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.

273312 RBN spots between 2025-07-09 00:00 and 23:59 UTC.
69688 spots (25.5%) were from reference skimmers (*).
Average spot flow was 190 per minute from 189 active CW skimmers.

130412 spots from 174 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     17   1.000000000
  3D2AG       +0.6     83   1.000000601
  5Z/VE3NZ    -0.8     64   0.999999182
  5Z4GO       +0.8     27   1.000000792
  7N4XCV      +0.2     30   1.000000159
  AA0O        +0.7    547   1.000000747
  AC0C-1*     -0.0   1635   0.999999983
  BA4OP       +0.0     14   1.000000000
  BA6KC       +0.2    149   1.000000191
  BG0AJO      +0.3     27   1.000000264
  BG0AJO/0    +0.0      9   1.000000000
  BG2TFW      +0.7    137   1.000000676
  BH4RRG      +0.0     33   1.000000000
  BH4XDZ      +0.0     31   1.000000000
  BI4MPH-1    +0.0     28   1.000000000
  CT1EYQ      +0.2   1136   1.000000214
  CX6VM       +0.3    305   1.000000273
  DE1LON      +1.4   1338   1.000001367
  DF2CK       +0.3    962   1.000000257
  DF4UE/1     -9.0    959   0.999990955
  DF7GB*      -0.0   1418   0.999999953
  DK0TE       -0.7    737   0.999999274
  DK3UA       +0.0     17   1.000000000
  DK3WW*      -0.1   1791   0.999999949
  DK9IP*      +0.1    899   1.000000106
  DK9IP-1*    -0.0   1404   0.999999959
  DL0PF       +7.2   1626   1.000007179
  DL1HWS      +0.6   2104   1.000000626
  DL8LAS      +1.4     20   1.000001422
  DL8TG*      -0.0   1872   0.999999970
  DM5GG       +0.6   1852   1.000000598
  DO4DXA      -0.0    892   0.999999956
  DR4W        -2.3   2238   0.999997668
  E28AC       -3.9     86   0.999996113
  EA2CW*      -0.1   1280   0.999999858
  EA2RCF-4    +0.3    757   1.000000266
  ES5PC*      +0.0   2003   1.000000006
  F4GOU       +8.1   1498   1.000008118
  F4VVG*      +0.0    849   1.000000021
  F6IIT       -0.5   1160   0.999999531
  F6KGL       +0.2    282   1.000000194
  G0KTN       +0.5   1371   1.000000452
  G3YPP       +0.6    140   1.000000645
  G4IRN       +0.2   2208   1.000000154
  G4ZFE       +1.0   1904   1.000000990
  GI4DOH-2    +0.3   1340   1.000000344
  GX0FRE      +0.3   1014   1.000000258
  HA1VHF      +0.6   1811   1.000000581
  HA5PP       +3.6    249   1.000003633
  HA6PX*      -0.0   1743   0.999999984
  HA8TKS      +0.4   1072   1.000000435
  HB9BXE*     +0.0   1510   1.000000041
  HG8A        +1.7   1629   1.000001653
  IK3STG      +1.1   1272   1.000001115
  IK7YTT*     +0.1   2639   1.000000108
  IW9GDC      +8.5    718   1.000008482
  JH7CSU1     +1.0    118   1.000000966
  JI1HFJ      -0.6     15   0.999999365
  JJ2VLY      +1.0    167   1.000000972
  JN1ILK      +0.0    484   1.000000031
  K2PO/7      +0.6    371   1.000000563
  K3PA-1*     +0.0   1306   1.000000005
  K4PP        +0.1    657   1.000000052
  K5EM        +2.4    489   1.000002390
  K5TR        +0.8    744   1.000000807
  K6FOD       -0.0    662   0.999999982
  K7CO        +0.7     66   1.000000732
