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.

317168 RBN spots between 2025-10-01 00:00 and 23:59 UTC.
85041 spots (26.8%) were from reference skimmers (*).
Average spot flow was 220 per minute from 198 active CW skimmers.

147670 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      9   1.000000000
  3D2AG       +0.3     99   1.000000323
  5Z4GO       +0.0      9   1.000000000
  AA0O        +1.5     45   1.000001547
  AC0C-1      -0.1    280   0.999999915
  BA4OP       -0.0     73   0.999999952
  BA6KC       -0.2     52   0.999999840
  BD4UNT      +0.1     53   1.000000067
  BD7JNA      -0.1     59   0.999999871
  BG0AJO      +0.1     89   1.000000147
  BG0AJO/0    +0.3     13   1.000000309
  BG2TFW      +0.1     98   1.000000146
  BG4GOV      +0.0     10   1.000000000
  BH4HKZ      +4.2     15   1.000004186
  BH4RRG      +0.4     23   1.000000414
  BH4XDZ      +0.2     31   1.000000179
  BI4MPH      +0.0     12   1.000000000
  CT1EYQ      -0.1   1195   0.999999880
  DE1LON      +0.5   1512   1.000000469
  DF1VB*      -0.1   1524   0.999999855
  DF2CK       -0.2   2872   0.999999835
  DF7GB       +0.0   1890   1.000000001
  DK0TE       -0.2   1568   0.999999774
  DK3WW*      -0.1   2163   0.999999915
  DK9IP*      -0.0   1024   0.999999963
  DK9IP-1*    -0.1   1291   0.999999918
  DL1HWS      +0.4   1872   1.000000442
  DL1HWS-3    +0.0     29   1.000000000
  DL8LAS*     +0.2   2058   1.000000165
  DL8TG*      -0.1   1867   0.999999863
  DM5GG*      +0.1   2030   1.000000109
  DO4DXA*     -0.1   2067   0.999999942
  DR4W        -3.1   1746   0.999996903
  DR5X        +1.9   1253   1.000001931
  EA/VE3NZ    +0.2     46   1.000000155
  EA2CW       -0.4   1489   0.999999557
  EA2RCF-4    -0.6    990   0.999999357
  EA5WU*      +0.0    777   1.000000006
  ES2RR*      -0.0   1583   0.999999979
  ES5PC*      +0.0   2195   1.000000004
  F1UVN      +16.6   1848   1.000016597
  F4GOU       +4.5   1754   1.000004525
  F4VVG*      +0.0    872   1.000000025
  F8DGY       -3.1    945   0.999996945
  G0KTN       +0.3   1355   1.000000306
  G3YPP       +0.5    157   1.000000468
  G4AON       +1.0     90   1.000000972
  G4HSO       +0.6   1675   1.000000628
  G4IRN       +0.2   1466   1.000000154
  G4ZFE       +0.5   1723   1.000000536
  GI4DOH      +0.2   1425   1.000000209
  GX0FRE      +0.4    740   1.000000430
  HA1VHF      +0.2   1833   1.000000175
  HA5JI-8     -2.3   1599   0.999997742
  HA5PP       -0.5    608   0.999999503
  HA6PX*      -0.1   1978   0.999999927
  HA8TKS*     +0.1   1199   1.000000122
  HA8TKS-2    +0.0    123   1.000000000
  HB9BXE*     +0.1   1605   1.000000134
  HB9DCO      -0.3   1335   0.999999740
  HB9GVO      +0.7    119   1.000000718
  HG0Y        +7.4    314   1.000007355
  HG8A        +0.6   1845   1.000000608
  IK3STG      +1.7   1667   1.000001696
  IK4VET      +1.6   2089   1.000001576
  IK7YTT*     +0.1   2602   1.000000059
  IT9GSF*     -0.0   1513   0.999999974
  IW9GDC      -0.5    662   0.999999484
  JH7CSU1     +1.8     21   1.000001756
  JI1HFJ      -0.4     17   0.999999581
  JJ2VLY      +1.7     21   1.000001736
  JN1ILK      -0.4    125   0.999999563
  K1RA        +1.0    818   1.000000978
