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Message |
    
Starface
Advanced Member
Username: Starface
Post Number: 900
Registered: 1-2005
| | Posted on Tuesday, November 21, 2006 - 2:05 am: | 
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I was just thinking how did the FCC or whom ever came up with the numbers for frequenies?
like most of us know that 144-148.??? is the 2 Meter band frequenies.
50.??? is 6 meter
and
27.??? is the 11 meter(CB Band)
The thing that puzzles me is why didn't they
use like 2.??? for 2 meter
6.??? for 6
11.??? for 11 meter
you know..
2 for 2
6 for 6
11 for 11
can someone give me an answer?
Starface
CEF476
CVC14 |
Airplane1
Advanced Member
Username: Airplane1
Post Number: 930
Registered: 5-2004
| | Posted on Tuesday, November 21, 2006 - 6:58 am: |
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I know what your saying, But why would they make it easy?? |
747
Intermediate Member
Username: 747
Post Number: 210
Registered: 8-2002
| | Posted on Tuesday, November 21, 2006 - 7:06 am: |
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Starface,
The "meters" is actually the physical length of one complete wave in the cycle. Why do you think a 108" (102" whip plus 6 inch spring) is so widely suggested? Because it's 1/4 of a complete wave. 11 meters = 433.070866142 inches ... 1/4 of that is 108.2677165355 inches.
The higher the frequency, the shorter the distance needed to complete the cycle, hence the shorter antenna lengths seen as you go higher in frequency.
Look at most public safety vehicles - your common VHF radio antenna is 18 inches... UHF would be 6 inches... and 800mhz would be 3 inches.
Hope this helps? |
Bruce
Senior Member
Username: Bruce
Post Number: 4181
Registered: 9-2003
| | Posted on Tuesday, November 21, 2006 - 8:05 am: |
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Radio waves travel at 186,000 MILES PER SEC.
SO ......
A 186 KHZ signal is 1 mile long
A 1.86 MHZ signal is .1 mile 528 FOOT
A 18.6 MHZ signal is .01 MILE or 52.8 Foot
A 186 MHZ signal is .001 MILE or 5.28 Foot
SO a 1/4 wave at 186 mhz is 15.8 inches
And 2 meters at 146 mhz its 20 inches
And at CB its 106 in for that 1/4 wave .... |
Starface
Advanced Member
Username: Starface
Post Number: 903
Registered: 1-2005
| | Posted on Tuesday, November 21, 2006 - 1:23 pm: |
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Ok Maybe i'm seeing these answers wrong but what I'm trying to figure out is how did the FCC or whom ever came up with the numbers for frequenies?
Ok like we all talk on 27.115 either AM or LSB and we know thats 11 meters
I'm trying to find the answer why it's 27.115
and/or why it wasn't/couldn't have been say 11.115?
Making the frequenies numbers the same as the band number..Like shown before
2 meter = something like 2.685
6 meter = Something like 6.525
10 meter = Something like 10.555
11 meter = Something like 11.115
12 meter = Something like 12.885
so on and so on....
or why they didn't do it like maybe this way.
11. would be the band = 11 meters
.345 would be channel = channel 34
11.345 11 meter band and channel 34 on that band
I'm not look for antenna size to know what band or frequenies and/or signals, I'm just looking for an answer to why/how they
Starface
CEF476
CVC14 |
Slugo4449
Intermediate Member
Username: Slugo4449
Post Number: 129
Registered: 7-2004
| | Posted on Tuesday, November 21, 2006 - 8:49 pm: |
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George:
Because 11 meters is the approx. length of a full wavelength that you need to transmit in the 27mhz's, hence 11 meter band.
40 meters would be the approx. length of the full wave on 7mhz, hence 40 meter band.
Here in the U.S. we don't have dibs on the amateur bands, it is world wide. Most of the world uses the metric system.
They use meters instead of feet or inches.
If it was just up to the U.S. you would be calling them a "foot band"? yuk yuk yuk.......
Marty
KG6QKJ |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1418
Registered: 6-2004
| | Posted on Tuesday, November 21, 2006 - 9:41 pm: |
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27 Megahertz is the frequency.
11 meters is the wavelength.
It's two ways of describing the same thing. |
Starface
Advanced Member
Username: Starface
Post Number: 906
Registered: 1-2005
| | Posted on Tuesday, November 21, 2006 - 10:02 pm: |
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ok thanks I'm starting to understand this clear now...
11 meter as in measuring in metric gives us 27 mhz right?
so with that said they took the 11 meter metric and turn it into plain 11 meter for the band and becouse it takes 11 meters to get the approx. length of a full wavelength that you need to transmit in the 27mhz's so they put the two together and came up with 27mhz's for the 11 meter band...Ok thanks guys I do believe I understand how and why now.
Again thanks I also wonder how it was done and why they did it that way..
Starface
CEF476
CVC14 |
Tech291
Moderator
Username: Tech291
Post Number: 453
Registered: 11-2004
| | Posted on Tuesday, November 21, 2006 - 10:12 pm: |
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FREQUENCY vs WAVELENGTH
credit Joseph J.Carr
There are different ways to indicate where to find a certain station on a radio dial. For example, we could say that a station is operating on 9680 kiloHertz (kHz), 9.68 megahertz (MHz), or on 31 meters. And all three ways would be correct!