  K7EK        +0.0    138   1.000000001
  K7RUT       -0.1    184   0.999999935
  K9IMM       -0.0    906   0.999999968
  K9LC        +0.7   1066   1.000000708
  KD2OGR      +0.4     33   1.000000432
  KD7EFG      +0.4    372   1.000000434
  KH6LC       +0.2     72   1.000000165
  KM3T-2*     +0.2    644   1.000000228
  KM3T-3      -0.3   1581   0.999999732
  KM3T-5      +0.1    607   1.000000121
  KO7SS       +1.0    225   1.000000980
  KP2RUM      +0.2    669   1.000000235
  KP3CW       +0.2    481   1.000000168
  KV4TT*      +0.0   1050   1.000000015
  KW7MM*      -0.1    895   0.999999925
  KW7MM/7     -0.1    646   0.999999914
  LA6TPA      +0.3    473   1.000000337
  LU8XW       +0.0      5   1.000000000
  LZ3CB*      +0.0   1191   1.000000002
  LZ4AE       -0.8   1134   0.999999226
  LZ4UX*      -0.0    829   0.999999978
  LZ5DI       +2.3   1516   1.000002270
  LZ7AA       +0.7   1114   1.000000747
  MM0GPZ      +0.3   1477   1.000000265
  MM0ZBH*     -0.0    813   0.999999954
  N2CR        +0.3    366   1.000000331
  N2YCH       -2.9    952   0.999997107
  N6TV        +0.9    356   1.000000912
  N7TUG       -0.8     47   0.999999241
  N9CO        -0.2    827   0.999999750
  ND7K        -0.2    835   0.999999803
  NG7M        +0.1    441   1.000000075
  NT6Q        -0.2    696   0.999999787
  NU4F        -0.1    726   0.999999908
  OE9GHV*     +0.1    590   1.000000080
  OH4KA       +0.3    314   1.000000301
  OH6BG       +0.2   1961   1.000000185
  OH8KA       +3.4    331   1.000003360
  OK1FCJ*     +0.1   2146   1.000000065
  OK1HRA      -4.6   1891   0.999995397
  OK4QRO      +2.4   1597   1.000002383
  ON6ZQ       +0.6   1232   1.000000593
  OZ1AAB      +0.4    268   1.000000372
  OZ4ADX      +0.1    274   1.000000052
  PA5KT       -0.2    217   0.999999790
  PA8MM       +0.4   1110   1.000000421
  PE5TT       +1.0   1207   1.000001050
  PI4CC*      +0.0   2304   1.000000049
  PR1T        -4.3     59   0.999995690
  PY2KNK      +1.1    252   1.000001089
  PY2PE       -5.7     65   0.999994277
  R4NCU       -1.3     39   0.999998721
  R6YY        -0.1     69   0.999999897
  RK3TD       +1.2    116   1.000001249
  RN4WA       +1.7    814   1.000001726
  S50U        +0.2    708   1.000000200
  S53A        +0.7   1771   1.000000740
  S53F        +2.1   1139   1.000002083
  S53WW       +0.7    900   1.000000677
  SE5E        +0.4   1698   1.000000403
  SM1HEV      +0.0    187   1.000000025
  SM7IUN*     -0.0    958   0.999999985
  SQ5J        +9.1    167   1.000009083
  SV1CDN      +4.8      8   1.000004755
  SZ1A        -1.1    630   0.999998850
  TF3Y        +1.6   1173   1.000001599
  TI7W        +0.8   1216   1.000000761
  UT5R        +5.0     53   1.000005011
  UT5R-1      +4.3    149   1.000004313
  UY2RA       -0.6    842   0.999999392
  VE6JY       +2.9   1761   1.000002939
  VE6WZ       +4.1    206   1.000004144
  VE7CC       +1.1    334   1.000001110
  VK2GEL      +0.0     46   1.000000000
  VK3RASA     -1.4    147   0.999998642