  K3PA-1      +0.2    896   1.000000228
  K3PA-2     -17.4     10   0.999982640
  K4PP        +0.4    686   1.000000405
  K5EM        +3.5    280   1.000003544
  K5TR        +1.9    930   1.000001865
  K7CO        -0.0    550   0.999999986
  K7EK        +1.0    173   1.000001050
  K9IMM       +0.1    708   1.000000123
  K9LC        +1.0    832   1.000000964
  KD2OGR      +0.3    423   1.000000331
  KD7EFG      +0.3    258   1.000000289
  KH6LC       -0.1     45   0.999999894
  KM3T-2*     +0.2    560   1.000000187
  KM3T-3      +0.1    112   1.000000127
  KM3T-5      -0.1    590   0.999999911
  KO7SS       +0.5    195   1.000000501
  KP2RUM      +0.0      5   1.000000000
  KP3CW       +0.0     52   1.000000000
  KV4TT*      +0.2    776   1.000000249
  KW7MM       +0.0    761   1.000000009
  KW7MM/7     +0.5    688   1.000000503
  LA6TPA      -0.7    278   0.999999320
  LB9KJ       -0.3    584   0.999999651
  LU8XW       +1.1     14   1.000001105
  LZ3CB*      +0.0   1362   1.000000023
  LZ4UX*      +0.0   1348   1.000000033
  MM0GPZ*     -0.0   1805   0.999999993
  MM0ZBH*     +0.1   1978   1.000000086
  MM3NDH      +0.2   1566   1.000000175
  N2CR        +0.4    392   1.000000424
  N2YCH*      +0.1    949   1.000000091
  N6TV        +1.0    383   1.000000953
  N7TUG       +0.1     49   1.000000145
  N8DXE       +1.6    315   1.000001580
  N9CO        +0.4    752   1.000000374
  ND7K        -0.3    715   0.999999667
  NG7M        -0.1    499   0.999999903
  NN3RP       +0.5    173   1.000000468
  NT6Q        +3.1    400   1.000003097
  NU4F*       +0.1    491   1.000000064
  OE3KLU      -5.7      5   0.999994330
  OE6ADD*     -0.1   2013   0.999999913
  OE9GHV*     -0.0    620   0.999999996
  OG66X       +0.2    443   1.000000193
  OH4KA       +1.1    194   1.000001126
  OH6BG       -0.4   1425   0.999999630
  OH8KA       +4.6    219   1.000004598
  OK1FCJ      +0.2   2230   1.000000177
  OK1HRA      -4.3   1680   0.999995716
  OK2ZAW*     -0.0   1086   0.999999984
  ON6ZQ*      +0.2   1209   1.000000188
  OZ1AAB      +0.4    304   1.000000370
  OZ1BZS      +0.4    331   1.000000366
  OZ4ADX      -0.1    181   0.999999921
  PA5KT-4*    +0.0   1939   1.000000021
  PA8MM       -5.3   1144   0.999994743
  PE5TT       +0.6   1367   1.000000555
  PI4CC       -0.0    231   1.000000000
  PY2KNK      +4.0     54   1.000003962
  PY2PE       -0.9     51   0.999999091
  R4NCU       -0.7    120   0.999999287
  RK3TD       +0.3    190   1.000000325
  RK3TD-2     +0.5   1006   1.000000460
  RN4WA       +1.5    909   1.000001535
  RU9CZD      -0.2    508   0.999999836
  S50U        -0.2   1315   0.999999806
  S53A        +0.7    218   1.000000696
  S53F        -2.0    227   0.999998011
  S53WW       -0.3   1939   0.999999678
  S54L*       -0.0   1013   0.999999956
  SE5E*       -0.0   2110   0.999999969
  SM1HEV      -0.6    508   0.999999435
  SM7IUN*     -0.1    490   0.999999913
  SQ5J        +7.4   1116   1.000007388
  SV1CDN      +0.2    321   1.000000244
  SZ1A        +0.4   1734   1.000000352
  TF3Y        +1.7    276   1.000001743
  TI7W        +1.3    735   1.000001285
  UA4CC      +14.2    784   1.000014183
  UT5R        +5.3    103   1.000005303
