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

297047 RBN spots between 2025-05-28 00:00 and 23:59 UTC.
59786 spots (20.1%) were from reference skimmers (*).
Average spot flow was 206 per minute from 205 active CW skimmers.

128168 spots from 197 skimmers qualified for analysis by meeting
the following criteria:
 * Mode of spot is CW.
 * Also spotted by a reference skimmer within 1000 spots.
 * Also spotted by a reference skimmer within 10s. 
 * SNR is 3dB or higher. 
 * Frequency is 7000kHz or higher. 
 * Frequency deviation from reference skimmer is 0.5kHz or less.
 * At least 5 spots from same skimmer in data set.

  Skimmer    [ppm]  Spots    Adjustment 
  -------------------------------------
  3D2AG       +0.0     49   1.000000000
  3V9A        -1.6    746   0.999998371
  5Z4GO       +0.8      9   1.000000791
  7N4XCV      +0.0      8   1.000000000
  AA0O        +0.4    458   1.000000380
  AC0C-1*     -0.0    664   0.999999957
  BA4OP       -0.2    158   0.999999819
  BA6KC       +0.0     60   1.000000000
  BD7JNA      +0.0      6   1.000000000
  BG0AJO      +6.3      9   1.000006328
  BG0AJO/0    +0.0     16   1.000000000
  BG2TFW      +0.0     13   1.000000000
  BG4WOM      -0.1     61   0.999999883
  BH4RRG      +0.0     16   1.000000000
  BH4XDZ      +0.0     20   1.000000000
  BI4MPH-1    -1.0      5   0.999999049
  BY4XRA      +0.0     31   1.000000000
  CT1EYQ      +0.2    893   1.000000179
  DD5XX       +0.9   1281   1.000000895
  DE1LON      +0.8    950   1.000000752
  DF2CK       +1.3   2677   1.000001279
  DF7GB*      -0.0   1597   0.999999974
  DK0TE       +1.2   1578   1.000001211
  DK3WW       +0.2   1827   1.000000250
  DK8NE       +0.2     38   1.000000210
  DK9IP*      -0.0    917   0.999999954
  DK9IP-1*    +0.1   1038   1.000000116
  DL1HWS      +0.3   1643   1.000000290
  DL1HWS-3    +0.7    875   1.000000666
  DL1HWS-4    +0.1    128   1.000000112
  DL8TG*      -0.0   1552   0.999999973
  DL9GTB      +0.4   1130   1.000000360
  DM5GG       +0.4   1703   1.000000416
  DM6EE*      +0.1   1351   1.000000062
  DO4DXA*     -0.1    813   0.999999900
  DO4ZT       -0.0    321   0.999999991
  DR4W        -2.3   1427   0.999997703
  DR5X        +0.8     36   1.000000792
  E28AC       -0.3     95   0.999999700
  EA2CW       +0.2   1289   1.000000231
  EA2RCF-4    +0.7    687   1.000000708
  EA5RQ       +0.1     63   1.000000113
  EA5WU*      -0.0   1546   0.999999972
  ES2RR*      -0.1   1441   0.999999897
  ES5PC*      -0.0   1898   0.999999999
  F4GOU       +4.8   1691   1.000004804
  F4VVG       +0.2    623   1.000000240
  G0KTN       +0.4   1252   1.000000428
  G3YPP       +0.3    102   1.000000348
  G4IRN       +0.7   1631   1.000000743
  G4ZFE       +0.5   1477   1.000000510
  GI4DOH-2*   +0.1    909   1.000000101
  HA1VHF      +0.5   1888   1.000000526
  HA6PX*      +0.1   1756   1.000000094
  HA8TKS      +0.3    901   1.000000328
  HB9BXE*     -0.1   1468   0.999999937
  HB9DCO      -0.3   1166   0.999999677
  HB9GVO      +0.7     39   1.000000731
  HG0Y        +7.5     20   1.000007485
  HG8A        +0.6   1674   1.000000565
  IK3STG      +1.8   1311   1.000001753
  IK4VET      +4.0   2138   1.000003998
  IK7YTT*     +0.1   1584   1.000000070
  IQ9RG*      -0.0   1845   0.999999994