  VK6ANC      -2.2     45   0.999997784
  VR2FUN-77   +0.4    481   1.000000400
  VU2CPL      +3.2      8   1.000003164
  VU2PTT      -0.2     25   0.999999810
  VU2TUM      +0.5     88   1.000000459
  W1NT-2*     -0.0   1422   0.999999993
  W1NT-6*     -0.1   1623   0.999999929
  W2LB        +2.9    132   1.000002909
  W2MV        +0.9     82   1.000000867
  W2NNN      +13.0    915   1.000012980
  W3OA        +0.2   1187   1.000000204
  W3RGA*      +0.1    884   1.000000064
  W4KAZ       +3.3     26   1.000003283
  W6YX        +0.4     32   1.000000424
  W8WTS       +0.4    616   1.000000387
  W8WWV       -1.5    577   0.999998549
  WA7LNW      +0.7   1132   1.000000664
  WB6BEE      -0.3     78   0.999999726
  WC2L*       +0.1    914   1.000000140
  WC8GOP     +13.2     40   1.000013243
  WE9V        +0.1   1055   1.000000102
  WS2C        +7.9    709   1.000007853
  WT9U        +5.5    106   1.000005460
  WV4P        +0.5    729   1.000000479
  WX7V/5      +0.6    109   1.000000588
  YO2CK       +0.3   1273   1.000000316
  YO2MAX*     -0.1   1722   0.999999911
  YO5LD       +0.6    541   1.000000609
  ZF9CW       -0.3   1286   0.999999653
  ZL3X        -0.6    120   0.999999406
  ZL4YL       +3.0     50   1.000002994
  ZS1NN       -4.4     35   0.999995565

Last updated 2025-07-10 00:15:26 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    0709  0708  0707  0706  0705  0704  0703  0702  0701  0630
---------------------------------------------------------------------
3B8GL      +0.0                                                      
3D2AG      +0.6  +0.2  +0.5  +0.1  +0.8                    +0.5  +0.9
5Z4GO      +0.8  +0.6  +0.5  -0.1  +0.6  +1.2  -0.1  +0.8  +0.0  +0.0
5Z/VE3NZ   -0.8                                                      
7N4XCV     +0.2  +0.8  +0.4  +0.0  +0.3  +0.2  +0.5  +0.1  -0.1  +0.8
AA0O       +0.7  +0.6  +0.7  +0.4  +0.9  +0.7  +0.9  +0.7  +0.7  +0.7
AC0C-1     -0.0  +0.0  +0.0  -0.1  -0.0  +0.0  -0.1  -0.1  +0.1  -0.1
BA4OP      +0.0  -0.1  -0.4  -0.1  -0.2  -0.1  +0.1              -0.2
BA6KC      +0.2  +0.2  +0.0  +0.2  +0.0  -0.1  +0.1  +0.1  +0.0  +0.1
BD7JNA                                                     +0.0  +0.8
BG0AJO/0   +0.0  +0.0  +0.0  -0.2  -0.4  -0.2  +0.3  +0.0  +0.0  +0.0
BG0AJO     +0.3  +0.4  +1.3  +0.2  +0.4  +0.3  +0.2  +0.5  +0.3  +0.3
BG2TFW     +0.7  +0.5  +1.1  +0.1  +0.4  +0.2  +0.4  +0.4  +0.4  +0.7
BG4WOM                             -0.6  +0.0  +0.3  +0.1  -0.0  +0.0
BH4HKZ                       +0.0  +0.0  +0.0              +0.0      
BH4RRG     +0.0  +0.3        +0.5  +1.9  +0.0  +0.0  +1.2  +0.2  +0.7
BH4XDZ     +0.0  +0.0  +0.0  +0.6  +0.2  +0.1  -0.1  +0.2  +0.6  -0.1
BI4MPH-1   +0.0  +0.0  -0.8                                +0.2      
CT1EYQ     +0.2  +0.1  +0.1  +0.1  +0.2  +0.1  +0.2  +0.2  +0.5  +0.5
CX6VM      +0.3  +0.4  +0.2  +0.0  +0.3  -0.2  -0.3  -0.3  -0.4  -0.1
DE1LON     +1.4  +1.1  +1.2  +1.7  +2.2  +1.9  +2.2  +2.8  +1.9  +2.0
