Need help clarifying

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smslavin
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Need help clarifying

#1

Post by smslavin » Fri May 21, 2010 4:03 pm

For some reason I've got a mental block that I can't get through. Hoping one of you has the answer.

The one thing I'm having trouble with on the practice tests is finding a frequency within a band. For example, which frequency is in the 6 meter band?

- 49.00 MHz
- 52.525 MHz
- 28.50 MHz
- 222.15 MHz

The answer is 52.525 and the only reason I know that now is from taking the practice so often this past week. Is there a formula or something I can memorize? I can't seem to find what I need in the study guide.

Mucho thanks.
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sdnative

Re: Need help clarifying

#2

Post by sdnative » Fri May 21, 2010 5:01 pm

300 divided by the band will get you the frequency and 300 divided by the frequency will get you the band (more or less).

It's not exact so be careful the test will have several close but only one right answer.

This is because the band is the wavelength of that frequency light and the speed of light is 3x10^8 m/s (thats 3 with 8 zeros)

So as an example 300000000 divided by 2 (the 2 meter band) will get you 150000000 Hz which is 150 mHz (as you can see its close but not exact)
Last edited by sdnative on Fri May 21, 2010 9:38 pm, edited 1 time in total.

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cruiserlarry
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Re: Need help clarifying

#3

Post by cruiserlarry » Fri May 21, 2010 5:04 pm

The formula you are looking for is:

Wavelenth (in meters) = 300 / Frequency (in megahertz)

Keep in mind that most "xx" meter bands extent over a range of frequencies, so while the answer is exact, the band name is more general. For example, 52.25 Mhz: 300/52.25= 5.75 meters, which is in the "6" meter band.
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jgorm
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Re: Need help clarifying

#4

Post by jgorm » Fri May 21, 2010 5:34 pm

sdnative wrote:This is because the band is the wavelength of that frequency light and the speed of light is 3x10^8 m/s (thats 3 with 8 zeros)
So as an example 300000000 divided by 2 (the 2 meter band) will get you 15000000 Hz which is 150 mHz (as you can see its close but not exact)
Thanks! I always hated using constants when i didn't know their background. I'll end up using 2.99E8 because i already remember that.

On the topic of frequencies and bands, I've been looking on the net for a while for a complete chart including the following; (I might mess up on some of the terms)

band (2m, 10m etc)
Frequency Hz
radio type (frs, CB, HF, VHF, etc)
Radio type's channel number (CB channel 15, FRS ch 15, etc)

Ideally I am looking for an excel sheet with all that info, but a picture would be fine. Something from the range of the lowest amateur radio fq to the highest, and everything in between. Something kind of like this, but more geared for radio people, and with more stuff like the specific frequencies for CB channel XX frequency, FRS channel XX frequency, etc. Kind of like this, but with the info listed above.
Its large so i'll just link it. http://www.icta.mu/images/spectrum.jpg

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smslavin
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Re: Need help clarifying

#5

Post by smslavin » Fri May 21, 2010 5:59 pm

Thanks for the info guys. That's exactly what I needed.
{ slavin photography | KJ6LDF }

sdnative

Re: Need help clarifying

#6

Post by sdnative » Fri May 21, 2010 8:13 pm

jgorm wrote:Thanks! I always hated using constants when i didn't know their background. I'll end up using 2.99E8 because i already remember that.
I think for testing purposes all you need to remember is 300 / wavelength = freq and 300 / freq = wavelength.
sdnative wrote:So as an example 300000000 divided by 2 (the 2 meter band) will get you 15000000 Hz which is 150 mHz (as you can see its close but not exact)
I should clarify here. 150 mHz is close to the frequencies in the 2m band (144.x mHz - 147.x mHz) but not exact. Obviously 300 / 2 is exactly 150 :lol:

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