  IW9GDC      +8.5    490   1.000008495
  JH7CSU1     +2.3     57   1.000002273
  JI1HFJ      +0.4     13   1.000000366
  JJ2VLY     +15.3     82   1.000015311
  JK1QLQ      +0.0      6   1.000000000
  JN1ILK      +0.2    217   1.000000212
  K1RA        -0.3    882   0.999999749
  K2PO/7      +0.6    563   1.000000641
  K3PA-1      -0.2    594   0.999999842
  K4PP        +0.6    465   1.000000564
  K5EM        +2.1    339   1.000002136
  K5TR        +0.9    505   1.000000885
  K6FOD       -0.2    253   0.999999784
  K7CO        +0.7    402   1.000000686
  K7EK        -1.4    203   0.999998561
  K9IMM       -0.7    691   0.999999252
  K9LC        +0.5    794   1.000000472
  KC4YVA      +6.1    191   1.000006067
  KD2OGR      +0.4    400   1.000000433
  KD7EFG      +0.2    238   1.000000240
  KH6LC       +0.3     26   1.000000274
  KM3T-2      +0.6    640   1.000000600
  KM3T-3*     -0.0    972   0.999999950
  KM3T-5*     -0.2    620   0.999999824
  KP2RUM      -9.6    334   0.999990435
  KP3CW       +0.1    502   1.000000142
  KV4TT       +0.1    936   1.000000141
  KW7MM       -0.1    436   0.999999935
  LA6TPA      -0.4    165   0.999999576
  LA7GIA      +0.0     26   1.000000000
  LB9KJ       -0.2    230   0.999999763
  LU6KK       +0.0      9   1.000000000
  LU8XW       +0.0      7   1.000000000
  LZ3CB*      -0.0   1056   0.999999985
  LZ4AE       +1.0   1542   1.000001012
  LZ4UX*      -0.2   1093   0.999999835
  LZ5DI       +1.0   1710   1.000000997
  LZ7AA       +0.6    920   1.000000634
  MM0GPZ      +0.2   1929   1.000000196
  MM0ZBH      -0.4   1353   0.999999554
  N2CR        -0.2    338   0.999999786
  N2QT        -0.3    574   0.999999694
  N6TV        +1.1    345   1.000001102
  N7OR        +0.1    113   1.000000105
  N9CO        +0.0    553   1.000000000
  ND7K        -0.4    420   0.999999620
  NG7M        +0.1    341   1.000000114
  NN3RP       +0.1    217   1.000000131
  NT6Q        -2.3    440   0.999997690
  NU4F        +0.1    568   1.000000131
  OE6ADD      +0.2   1846   1.000000208
  OE9GHV      +0.1    559   1.000000147
  OH4KA*      -0.3    194   0.999999721
  OH6BG       +0.1   1288   1.000000134
  OH8KA       -6.6    100   0.999993373
  OK1FCJ*     +0.1   1610   1.000000059
  OK1HRA      -4.2   1666   0.999995835
  ON6ZQ       -0.1   1235   0.999999851
  OZ1AAB      +0.4    237   1.000000421
  OZ1BZS      +0.3    195   1.000000280
  OZ4ADX*     -0.1    190   0.999999925
  PA0MBO      +1.6     18   1.000001581
  PE5TT       +0.5   1153   1.000000515
  PI4CC*      -0.0   1785   0.999999956
  PY2KJ       +2.1     62   1.000002052
  PY2KNK      +2.4     79   1.000002365
  PY2PE       +1.3     15   1.000001268
  R1LB        -0.0    264   0.999999990
  R4NCU       -0.8    319   0.999999240
  R6YY        -0.1    183   0.999999916
  R9IR        +0.6     62   1.000000575
  RN4WA       +1.2    665   1.000001226
  RU9CZD      +0.2    642   1.000000153
  S50U        +0.5    398   1.000000465
  S53A        +0.7   2220   1.000000661
  S53F        +0.8    155   1.000000771
  S53WW       +0.3   1729   1.000000347
  SE5E        +0.5   1853   1.000000451
  SM0TCZ      -0.2     35   0.999999830
  SM1HEV      +0.3    295   1.000000251
  SM7IUN*     -0.1   1031   0.999999904
  SQ5J        +9.8   1474   1.000009778
