Skimmer frequency accuracy
To be a good RBN citizen a skimmer should have a frequency accuracy of 2ppm or better.
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 here is based on archived RBN data from the previous day, 00:00 to 23:59 UTC. When making adjustments, this means that changes in calibration will not have full impact on the listed data until the second day after the change.
The deviation estimates listed below are based on spots on all active bands (40m and above) from the respective skimmer. If different hardware is used for different bands, the deviation number may thus not represent the actual deviation for a particular band.
The software used to calculate the tables below can be found here. It runs as a cron job in an Ubuntu container on my server and uploads to this WordPress site ten minutes after midnight UTC every night.
The calculation of deviation estimates 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 criterion of spots are outlined below.)
Repeating the analysis with this this extended set of skimmers as frequency reference drastically increases the geographical coverage of the algorithm, in turn increasing the number of qualifying spots, thus leading to 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 is 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.
Due to propagation characteristics, operator behavior (e.g. small QSY), and just statistical variations, 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.
243951 RBN spots between 2021-08-05 00:00 and 23:59 UTC. 44504 spots (18.2%) were from reference skimmers (*). Average spot flow was 169 per minute from 164 active CW skimmers. 103850 spots from 155 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 ------------------------------------- 3B8CW +0.0 16 1.000000000 3V8SS +1.1 1648 1.000001104 5W1SA +0.2 39 1.000000183 9A1CIG +9.1 321 1.000009107 AC0C-1* +0.2 664 1.000000195 BA7KW +5.3 50 1.000005324 BA7PC +23.0 73 1.000023001 BD8SZ +0.1 223 1.000000128 BG6SNJ +0.5 59 1.000000483 BG8DIV -6.0 36 0.999993960 BG8PA -0.0 68 1.000000000 BH4RRG1 -1.0 35 0.999998982 BH4RRG4 -0.2 35 0.999999796 BH4XDZ -0.0 7 0.999999999 BI4RFP +5.9 18 1.000005941 CX6VM -0.4 17 0.999999581 DD5XX +0.4 1294 1.000000395 DE1LON +0.2 1542 1.000000196 DF4XX +1.1 586 1.000001106 DF7GB* +0.0 1443 1.000000045 DJ2BC* +0.1 1602 1.000000075 DK0TE +2.9 1318 1.000002930 DK3UA -0.6 136 0.999999427 DK9IP +0.2 1371 1.000000200 DL0LA +1.4 1402 1.000001378 DL3DTH +0.2 2023 1.000000197 DL8LAS +1.5 1226 