Radio waves are transmitted as a series of cycles, one after the other. The hertz (abbreviated Hz) is equal to one cycle per second. Hertz was named after Heinrich Hertz, a German physicist [1857-1894] who experimentally proved the existence of electromagnetic waves. You may have noticed that the electric power supplied to your home is rated at 60 Hz. Electric power is distributed as alternating current (AC), meaning it goes through a cycle of changing directions of flow. When we say that electric power is "60 Hz," we mean 60 cycles per second (in which time the direction of flow changes 120 times).
Radio waves go through far more cycles in a second than electric current, and we need to use bigger units to measure them. One is the kilohertz (kHz), which is equal to 1000 cycles per second. Another common one is the megahertz (MHz), which is equal to 1,000,000 cycles per second----or 1000 kHz. The relationship between these units is like this:
1,000,000 Hertz = 1000 kilohertz = 1 megahertz
Radio is usually thought of "beginning" at frequencies of approximately 5 kHz, although most available receivers can only tune down to about 150 kHz.
The term "wavelength" is left over from the early days of radio. Back then, frequencies were measured in terms of the distance between the peaks of two consecutive cycles of a radio wave instead of the number of cycles per second. Even though radio waves are invisible, there is a measurable distance between the cycles of electromagnetic fields making up a radio wave. The distance between the peaks of two consecutive cycles is measured in meters. The relationship between a radio signal's frequency and its wavelength can be found by the following formula:
wavelength = 300 / frequency in MHz
According to this formula, a frequency of 9680 kHz would be equivalent to a wavelength of 30.99 meters, which we would round to 31 meters. Thus, 9680 kHz, 9.68 MHz, and 31 meters all refer to the same operating frequency!
As the formula indicates, the wavelength of a radio signal decreases as its frequency increases. This is important because the length or height of various types of antennas must often be a fraction (usually one-quarter or one-half) of the wavelength of the signal to be transmitted or received. This means that most antennas designed for frequencies near 4000 kHz will be physically much larger than antennas designed for frequencies near 30 MHz.
Frequencies are seldom given in terms of wavelength anymore. However, certain segments of the shortwave bands are referred to in terms of "meter bands" as a convenient form of shorthand. For example, the term "10-meter band" is used to refer to the ham radio band that extends from 28000 to 29700 kHz. The following is a table of the most common ham radio and shortwave broadcasting "meter bands" found on frequencies below 30 MHz:
Meter Band Frequency Range and Use
160 meters 1800-2000 kHz ham radio
120 meters 2300-2498 kHz broadcasting
90 meters 3200 to 3400 kHz broadcasting
80 meters 3500 to 4000 kHz ham radio
60 meters 4750 to 4995 kHz broadcasting
49 meters 5950 to 6250 kHz broadcasting
41 meters 7100 to 7300 kHz broadcasting
40 meters 7000 to 7300 kHz ham radio
31 meters 9500 to 9900 kHz broadcasting
30 meters 10100 to 10150 kHz ham radio
25 meters 11650 to 11975 kHz broadcasting
22 meters 13600 to 13800 kHz broadcasting
20 meters 14000 to 14350 kHz ham radio
19 meters 15100 to 15600 kHz broadcasting
17 meters 18068 to 18168 kHz ham radio
16 meters 17550 to 17900 kHz broadcasting
15 meters 21000 to 21450 kHz ham radio
13 meters 21450 to 21850 kHz broadcasting
12 meters 24890 to 24990 ham radio
11 meters 25670 to 26100 kHz broadcasting
10 meters 28000 to 29700 kHz ham radio
You'll notice some inconsistencies in the table above. For example, the 17-meter ham radio band is actually higher in frequency than the 16-meter broadcasting band. These inconsistencies have come about from years of use (misuse?) of a particular "meter band" to refer to a certain range of frequencies. |
Wildrat
Senior Member
Username: Wildrat
Post Number: 1134
Registered: 12-2003
| | Posted on Tuesday, November 28, 2006 - 9:19 am: |
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Starface are you a ham? I don't have my ticket yet and don't know if I will ever bother, but I do know that when I picked up a study book that was one of the first things they spoke of. I guess there are two types of Hams, ones that study and those that practise the test. Anyway I find the frequency discussion with my one son that ask questions very entertaining. I remember when he was looking at my charts on the wall and asked about the frequency/meter. I explained to him that the band I speak on is the 11M band. Then I tell him that 11M is the length of one wave length. He just kind of gave me a stunned look, from there he was cking out the rest of them. I really need to get his radio fixed.
WR |
Starface
Advanced Member
Username: Starface
Post Number: 970
Registered: 1-2005
| | Posted on Tuesday, December 12, 2006 - 6:45 pm: |
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Well Wildrat a little late on answering this but we all have are ways of doing things and it really don't matter how things get done as along as it gets done if we really want something.
But I'll answer this.
yes I practise the test 1st so I could my ticket that way I can get the on hands learning just the way I do things..
I learn as I go, I'm not book smart never have been but if one shows me how things are done I'm a very fast learner that way.
And I got my answers and understand the answers and thats all I was asking..
73 to you and Merry Christmas
Starface
KI4NBE
CEF476
CVC14
Ham181 |