  SV1CDN      -0.6      6   0.999999405
  TF3Y        +1.2    426   1.000001246
  TI7W        +0.4    248   1.000000438
  UA0S        +3.4    365   1.000003442
  UA4CC      +13.9    609   1.000013919
  UT5R        +4.4    113   1.000004433
  UT5R-1      +2.2    258   1.000002248
  UY2RA       -1.3    993   0.999998716
  V51YJ       +0.0     29   1.000000000
  VE3EID      +0.3    274   1.000000321
  VE6JY       +3.4    660   1.000003409
  VE6WZ       +3.9    416   1.000003865
  VE7CC       +0.9    167   1.000000882
  VK2GEL      +0.0     92   1.000000000
  VK3RASA     -0.8    151   0.999999246
  VK6ANC      -0.2     43   0.999999770
  VR2FUN-77   +0.9    598   1.000000879
  VU2CPL      +4.8     12   1.000004750
  VU2PTT      +1.6     33   1.000001619
  VU2TUM      +0.1     67   1.000000131
  W1NT-2      +0.1   1121   1.000000131
  W1NT-6*     +0.2   1185   1.000000166
  W2LB        +2.5    166   1.000002482
  W2MV        +0.3     83   1.000000343
  W2NAF       +1.4    290   1.000001398
  W3LPL       -0.3    177   0.999999679
  W3OA        +0.2    778   1.000000182
  W3RGA       -0.2    741   0.999999795
  W3UA*       -0.1    814   0.999999941
  W4AX        +4.1     69   1.000004131
  W4KAZ       -0.7    738   0.999999299
  W6YX        +0.3    567   1.000000320
  W8WTS       -0.3    402   0.999999664
  W8WWV       -1.2    464   0.999998796
  WA7LNW      +1.5    614   1.000001464
  WB6BEE*     -0.2    496   0.999999817
  WC2L        +0.6    656   1.000000553
  WC8GOP      +9.2     28   1.000009161
  WE9V        +1.9    638   1.000001903
  WS2C        +7.1    438   1.000007054
  WS3W       -12.2    132   0.999987770
  WT9U        +5.6     53   1.000005606
  WV4P        +0.6    427   1.000000633
  WX7V/5      +0.3     47   1.000000269
  WZ7I        +0.5   1368   1.000000474
  YO2CK       +0.3   1365   1.000000325
  YO2MAX      +0.2   1075   1.000000237
  YO5LD       +0.4   1162   1.000000369
  ZL3X        -0.7    264   0.999999342
  ZL4YL       +1.2    254   1.000001153
  ZS1NN       -3.7     24   0.999996300

Last updated 2025-05-29 00:15:29 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    0528  0527  0526  0525  0524  0523  0522  0521  0520  0519
---------------------------------------------------------------------
3B8GL                                    +0.5  +0.9  +0.2  +0.3      
3D2AG      +0.0  +0.0  +0.0  +0.4  +0.4  +0.0  +0.1  +0.2  +0.1  +0.3
3V9A       -1.6  -1.6  -1.2  -4.4  -5.5  -5.3  -6.4                  
5Z4GO      +0.8  +1.2  +0.6  +0.6  +0.7  -1.1  +0.3  +1.7  +0.0  +0.8
7N4XCV     +0.0  +0.6  +0.8  +0.3  +0.5  +0.4  +0.8  +0.0  +0.4  +0.6
AA0O       +0.4  +0.5  +0.6  +0.8  +0.7  +0.6  +0.6  +0.8  +0.3  +0.5
AC0C-1     -0.0  +0.1  -0.1  -0.0  -0.0  +0.0  +0.1  +0.1  +0.3  -0.1
BA4OP      -0.2  -0.2  -0.2  -0.2  -0.2  -0.3  -0.2  +0.1  -0.7  -0.1
BA6KC      +0.0  -0.1  +0.4  -0.0  +0.0  +0.1  +0.1  +0.2  -0.3  +0.1
BD7JNA     +0.0  -0.6  +0.5  +0.3  +0.3  +0.1  -7.0                  
BG0AJO/0   +0.0  -0.5  +0.2  +0.4  -0.1  +0.0  +0.0  +0.1  +0.0  +0.3
BG0AJO     +6.3  +0.9  +0.9  +0.4  +0.5  +0.2  +0.5  +0.2  +0.1  +0.4
BG2TFW     +0.0  +0.2  +0.4  +3.2  +9.8  +9.7  +9.1  +8.9  +8.9 +10.3
BG4GOV                 +0.0  +0.4  +0.5  +0.1  +0.0                  
