3
$\begingroup$

I know that there are various bands referenced in meters (or cm). My question refers to what exactly the word "meter" is referring to when identifying the 5MHz band? I know that the 60-meter band is 5MHz, and considering that communications on that band can go farther than 60 meters, I am assuming that "meter" refers to the wavelength. Is that assumption correct?

$\endgroup$
7
$\begingroup$

That's right, the 5 MHz band has approximately a 60 m wavelength. Back in the early days of radio people often measured where they were on the airwaves by wavelength rather than frequency. Nowadays the radio display shows the frequency, but amateurs still refer to bands by their approximate wavelength.

Wavelength x frequency = speed of light, 2.99792e8 m/s. Or to put it another way, wavelength = 299.792 / frequency in MHz.

$\endgroup$
  • $\begingroup$ AH! I see, that makes total sense now. I didn't even consider the speed of light releationship. I should have. After your answer I searched and found this link for future readers. Thanks! qrg.northwestern.edu/projects/vss/docs/Communications/… $\endgroup$ – RedDogAlpha Mar 11 '16 at 3:23
  • 2
    $\begingroup$ The most useful mnemonic in amateur radio is "metres times MegaHertz equals 300". $\endgroup$ – Harry Weston Mar 12 '16 at 11:50
1
$\begingroup$

The wavelength also literally defines the length of a full-wave resonant wire antenna -- and specifies where along the wire the voltage will have peaks and valleys! So it has practical value when constructing an antenna, which is probably why amateurs still use it.

$\endgroup$
  • $\begingroup$ Well that would be a very big antenna for the 60 meter band! $\endgroup$ – RedDogAlpha Mar 11 '16 at 23:07
  • $\begingroup$ Full wavelength antennas are often loops such as a horizontal square loop or delta loop where the words "square" and "delta" refer to the number of sides to the loop. A perfect horizontal loop would be round but round antennas are hard to make. Most other wire antennas are half-wave dipoles so a 60-meter dipole antenna would be about 30-meters in length. I have a 80-meter dipole that is approximately 140 feet in length. $\endgroup$ – K7PEH Mar 11 '16 at 23:23
  • $\begingroup$ @K7PEH Don't forget the all-too-popular (IMO) vertical quarter-wave antennae. An unloaded, resonant vertical quarter for 60m would only need to be about 48 feet tall. $\endgroup$ – Robherc KV5ROB Mar 13 '16 at 19:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.