RBN Analytics

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.