BG4WOM     -0.1  +0.1  +0.4  +0.0  +0.1  +0.0  -0.4  -0.0  +0.0      
BH4RRG     +0.0  +0.1  +0.2  +0.3  +0.4  +0.2  -0.4  +0.0  +0.2  +0.5
BH4XDZ     +0.0  +0.0  +0.1  -0.0  +0.0  -0.2  -0.4  +0.0  +0.0  +0.0
BI4MPH-1   -1.0  +0.0  -0.6  +0.1  +0.1  -0.0  +0.4  +0.0  +0.1      
BY4XRA     +0.0  +0.0  +0.1  +0.1  +0.2  +0.0  +0.6  +0.1  +0.0  +0.0
CT1EYQ     +0.2  -0.2  -0.2  -0.2  -0.1  -0.1  -0.0  +0.0  +0.2      
CX6VM                  +0.6  +1.0  +0.8  +0.2  +0.4  +0.4  +0.1  +0.9
CX7ACH                      +17.9 +17.6                              
DD5XX      +0.9  +0.9  +0.9  +1.1  +1.0  +0.8  +0.9  +1.0  +1.2  +1.1
DE1LON     +0.8  +0.8  +0.8  +0.8  +0.9  +1.3  +1.2  +1.1  +1.2  +1.2
DF2CK      +1.3  +1.3  +1.4  +1.6  +1.5  +1.2  +1.3  +1.3  +1.0  +0.9
DF7GB      -0.0  -0.0  +0.0  -0.0  -0.0  -0.0  +0.0  -0.0  -0.0  -0.1
DK0TE      +1.2  +1.1  +1.1  +1.4  +1.7  +1.1  +1.3  +1.3  +1.3  +1.2
DK3UA            +0.0  +0.0  +1.0  +0.7  +0.4  +0.1  -0.1  +0.2  -0.4
DK3WW      +0.2  -0.1  -0.1  +0.4  +0.4  -0.1  +0.2  +0.1  +0.1  -0.1
DK8NE      +0.2  +0.0                    +0.4  -0.0        +1.0      
DK9IP      -0.0  -0.1  +0.0  +0.0  +0.0  -0.0  +0.0  -0.1  -0.1  +0.0
DK9IP-1    +0.1  -0.0  +0.0  -0.0  -0.0  +0.0  +0.0  -0.1  -0.0  -0.0
DL0PF                                                +8.1  +8.1  +8.5
DL1HWS     +0.3  +0.2  +0.2  +0.4  +0.4  +0.3  +0.2  +0.3  +0.2  +0.2
DL1HWS-3   +0.7  +0.7  +0.5  +0.9  +1.0  +0.6  +0.7  +0.6  +0.6  +0.6
DL1HWS-4   +0.1  +0.2  +0.2  +0.2  +0.2  +0.0  +0.1  +0.4  +0.0  +0.1
DL5RCN                       +2.4             +13.1 +13.2       +13.0
DL5RMH                 +0.1  -0.2  -0.1  -0.2                        
DL8LAS                                   +0.1  +0.0  +0.1  +0.3  +0.7
DL8TG      -0.0  -0.0  +0.0  -0.0  +0.0  -0.1  -0.1  +0.0            
DL9GTB     +0.4  +0.2  -0.1  +0.0  +0.2  +0.4                        
DM5GG      +0.4  +0.4  +0.5  +0.7  +0.6  +0.3  +0.4  +0.5  +0.4  +0.4
DM6EE      +0.1  +0.0  +0.0  +0.0  +0.1  +0.0  +0.0  +0.1  +0.0  -0.0
DO4DXA     -0.1  -0.1  -0.1  -0.0  -0.0  -0.1  -0.2  +0.0  -0.0  -0.0
DO4ZT      -0.0  +0.0  -0.1  -0.0  +0.0  -0.0  +0.1  +0.0  -0.1  -0.1
DR4W       -2.3  -2.1  -1.2  -2.6  -2.8  -2.9  -1.7  -1.3  -2.2  -2.1
DR5X       +0.8  +0.6  +0.8  +1.1                                    
E28AC      -0.3  -0.8  -0.8  -0.8        -0.2  -0.2  -0.8  -0.9  -0.4
EA2CW      +0.2  +0.1  +0.1  +0.1  +0.1  +0.0  +0.0  -0.0  +0.0  +0.1
EA2RCF-4   +0.7  +0.9  +0.8  +1.1  +1.0  +0.6  +0.8  +0.7  +0.7  +0.7
EA5RQ      +0.1  -0.4  +0.1  -0.1  -0.0              -0.1  -0.1  -0.0
EA5RQ/A                            +0.0                              
EA5WU      -0.0  +0.0  +0.0  -0.0  +0.0  +0.0  +0.0  +0.1  -0.0  +0.0
EA7CJK                +14.3 +10.9                                    
ES2RR      -0.1  +0.0  -0.1  -0.0  -0.0  -0.0  +0.0  -0.0  -0.0  -0.0
ES5PC      -0.0  -0.0  +0.1  -0.0  -0.0  +0.0  +0.0  +0.0  +0.0  -0.0
EU1ST            +2.4        +4.9  +4.8  +3.7  +3.1  +2.9  +3.0  +3.1
F4BPO                                                -0.1  -0.2  -0.0
F4GOU      +4.8  +5.1  +5.4  +5.7  +5.8  +5.5  +5.4  +5.3  +5.5  +5.7
F4VVG      +0.2  +0.1  +0.2  +0.3  +0.3  +0.2  +0.3  +0.1  +0.2  +0.1
F6KGL                        +0.3  +0.3  +0.2  +0.2  +0.2  +0.2  +0.2