DF2CK      +0.3  +1.3  +1.4  +1.6  +1.3  +1.6  +1.8  +1.2  +1.4  +1.4
DF4UE                 -10.0 -10.0                                    
DF4UE/1    -9.0  -9.4  -9.3                                          
DF7GB      -0.0  +0.0  +0.0  +0.0  +0.0  +0.0  -0.0  -0.0  +0.0  -0.0
DJ3AK                        +2.2                                    
DK0TE      -0.7  +0.1  +0.1  +1.6  +1.8  +1.4  +1.4  +0.8  +0.7  +1.8
DK3UA      +0.0  +0.1  -0.3  -0.3              +0.0  -0.2  +0.1  +0.2
DK3WW      -0.1  -0.2  -0.3  -0.2  -0.2  -0.3  -0.1  -0.1  -0.2  -0.1
DK8NE            +0.2        -0.1        +0.0                    -0.0
DK9IP      +0.1  +0.0  +0.1  +0.2  +0.2  +0.1  +0.1  +0.2  +0.2  +0.5
DK9IP-1    -0.0  +0.0  +0.1  +0.0  +0.2  +0.1  +0.0  +0.2  +0.2  +0.2
DL0PF      +7.2  +7.4  +9.0  +7.1 +13.4       +12.1 +11.8 +11.6 +11.8
DL1HWS     +0.6  +0.4  +0.5  +0.7  +0.8  +0.5  +0.5  +0.4  +0.5  +0.5
DL1HWS-3                                       +0.6  +0.6  +0.5  +0.5
DL1HWS-4                                       +0.1  +0.3  +0.3  +0.6
DL5RCN           +9.7                   +13.6       +14.1 +14.4      
DL5RMH                       +0.0  +0.2                              
DL8LAS     +1.4  +0.7  +1.4  +1.6  +1.5  +1.5  +2.0  +2.2  +1.7  +1.4
DL8TG      -0.0  -0.1  -0.2  -0.0  -0.1  +0.0  -0.0  -0.1  +0.1  +0.0
DM5GG      +0.6  +0.6  +0.7  +0.9  +0.9  +0.5  +0.5  +0.4  +0.6  +0.8
DM6EE                  -0.1  +0.1  +0.1  +0.1  +0.0  +0.1  +0.1  -0.0
DO4DXA     -0.0  -0.1  -0.0  +0.0  +0.0  +0.0  -0.0  -0.1  +0.1  -0.1
DR4W       -2.3  -1.9  -0.7  -1.3  -1.1  -0.9  -0.5  -0.5  -1.0  -0.1
E28AC      -3.9  -4.2  -2.9  -3.7  -3.2  -4.0  -3.1  -2.9  -3.2      
EA2CW      -0.1  -0.3  -0.3  -0.0  +0.1  -0.1  -0.1  +0.0  +0.2  +0.5
EA2RCF-4   +0.3  +0.3  +0.3  +0.3  +0.4  +0.3  +0.5  +0.5  +0.5  +0.5
EA5RQ/A                      +0.5  -0.0                    +0.0      
EA5WU            -0.0  -0.0  -0.0  +0.0  +0.0  +0.0  +0.1  +0.0  +0.1
ES2RR            -0.0  -0.1  +0.0  -0.0  -0.1  -0.0  -0.0  -0.1  +0.0
ES5PC      +0.0  -0.1  -0.1  -0.0  +0.1  +0.0  -0.0  +0.0  +0.0  +0.0
EU1ST                                                      +4.0      
F4GOU      +8.1  +8.4  +8.4  +8.7  +8.9  +9.0  +9.1  +9.1  +9.1  +9.6
F4VVG      +0.0  -0.1  -0.0  +0.0  -0.1  -0.1  -0.1  -0.3  -0.3      
F6IIT      -0.5  -0.5  -0.4  -0.3  -0.2  -0.1  -0.0  +0.2  +0.0  +0.0
F6KGL      +0.2  +0.1  +0.2  +0.1  +0.1                              
G0KTN      +0.5  +0.5  +0.5  +0.5  +0.5  +0.4  +0.5  +0.5  +0.4  +0.6
G3YPP      +0.6  -0.3  +0.1  +0.2  +0.2  +0.5  +0.2  +0.9  +0.0  +0.1
G4IRN      +0.2  +0.2  +0.3  +0.4  +0.4  +0.2  +0.3  +0.3  +0.3  +0.2
G4ZFE      +1.0  +0.8  +0.8  +0.9  +1.1  +0.7  +0.8  +1.2  +1.1  +1.3
GE0FRE                       +2.4  +1.4                              
GI4DOH-2   +0.3  +0.1  +0.1  +0.3  +0.3                              
GX0FRE     +0.3  +0.0  +0.0  +0.2  +0.3  +0.1  +0.1  +0.1  +0.1  +0.2
HA1VHF     +0.6  +0.7  +0.8  +1.2  +1.3  +0.9  +1.2  +1.0  +1.0  +1.1