  UT5R-1      +3.1    217   1.000003132
  UY2RA       -2.0    394   0.999998048
  V51YJ       +1.3    129   1.000001293
  VE3EID      -0.1    213   0.999999944
  VE6AO       -1.1    177   0.999998939
  VE6JY       +1.0    457   1.000000998
  VE6WZ       +0.6    120   1.000000626
  VE6WZ-3     -1.2     12   0.999998813
  VE7CC       -5.5      9   0.999994455
  VK2RH       +0.0      8   1.000000000
  VK3RASA     -0.2     63   0.999999774
  VK6ANC      -0.1     64   0.999999889
  VU2CPL      +0.1     90   1.000000079
  VU2OY       +9.9    178   1.000009892
  VU2TUM      +1.4    146   1.000001393
  W1NT-2*     -0.2    978   0.999999777
  W1NT-6*     -0.1   1075   0.999999869
  W2MV        +1.2     58   1.000001226
  W2NAF       +1.6    975   1.000001612
  W2NNN      +12.9    691   1.000012895
  W3DAN       +1.4    341   1.000001418
  W3OA        +0.3    773   1.000000267
  W3RGA*      -0.2    998   0.999999774
  W4KAZ       -0.3    578   0.999999698
  W8WTS       +0.3    557   1.000000272
  W8WWV       -1.8    803   0.999998236
  WA7LNW      +3.1    682   1.000003092
  WB6BEE      -0.1    236   0.999999950
  WC2L        +0.4    727   1.000000422
  WC8GOP     +13.4     32   1.000013391
  WE9V        +0.1    885   1.000000077
  WS2C       +10.3    454   1.000010255
  WS3W        +0.8    466   1.000000763
  WT9U        +6.4    169   1.000006443
  WV4P        +0.6    677   1.000000557
  WX7V/5      +0.0     21   1.000000000
  WZ7I        -2.4   1098   0.999997609
  YO2CK       +0.3   1676   1.000000339
  YO2KAR      -0.4   1279   0.999999605
  YO5LD       +0.3     96   1.000000296
  ZF1A        +9.2    918   1.000009209
  ZL2KS       -2.5     14   0.999997457
  ZS1NN       -4.6     46   0.999995410

Last updated 2025-10-02 00:10:33 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    1001  0930  0929  0928  0927  0926  0925  0924  0923  0922
---------------------------------------------------------------------
3B8GL      +0.0  +0.5  +0.8  +1.6              +1.0  +0.0  +0.0  +1.5
3D2AG      +0.3  +0.1  +0.3  +0.0  +0.3  +0.3  +0.7  +0.4  +0.3  +0.2
3V9A                   -1.4                                          
3V/KF5EYY              -1.5                                          
5Z4GO      +0.0  +1.1  +1.4  +0.8  +0.5  +1.1  +0.5  +0.2  +0.7  +0.6
7N4XCV                       +0.9  +0.2  +2.4  +0.6  +0.2  +1.2  +1.3
AA0O       +1.5  +0.8  +0.6  +0.7  +1.1  +0.6  +0.8  +0.9  +0.7  +0.7
AC0C-1     -0.1  -0.1  +0.1  -0.1  -0.0  +0.0  -0.0  -0.1  -0.1  +0.0
BA4OP      -0.0  +0.0  +0.0  -0.1  +0.0  +0.1  -0.1  -0.1  -0.2  +0.1
BA6KC      -0.2  -0.4  +0.1  +0.0  -0.1  +0.2  -0.1  -0.0  +0.1  -0.1
BD4UNT     +0.1  +0.5  +0.6  +0.2  +0.1  +0.2  -0.0  -0.4  +0.1  +0.2
BD7JNA     -0.1  -0.6  +0.0  +0.0  +0.0  +0.0                        
BG0AJO/0   +0.3  +0.0  +0.4  +0.3  +0.3  +0.0  +0.4  +0.6  +0.3  +0.3
BG0AJO     +0.1  +0.1  -0.0  +0.1  +0.1  -0.1  -0.1  -0.0  -0.0  +0.0
BG2TFW     +0.1  +0.0  +0.6  +0.3  +0.3  +0.3  +0.3  +0.2  +0.2  +0.5
BG4GOV     +0.0  +0.0  +0.0  +0.3  +0.2  +0.1  -0.2  +0.1  +0.0  +0.9
BH4HKZ     +4.2        +4.8                                          
BH4RRG     +0.4  +0.0  +0.9  +0.1  +0.7  +0.2  +0.1  +0.1  -0.1  +0.2