G0KTN      +0.4  +0.3  +0.3  +0.5  +0.5  +0.4  +0.4  +0.4  +0.3  +0.3
G3YPP      +0.3  -0.0  +0.2  +1.3  +1.3  -0.1  +5.1  +0.0  +0.2  +0.1
G4AON                                                            +0.5
G4IRN      +0.7  +0.6  +0.7  +0.9  +1.0  +0.7        +0.4  +0.5  +0.6
G4YBU                                    +0.3  +0.2  +0.6  +0.3  +0.4
G4ZFE      +0.5  +0.5  +0.6  +0.9  +0.8  +0.4  +0.5  +0.6  +0.6  +0.5
GI4DOH-2   +0.1  +0.1  -0.0  +0.2  +0.3  +0.1  +0.5  -0.1  +0.3  +0.4
GX0FRE           +0.8  +0.3  +0.6  +0.6  +0.5  +0.3  +0.4  +0.2  +0.1
HA1VHF     +0.5  +0.3  +0.5  +0.5  +0.5  +0.4  +0.5  +0.5  +0.4  +0.3
HA5PP                                    +1.8  -1.4                  
HA6PX      +0.1  -0.0  +0.0  -0.0  -0.0  +0.0  -0.0  +0.0  -0.0  +0.0
HA8TKS     +0.3  +0.3  +0.3  +0.4  +0.5  +0.3  +0.3  +0.3  +0.2  +0.2
HB9BXE     -0.1  -0.0  +0.1  +0.2  +0.1  +0.1  +0.1  +0.1  +0.1  -0.1
HB9DCO     -0.3  -0.4  -0.4  -0.6  -0.5  -0.3  -0.3  -0.3  -0.1  -0.5
HB9GVO     +0.7  +1.4  +1.3  +1.3                          +0.9  +0.0
HG0Y       +7.5  +7.7  +7.8  +8.5  +8.4  +7.5              +7.3  +7.2
HG8A       +0.6  +0.3  +0.2  +0.2  +0.3  +0.4  +0.4  +0.3  +0.2  +0.1
IK2LFF                       +0.5                                    
IK3STG     +1.8  +1.9  +1.9  +2.7  +2.7  +1.7  +1.8  +1.9  +1.6  +1.7
IK4VET     +4.0  +4.2  +4.0  +4.2  +4.2  +3.8  +4.2  +3.8            
IK7YTT     +0.1  +0.0  +0.1  +0.1  +0.1  +0.1  +0.1  +0.0  +0.1  +0.0
IQ9RG      -0.0  -0.0  +0.0              -0.1                        
IT9GSF           +1.0  +0.5  +0.7  +1.0  +1.0  +1.1  +1.1  +1.0  +1.1
IW9GDC     +8.5  +8.2  +7.9  +7.9  +8.2  +7.9  +8.1  +7.9  +0.9  -0.3
JG1DLY                       -0.5  -0.5  -1.1                        
JH4UTP                       -0.4  -0.3  +0.0        +0.0  +0.0  +0.9
JH7CSU1    +2.3  +1.3  +1.9  +2.0  +2.2  +1.5  +1.6  +1.3        +1.2
JI1HFJ     +0.4  +0.2  +0.5  +1.3  +4.8  +5.2  +5.0  +3.8  +3.2  +6.7
JJ2VLY    +15.3 +14.7 +15.0 +15.3 +15.1 +15.0 +15.3 +15.7 +15.4 +14.9
JK1QLQ     +0.0  +0.0  +1.0  +0.1  +0.2  +0.1  +0.0  +0.0        +0.0
JN1ILK     +0.2  +0.2  +0.5  +0.4  +0.2  +0.3  +0.7  +0.7  +0.6  +0.2
K1RA       -0.3  +0.0  +0.3  +0.5  +0.2  +0.1  +0.3  +0.5  +0.3  +0.5
K2PO/7     +0.6  +0.5  +0.4  +0.8  +0.8  +0.4  +0.7  +0.7  +0.5  +0.6
K3PA-1     -0.2  -0.1  -0.0  -0.1  -0.0  -0.1  -0.0  +0.0  -0.0  -0.1
K3PA-2           -0.2  +0.0  -0.2  -0.2  -0.2  -0.2  +0.0  -0.4      
K4PP       +0.6  +0.4  +0.5  +0.3  +0.5  +0.3  +0.4  +0.7  +0.5  +0.6
K5EM       +2.1  +1.5  +1.2  +2.0  +2.0  +1.0  +0.9  +1.4  +1.1  +1.2
K5TR       +0.9  +0.8  +0.7  +1.8  +1.7  +1.0  +0.9  +0.9  +0.7  +0.9
K6FOD      -0.2  -0.0  -0.1                                          
K7CO       +0.7  +0.8  +0.7  +1.0  +0.9  +0.7  +0.7  +0.3  +0.1  -0.6
K7EK       -1.4  -2.2  -1.0  +1.1  +1.7        -1.8  -0.5  +0.2      
K9IMM      -0.7  -0.4  -1.0  -0.6  +0.1  +0.1  -0.0  +0.0  +0.0  +0.2
K9LC       +0.5  +0.3  +0.2  +0.5  +0.5  +0.3  +0.4  +0.5  +0.3  +0.7
KC4YVA     +6.1  +6.1  +6.7  +6.4  +6.6  +6.7  +6.1  +6.7  +6.1  +6.2
KD2OGR     +0.4  +0.2  +0.4  +0.5  +0.6  +0.2  +0.5  +0.5  +0.4  +0.5
KD7EFG     +0.2  +0.1  +0.4  +0.5  +0.5  +0.2  +0.4  +0.4  +0.4  +0.6
KH6LC      +0.3  +0.0  +0.0  +0.1  +0.1  +0.1  +0.4  +0.2  +0.6  +0.0