HA5PP      +3.6  -0.1                                -0.5            
HA6PX      -0.0  -0.0  -0.0  -0.2  -0.1  +0.0  +0.0  +0.1  +0.1  +0.1
HA8TKS     +0.4  +0.2  +0.5  +0.4  +0.4  +0.3  +0.3  +0.3  +0.3  +0.4
HB9BXE     +0.0  +0.1  +0.1  +0.2  +0.3  +0.3  +0.2  +0.3  +0.3  +0.4
HB9DCO           -0.2  -0.1  -0.3  +0.1  +0.0  +0.2  +0.2  +0.1  +0.1
HG0Y                                                             +7.9
HG8A       +1.7  +2.8  +3.2  +3.3  +3.3  +3.1  +3.2  +3.1  +2.5  +3.1
IK3STG     +1.1  +0.7  +0.7  +0.9  +0.8  +0.7  +1.2  +0.6  +0.6  +0.8
IK4VET                                               +4.6  +3.6  +3.6
IK7YTT     +0.1  +0.1  +0.1  +0.1  +0.1  +0.1  +0.1  +0.1  +0.1  +0.2
IQ9RG                                    +0.0  +0.1  +0.1  +0.1  +0.0
IW9GDC     +8.5  +8.4  +8.8  +8.7  +8.8  +8.7  +8.6  +8.4  +8.6  +8.8
J68HZ                                   +18.4                        
JG1DLY                             +0.0  -1.5  -0.4                  
JH7CSU1    +1.0  +1.6  +0.9  +1.4  +1.4  +1.5  +1.7  +1.3  +1.9  +1.2
JI1HFJ     -0.6  +0.0        +0.4  +0.4  +0.6  -0.6  -0.1  +1.4  +0.7
JJ2VLY     +1.0  +1.8  +1.4  +1.5  +1.7  +1.4  +2.6  +1.3  +1.8  +1.3
JK1QLQ           +0.0              +0.0  +0.4  +0.0              +0.0
JN1ILK     +0.0  +0.1  -0.3              +0.1  +0.1  +0.1  +0.1  +0.2
K1RA             +1.3  +1.3  +0.7  +0.9  +0.8  +0.9  +0.9  +1.2  +1.0
K2PO/7     +0.6  +0.4  +0.7  +0.5  +0.7  +0.6  +0.7  +0.9  +0.9  +0.7
K3PA-1     +0.0  -0.0  +0.1  -0.0  +0.1  -0.0  -0.0  -0.1  +0.0  +0.0
K3PA-2                             -0.2  -0.1  -0.3              -1.2
K4PP       +0.1  +0.2  +0.1  +0.0  +0.2  -0.0  -0.1  +0.2  +0.6  +0.2
K5EM       +2.4  +3.2  +3.2  +3.8  +4.0  +3.4  +3.7  +3.3  +3.6  +3.9
K5TR       +0.8  -4.8  -4.9  -4.9  -3.6  -3.9  -4.7  -3.7  -4.5  -3.6
K6FOD      -0.0  -0.1  +0.1  +0.1  +0.1  -0.1  +0.0  -0.0  +0.1  +0.0
K7CO       +0.7  +1.1  +0.5  +1.3  +1.1  +1.2  +1.0  +1.2  +1.4  +1.1
K7EK       +0.0  -1.5  -0.9  -0.5  +0.4  +0.6  -1.4  +0.2  -0.7  -0.6
K7RUT      -0.1                                                      
K9IMM      -0.0  -0.1  -0.0  -0.2  -0.4  -0.4  -0.3  -0.6  -0.7  -0.9
K9LC       +0.7  +0.7  +0.6  +0.3  +0.7  +0.7  +0.6  +0.8  +1.0  +0.5
KC4YVA                             +3.1  +4.5  +3.9  +4.7  +4.6  +4.5
KD2OGR     +0.4  +1.0  +0.2  +0.0  +0.4  +0.2  +0.1  +0.4  +0.3  +0.3
KD7EFG     +0.4  +0.1  +0.3  -0.2  +0.3  +0.4  +0.4  +0.3  +0.4  +0.4
KH6LC      +0.2  +0.6  +0.4  +0.2  +0.3  +0.3  +0.0  -0.0  +0.4  +0.0
KM3T-2     +0.2  +0.0  +0.1  +0.0  +0.2  +0.1  +0.3  +0.2  +0.2  +0.1
KM3T-3     -0.3  -0.2  -0.2  -0.1  -0.1  -0.2  -0.3  -0.3  -0.3  -0.2
KM3T-5     +0.1  +0.1  +0.1  -0.1  +0.0  -0.1  -0.0  -0.1  +0.2  -0.0
KM4SII                                                     +0.5  +1.4
KO7SS      +1.0  +0.7  +0.7  +0.6  +1.6  +1.1  +0.7  +1.1  +1.1  +0.9
KP2RUM     +0.2  -0.2  -0.3  +0.2  +0.4  +0.0  -0.1  -0.1  +0.1  +0.2
KP3CW      +0.2  +0.2  +0.3  +0.1  +0.1  -0.1  -0.0  +0.2  +0.3  +0.2