BH4XDZ     +0.2  +0.0  +0.2  +0.1  +0.1  +0.5  +0.0  +0.1  +0.0  -0.0
BI4MPH     +0.0  +0.0  +0.8  +0.3  +0.4  +0.8  +0.0  +0.8  +0.0  +0.3
BI4UYX                                         +0.0                  
CN3A                                                      +10.5 +10.1
CT1EYQ     -0.1  -0.2  -0.3  -0.7  -0.6  -0.4  -0.4  -0.4  -0.5  -0.6
DE1LON     +0.5  +0.4  +0.8  +0.7  +0.7  +0.4  +0.4  +0.5  +0.6  +0.8
DE2SAX                                               -1.0  -0.7  -0.5
DF1VB      -0.1  -0.1  -0.1                                          
DF2CK      -0.2  -0.2  -0.1  +0.3  +0.0  -0.2  -0.4  -0.2  +0.2  +0.1
DF2JP                        +0.0 +19.4                              
DF7GB      +0.0  +0.0  -0.0        +0.0  +0.0  +0.0  +0.0  -0.1  -0.0
DK0TE      -0.2  -0.5  -0.5  -0.3  -0.2  -0.1  -0.1  -0.1  -0.1  -0.3
DK3WW      -0.1  -0.2  -0.0  +0.1                    -0.1  -0.0  +0.1
DK9IP      -0.0  -0.1  +0.0  -0.0  +0.0  -0.1  +0.1  +0.0  +0.0  +0.1
DK9IP-1    -0.1  -0.1  +0.0  -0.1  -0.0  -0.1  +0.0  -0.1  +0.0  +0.1
DL0LA                              -0.2  -0.1  -0.2  -0.1  -0.1  -0.0
DL1AMQ                                   +0.1              -0.8      
DL1EFW                                               -0.8            
DL1HWS     +0.4  +0.4  +0.6  +0.7  +0.7  +0.5  +0.6  +0.6  +0.5  +0.6
DL1HWS-3   +0.0  +0.7  +0.9  +0.0                                    
DL5RCN                      +12.8 +12.6 +12.8       +12.5 +13.2 +13.2
DL8LAS     +0.2  +0.2  +0.3  +0.3  +0.4  +0.2  +0.3  +0.3  +0.2  +0.3
DL8TG      -0.1  -0.2  -0.0  -0.2        -0.1  -0.4                  
DM5GG      +0.1  +0.4  +0.3  +0.7  +0.2  -0.3  +0.4  -0.1  +0.0  +0.6
DM6EE                  +0.1  -0.0  -0.1  +0.0        -0.0  +0.0  -0.0
DO4DXA     -0.1  -0.1  +0.1              -0.0  -0.0  -0.0  -0.0  -0.1
DR4W       -3.1  -2.3  -1.6  -2.6  -2.4  -2.8  -2.7  -2.4  -2.6  -2.0
DR5X       +1.9  +2.0  +2.1  +2.2  +2.2  +2.0  +2.3  +2.6  +1.9  +2.1
EA1URA                                                           +1.0
EA2CW      -0.4  -0.5  -0.3  -0.6  -0.7  -0.7  -0.6  -0.5  -0.4  -0.3
EA2RCF-4   -0.6  -0.7  -0.6  -0.7  -0.9  -0.7  -0.7  -0.5  -0.3  -0.2
EA5WU      +0.0  -0.0        +0.0  +0.0  -0.1  +0.0  -0.0  -0.1  +0.0
EA8/DF4UE                          -0.1  -0.0  -0.0  -0.1  -0.1  -0.0
EA/VE3NZ   +0.2  -0.2  -0.3                                          
ES2RR      -0.0  -0.0  +0.0  -0.1  -0.0  -0.1  -0.1  +0.0  -0.0  -0.0
ES5PC      +0.0  -0.1  -0.0  -0.0  -0.0  -0.0  -0.1  +0.0            
ET3AA                                                     -12.7 -11.2
EU1ST                                                -0.1        -0.2
F1UVN     +16.6 +16.2 +16.6 +15.4 +16.0 +15.1 +15.2 +15.6 +15.5 +15.4
F4GOU/1                      +7.5        +5.5                        
F4GOU      +4.5  +4.6  +4.9  +5.4  +5.1  +4.5  +5.1  +5.1  +4.9  +5.8
F4VVG      +0.0  +0.1  +0.2  +0.2  +0.3                              
F6KGL                              +0.3  +0.1  +0.3  +0.2  +0.1  +0.3
F8DGY      -3.1  -3.3  -3.2  -2.9                                    
G0KTN      +0.3  +0.3  +0.4  +0.3  +0.3  +0.2  +0.2  +0.3  +0.2  +0.3
G1VWC                                                            +6.4
