How do we not have infinite number of bands available if we just use more decimals? Ie, 99.3 FM becomes 99.35, 99.353, and so on… how “close” can stations be?
How do some stations interference with each other while being far away numerical, but other stations are a decimal point away with no interference?
I’m doing HAM radio study for no reason other than it sounds neat and it’s cool to have a technical skill, but I’m having trouble wrapping my head around how we can’t just subdivide a limited band X number of times to fit more people in without interference.
In: 0
It is the accuracy of the radios picking up the transmission. Signals are broadcast over a band of frequencies plus or minus 0.1 GHz for example. This is to ensure that the inaccuracies in the radios can still pick it up. Yes in a perfect world you can have infinite but precision is poor.
Humans can hear a range of frequencies, say 20Hz to 20kHz, and you need to record up to twice the maximum of that to get full reproduction. Then you put that 40kHz band of frequencies on top of a given carrier radio frequency, and that is the band that is occupied by your broadcast (sort of). The quoted frequency is basically the middle of a band where the deviation from nominal tells your radio what sound to play at a given moment. If another band overlaps then they will interfere.
Generally, radio waves occupy a certain “space” (bandwidth) of the radio spectrum based upon the information they carry. Voice cannot be less than 20khz wide since that is the range of human speech. You cannot overlap two signals since both will interfere with each other and be unintelligible.
Think of a highway. Cars are 8ft wide, but if you paint the road lines 6ft wide, you still can’t fit more cars in the road since they are still the same width and didn’t get smaller.
There is a shift in the vhf and uhf spectrum away from analog modes towards digital modes and narrower bandwidths due to the high demands for radio spectrum.
The frequency that is used for FM is the center frequency of what is used by a station, not the single used frequency. The common allocation for FM radio is 200kHz per station so 99.3 is really 99.2 to 99.4 So station needs to be 0.2MHz apart.
There is no way to transmit any information in a single frequency you could just send a sine wave that does not change in amplitude of phase. Even if you just change amplitude or phase whe you do that the signal will contain more then just a single frequency. So you need a frequency band to transmit any information, the largest the band the more information you can transmit.
This is how a typical FM radio station signal looks at the baseband [https://en.wikipedia.org/wiki/File:RDS_vs_DirectBand_FM-spectrum2.svg](https://en.wikipedia.org/wiki/File:RDS_vs_DirectBand_FM-spectrum2.svg) the frequency is only to 99kHz not 200 because you get a mirror signal on the other side of the mid signal.
You could reduce the signal and just transmit the mone and stereo sound that go to 53kHz and add a bit of space for interference and 60kHz could be enough for just sound, which means you could put station 120kHz apart. If you modified the sigan you could get it into 100kHz.
In practice if you what to change the standard the reasonable solution is to go digital. It will be more frequency efficiency, a single DAB mux that use 1.5MHz can transmit between 9 and 12 stations, with FM you could only fit 7.5
The advantage is even higher f you what to cover a large are with the same station like a whole country. With DAB you can have multiple transmitters that send of the exact same frequency and receive multiple signals just make the signal you receive stronger, there is no interference. So a single mux can cover a whole country and only need a single band of 1.5MHz compared to FM where two transmitters of the same station that overlap in coverage need to use a diffrent frequency.
There is not
Latest Answers