KV4TT      +0.0  +0.0  -0.1  -0.1  +0.1  -0.1  -0.1  -0.0  +0.1  -0.1
KW7MM      -0.1  -0.0  +0.0  -0.1  +0.1  +0.0  +0.0  +0.1  +0.2  +0.2
KW7MM/7    -0.1  +0.1  +0.2  +0.1  +0.8  +0.5  +0.6  +0.5  +0.3  +0.2
LA6TPA     +0.3  +0.3  +0.2  +0.2  +0.2  +0.2  -0.2  -0.0  +0.0  -0.1
LA7GIA                 +0.0  -0.2  -0.0  +0.1  -0.2  -0.0  -0.0  -0.0
LU6KK            +0.0  +0.0  +0.0  -0.2  +0.2  +0.0  +0.0  +0.2  +0.0
LU8XW      +0.0        +0.0  +0.0                                    
LY3G                                     +0.6                        
LZ3CB      +0.0  -0.1  +0.0                                          
LZ4AE      -0.8  +0.5  -0.0  -0.1  +0.6  +0.1  +0.4  +1.9  +2.1  +1.4
LZ4UX      -0.0  +0.2  -0.3  -0.2  -0.3  +0.0  -0.0  +0.0  -0.1  -0.1
LZ5DI      +2.3  +3.4  +3.8  +4.3  +3.3  +3.2  +3.1  +2.6  +2.9  +2.9
LZ7AA      +0.7  +0.8  +0.9  +0.9  +0.9  +0.6  +0.8  +0.7  +0.7  +0.9
M0ORD                                                -1.1  -1.4  -1.6
MM0GPZ     +0.3  +0.1  +0.2  +0.3  +0.3  +0.2  +0.1  +0.2  +0.2  +0.3
MM0ZBH     -0.0  -0.0  -0.1  -0.4  -0.1  -0.3  -0.2  -0.3  -0.1  +0.0
N2CR       +0.3  +0.2  +0.1  -0.1  +0.1  -0.1  -0.2  -0.0  +0.0  -0.2
N2YCH      -2.9 +12.5                                           +12.2
N6TV       +0.9  +0.3  +0.7  +0.7  +1.0  +0.8  +0.7  +1.0  +0.9  +0.8
N7TUG      -0.8  +0.0  -1.3  -0.4  -1.0  -0.8  -2.4  +0.5  +3.8 +21.5
N8DXE            +2.8  +1.4  +0.8                          +0.0      
N9CO       -0.2  -0.1  +0.5  +0.2  +0.3  -0.3  -0.4  +0.2  -0.0  -0.8
ND7K       -0.2  -0.1  -0.1  -0.1  -0.1  -0.2  -0.1  -0.2  +0.0  -0.2
NG7M       +0.1  +0.0  -0.1  -0.1  +0.1  -0.1  -0.0  -0.0  +0.2  -0.2
NN3RP            +0.4  +0.4  +0.2  +0.0                              
NT6Q       -0.2  -1.9  -0.7  -0.8  +0.1  +0.2  +0.6  -0.2  +1.0  +0.3
NU4F       -0.1  -0.1  -0.1  -0.2  +0.0  +0.0  +0.2  +0.5  +0.5  +0.3
OE3KLU                                   -0.7                        
OE9GHV     +0.1  -0.1  -0.1  +0.0  +0.7  -0.0  +0.1  -8.2  +0.1  +0.1
OG73X                        -0.4                                    
OH4KA      +0.3  +0.7  +0.1  +0.3  -0.2  +0.9  -0.3  +0.3  +0.4  +0.3
OH6BG      +0.2  +0.1  +0.1  +0.2  +0.4  +0.2  +0.0  +0.2  +0.3  +0.2
OH8KA      +3.4  +3.8  +3.3  +3.3  +4.0  +3.7  +4.0  +4.3  +3.8  +4.2
OK1FCJ     +0.1  +0.1  +0.1  +0.1  +0.1  +0.1  +0.0  +0.0  -0.1  -0.0
OK1HRA     -4.6  -4.5  -4.2  -4.4  -4.1  -4.0        -3.6  -4.3  -3.8
OK4QRO     +2.4  +2.3  +2.3  +2.5                    +2.9  +2.1  +2.6
ON6ZQ      +0.6  +0.5  +0.6  +0.8  +0.9  +0.6  +0.7  +0.9  +0.7  +0.9
ON7KEC                       +0.0                                    
OZ1AAB     +0.4  +0.2  +0.3  +0.2  +0.3  +0.1  +0.1  +0.2  +0.1  +0.3
OZ4ADX     +0.1  -0.0  +0.1  +0.1  +0.1  +0.0  +0.1  +0.3  +0.2  -0.1
PA5KT      -0.2  +0.1  -0.0  -0.9  -0.0  +0.1  -0.1  -0.1  -0.1  -0.3
PA5WT                                                            +0.0
PA8MM      +0.4              +0.3  +0.4  +0.3  +0.1  +0.6  +0.5  +0.5