G3BJ                                           +0.0                  
G3YPP      +0.5  +0.1  +0.6  +0.3  +0.5  +0.2  +0.2  +0.6  +0.2  +0.0
G4AON      +1.0  +0.7  +0.9              +1.0  +1.1  +1.2  +1.2      
G4HSO      +0.6  +0.7  +0.7  +0.7                                    
G4IRN      +0.2  +0.1  +0.2  +0.2  +0.3  +0.2  +0.2  +0.2  +0.2  +0.2
G4ZFE      +0.5  +0.5  +0.7  +0.6  +0.8  +0.5  +0.6  +0.6  +0.3  +0.5
GI4DOH     +0.2  -0.0  -0.0  -0.1  +0.1  +0.0  +0.1  +0.1  -0.1  -0.6
GX0FRE     +0.4  +0.3  +0.3  +0.2        +0.3  +0.4        +0.0      
HA1VHF     +0.2  +0.1  +0.3  +0.4  +0.4  +0.2  +0.4  +0.4  +0.5  +0.8
HA5JI-8    -2.3  -1.3  -0.6  +0.1  +0.2  -1.1  -2.7  -1.7  -0.9  -0.8
HA5PP      -0.5  -0.9  -0.2              -0.4  -0.3  +0.2  +0.7  +0.2
HA5PP-2                                  +0.1  -0.2                  
HA6PX      -0.1  -0.1  +0.0  -0.0  -0.1                              
HA8TKS     +0.1  +0.1  +0.2  +0.2  +0.1  +0.2  +0.3  +0.3  +0.1  +0.3
HA8TKS-2   +0.0  +0.1  +0.1  +0.0  +0.0  -0.0  +0.0  -0.0  -0.0  +0.1
HB9BXE     +0.1  +0.1  +0.0  +0.1  +0.2  +0.0  +0.0  +0.1  +0.1  +0.3
HB9DCO     -0.3  -0.3  -0.2  -0.4  -0.4  -0.3  -0.3  -0.4  -0.3  -0.1
HB9GVO     +0.7  +0.6  +0.3  +1.2  +1.0  +0.6  +1.1  +0.8  +0.7  +0.5
HG0Y       +7.4  +7.5  +7.5  +7.4              +7.5  +7.8  +7.7  +8.0
HG8A       +0.6  +0.7  +0.9  +1.4  +1.7  +1.2  +1.6  +2.1  +2.5  +2.8
IK3STG     +1.7  +1.5  +1.4  +1.9  +1.9  +1.5  +1.5  +1.6  +1.1  +1.3
IK4VET     +1.6  +2.2  +2.3  +2.1  +2.3  +1.9  +2.3  +3.1  +3.2  +3.2
IK7YTT     +0.1  -0.0  +0.0  +0.0  +0.0  +0.0  +0.0  +0.0  +0.0  +0.0
IT9GSF     -0.0  -0.1  -0.0        -0.1  +0.1  +0.1  +0.1  -0.0  +0.0
IU0MVD                       -6.1                                    
IW9GDC     -0.5  -0.4  -0.3  -0.6  -0.5  -0.3  -0.3  -0.4  -0.3  -0.2
JG1DLY                                   +0.0                    -0.3
JH7CSU1    +1.8  +1.8  +2.1  +2.3  +1.6  +2.8  +1.6  +2.2  +1.6  +1.9
JI1HFJ     -0.4  +1.5  +1.1  +0.2  -0.5  +0.5  -0.4  +0.4  +0.2  -0.8
JJ2VLY     +1.7  +1.4  +1.7  +2.5  +2.5  +2.1  +2.0  +2.3  +0.8  +2.3
JK1QLQ                                               +0.0        +0.0
JN1ILK     -0.4  +0.1  +0.3  +0.0  -0.1  +0.0  -0.4  -0.7  -0.6  -0.8
K1RA       +1.0  +0.8  +0.9  +0.8  +1.6  +1.0  +1.3  +1.3  +0.9  +0.7
K2PO/7                             +0.6  +0.1  +0.5  +0.6  +0.5  +0.2
K3PA-1     +0.2  +0.3  +0.1  +0.0  +0.1  +0.1  +0.1  -0.0  +0.0  +0.1
K3PA-2    -17.4 -17.4 -16.8 -16.9 -17.1 -17.1 -17.0 -17.0 -17.0 -17.1
K4PP       +0.4  +0.2  +0.2  +0.4  +0.8  +0.3  +0.3  +0.3  +0.2  +0.3
K5EM       +3.5  +2.7  +2.3  +2.3  +3.1  +2.8  +3.3  +2.6  +2.4  +2.0
K5TR       +1.9  +1.5  +1.5  +2.0  +2.2  +1.6  +1.9  +1.8  +2.0  +1.8
K7CO       -0.0  +0.2  +0.5  +0.2        +0.7  +0.5  +0.1  +0.0  +0.3
K7EK       +1.0  +1.1  -0.0  +1.4  -0.3  +0.7  -0.6  -0.2  -0.7  +0.4
K7RUT                  -1.3  -1.6  -2.1  -3.0  -1.9  -2.1  -1.1  -1.4
K9IMM      +0.1  +0.1  -0.0  -0.1  +0.0  -0.1  -0.0  -0.0  -0.0  +0.0
K9LC       +1.0  +0.5  +0.8  +0.5  +1.1  +0.6  +0.9  +1.0  +0.9  +0.8
KC4YVA           +1.6  +3.1  +4.3  +0.2  -3.5  -4.2  -3.0  -4.9  -4.0
KD2OGR     +0.3  +0.2  +0.3  +0.3  +0.5  +0.3  +0.5  +0.5  +0.0  +0.0
