA-2 -17.3 -17.1 -17.3 -17.0 K4PP +0.0 +0.0 +0.2 +0.3 +0.2 +0.5 +0.1 +0.7 +0.2 +0.4 K5EM +2.5 +2.0 +1.9 +2.4 +3.5 +1.8 +2.2 +2.4 +2.9 +2.8 K5KHK -5.7 K5TR +2.1 +2.1 +1.8 +1.7 +2.0 +1.9 +1.9 +2.6 +2.1 +1.6 K7CO -0.5 -0.6 +0.0 +0.0 -0.3 -0.2 -1.1 -0.6 -0.1 -0.2 K7EK +0.9 +2.4 +1.6 -0.0 +0.4 +0.8 +0.4 +0.0 +2.4 +3.0 K7RUT +0.0 -4.4 K9IMM -0.0 -0.0 -0.1 -0.0 -0.0 -0.1 -0.1 +0.0 +0.0 K9LC +0.6 +0.6 +0.5 +0.7 +0.8 +0.7 +0.5 +0.9 +0.5 +0.6 KD2OGR +0.4 +0.2 +0.2 +0.4 +0.3 +0.2 +0.2 +0.5 +0.2 +0.3 KD7EFG +0.4 +0.2 +0.3 +0.4 +0.3 +0.3 +0.3 +0.4 +0.3 +0.4 KH6LC +0.1 +0.0 -0.1 -0.1 -0.1 +0.1 -0.1 -0.3 +0.1 +0.0 KL2R -0.7 -0.7 +0.0 -0.2 +0.0 -0.3 -0.2 -0.5 +0.0 KM3T-2 -0.0 +0.0 -0.0 +0.0 -0.0 +0.1 +0.0 +0.2 +0.0 +0.0 KM3T-3 +0.2 +0.3 +0.1 +0.1 +0.0 +0.1 -0.1 KM3T-5 -0.1 -0.1 -0.1 -0.1 -0.1 -0.0 -0.1 +0.0 KO7SS +0.5 +0.3 +0.4 +0.1 +0.2 +0.4 +0.5 +0.3 +0.4 +0.3 KP2RUM -0.1 -0.1 +0.0 KP3CW -0.5 -0.3 -0.9 -0.6 -0.7 -0.6 -0.6 -0.4 KV4TT +0.0 -0.1 -0.1 -0.1 -0.1 -0.0 -0.0 -0.0 -0.1 +0.0 KW7MM -0.0 +0.0 +0.1 +0.0 +0.0 -0.1 +0.0 -0.1 +0.1 KW7MM/7 +0.5 +0.3 +0.2 +0.2 +0.5 +0.3 +0.5 +0.4 +0.5 LA6TPA -1.2 -1.3 -1.8 -1.9 -1.2 -1.6 -1.1 -0.6 -0.8 -1.2 LA7GIA -0.7 +0.0 -0.3 +0.0 +0.0 LB9KJ +2.5 +1.6 -0.3 -0.6 +0.3 +1.2 +0.4 +1.0 +0.9 -2.1 LU6KK +0.0 +0.0 +0.0 LU8XW +0.9 +0.3 +0.5 +1.7 +0.9 +0.7 -0.0 +1.3 +0.5 +0.7 LY2XW +0.5 +0.5 LZ3CB -0.0 -0.0 -0.0 +0.0 -0.0 -0.0 +0.0 -0.1 LZ4AE -1.0 -1.7 -1.6 -0.7 -0.7 -1.0 -0.6 -0.6 -0.8 -0.5 LZ4UX -0.0 -0.1 -0.1 -0.1 -0.1 -0.0 -0.1 -0.0 -0.0 +0.0 LZ5DI +0.6 +0.6 +0.4 +0.2 +0.8 +0.5 +0.4 +0.5 +0.3 +5.8 LZ7AA +0.8 +0.6 +1.0 +0.4 +0.5 M0ORD -0.8 -0.6 -0.3 -0.6 MM0GPZ -0.4 -0.2 -0.3 -0.4 -0.4 -0.4 -0.4 -0.3 -0.1 -0.1 MM0ZBH +0.2 +0.1 +0.1 +0.2 +0.2 +0.2 +0.1 +0.1 +0.1 +0.1 N2CR +0.2 +0.2 +0.1 +0.2 +0.2 +0.0 -0.0 +0.6 +0.4 +0.3 N2QT +0.1 N2YCH -0.0 -0.5 -0.2 -0.4 -0.4 -0.3 -0.4 -0.1 -0.3 -0.4 