1.000001519 DL8TG -0.8 578 0.999999171 DM6EE -0.9 1554 0.999999060 DO4DXA* -0.2 809 0.999999839 DR4W +0.6 1616 1.000000553 E28AC +3.3 239 1.000003318 EA1RX +0.5 42 1.000000509 EA1URA +4.7 1313 1.000004662 ET3AA +0.2 36 1.000000197 F4VSQ +4.9 313 1.000004916 F5AHD +0.3 221 1.000000269 F8DGY +1.6 1314 1.000001617 G3XBI +0.0 8 1.000000000 G4AON +0.7 99 1.000000672 G4ZFE -0.3 1710 0.999999741 GI4DOH +0.6 607 1.000000589 GM6DX +0.5 313 1.000000547 HA1AG +0.8 545 1.000000840 HA1VHF +0.1 2168 1.000000113 HA6PX -0.8 790 0.999999182 HA7GN +0.3 628 1.000000307 HB9BXE +1.9 1524 1.000001931 HB9DCO* -0.1 2472 0.999999923 HB9JCB +1.8 1618 1.000001774 HG8A -0.0 1449 0.999999980 IK3STG +1.6 507 1.000001566 IK4VET +3.1 41 1.000003131 IK4VET-1 +3.0 2084 1.000003019 JA4ZRK -0.8 83 0.999999227 JH7CSU1 +5.4 84 1.000005404 JI1HFJ -2.8 35 0.999997192 JJ2VLY +1.8 244 1.000001783 JQ1BVI +0.0 186 1.000000000 K1TTT -0.3 1238 0.999999702 K3PA-1 -0.1 778 0.999999881 K4PP +0.6 339 1.000000587 K4XD +23.5 299 1.000023514 K5TR +0.4 708 1.000000397 K7EG +1.8 170 1.000001780 K7MJG +0.7 122 1.000000699 K9IMM +0.2 1021 1.000000185 K9LC* +0.0 903 1.000000033 K9TM-4 +0.6 610 1.000000593 KC0VKN -0.8 291 0.999999154 KC4YVA +5.4 456 1.000005369 KD2OGR -0.8 245 0.999999239 KD7YZ +1.0 978 1.000000979 KH6LC +0.0 18 1.000000000 KM3T* +0.2 422 1.000000213 KM3T-2* -0.2 1256 0.999999795 KO7SS +0.2 980 1.000000229 KO7SS-7 +1.2 425 1.000001181 KQ8M +8.0 331 1.000007950 KU7T +1.1 477 1.000001070 LA6TPA +2.5 745 1.000002518 LZ3CB* +0.1 755 1.000000106 LZ4AE +1.7 812 1.000001662 LZ4UX* -0.3 425 0.999999675 LZ7AA +0.4 840 1.000000352 MM0ZBH* -0.1 1013 0.999999874 N4RLI -2.2 77 0.999997783 N4TVC +0.9 483 1.000000903 N4ZR +0.3 540 1.000000349 N6TV +0.5 221 1.000000547 N7TUG +2.4 188 1.000002420 N9MKC +0.0 486 1.000000038 NA0B +1.2 210 1.000001218 NC7J +1.3 474 1.000001256 OE6ADD +1.3 1636 1.000001347 OE9GHV* -0.0 1924 0.999999974 OH6BG* +0.5 1017 1.000000481 OL7M +1.4 1158 1.000001355 ON3URE +0.5 1461 1.000000462 ON6ZQ +1.1 1176 1.000001052 PA0MBO -0.0 260 0.999999965 PJ2A -1.5 239 0.999998457 R6YY +0.7 138 1.000000660 RK3TD -0.7 1303 0.999999317 RN4WA* -0.0 1389 0.999999964 RU9CZD +3.6 357 1.000003565 S50ARX +0.6 500 1.000000645 SE5E* -0.1 2080 0.999999861 SJ2W +0.1 2145 1.000000150 SM0TCZ +1.9 75 1.000001898 SM6FMB +0.1 1335 1.000000093 SM7IUN* +0.1 2055 1.000000102 SP8R +0.0 92 1.000000001 SV1CDN +11.8 241 1.000011820 SV8RV +0.4 352 1.000000410 SZ1A +4.1 139 1.000004102 TF3Y -0.5 543 0.999999452 TF4X -1.4 2541 