KD7EFG     +0.3  +0.2  +0.4  +0.3  +0.4  +0.3  +0.5  +0.3  +0.4  +0.2
KH6LC      -0.1        +0.0  +0.0  -0.0  -0.1  -0.0  -0.1  +0.2  -0.1
KL2R                                     +0.0  -0.5  -0.4  +0.0  +0.0
KM3T-2     +0.2                          +0.2                        
KM3T-3     +0.1  +0.1  -0.1  -0.1  -0.2  -0.3  -0.1  -0.1  -0.0  +0.2
KM3T-5     -0.1  +0.0  +0.1  -0.0  -0.1  -0.0  -0.0  +0.0  -0.1  -0.1
KO7SS      +0.5  +0.3  +1.0  +0.1  +1.1  +0.6  +1.2  +1.0  +1.1  +0.9
KP2RUM     +0.0  -0.1  +0.2  -0.1  -0.1  +0.0  +0.1  +0.0  +0.2  +0.2
KP3CW      +0.0  -0.2  -0.3  -0.4  -0.4  -0.6  -0.6  -0.6  -0.8  -0.4
KV4TT      +0.2  +0.1  +0.0  +0.2  +0.2  +0.1  +0.1  +0.1  +0.1  +0.1
KW7MM      +0.0  -0.2  +0.1        +0.3  -0.0  +0.0  +0.1  +0.1  +0.0
KW7MM/7    +0.5  +0.3  +0.6        +0.7  +0.4  +0.3  +0.3  +0.5  +0.4
LA6TPA     -0.7  -0.9  -0.4  -1.2  -1.4  -1.6  -1.6  -2.1  -1.9  -1.6
LA7GIA                                  +20.1        -0.5  -0.1  +0.0
LB9KJ      -0.3  +0.1  -2.0  +1.3  +2.9  +0.1        +2.2  +1.4  +1.9
LU8XW      +1.1  +0.0  +0.2  +0.2  +0.9  +0.3  +0.5  +0.3  +0.0  +0.7
LY2XW                        +0.5  +0.6                              
LZ3CB      +0.0  -0.0  -0.1  -0.0  -0.0  -0.1  -0.0  -0.1  +0.0  -0.1
LZ4AE                                          -0.4  +0.3  +0.0  -0.3
LZ4UX      +0.0  +0.1  +0.0  +0.1  +0.1  +0.0  +0.0  +0.1  +0.1  +0.0
LZ5DI                  +1.8  +2.2  +2.2  +2.4  +2.8  +3.1  +2.9  +2.7
M0ORD            -2.3  -0.5  -0.9  -0.9  -0.5              -0.8  -0.6
MM0GPZ     -0.0  -0.3  -0.1  -0.0  +0.2  +0.1  +0.2  +0.1  +0.1  +0.1
MM0ZBH     +0.1  +0.0  -0.5        +0.1  -0.7  -0.5  -0.7  -0.6  -0.5
MM0ZBH-2               +0.1  +0.1  +0.1                              
MM3NDH     +0.2  +0.1  +0.3  +0.2  +0.3  +0.2  +0.3  +0.2            
N2CR       +0.4  +0.2  +0.6  +0.3  +0.5  +0.4  +0.6  +0.5  +0.4  +0.4
N2QT                   +0.0  +0.1  +0.3  +0.1  +0.4  -1.4            
N2YCH      +0.1  -0.1  -0.0  -0.1  -0.0  -0.0  +0.1  +0.2  +0.2  +0.2
N6TV       +1.0  +0.7  +0.6  +0.6  +1.1  +0.7  +0.8  +1.0  +1.0  +0.7
N7TUG      +0.1  +0.0  +0.0  +0.1  +0.3  +0.1  +0.4  -0.0  +0.0  -0.4
N8DXE      +1.6  +1.4  +1.0                                +0.0  +1.3
N9CO       +0.4  +0.1  -0.1  -0.3  -0.1  +0.0  +0.0  +0.2  +0.2  +0.1
ND7K       -0.3  -0.5  -0.3  -0.4  -0.6  -0.6  -0.5  -0.6  -0.4  -0.3
NG7M       -0.1  -0.1  +0.1  +0.1  +0.0  -0.1  +0.0  +0.0  -0.1  +0.1
NN3RP      +0.5  +0.2  +0.3  +0.5  +0.6  +0.2  +0.2                  
NT6Q       +3.1  +2.5  +2.2  +3.1  +3.2  +3.6  +3.9  +3.5  +3.0  +3.0
NU4F       +0.1  +0.3  -0.3  +0.0  +0.1  +0.1  -0.1  +0.1  +0.1  +0.2
NX5M                                                             +1.0
OE3KLU     -5.7        -4.3        -4.6  -3.9  -1.6 +11.2 +10.6 +11.1
OE6ADD     -0.1  -0.4  -0.3  -0.0  +0.0  -1.7  -1.8  -1.6  -0.8  -0.8
OE9GHV     -0.0  -0.0  +0.0  -0.0  -0.1  -0.0  +0.0  +0.1  +0.1  +0.1
OG66X      +0.2  -0.1  +0.3  -1.1  +0.1  +0.0  +0.7        +0.0      
OG73X                              +1.5                              
OH4KA      +1.1  +0.7  +0.7  +1.5  +2.0  +1.0  +0.8  +0.8  +1.1  +1.1
OH6BG      -0.4  -0.3  -0.1  -0.2  -0.2  -0.2  -0.2  -0.3  -0.2  -0.1
