Kilohertz to Meters Conversion Charts

Thomas H. White -- January 1, 2000

NOTE: In the charts below, "khz" refers to the frequency in kilohertz, while "meters" is the corresponding wavelength in meters.

Kilohertz to Meters (Rough Calculation--Using 300,000 km/sec as the Speed of Light)
 
khz meters khz meters khz meters khz meters khz meters khz meters khz meters
540 556 700 429 860 349 1020 294 1180 254 1340 224 1500 200
550 545 710 423 870 345 1030 291 1190 252 1350 222 1510 199
560 536 720 417 880 341 1040 288 1200 250 1360 221 1520 197
570 526 730 411 890 337 1050 286 1210 248 1370 219 1530 196
580 517 740 405 900 333 1060 283 1220 246 1380 217 1540 195
590 508 750 400 910 330 1070 280 1230 244 1390 216 1550 194
600 500 760 395 920 326 1080 278 1240 242 1400 214 1560 192
610 492 770 390 930 323 1090 275 1250 240 1410 213 1570 191
620 484 780 385 940 319 1100 273 1260 238 1420 211 1580 190
630 476 790 380 950 316 1110 270 1270 236 1430 210 1590 189
640 469 800 375 960 313 1120 268 1280 234 1440 208 1600 188
650 462 810 370 970 309 1130 265 1290 233 1450 207 ----------
660 455 820 366 980 306 1140 263 1300 231 1460 205 1500 200
670 448 830 361 990 303 1150 261 1310 229 1470 204 833 360
680 441 840 357 1000 300 1160 259 1320 227 1480 203 750 400
690 435 850 353 1010 297 1170 256 1330 226 1490 201 619 485
 
Kilohertz to Meters (More Precise--Using 299,820 km/sec as the Speed of Light)
 
khz meters khz meters khz meters khz meters khz meters khz meters khz meters
540 555.2 700 428.3 860 348.6 1020 293.9 1180 254.1 1340 223.7 1500 199.9
550 545.1 710 422.3 870 344.6 1030 291.1 1190 251.9 1350 222.1 1510 198.6
560 535.4 720 416.4 880 340.7 1040 288.3 1200 249.9 1360 220.5 1520 197.3
570 526.0 730 410.7 890 336.9 1050 285.5 1210 247.8 1370 218.8 1530 196.0
580 516.9 740 405.2 900 333.1 1060 282.8 1220 245.8 1380 217.3 1540 194.7
590 508.2 750 399.8 910 329.5 1070 280.2 1230 243.8 1390 215.7 1550 193.4
600 499.7 760 394.5 920 325.9 1080 277.6 1240 241.8 1400 214.2 1560 192.2
610 491.5 770 389.4 930 322.4 1090 275.1 1250 239.9 1410 212.6 1570 191.0
620 483.6 780 384.4 940 319.0 1100 272.6 1260 238.0 1420 211.1 1580 189.8
630 475.9 790 379.5 950 315.6 1110 270.1 1270 236.1 1430 209.7 1590 188.6
640 468.5 800 374.8 960 312.3 1120 267.7 1280 234.2 1440 208.2 1600 187.4
650 461.3 810 370.1 970 309.1 1130 265.3 1290 232.4 1450 206.8 ----------
660 454.3 820 365.6 980 305.9 1140 263.0 1300 230.6 1460 205.4 1499.1 200
670 447.5 830 361.2 990 302.8 1150 260.7 1310 228.9 1470 204.0 832.8 360
680 440.9 840 356.9 1000 299.8 1160 258.5 1320 227.1 1480 202.6 749.5 400
690 434.5 850 352.7 1010 296.9 1170 256.3 1330 225.4 1490 201.2 618.2 485


Background

Radio waves, as they vibrate their way through the ether, can be identified either by their "wavelength", or their "frequency". (Wavelengths are measured as the distance between wave troughs, frequencies are measured by the number of vibrations that pass a point in a set period of time.)

Through the early nineteen-twenties, it was the standard practice internationally to classify transmissions by their wavelengths. Therefore, with the development of the broadcast service in the United States, stations were initially assigned to use wavelengths of 360, 400, and 485 meters. This worked fine for the widely spaced signals used in the initial development of the service, but with the rapid expansion of radio assignments in the early 1920s, it became necessary to switch to the more precise specification provided by frequencies.

Wavelength and Frequency

First a bit of background on frequency terminology. Frequencies are measured in terms of the number of "cycles per second". In the case of AM broadcast stations, which use frequencies of hundreds of thousands of cycles per second, the prefix "kilo", is usually used. For example, as of May 15, 1923 KFI in Los Angeles, California was assigned a frequency of "640,000 cycles per second", or to express it more conventionally, "640 kilocycles per second", which was usually contracted to "640 kilocycles", or even more succinctly, "640 kc". Later, the term "hertz" was adopted by international convention as standing for "cycles per second". So nowadays KFI is assigned to "640 kilohertz", or if you prefer abbreviations, "640 khz"--which should cover all the various ways of saying, for the past 80-plus years, that KFI is located at "640 on your radio dial".

Conversion Charts

The Bureau of Navigation first started specifying station frequencies, rather than wavelengths, with the May 15, 1923 expansion of the broadcast service. This introduced a band of frequencies, running in 10-kilohertz steps from 550 to 1350 kilohertz.

The general public, used to wavelengths, had to be coaxed into making the transition to frequencies, and it was a good fifteen years before you stopped seeing references to wavelengths in the U.S. (In Europe, where mediumwave stations are assigned in 9 khz steps, they still are commonly reported by wavelength). In 1923 many publications started to print conversion charts like the two listed above, with explanations about this newfangled frequency concept. However, there was one area of inconsistency, which explains why I've included two slightly different charts.

Since frequencies and wavelengths are mathematical reciprocals, all you need to do to convert from one to the other is to divide the value into the speed of light, as measured in kilometers per second. The two charts reflect the two major philosophies used in doing the calculation: "rough value" versus "higher accuracy".

In the early 1920s, the best estimate for the speed of light was 299,820 kilometers per second. (This was actually a little high--the current accepted value is 299,792.458 kilometers per second). Many people rounded this to an even 300,000, to make the calculations easier. Also, they just reported the result to the nearest whole meter. In contrast, the more precise people, using 299,820, generally carried the result to the nearest tenth of a meter. Thus, in the above charts, 560 kilohertz was said by the 300,000 people to be equal to a wavelength of 536 meters, while the more precise 299,820 crowd came up with 535.4 meters. (Today, armed with a computer and an up-to-date speed-of-light estimate, I'm happy to report that the actual answer is 535.343675 meters [calculated as 299,792.458 divided by 560])

Please keep in mind that after May 15, 1923 most U.S. stations operated on a frequency evenly divisible by ten. Therefore, most reports after that date that specify wavelengths are actually conversions of the station's frequency, and thus are merely approximations. For example, a report in 1925 that "KZZZ is on 226 meters" meant it really was at 1330 kilohertz. (Some people make the mistake of saying that 226 is 1327.4 khz. In other words don't divide 226 into 300,000--use the chart for the conversion). Also, in most cases where a wavelength is given that doesn't seem to fit, it is usually a typo--they didn't have calculators back then.