PC5Q                         -2.8  -2.6                              
PD0WAG                                   +0.3                        
PE5TT      +1.0  +0.6  +1.2  +1.0  +1.3  +1.0  +1.1  +0.8  +0.8  +1.3
PI4CC      +0.0  +0.1  +0.0  -0.0  +0.0  +0.0  -0.1  +0.0  +0.3  -0.1
PR1T       -4.3  -5.1  -3.3  -3.6  -3.6  -3.8  -3.9  -4.0  -3.6  -2.7
PY2KNK     +1.1  +0.9  +1.5  +1.0  +1.5  +1.1  +0.8  +0.5  +1.1  +1.7
PY2PE      -5.7  -3.8  -3.8  -3.3  -4.4  -5.6  -5.8  -5.8  -4.7  -2.5
R1LB                         -0.2  +0.0  -0.3  -0.3  -0.1  +0.1  +0.0
R4NCU      -1.3  -0.4  -0.8  -0.5  -1.0  -0.6  -0.4  -0.4  -0.5  -0.5
R6YY       -0.1                                      +0.1            
RK3TD      +1.2  +0.1  -0.0  +0.1  +0.1  +0.6  +0.5  +0.4  -0.2  +0.5
RK3TD-2          +0.2  +0.2  +0.4  +0.4  +0.3  +0.3  +0.3  +0.3  +0.4
RN4WA      +1.7  +1.4  +1.3  +1.6  +1.9  +1.2  +1.4  +1.4  +1.3  +1.5
RU4FMM           +7.1  +7.1  +5.9  +5.3  +6.3  +4.9  +2.5            
S50U       +0.2  +0.3  +0.6  +0.6  +0.7  +0.5  +0.4  +0.4  +0.5  +0.9
S53A       +0.7  +0.7  +0.8  +0.9  +1.0  +0.7  +0.8  +0.7  +0.8  +0.9
S53F       +2.1        +1.5                                      +2.6
S53WW      +0.7  +0.7  +1.0  +1.1  +1.1  +0.9  +1.0  +1.0  +0.9  +1.0
SE5E       +0.4  +0.3  +0.4  +0.3  +0.4  +0.3  +0.4  +0.3  +0.3  +0.5
SM1HEV     +0.0  -0.8  +0.3  -0.1  +0.1  +0.1  +0.3  +0.5  +0.2  +0.5
SM7IUN     -0.0  -0.1  +0.0  +0.0  -0.1  +0.0  +0.0  +0.0  -0.1  -0.0
SQ5J       +9.1  +9.6  +9.8  +9.6  +9.8  +9.3  +9.7  +9.6  +9.6 +10.0
SV1CDN     +4.8  +4.8  +6.1  +5.3  +5.9  +5.5  +5.1  +0.6  +0.8      
SZ1A       -1.1  -0.2  +0.4  +0.1  -0.7  +0.1  +0.4  +1.6  -1.5  +1.0
TF3Y       +1.6  +1.3  +1.4  +1.4  +1.6  +1.5  +1.8  +1.4  +1.3  +1.3
TI7W       +0.8  +0.5  +0.6  +0.5  +0.7  +0.4  +0.5  +0.6  +0.7  +0.3
UA0S                         +4.7  +3.4  +3.4  +3.6  +3.8  +3.5  +2.9
UA4CC                             +13.2 +13.7 +13.8 +13.5 +13.3 +13.5
UT5R-1     +4.3              +4.0  +3.7        +3.8  +3.3  +2.9  +2.8
UT5R       +5.0  +5.5        +5.7  +5.0  +4.5  +5.7  +5.6  +5.6  +5.8
UY2RA      -0.6  -0.5  -0.8  -1.2  -0.8  -0.9  -1.0  -1.3  -1.3  -1.1
V51YJ            +0.6  +1.8  +1.4  +1.2  +1.8  +1.5  +1.9  +0.0      
VE3EID           -0.1  +0.2  +0.2  -0.1  -0.5  -0.2  +0.2  +0.6  +0.2
VE6AO                                                -0.3  -0.3  -0.4
VE6JY      +2.9  +2.7  +2.1  +1.9  +1.9  +1.7  +2.9  +2.4  +2.6  +2.6
VE6WZ      +4.1  +3.5  +2.8  +4.5  +3.7  +3.0  +4.2  +3.9  +4.4  +4.4
VE7CC      +1.1  +1.2  +1.1  +0.8  +1.2  +0.7  +1.1  +1.4  +1.5  +0.4
VK2EBN                       +0.0              +0.0        +0.0      
VK2GEL     +0.0  +0.0  +0.5  +0.2  +0.2  +0.0  +0.0  -0.2  +0.1  -0.1
VK2RH                  +1.8  +0.0  +2.4  +0.0  +0.0  +0.0  +0.0  +2.8
VK3RASA    -1.4  -0.9  -2.0  -1.5  -2.3  -1.4  -1.0  -1.1  -1.2  -1.5
VK6ANC     -2.2  +0.0  +0.0  +0.0  -1.1  -0.4  -0.3  -0.2  +0.0  -0.4