OH8KA      +4.6        +4.2              +2.6 -10.8                  
OK1FCJ     +0.2  +0.1  +0.2  +0.2  +0.2  +0.1  +0.2  +0.2  +0.2  +0.2
OK1HRA     -4.3  -4.2  -4.4  -4.4  -4.4  -4.4  -4.7  -4.5  -4.2  -4.4
OK2ZAW     -0.0  +0.1  +0.1  +0.0  +0.0  +0.0  +0.0  +0.0  -0.0  -0.0
ON6ZQ      +0.2  +0.1  +0.1  +0.1  +0.2  +0.2  +0.1  +0.2  +0.2  +0.4
OZ1AAB     +0.4  +0.1  +0.2  +0.4  +0.3  +0.2  +0.4  +0.2  +0.2  +0.4
OZ1BZS     +0.4  +0.7  +0.4  +0.6  +0.7  +0.6  +0.4  +0.7  +0.6  +0.6
OZ4ADX     -0.1  +0.1  -0.1  +0.2  +0.2  +0.1  +0.0  +0.1  -0.0  -0.0
PA5KT-4    +0.0  +0.1  +0.3  +0.9  +2.7  -0.1  -0.2  -0.2  -0.3  -0.3
PA5KT-5                                                    +0.0  -0.6
PA8MM      -5.3  -5.5  -6.0  -6.1  -6.2  -6.1  -6.0  -6.0  -5.4  -6.1
PE5TT      +0.6  +0.5  +0.5  +0.4  +0.9  +0.4  +0.5  +0.8  +0.4  +0.4
PI4CC      -0.0  +0.1  -0.0        +0.4  -0.1  +0.0  +0.1  +0.3  -0.1
PY2KNK     +4.0  +2.5  +4.7  +4.1  +3.1  +2.4  +1.5  +1.7  +2.4  +3.4
PY2PE      -0.9  -0.2  -1.2  -2.8  -3.0  -4.0  -4.2  -3.8  -2.7  -2.6
R4NCU      -0.7  -0.4  -0.3  -0.5  -0.3  -0.2  -0.4  -0.8  -0.3  -0.4
R6YY                                     -0.1                        
RK3TD      +0.3  -0.0  +0.6  +0.6  +0.2  +0.7                        
RK3TD-2    +0.5  +0.1  +0.4  +0.3  +0.4  +0.3  +0.3  +0.3  +0.3  +0.3
RN4WA      +1.5  +1.0  +1.1  +2.1  +2.1  +1.7  +1.6  +1.7  +1.3  +1.7
RU9CZD     -0.2  -0.2  -0.6  -0.0  -0.2  -0.2  +0.1  -0.1  +0.3  -0.1
S50U       -0.2  +0.2  +0.4  +0.7  +0.7  +0.3  +0.4  +0.4  +0.3  +0.2
S53A       +0.7  +0.4  +0.6  +0.2  +0.7  +0.5  +0.6  +0.7  +0.7  +0.8
S53F       -2.0        -1.4                          -1.1  -0.7  -1.2
S53WW      -0.3  -0.3  -0.0  -0.1  -0.0  +0.0  +0.1  +0.1  +0.2  +0.3
S54L       -0.0                          +0.2  +0.1  -0.1  +0.4  +0.8
SE5E       -0.0  -0.1  +0.0  -0.0  -0.1  -0.1  -0.0  +0.0  +0.0      
SM0TCZ                                               +0.9  -0.0  +0.9
SM1HEV     -0.6  -0.6  -0.4  -1.5  -1.6  -1.4  -1.4  -1.1            
SM7IUN     -0.1  -0.1  -0.0  -0.0  +0.2  +0.0  -0.1  -0.1  -0.2  +0.0
SQ5J       +7.4  +7.1  +7.1  +7.4  +7.3  +7.1  +7.2  +7.5  +7.6  +7.6
SV1CDN     +0.2  +0.1        +1.3  +0.3  +0.1  +0.3  +0.2  +0.0  +0.2
SZ1A       +0.4  +0.2  +0.4        +0.2  +1.0                        
TF3Y       +1.7  +1.4  +1.6  +2.0  +2.2  +1.9  +2.0  +2.1  +1.8  +2.0
TI7W       +1.3  +0.9  +1.0  +1.5  +1.8  +1.3  +1.7  +1.4  +1.5  +1.3
UA4CC     +14.2 +14.0 +13.8 +13.3 +13.9                              
UR6EA                  +3.9                                          
UT5R-1     +3.1  +2.0  +2.3  +2.7  +2.9  +2.7        +3.7  +3.7  +4.5
UT5R       +5.3  +5.1  +4.7  +5.1  +4.9  +5.5        +5.0  +5.3  +5.2
UY2RA      -2.0  -1.7                    -1.7  -1.5  -1.0  -0.7  -1.0
V51YJ      +1.3  +0.8  +1.1  +1.5  +2.1  +1.9  +2.4  +2.1  +0.5  +2.3
VE3EID     -0.1  +0.0  +0.1  -0.0  -0.1  -0.2  +0.2  +0.6  +0.7  +0.5
VE6AO      -1.1  -0.3  -0.6  -0.7  -1.1  -1.0  -0.9  -0.9  -0.7      
VE6JY      +1.0  +1.1  +1.2  +0.9  +1.3  +1.1  +1.5  +1.5  +1.8  +2.0
VE6WZ      +0.6  +1.0  +0.3  +0.2  -0.0  -0.0  +0.0  -0.1  -0.0  -0.2
VE6WZ-3    -1.2  +0.0  -1.2  -0.7  -1.3  -1.6  -1.7  -2.0  -1.6  -1.9