KM3T-2     +0.6  +0.6  +0.4  +0.7  +0.7  +0.4  +0.6  +0.7  +0.5  +0.6
KM3T-3     -0.0  -0.0  -0.0  +0.1  +0.0  +0.1  +0.4  +0.0  +0.0  -0.1
KM3T-5     -0.2  -0.0  -0.1  -0.0  +0.0  +0.0  -0.1  -0.0  -0.0  -0.1
KP2RUM     -9.6  -7.6  -7.3              -0.3  -0.1  +0.2  +0.1  +0.5
KP3CW      +0.1  +0.1  +0.1  +0.1  +0.2  +0.1  +0.3  +0.3  -0.1  -0.2
KV4TT      +0.1  +0.0  +0.0  +0.1  +0.1  +0.0  +0.1  +0.0  +0.1  +0.1
KW7MM      -0.1  -0.0 +10.4                                          
LA6TPA     -0.4  -0.7  -1.7  -1.4  -2.1  -2.1  -2.0  -2.3  -2.1  -1.5
LA7GIA     +0.0                                +0.0                  
LB9KJ      -0.2  -0.4  -0.4  -0.8  -0.8  -0.2  -0.3  -0.3  -0.2  -0.2
LU6KK      +0.0  +0.0        -0.0  +0.1  +0.0  +0.0  +0.0  +0.0  +0.0
LU8XW      +0.0  +0.0        +0.1  +0.3        +0.9  -0.0            
LY2XW                        +0.6  +0.6  +1.0                        
LZ3CB      -0.0  +0.0  +0.0  -0.0  -0.0  -0.1  +0.1  -0.0  -0.0  -0.0
LZ4AE      +1.0  +0.6  -0.0  +0.4  +0.9  +1.3  +1.0  +1.0  +0.6  +0.5
LZ4UX      -0.2  -0.0  -0.0  -0.0  -0.0  +0.0  -0.0  -0.0  +0.0  +0.1
LZ5DI      +1.0  +0.9  +0.7  +1.0  +1.5  +1.1  +1.0  +1.1  +0.8  +0.9
LZ7AA      +0.6  +0.5  +0.6  +0.8  +1.0  +0.7  +0.9  +0.8  +0.6  +0.5
M0ORD                                                      -4.9  -3.7
MM0GPZ     +0.2  -0.0  +0.0  +0.1  +0.2  +0.1  -0.0  -0.1  -0.1  -0.2
MM0ZBH     -0.4  +0.2  +0.0  +0.3  +0.8  +0.4  +0.0  +0.6  +0.5  +0.1
N2CR       -0.2  +0.3  -0.0  -0.3  -0.5  +0.0  -0.2  -0.3  +0.2      
N2QT       -0.3  +0.1  +0.1  +0.1  +0.1  +0.1  +0.2  +0.2  +0.1      
N6TV       +1.1  +0.6  +0.7  +0.9  +1.0  +0.7  +0.8  +0.9  +0.5  +1.0
N7OR       +0.1        +0.0  -0.1  +0.0  -0.0  +0.0  +0.0  +0.1  +0.1
N8DXE            +1.5  +1.2  +2.1  +2.1  +1.3  +0.9              +2.8
N9CO       +0.0  -0.1  -0.1  -0.0  +0.0  -0.1  -0.1  +0.1  +0.1  +0.0
N9XG                               +0.6                              
ND7K       -0.4  -0.1  -0.1  -0.3  -0.2  -0.2  -0.2  -0.1  -0.1  -0.4
NG7M       +0.1  -0.1  +0.2  +0.1  +0.0  +0.1  +0.0  -0.4  -0.2  +0.5
NN3RP      +0.1  +0.2  +0.1  +0.2  +0.2  +0.2  +0.3  +0.0  +0.1  +0.4
NT6Q       -2.3  -3.0  -1.7  -2.6  -2.6  -2.4  -2.2  -2.9  -4.1  -3.0
NU4F       +0.1  +0.2  +0.0  +0.1  -0.0  -0.1  +0.1  +0.3  +0.2  +0.2
OE3KLU                 +0.0                    -1.2                  
OE3KLU-3                     +5.2  +5.6              +2.1            
OE6ADD     +0.2  +0.0        +0.3  +0.3  +0.2  +0.2  +0.2  +0.2  +0.4
OE6TZE                       -0.4  -0.1  +0.0  +0.0  +0.0  +0.0  -0.3
OE9GHV     +0.1  -0.2  -0.1  -0.0  -0.0  +0.1  +0.0  -0.1  +0.0  +0.0
OG66X                        -0.3        +0.3  +0.1  +0.6  -0.2  +0.2
OG73X                                    -0.2                        
OH4KA      -0.3  +0.0  +0.7  +1.2  +1.2  +0.7  +0.1  +0.9  +0.4  +0.2
OH6BG      +0.1  +0.1  -0.0  +0.0  -0.1  -0.2  -0.2  -0.1  +0.0  +0.0
OH8KA      -6.6  +5.1  +4.3  +4.2  +4.1  +4.2  +4.0  +4.1  +4.1  +4.5
OK1FCJ     +0.1  +0.1  +0.2  +0.1  +0.1  +0.0  +0.0  +0.1  +0.0  +0.1
OK1HRA     -4.2  -4.0  -4.3  -4.3  -4.2  -4.0        +0.0  -4.7  -4.5
OK4QRO                       +2.3  +2.4                              
ON6ZQ      -0.1  -0.3  -0.3  -0.7  -0.7  -0.4  -0.2  -0.2  -0.3  -0.2