N6TV +0.8 +0.7 +0.7 +0.9 +0.7 +0.7 +0.8 +0.8 +0.5 +0.7 N7TUG -0.4 -0.2 -0.2 -0.2 -0.1 +0.3 -0.2 -0.3 -0.1 -0.4 N8DXE +1.5 +1.5 +1.3 +1.9 +1.5 +1.0 +1.9 +1.2 +1.2 +1.2 N9CO -0.0 +0.0 -0.1 +0.0 +0.0 -0.2 -0.1 +0.1 +0.0 +0.1 ND7K -0.4 -0.4 -0.4 -0.4 -0.6 -0.5 -0.7 -0.5 -0.4 -0.3 NG7M -0.1 -0.0 +0.0 -0.0 +0.1 -0.1 -0.1 +0.1 -0.1 +0.0 NN3RP +0.3 +0.2 +0.1 +0.1 +0.2 +0.1 +0.1 +0.4 +0.4 NT6Q +3.1 +3.3 +2.4 +2.5 +3.5 +3.0 +2.6 +2.9 +2.8 +3.4 NU4F +0.0 +0.0 -0.1 +0.2 +0.0 -0.3 -0.1 +0.2 -0.1 -0.0 OE3KLU -7.2 -7.6 -7.1 -7.6 -6.9 +1.3 +13.0 +10.6 +11.3 OE9GHV -0.0 +0.0 -0.0 -0.0 -0.0 +0.0 -0.0 +0.0 +0.0 -0.1 OG66X +0.3 -0.3 OH4KA +0.1 +1.3 +0.9 +0.8 +0.9 +0.6 +1.2 +0.9 +0.9 +1.3 OH6BG +0.0 -0.0 -0.1 -0.1 -0.1 -0.0 +0.0 -0.4 -0.5 -0.7 OH8KA -4.8 +4.3 +3.0 +4.2 +4.1 +4.7 +0.6 +3.6 OK1FCJ +0.3 +0.3 +0.2 +0.2 +0.3 +0.3 +0.2 +0.2 +0.2 +0.3 OK1HRA -4.2 -3.9 -4.4 -3.8 -4.2 -4.4 -4.2 -4.2 -3.7 -4.0 OK2ZAW +0.0 ON6ZQ +0.2 +0.3 +0.3 +0.1 +0.1 +0.2 +0.2 +0.2 +0.1 +0.2 OZ1AAB +0.3 +0.4 +0.3 +0.3 +0.4 +0.3 +0.4 +0.3 +0.3 +0.4 OZ1BZS +0.7 +0.7 +0.7 +0.7 +0.7 +0.6 +0.8 +0.7 +0.4 +0.6 OZ4ADX +0.2 +0.2 +0.2 +0.1 +0.1 +0.2 +0.3 +0.0 -0.1 +0.2 PA5KT-4 -0.1 -0.0 -0.1 +0.2 +0.1 -0.0 -0.1 +0.1 +0.2 +0.0 PA8MM +0.1 +0.0 +0.1 +0.0 +0.1 PE5TT +1.0 +0.3 +0.4 +0.5 +0.2 +0.1 +0.3 +0.5 +0.4 +0.6 PI4CC +0.2 +0.4 -0.0 +0.1 +0.1 +0.0 +0.0 +0.1 +0.2 +0.1 PY2KNK +2.8 +2.2 +2.2 +2.3 +3.5 +4.5 +3.0 +4.2 +3.3 +3.4 PY2PE -3.5 -3.4 -2.8 -1.2 -1.5 -0.9 -1.6 -2.0 -1.4 -1.4 R4NCU -0.5 -0.3 -0.6 -0.6 -0.4 -0.5 -0.6 -0.3 +0.0 -0.3 RK3TD +0.8 +0.5 +0.5 +0.4 +0.4 +0.5 +0.9 +0.7 +0.3 +0.3 RK3TD-2 +0.7 +0.5 +0.3 +0.3 +0.3 +0.3 +0.4 +0.4 +0.3 +0.4 RN4WA +1.4 +1.6 +1.2 +1.7 +1.9 +1.8 +1.7 +1.3 +1.5 +1.4 RU9CZD +0.0 -0.0 -0.3 +0.0 -0.0 +0.2 -0.1 -0.2 +0.2 -0.3 S50U +0.5 +0.4 +0.4 +0.5 +0.6 +0.5 +0.4 +0.5 +0.3 +0.4 S53A +0.8 +0.5 +0.5 +0.9 +1.1 +0.8 +0.8 +0.9 +0.6 +0.9 S53F -0.5 -1.0 -2.9 -2.4 -2.2 -1.8 -1.6 S53WW -0.5 -0.6 -0.8 -0.9 -0.8 -0.7 -0.6 -0.3 -0.2 -0.2 S54L -0.2 -0.4 -0.6 -0.7 -0.6 -0.6 -0.4 -0.2 -0.1 -0.2 SE5E +0.1 -0.0 -0.2 -0.4 -0.2 -0.2 -0.0 -0.0 -0.1 -0.0 SM0TCZ +2.3 +1.3 +2.0 +2.9 +1.2 +0.4 +0.4 SM1HEV +0.4 -0.1 -0.4 -0.5 -0.5 -0.5 -0.1 -0.1 -0.5 -0.5 SM7IUN +0.1 +0.1 -0.1 -0.1 -0.1 -0.1 -0.0 -0.1 -0.0 +0.0 SQ5J +7.1 +6.8 +6.3 +6.5 +4.2 +2.9 +2.4 SV1CDN +0.4 +0.4 +0.0 +0.3 +0.2 +0.4 +0.4 +0.3 +0.2 +0.1 SZ1A -0.5 -0.0 -0.2 -0.5 -0.4 -0.8 -0.5 -2.7 -0.1 -0.1 TF3Y +2.2 +2.5 +1.9 +2.2 +2.6 +2.1 +2.3 +2.1 +1.7 +1.8 TI7W +1.5 +1.3 +1.2 +1.2 +1.6 +1.8 +1.8 +2.0 +1.6 +1.1 UA4CC +14.1 +13.8 +14.0 +14.1 +14.1 +14.1 +13.9 +14.0 +14.0 +13.9 UT5R-1 +2.2 +2.4 +2.2 +2.4 +2.0 +1.8 +1.9 +2.0 UT5R +3.7 +2.3 +3.5 +4.2 +4.8 +4.7 +4.0 +4.1 +4.7 +4.1 UY2RA -2.9 -3.2 -3.1 -2.8 -2.8 -2.5 -1.9 -1.4 -2.2 -2.2 V51YJ +0.8 +0.5 +1.8 +1.8 +1.9 +1.3 +2.4 +1.4 +1.7 +0.9 VA2NM +0.2 +0.4 +0.2 +0.4 +0.3 +0.3 +0.3 +0.4 +0.2 +0.1 VE3EID -0.1 +0.1 +0.4 +0.4 -0.1 -0.5 -0.3 -0.0 +0.0 +0.2 VE6AO -1.3 -1.3 -1.1 -1.4 -1.6 -1.3 -0.9 -1.2 -1.7 -1.1 VE6JY +1.0 +0.9 +1.4 +2.4 +2.1 +1.4 +1.4 +1.8 +0.8 +1.1 VE6WZ +0.3 +0.8 +0.8 +1.0 +0.6 +0.6 +0.5 +0.7 +0.7 +0.6 VE6WZ-3 -1.3 -1.8 -1.7 -1.6 -0.3 -2.4 -1.5 -2.9 -0.7 -1.6 VE7CC -5.1 -5.0 -4.6 -5.3 -5.5 -4.8 -5.4 -5.8 -5.4 -5.8 VK2GEL +0.7 +1.0 +1.5 +1.0 +0.3 +0.3 VK2RH +0.7 +0.5 +0.2 +0.7 +0.5 +0.0 +0.0 +0.8 +0.0 VK3RASA -1.3 -0.0 -0.9 +0.1 -1.7 -1.6 -0.2 -0.2 -1.0 -1.7 VK3VB +4.3 +0.0 VK4CT +0.2 +0.3 +0.0 +0.6 -0.0 -7.1 -7.6 -7.6 -7.6 -7.7 VK6ANC -0.0 +0.0 -0.3 -0.1 -0.3 +0.0 +0.1 +0.1 +0.0 +0.0 VR2FUN-77 +0.9 +0.9 +0.9 +1.0 +1.0 +0.8 +0.7 +0.9 +0.7 +0.9 VU2CDP +17.0 VU2CPL +0.3 -0.9 +0.0 +0.4 -0.1 -0.3 +0.0 +0.4 +0.1 VU2OY +9.4 +8.6 +9.4 +9.1 +8.8 +9.2 +9.6 +8.8 +9.7 +10.0 VU2TUM +2.0 +1.7 +1.2 +2.1 +1.6 +1.4 +1.5 +1.9 +0.9 +1.0 W1NT-2 +0.1 +0.0 -0.0 +0.0 +0.1 +0.3 -0.1 +0.0 -0.1 -0.0 W1NT-6 +0.1 +0.1 +0.0 +0.1 +0.2 +0.4 -0.1 -0.0 -0.2 -0.0 W2MV -13.0 +0.4 +0.1 +0.4 +0.2 +0.3 +0.5 +0.4 +0.6 +0.3 W2NAF +2.0 +1.6 +1.4 +1.8 +1.7 +1.6 +1.5 +2.0 +1.4 +1.3 W2NNN +12.7 +12.7 +12.5 +12.6 +12.7 +12.6 +12.9 +12.2 +11.9 W3DAN +1.5 +1.2 +1.3 +2.2 +1.6 +1.1 +1.8 +1.7 +1.1 +1.1 W3OA +0.2 +0.2 +0.0 +0.2 +0.2 +0.2 +0.2 +0.4 +0.1 +0.2 W3RGA +0.0 -0.0 +0.0 +0.1 +0.2 +0.1 -0.0 +0.1 -0.1 +0.1 W4AX +6.7 +6.2 +6.7 +4.5 +4.5 +3.6 +1.6 W4KAZ -0.8 -1.1 -1.0 -0.8 -1.1 -1.3 -0.6 -0.8 -0.6 -0.6 W6YX +0.5 +0.4 +0.4 +0.4 +0.4 +0.4 +0.1 +0.4 -0.1 +0.4 W8WTS +0.1 +0.1 +0.1 +0.1 +0.1 +0.2 -0.0 +0.2 +0.0 +0.2 W8WWV -1.6 -1.5 -1.6 -1.2 -1.6 -1.5 -1.8 -1.4 -1.0 WA7LNW +2.3 +1.7 +2.5 +2.5 +1.2 +1.7 +1.2 +1.7 +1.1 +2.6 WB6BEE -0.1 +0.1 -0.1 -0.0 -0.0 +0.0 -0.2 +0.1 -0.0 +0.1 WC2L +0.5 +0.4 +0.3 +0.2 -0.0 -0.1 +0.0 +0.3 -0.1 -0.0 WC8GOP +12.5 +13.2 +12.9 +14.6 +13.3 +14.4 +13.8 +12.8 +14.7 +13.9 WE9V +0.0 -0.0 -0.4 +0.2 -0.4 -0.1 -0.0 -0.4 -0.0 -0.1 WS2C +9.8 +10.0 +9.4 +9.7 +9.4 +9.9 +10.1 +9.6 +10.0 +9.7 WS3W +0.6 +0.5 +0.5 +0.5 +0.6 +0.4 +0.6 +0.7 +0.3 +0.5 WT9U +6.3 +6.2 +6.7 +6.5 +6.5 +6.7 +6.5 +6.9 +6.5 +6.3 WV4P +0.3 +0.3 +0.2 +0.4 +0.6 +0.5 +0.4 +0.5 +0.2 +0.4 WX7V/5 +0.0 +0.3 +0.2 +0.0 +0.5 +0.3 -0.3 +0.7 WZ7I +0.7 +0.6 +0.5 +0.7 +0.7 +0.6 +0.5 +0.8 +0.5 +0.6 YO2CK +0.4 +0.4 +0.3 +0.5 +0.5 +0.4 +0.4 +0.4 +0.3 +0.3 YO2KAR +0.4 +0.1 +0.3 +0.1 +0.0 +0.0 -0.1 +0.1 +0.1 +0.2 YO5LD +0.3 +0.3 +0.3 +0.2 +0.2 +0.2 +0.0 +0.0 ZF1A +9.6 +9.8 +9.4 +10.0 +9.1 +9.8 +9.8 +9.6 +10.0 +9.5 ZL3X +0.2 +1.7 +0.6 +0.1 -0.2 +0.3 -0.4 -0.0 -0.5 -0.3 ZS1NN -4.0 -3.9 -4.2 -3.9 -4.2 -3.5 -3.5 -4.3 -3.5 -3.9 Last updated 2025-10-23 00:11:04 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 OE9GHV WB6BEE Last updated 2025-10-23 00:11:04 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.