0.999998646 UA0S -2.0 55 0.999997961 UY2RA +0.3 152 1.000000310 V51YJ +1.3 48 1.000001285 VE2WU -0.5 742 0.999999510 VE6AO -0.5 55 0.999999482 VE6JY +0.3 449 1.000000253 VE6WZ +2.6 462 1.000002554 VE7AB +1.1 26 1.000001095 VE7CC +1.0 326 1.000001026 VK2GEL +2.8 5 1.000002849 VK3RASA +0.3 29 1.000000341 VK4CT -2.2 194 0.999997808 VK6ANC -1.7 39 0.999998283 VU2PTT -0.1 102 0.999999914 VY0ERC -0.8 17 0.999999161 W1NT-2 -0.6 1238 0.999999366 W1NT-6 +0.0 1600 1.000000017 W2AXR +1.3 805 1.000001294 W2LB +3.8 154 1.000003785 W2MV +0.1 122 1.000000058 W3LPL +1.3 1732 1.000001314 W3OA +0.6 298 1.000000557 W3UA +3.9 1501 1.000003876 W4AX +4.7 261 1.000004651 W4KAZ -0.4 718 0.999999568 W6YX +0.1 196 1.000000073 W7HR +1.1 196 1.000001088 W8WTS -0.4 524 0.999999597 W8WWV +0.5 925 1.000000457 WA7LNW -0.6 573 0.999999403 WB6BEE -0.2 274 0.999999750 WC2L +0.3 698 1.000000273 WE9V +1.3 1150 1.000001339 WF7T +0.2 40 1.000000178 WS3W* +0.0 631 1.000000001 WZ7I -0.1 1436 0.999999944 ZL4YL +2.7 85 1.000002680 Last updated 2021-08-06 00:10:22 UTC
Historical skimmer frequency accuracy
Below you will find historical accuracy data for the past five 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 21-08-05 21-08-04 21-08-03 21-08-02 21-08-01 ------------------------------------------------------------- 3B8CW +0.0 -0.3 +0.0 +0.0 -0.1 3V8SS +1.1 +1.0 +0.7 +1.0 +1.4 5W1SA +0.2 +0.3 +0.0 +0.2 +0.6 9A1CIG +9.1 +6.6 +7.2 +8.3 +9.7 AC0C-1 +0.2 -0.1 +0.1 -0.0 +0.1 BA7KW +5.3 +4.4 +3.8 +5.5 +3.9 BA7PC +23.0 +22.2 +22.5 +23.0 +22.3 BD8SZ +0.1 +0.2 +0.1 +0.4 +0.4 BG0ARE +22.0 BG4WOM +9.4 +10.3 +9.8 BG6SNJ +0.5 +0.1 +0.7 +1.0 +0.4 BG6SZD +6.5 BG7DOD +2.6 BG8DIV -6.0 -6.7 -3.9 -5.3 -3.6 BG8PA -0.0 -0.0 -0.1 +0.0 -0.0 BH4RRG1 -1.0 -0.3 -0.4 +0.0 -6.6 BH4RRG4 -0.2 +1.2 +0.2 +0.0 +7.7 BH4XDZ -0.0 +0.7 +0.0 +2.8 BI4RFP +5.9 +5.3 +4.3 +4.8 +2.1 CX6VM -0.4 +0.0 +0.0 +0.0 -1.6 DD5XX +0.4 +0.4 +0.3 +0.3 +0.4 DE1LON +0.2 +0.0 +0.0 +0.1 +0.2 DF4XX +1.1 +1.1 +1.0 +0.9 +1.2 DF7GB +0.0 +0.0 +0.0 -0.1 +0.0 DJ2BC +0.1 +0.1 +0.2 +0.1 +0.1 DK0TE +2.9 +2.5 +2.4 +2.6 +2.9 DK3UA -0.6 -0.4 -1.1 -0.5 -0.9 DK8NE +0.0 -0.5 DK9IP +0.2 +0.2 +0.1 +0.2 +0.2 DL0LA +1.4 +1.3 +1.1 +0.8 DL3DTH +0.2 +0.1 +0.3 +0.2 +0.2 DL8LAS +1.5 +1.3 +1.3 +1.0 +1.4 DL8TG -0.8 -1.1 -1.1 -0.8 -1.2 DL9GTB -0.1 -0.6 DM6EE -0.9 -0.6 -1.2 -0.8 -1.7 DO4DXA -0.2 -0.2 -0.1 -0.1 +0.1 DR4W +0.6 +0.3 -6.1 -11.5 -11.1 E28AC +3.3 EA1RX +0.5 +0.3 EA1URA +4.7 +4.1 +4.0 +3.9 +2.2 ET3AA +0.2 +0.0 -0.6 +0.0 -0.1 F4VSQ +4.9 +5.4 +5.8 +7.3 F5AHD +0.3 +0.3 -0.1 +0.4 F8DGY +1.6 +1.2 +1.1 +1.3 +1.6 G0KTN +0.4 +0.7 G3XBI +0.0 +0.0 +0.2 G4AON +0.7 +1.3 +0.8 +1.9 G4ZFE -0.3 -0.3 -0.1 +0.1 +0.2 GI4DOH +0.6 +0.4 +0.4 +0.4 +0.5 GM6DX +0.5 +0.8 +0.8 +0.5 +0.6 HA1AG +0.8 +1.0 +1.1 +1.1 HA1VHF +0.1 +0.1 +0.1 +0.1 +0.4 HA5PP +1.5 HA6PX -0.8 -0.5 -0.5 -0.7 +0.2 HA7GN +0.3 +0.7 +0.7 +0.8 +1.0 HA8TKS +0.1 +0.0 HB9BXE +1.9 +1.3 +1.1 +1.3 +1.6 HB9DCO -0.1 -0.1 -0.1 -0.1 +0.0 HB9JCB +1.8 +1.6 +1.4 +1.4 +1.6 HG8A -0.0 -0.1 -0.1 +0.1 +0.5 HS8KVH -0.6 IK3STG +1.6 +1.2 +1.6 +1.5 +1.5 IK4VET-1 +3.0 +3.0 +2.7 +3.0 +3.2 IK4VET +3.1 JA4ZRK -0.8 +0.1 -0.0 +0.0 -0.1 JH7CSU1 +5.4 +3.4 +2.9 +2.9 +3.6 JI1HFJ -2.8 -6.4 -6.2 -5.4 JJ2VLY +1.8 +1.5 +1.8 +1.4 +1.7 JQ1BVI +0.0 +0.4 -0.0 +0.2 +0.2 K1TTT -0.3 -0.4 -0.3 -0.2 -0.4 K3PA -0.0 K3PA-1 -0.1 +0.1 +0.0 -0.2 +0.1 K4PP +0.6 +0.3 +0.3 +0.2 +0.4 K4XD +23.5 +23.3 +24.1 +25.3 +25.0 K5TR +0.4 +0.1 +0.2 +0.4 +0.2 K7EG +1.8 +0.9 +0.7 +1.1 +1.5 K7MJG +0.7 +0.0 +0.4 -0.1 +0.4 K9IMM +0.2 +0.4 +0.2 +0.2 +0.4 K9LC +0.0 +0.1 -0.1 +0.1 +0.2 K9TM-4 +0.6 +0.7 +0.5 +0.3 +0.3 KC0VKN -0.8 -0.7 -0.5 -0.8 -1.3 KC4YVA +5.4 +5.0 +4.1 +3.8 +4.4 KD2OGR -0.8 -0.3 -0.3 -0.3 -0.1 KD7YZ +1.0 +1.0 +0.6 +0.6 +0.6 KH6LC +0.0 +0.0 +0.6 +0.0 +0.0 KM3T +0.2 +0.0 +0.4 -0.0 +0.0 KM3T-2 -0.2 -0.2 -0.2 -0.1 -0.2 KO7SS +0.2 +1.0 +0.3 -0.0 -0.2 KO7SS-7 +1.2 +0.3 +0.6 KQ8M +8.0 +5.9 +5.4 +6.0 +4.9 KU7T +1.1 +0.6 +0.4 +0.7 +0.7 KV4TT +0.4 +0.4 -0.4 LA6TPA +2.5 +1.1 +0.7 +1.2 +0.8 LU1MAW +14.3 +13.2 LZ3CB +0.1 -0.0 +0.3 -0.1 -0.0 LZ4AE +1.7 +1.7 +1.1 +1.2 +1.5 LZ4UX -0.3 -0.2 -0.1 -0.3 -0.2 LZ7AA +0.4 +0.3 +0.1 +0.1 +0.4 MM0ZBH -0.1 +0.1 -0.0 -0.3 -0.1 N4RLI -2.2 -3.0 -0.7 N4TVC +0.9 +0.6 +0.5 +0.5 +0.5 N4ZR +0.3 -0.2 -0.2 -0.0 +0.2 N6TV +0.5 +0.5 +0.6 +0.5 +0.6 N7TUG +2.4 +0.8 +0.7 +1.4 +2.1 N9MKC +0.0 -0.1 -0.0 -0.1 -0.0 NA0B +1.2 -0.2 -0.7 -0.8 +0.1 NC7J +1.3 +0.9 +0.5 +0.6 +0.6 OE6ADD +1.3 +1.4 +1.1 +1.3 +1.4 OE9GHV -0.0 -0.1 -0.0 +0.0 -0.0 OG73X +0.5 OH6BG +0.5 -0.0 +1.7 OL7M +1.4 +1.6 +1.2 +1.2 +1.5 ON3URE +0.5 +0.3 +0.8 +0.3 +1.0 ON6ZQ +1.1 +0.8 +0.9 +0.9 +1.0 PA0MBO -0.0 PA2SQ +1.9 +4.7 +0.2 +5.5 PE1RDP +11.4 PJ2A -1.5 R6YY +0.7 +2.7 +1.1 +0.6 RK3TD -0.7 -0.7 -0.6 -0.8 -0.9 RN4WA -0.0 +0.2 +0.3 -0.1 +0.1 RU9CZD +3.6 +3.3 +1.9 +3.0 +3.0 S50ARX +0.6 +1.0 +1.0 +0.4 +1.1 SE5E -0.1 -0.1 +0.1 -0.0 -0.2 SJ2W +0.1 +0.1 +0.2 +0.2 +0.2 SM0TCZ +1.9 +1.4 +0.4 +1.5 +2.0 SM6FMB +0.1 +0.1 +0.3 +0.1 +0.2 SM7IUN +0.1 -0.1 -0.0 -0.2 +0.0 SP8R +0.0 +0.4 +0.6 +0.7 +1.1 SV1CDN +11.8 +12.3 +10.7 +11.7 +11.6 SV8RV +0.4 -0.4 -0.1 -0.2 +0.1 SZ1A +4.1 +3.2 +2.8 +4.2 +2.6 TF3Y -0.5 -0.5 -0.7 -0.4 -0.5 TF4X -1.4 -1.4 -1.5 -1.4 -1.6 UA0S -2.0 -1.8 -2.6 -3.3 -2.7 UY2RA +0.3 +0.0 +0.7 +0.1 +0.5 V51YJ +1.3 +1.7 +0.7 +1.0 +0.9 VE2WU -0.5 +0.4 +0.7 +0.2 -0.0 VE6AO -0.5 -0.7 -0.4 -0.2 -0.4 VE6JY +0.3 +0.4 +0.3 +0.5 +0.4 VE6WZ +2.6 +1.8 +1.4 +1.9 +2.1 VE7AB +1.1 +0.0 +1.5 +0.6 VE7CC +1.0 +0.2 +0.3 +0.3 +0.3 VK2GEL +2.8 +0.0 VK3RASA +0.3 -1.0 -0.9 -1.0 -0.4 VK4CT -2.2 -3.8 -1.8 -0.7 -0.8 VK6ANC -1.7 -2.1 -1.6 -0.9 -0.9 VU2PTT -0.1 +0.4 +0.1 -0.1 -0.2 VY0ERC -0.8 +0.0 +0.0 +0.0 W1NT-2 -0.6 -0.7 -0.7 -0.6 -0.7 W1NT-6 +0.0 -0.1 -0.1 +0.1 -0.0 W2AXR +1.3 +0.6 +1.0 +0.8 W2LB +3.8 +1.4 +1.8 +5.5 W2MV +0.1 +0.5 +0.4 +0.2 +0.6 W3LPL +1.3 +1.4 +1.3 +1.4 W3OA +0.6 +0.2 +0.0 +0.2 +0.1 W3UA +3.9 +3.9 +3.5 +3.8 +3.9 W4AX +4.7 +4.9 +3.4 +3.7 +4.0 W4KAZ -0.4 -0.1 -0.1 +0.2 +0.2 W6YX +0.1 +0.4 +0.6 +0.6 +0.5 W7HR +1.1 +0.6 +0.0 +0.2 +0.8 W8WTS -0.4 -0.9 -0.7 -0.6 -0.3 W8WWV +0.5 +0.3 +0.4 +0.4 +0.4 WA7LNW -0.6 -0.9 -0.7 -0.9 -0.7 WA9VEE +0.0 +0.0 +0.0 WB6BEE -0.2 -0.1 -0.0 -0.1 -0.1 WC2L +0.3 +0.3 +0.4 +0.4 +0.4 WE9V +1.3 +1.0 +0.9 +0.7 +1.3 WF7T +0.2 +0.7 +0.7 +0.9 +0.0 WS3W +0.0 +0.5 -1.6 -2.1 -1.1 WZ7I -0.1 +0.1 +0.0 +0.0 +0.1 ZL2BR -7.1 ZL4YL +2.7 +2.3 +1.4 +0.6 +1.2 Last updated 2021-08-06 00:10:26 UTC
Activity statistics
Summary of unique calls spotted and active skimmers per band and continent.
RBN activity between 2021-08-05 00:00 and 23:59 UTC.
243951 spots with 6909 unique callsigns from 170 active skimmers.
Unique callsigns spotted per continent and band
---------------------------------------------------------------
160m 80m 60m 40m 30m 20m 17m 15m 12m 10m 6m
AF 0 9 1 40 5 46 3 4 0 1 2 90
AS 6 36 0 325 58 254 67 63 13 10 32 672
EU 42 402 67 1226 536 1877 317 192 35 248 81 3547
NA 21 242 22 1192 288 966 127 87 21 164 126 2388
OC 6 12 1 56 9 34 3 4 0 1 2 102
SA 1 11 0 42 2 51 13 18 1 3 0 110
76 712 91 2881 898 3228 530 368 70 427 243
Active skimmers per continent and band
---------------------------------------------------------------
160m 80m 60m 40m 30m 20m 17m 15m 12m 10m 6m
AF 1 2 0 4 3 4 4 4 2 1 0 4
AS 3 9 0 20 15 20 17 20 10 6 7 21
EU 38 56 12 61 55 63 42 54 25 48 15 69
NA 38 45 14 53 42 55 39 43 24 37 15 64
OC 5 6 0 8 6 7 3 4 0 0 0 9
SA 1 1 0 2 2 3 2 2 1 0 0 3
86 119 26 148 123 152 107 127 62 92 37
Last updated 2021-08-06 00:10:47 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.
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.
AC0C-1 DF7GB K3PA-1 KM3T LZ3CB OE9GHV WB6BEE Last updated 2021-08-06 00:10:47 UTC