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 Boat Design Forums stupid question about what "2 meter" and 70cm bands mean VS freq.
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#1
03-19-2017, 04:33 PM
 Squidly-Diddly Senior Member Join Date: Sep 2007 Rep: 304 Posts: 1,174 Location: SF bay
stupid question about what "2 meter" and 70cm bands mean VS freq.

https://www.youtube.com/watch?v=bFC1quZJGs8

I've got some vague idea that freq = speed of light/wave length, and that by some electronic wizardry a little radio can broadcast on a wide range of freq without needing to physically shorten or lengthen its antenna.

So what do they mean when they say this radio is "2m and 70cm"?

Any good links to radio basics? I just got my HAM lic but I'm not getting a few concepts.

I've got time to watch youtubes but not time to join any clubs at the moment.
#2
03-19-2017, 06:21 PM
 jehardiman Senior Member Join Date: Aug 2004 Rep: 2040 Posts: 2,253 Location: Port Orchard, Washington, USA
2m or 70cm is the wave length. Speed of light (i.e. effective speed of em emissions) is 299,792,458 m/s. So 2m wave length would be 149896229 Hz ~ 149.8 MHz. (i.e. Hz =Speed of light (c)/ wave length (lambda)

http://www.translatorscafe.com/unit-...velength/27-1/
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A vessel is nothing but a bunch of opinions and compromises held together by the faith of the builders and engineers that they did it correctly. Therefor the only thing a Naval Architect has to sell is his experiences.
#3
03-19-2017, 06:36 PM
 jehardiman Senior Member Join Date: Aug 2004 Rep: 2040 Posts: 2,253 Location: Port Orchard, Washington, USA
Sorry, didn't realize the actual question. Basically the discussion of wavelength for a particular xmitter/receiver is more in line towards the antenna size/length than the frequency. All xmitters are tuned for a particular frequency and are expecting a particular sized antenna for maximum effect. Receivers are more tolerant but suffer from gain effects. Sorry, but antennae design is a little out of my field.

https://www.electronics-tutorials.co...nna-basics.htm
__________________
A vessel is nothing but a bunch of opinions and compromises held together by the faith of the builders and engineers that they did it correctly. Therefor the only thing a Naval Architect has to sell is his experiences.
#4
03-19-2017, 10:28 PM
 philSweet Senior Member Join Date: May 2008 Rep: 1067 Posts: 1,975 Location: Beaufort, SC and H'ville, NC
#5
03-20-2017, 03:52 AM
 CDK retired engineer Join Date: Aug 2007 Rep: 1819 Posts: 3,276 Location: Adriatic sea
Quote:
 Originally Posted by Squidly-Diddly I've got some vague idea that freq = speed of light/wave length, and that by some electronic wizardry a little radio can broadcast on a wide range of freq without needing to physically shorten or lengthen its antenna.
It is very simple. For maximum performance an antenna must resonate at a particular frequency. If you are satisfied with less than maximum and/or want a shorter antenna, a coil is added in the base, if you want to cover two frequency bands, two different coils are added.
In your example the radio works reasonable well in the 2 meter and 70 cm band.
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