ON7KEC                 +8.6  +8.5  +8.5  +7.7                        
OZ1AAB     +0.4  +0.0  +0.1  +0.4  +0.4  +0.1  +0.1  +0.2  +0.2  +0.1
OZ1BZS     +0.3  +0.5  +0.9              +0.6  +0.5  +0.5  +0.8  +0.4
OZ4ADX     -0.1  -0.2  -0.1  -0.1  -0.1  -0.2  -0.3  +0.0  +0.0  +0.1
PA0MBO     +1.6  +0.0                                                
PA2SQ                        +1.1  +1.1  +0.8  +0.3  +1.2            
PA5KT                  -0.3  -0.8  -0.8                              
PA8MM                                          +0.0  +0.3  +0.4  +0.1
PC5Q                               -1.4  +0.9  -0.6  +1.0  +0.1      
PE5TT      +0.5  +0.6  +0.6  +0.5  +0.2  +0.5  +0.5  +0.7  +0.8  +0.8
PI4CC      -0.0  +0.1  -0.1  -0.2  -0.1  -0.2  -0.1  -0.1  +0.2  -0.3
PY2KJ      +2.1  +3.3  +4.6  +3.8  +4.3  +5.0  +7.1  +7.4  +4.5  +5.2
PY2KNK     +2.4  +2.5  +2.3  +2.8  +2.8  +2.1  +2.4  +3.1  +3.6  +4.3
PY2PE      +1.3  -2.5  -2.5  +1.9  +1.4  -0.4  +1.8  +0.1  +0.2  -0.5
R1LB       -0.0  -0.2  -0.1  -0.1  -0.1  -0.5  -0.2  -0.1  -0.0  -0.0
R4NCU      -0.8  -0.8  -0.5  -0.9  -0.7  -0.4  -0.7  -0.7  -0.8  -0.7
R6YY       -0.1  -0.2  +0.1  +0.1  -0.5  -0.0  -0.1  -0.0  -0.4  +0.1
R9IR       +0.6  +0.3  +0.3  +0.5  +0.6  +0.4  +0.3  +0.5  +0.3  +0.3
RK3TD            +0.6  +0.5  +0.8  +0.6  +0.6  +0.5  +0.5  +0.4  +0.3
RK3TD-2          -0.1  -0.1  -0.1        -3.5  -2.7  -3.0  -3.2  -3.0
RN4WA      +1.2  +1.1  +1.1  +1.5  +1.6  +0.8  +1.0  +1.2  +0.7  +0.8
RU9CZD     +0.2  +0.1  +0.0  +0.1  -0.2  -0.0  -0.1  +0.0  -0.2  -0.1
S50U       +0.5  +0.4  +0.2  +0.4  +0.3  +0.2  +0.2  +0.4  +0.3  +0.4
S53A       +0.7  +0.6  +0.7  +0.9  +0.9  +0.5  +0.5  +0.6  +0.5  +0.6
S53F       +0.8  +0.6  +0.8  +1.8  +1.8  +0.8  +0.8  +0.9  +0.6  +0.3
S53WW      +0.3  +0.2  +0.2  +0.2  +0.0  +0.0  +0.4  +0.4  +0.3  +0.1
SE5E       +0.5  +0.4  +0.3  +0.3  +0.5  +0.4  +0.4  +0.5  +0.4  +0.4
SM0TCZ     -0.2  -0.5  -0.2  +0.8  +0.8  -0.2  +0.1  +0.1  -1.5  -0.3
SM1HEV     +0.3  +0.2  +0.6  +0.3  +0.5  +0.3  +0.2  +0.4  +0.5  +0.5
SM7IUN     -0.1  -0.0  -0.0  -0.1  -0.1  -0.1  -0.1  +0.1  +0.1  -0.1
SQ5J       +9.8  +9.7  +9.4  +9.7  +9.8  +9.6  +9.5  +9.7  +9.6  +9.7
SQ8J                        +15.1                                    
SV1CDN     -0.6  +0.3              +0.2  +0.0  +0.0  +0.0            
SZ1A                   +0.9  +2.0  +3.4  -2.3  -2.4  +0.1  +0.6  +1.0
TF3Y       +1.2  +1.4  +1.5  +2.1  +2.2  +1.5  +1.7  +1.7  +1.7  +1.8
TI7W       +0.4  +0.2        +0.8  +0.0  +2.9  +1.6  +0.0  +0.0  +0.0
UA0S       +3.4  +6.1  +6.7  +6.1  +6.3  +5.6  +5.8  +4.6  +4.8  +5.3
UA4CC     +13.9 +13.3 +13.1 +13.7 +13.6 +13.8 +13.8 +13.5            
UT5R-1     +2.2                                                      
UT5R       +4.4                                                      
UY2RA      -1.3  -1.2  -1.0  -1.6  -1.6  -1.1  -1.0  -1.0  -1.1  -1.6
V51YJ      +0.0  +0.2  -0.2  +1.6  +2.2  +0.4  +1.7  +1.3  +1.1  +1.9
VE3EID     +0.3  +0.0        +0.0        +0.3  +0.2  -0.4  -0.4  -0.1
VE6AO            -0.3  -0.3  -0.8  -1.0                              
VE6JY      +3.4  +4.5  +4.0  +2.9  +1.7  +0.9  +1.0  +1.9  +2.3  +2.5
VE6WZ      +3.9  +3.8  +4.4  +4.0  +3.6  +2.9  +2.1  +2.2  +1.8  +2.5
VE7CC      +0.9  +0.8  +0.5  +1.3  +1.5  +0.8  +1.5  +0.7  +1.1  +0.9