VE7CC      -5.5  -5.9  -7.8  -6.4  -6.4  -5.8  -6.1  -2.2  +0.6  +0.7
VK2GEL           +0.0  +0.6        +0.9  +0.4  +0.3  +0.4  +0.1  +0.1
VK2RH      +0.0  +0.4  +1.0  +0.6  +0.7  +0.3  +0.6  +0.0  +0.2  +0.2
VK3RASA    -0.2  -1.3  -0.3  -0.8  -0.9  -0.2  -0.5  -0.9  -0.9  -1.6
VK3VB                  +0.0  +0.0              +0.0  +0.0            
VK6ANC     -0.1  +0.0  -0.6  +0.1  -0.4  +0.1  +0.1  -0.1  -0.3  -0.1
VR2FUN-77                          +2.0  +1.1  +1.3  +1.0  +0.6  +1.2
VU2CDP                            +18.3 +18.8 +18.9 +18.4 +17.7 +19.1
VU2CPL     +0.1  +0.0  +0.1  +0.1  +0.1  +0.0  -0.1  -0.1  -0.0  -0.1
VU2OY      +9.9 +11.3 +10.9 +10.4  +9.8  +8.9  +9.8  +9.6  +9.1 +10.7
VU2TUM     +1.4  +0.8  +1.8  +2.2  +1.3  +1.6  +1.7  +1.1  +1.0  +1.8
W1NT-2     -0.2  -0.0  +0.2  +0.1  +0.1  -0.0  -0.0  -0.0  -0.0  -0.1
W1NT-6     -0.1  -0.1  +0.1  +0.1  +0.2  +0.1  +0.0  +0.2  -0.0  -0.2
W2LB                               +3.9  +1.5  +2.1  +2.4  +2.1  +1.1
W2MV       +1.2  +0.0  +0.2  +0.2  +0.2  +0.5  +0.7  +0.8  -0.1  +0.2
W2NAF      +1.6  +1.1  +1.2  +1.3  +2.0  +1.3  +1.7  +1.8  +1.6  +1.4
W2NNN     +12.9 +13.2 +13.0 +13.3 +13.0 +13.3 +12.9 +13.0 +13.0 +12.2
W3DAN      +1.4  +1.4  +1.4                                          
W3OA       +0.3  +0.2  +0.3  +0.2  +0.3  +0.2  +0.3  +0.2  +0.2  +0.2
W3RGA      -0.2  +0.1  -0.0  -0.0  -0.0  -0.1  -0.0  -0.1  -0.1  -0.0
W4AX                   +7.1  +4.1  +5.1  +5.2                        
W4KAZ      -0.3  -0.3  +0.1  +0.1  +0.1  +0.0  +0.4  -0.0  -0.2  -0.1
W6YX                   +0.6  +0.4  +0.9  +0.6  +0.7  +0.9  +0.4      
W8WTS      +0.3  +0.5  +0.1  +0.2  +0.3  +0.1  +0.2  +0.3  +0.3  +0.4
W8WWV      -1.8  -1.3  -1.4  -1.4  -1.8  -1.5  -1.6  -1.9  -1.9  -1.4
WA7LNW     +3.1  +3.2  +3.1  +3.1  +1.1  -0.4  -0.2  -0.3  -0.2  -0.1
WB6BEE     -0.1  +0.0  -0.1  +0.1  -0.1  -0.1  -0.0  -0.0  -0.1  +0.0
WC2L       +0.4  +0.4  +0.6  +0.5  +0.8  +0.6  +0.5  +0.5  +0.3  +0.3
WC8GOP    +13.4 +16.6 +14.0 +14.5 +15.3 +12.4 +15.8 +12.7 +12.6 +13.2
WE9V       +0.1  +0.4  +0.2  +0.6  +0.5  -0.0  +0.4  -0.1  +0.5  +0.3
WS2C      +10.3 +10.4  +9.6  +9.3  +9.7  +9.3 +10.0 +10.1  +9.9  +9.2
WS3W       +0.8  +0.6  +0.7  +0.5  +0.9  +0.4  +0.7  +0.6  +0.6  +0.5
WT9U       +6.4  +5.4  +5.7  +6.8  +6.9  +6.0  +6.0  +6.1  +5.3  +5.6
WV4P       +0.6  +0.5  +0.3              +0.3  +0.6  +0.6  +0.4  +0.5
WX7V/5     +0.0  +0.8  +1.0  +0.3        +0.4  +0.3  +0.4  +0.0  +0.5
WZ7I       -2.4  -3.3  -3.7  -2.0  -1.2  -1.5  -1.9  -0.7  -2.2  -2.0
YO2CK      +0.3  +0.2  +0.4  +0.3  +0.4  +0.3  +0.4  +0.3  +0.2  +0.3
YO2KAR     -0.4  -0.4  -0.2  +0.4  +0.0  -0.2  -0.1  +0.2  +0.1  +0.1
YO5LD      +0.3  +0.2  +0.2  +0.2  +0.3  +0.4  +0.6  +0.7  +0.4  +0.5
ZF1A       +9.2 +10.0  +9.1  +7.8        +8.6                        
ZL2KS      -2.5  -2.4  +0.0  -1.1  -2.2  -1.7  -2.2  -1.3  -3.2      
ZL3X                   -0.3  +0.5  +0.1  -0.6  +1.8  -0.1  -0.3  +0.3
ZS1NN      -4.6  -3.9  -4.8  -4.2  -4.3  -4.3  -4.9  -4.9  -4.5  -4.5

Last updated 2025-10-02 00:10:41 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 2025-10-02 00:10:41 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.