VR2FUN-77  +0.4  +0.6  +0.5  +0.6  +0.4  +0.3  +0.5  +0.6  +0.7  +0.0
VU2CPL     +3.2  -1.3  +0.0  +0.5  +0.2  -0.2  +0.3  -0.3  +0.0  +0.4
VU2PTT     -0.2  +0.0        +0.0  +0.1  -0.0  -0.0  -0.1  +0.0  +0.3
VU2TUM     +0.5  +0.6  +0.4  +0.7  +0.8  +0.7  +0.8  +1.3  +0.9  +0.8
W1NT-2     -0.0  +0.0  +0.1  +0.0  +0.0  +0.1  +0.1  +0.0  +0.2  +0.0
W1NT-6     -0.1  +0.1  +0.1  +0.0  -0.0  -0.0  +0.1  +0.1  +0.3  +0.1
W2LB       +2.9  +1.0  +2.1  +0.9  +1.5  +2.1  +1.6  +1.4            
W2MV       +0.9  +0.6  +0.2  +0.4  +0.8  +0.4  +0.3  +0.4  +0.4  +0.3
W2NAF            +0.9  +1.8  +0.6  +1.2  +1.0  +1.1  +1.4  +1.7  +1.1
W2NNN     +13.0 +13.1 +13.0 +13.0 +12.4 +12.4 +12.2 +12.4 +12.7 +12.6
W3DAN                  +1.2  +0.0              +1.3  +0.0  +0.0      
W3OA       +0.2  +0.1  +0.2  +0.2  +0.2  +0.2  +0.2  +0.3  +0.4  +0.2
W3RGA      +0.1  +0.2  +0.3  +0.3  +0.3  +0.2  +0.2  +0.2  +0.4  +0.1
W3UA                         +0.1  +0.0                              
W4AX                                     +6.9                        
W4KAZ      +3.3  +0.4  +0.7  +0.4  +1.1  +0.7  -0.2  +0.6  +0.8  +0.5
W6YX       +0.4  +0.3  +0.7  +0.0  +0.9  +0.1  +0.2  +1.0  +0.6  +0.5
W8WTS      +0.4  +0.1  +0.4  +0.0  +0.5  +0.5  +0.4  +0.4  +0.6  +0.4
W8WWV      -1.5  -1.3  -1.1  -1.1  -1.2  -1.3  -1.2  -1.4  -1.8  -1.7
WA7LNW     +0.7  +0.7  +0.4  +0.4  +0.7  +0.4  +0.6  +0.7  +0.6  +0.5
WB6BEE     -0.3  -0.3  +0.0  +0.0  +0.0  -0.2  +0.1  -0.4  +0.2  +0.1
WC2L       +0.1  +0.0  +0.2  +0.1  +0.3  +0.1  +0.2  +0.2  +0.4  +0.2
WC2L-2                                   -0.2  -0.5  -0.8  -1.9  +0.0
WC8GOP    +13.2 +12.0 +13.5 +14.3 +13.7 +13.1                   +12.9
WE9V       +0.1  +0.5  +0.4  +0.6  +0.3  +0.2  +0.3  +0.4  +0.4  -0.0
WS2C       +7.9  +8.2  +8.8  +7.6  +7.2  +7.6  +7.6  +8.0  +8.5  +8.3
WT9U       +5.5  +5.4  +6.3  +5.4  +5.9  +5.0  +5.0  +5.2  +5.1  +4.8
WV4P       +0.5  +0.5  +0.3  +0.2  +0.7  +0.3  +0.6  +0.3  +0.6  +0.4
WW1L                               +0.0                              
WX7V/5     +0.6  +0.0  +1.1  +0.3  +1.0  +0.8  +0.6  +0.9  +1.0  +0.4
WZ7I                   +0.0  +0.6  +0.7  +0.8  +0.7  +0.6        +0.6
YO2CK      +0.3  +0.3  +0.4  +0.3  +0.3  +0.2  +0.3  +0.4  +0.4  +0.4
YO2MAX     -0.1  -0.0  +0.1  +0.1  +0.2  +0.1  +0.0  +0.2  +0.0  +0.4
YO5LD      +0.6  +0.9  +0.8  +0.5  +0.6  +0.3  +0.5  +0.4  +0.5  +0.9
ZF1A                                                 +8.6  +8.1  +8.2
ZF9CW      -0.3  -0.3  -0.4  -0.2  +0.0                              
ZL2KS                  -2.7  -2.7  -3.2  -2.7  -4.0  -3.5  -4.6  -2.7
ZL3X       -0.6  -0.4  -0.3  -0.9  -0.7  -0.3  -1.0  -1.0  -0.7  -1.5
ZL4YL      +3.0  +3.0  +4.2  +2.9  +3.8  +4.8  +4.3  +3.7  +3.6  +4.1
ZS1NN      -4.4  -7.9  -4.8  -5.0  -4.9  -4.3  -4.2  -4.5  -3.9  -3.5

Last updated 2025-07-10 00:15:32 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 KM3T-5 LZ3CB LZ4UX OE9GHV WB6BEE 

Last updated 2025-07-10 00:15:32 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.