VK2EBN           +1.2                                                
VK2GEL     +0.0  +0.0  +0.4  +0.3  +0.2  +0.2  +0.7  +0.4  +0.3  -0.1
VK2RH            -1.3  +1.0  -0.1  -0.0  +0.2  +0.4  +0.5  +0.0  +0.0
VK3RASA    -0.8  -1.1  +0.1  -0.6  -0.7  -0.4  -0.2  -1.5  -1.3  -2.1
VK6ANC     -0.2  -0.5  -1.0  -0.7  -0.5  -0.4  -0.3  -0.4  -0.9  -0.4
VR2FUN-77  +0.9  +0.9  +0.7  +1.0  +1.1  +0.4        +0.4  +0.7  +0.8
VU2CPL     +4.8                          +5.0  +5.2  +4.0  -6.6      
VU2PTT     +1.6  +1.7  +0.4  +1.7  +1.7  +1.1  +3.2  +1.3  +2.4      
VU2TUM     +0.1  +0.3  +0.5  +0.5  +0.5  +0.4  +0.4  +0.7  +0.5  +0.2
W1NT-2     +0.1  +0.0  +0.1  +0.0  -0.1  -0.2  -0.0  -0.2  -0.1  -0.0
W1NT-6     +0.2  +0.2  +0.1  +0.1  -0.1  -0.3  -0.1  -0.2  -0.2  -0.0
W1WRA                  +0.9  +0.1  +0.1                              
W2LB       +2.5  +1.1  +2.0  +2.4  +2.2  +1.9  +1.5  +1.3            
W2MV       +0.3  +0.2  +0.0  +0.5  +0.6  +0.2  +0.7  +0.1  +0.0  +0.0
W2NAF      +1.4  +1.0  +0.9  +1.9  +2.0  +1.4  +1.4  +1.5  +1.1  +1.3
W3DAN            +1.5  +0.9  +2.2  +2.1  +1.3  +1.2              +3.6
W3LPL      -0.3  -0.2  -0.1  -0.4  -0.8                              
W3OA       +0.2  +0.1  +0.2  +0.3  +0.3  +0.1  +0.3  +0.2  +0.3  +0.3
W3RGA      -0.2  +0.1  -0.1  -0.2  -0.1  -0.1  -0.5  -0.7  -0.3  -0.4
W3UA       -0.1  -0.1  -0.1  -0.0  -0.0  -0.0  -0.2  +0.0  +0.0  +0.0
W4AX       +4.1  +4.4  +4.3  +5.0  +4.9  +4.9  +5.3  +5.0  +5.5  +5.4
W4KAZ      -0.7  -0.4  -0.3  -0.5  -0.5  -0.2  -0.1  -0.1  +0.0  -0.0
W6YX       +0.3  +0.2  +0.3  +0.5  +0.5  +0.2  +0.3        +0.4  +0.6
W7MRF                  +0.1  -0.1  -0.0                              
W7VJ                               -1.2  -0.5                        
W8WTS      -0.3  -0.1  -0.1  -0.1  -0.1  +0.0  -0.1  -0.2  +0.1      
W8WWV      -1.2  -0.9  -1.1  -1.7  -1.6  -1.4  -1.3  -1.5  -1.9  -1.8
WA7LNW     +1.5  +1.3  +1.4  +1.8  +2.0  +1.2  +1.2  +1.0  +0.7  +0.8
WB6BEE     -0.2  -0.1  -0.1  -0.0  +0.0  -0.1  -0.1  +0.0  -0.2  -0.0
WC2L       +0.6  +0.5  +0.3  +0.5  +0.5  +0.3  +0.5  +0.5  +0.3  +0.3
WC8GOP     +9.2 +10.5 +10.8 +10.4  +9.4  +9.4  +9.8  +9.4 +10.6 +10.4
WE9V       +1.9  +2.2  +1.3  +1.1  +0.4  +1.3  +2.5  +2.3  +1.7  +2.2
WS2C       +7.1  +6.9  +6.5  +6.3  +6.4  +6.5  +5.0  +6.3  +7.1  +7.7
WS3W      -12.2 -12.1  -5.5 +13.2 +13.3 +13.7 +13.7 +13.8 +13.8 +13.6
WT9U       +5.6  +5.9  +5.8  +5.9  +5.9  +5.1  +5.8  +5.8            
WV4P       +0.6  +0.3  +0.3  +0.6  +0.3  +0.2  +0.2  +0.3  +0.3  +0.5
WX7V/5     +0.3  +0.7  +0.2  +0.7  +0.6  +0.8        +0.2  +0.0  +0.6
WZ7I       +0.5  +0.5  +0.5  +0.7  +0.7  +0.4  +0.5  +0.6  +0.5  +0.5
YO2CK      +0.3  +0.3  +0.3  +0.5  +0.5  +0.6  +0.6  -4.1 -13.0 -13.0
YO2MAX     +0.2  +0.0  +0.0  +0.1  +0.2  -0.0  +0.1  +0.0  -0.0  +0.0
YO5LD      +0.4  +0.2  +0.4  +1.0  +1.1  +0.7                        
ZL3X       -0.7  -0.7  -0.9  +0.4  -0.3  -0.8  -0.8  -1.0  -0.4  -0.9
ZL4YL      +1.2  +1.3  +1.0  +1.5  +1.6  +0.9  +0.9  +1.2  +1.0  +1.3
ZS1NN      -3.7  -4.2  -5.5  -4.2  -4.1  -4.7  -4.6  -4.1  -3.9  -4.6

Last updated 2025-05-29 00:15:35 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 2025-05-29 00:15:35 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.