Why do the AM and FM bands start with seemingly random frequencies like 85 MHZ? Why can't I tune into 1 HZ or something?
because it's reserved for shortwave communication
>>8191507
The entire electromagnetic spectrum may just be waves of different length explained by the same physics, but how waves interact with matter critically depends on material properties. For instance, glass may be transparent to visible light, but you'd have trouble getting a tan because glass is largely opaque in the UV. Same principle appliesto the atmosphere; some waves get through, and some don't. Furthermore spectrum is a finite resource. Without careful regulation, radio would be largely useless because of jamming.
As an extra, here's a neat fact: have you ever noticed that all FM stations have odd frequencies? This isn't unintentional.The hardware used to detect the signal also detects twice the frequency of the signal. An odd number times an even number is even, so by having odd station frequencies, you prevent multiple stations from being detected when you tune into a specific one.
>>8191507
>>8191588
>The hardware used to detect the signal also detects twice the frequency of the signal.
wew lad
These frequencies arnt random. AM and FM are two different forms of communications. AM is amplitude modulation, and FM is frequency modulation.
The 85MHz you are reffering to is the carrier frequency of the signal. It allows the signal to cross the channel in between devices, and not get altered by external variables (Like noise or other types of signals). The reason you cant tune into something with 1Hz is because that frequency is not strong enough to carry it across the channel to your device. This is also the reason why you can use the same carrier frequency in Toronto and Detroit for example, because the signal coming from Toronto isnt strong enough to carry it all the way to Detroit before it gets completely distorted, where all you hear is static.
you'll need a big ass antenna for a 1 Hz EE-wave.
Like half way between Earth and Moon size
>>8191588
>all FM stations have odd frequencies
But not for the reasons stated. It's merely because the lowest allocated channel is 88.1 MHz and channel spacing is 0.2 MHz. AM and FM is American jargon for the MF ('Medium Wave' 520..1710 kHz) and VHF (88..108 MHz) broadcast bands. Elsewhere it denotes a type of carrier modulation and allocation schemes may be different.
>>8192137
>It's merely because the lowest allocated channel is 88.1 MHz and channel spacing is 0.2 MHz
There is a reason that it was set up like this, and it is precisely to suppress the image frequency in a superheterodyne receiver.
>>8192397
Never mind, I may be wrong. A lot of sites say that it is arbitrary. I totes thought it was to help with the image frequency issue. Some sites support my claim, but many more support that it is arbitrary.
>>8191507
Politically: frequency bands are allocated to specific use, many of the decisions are there for historical reasons. It is a mess, as >>8191608 demonstrates. Big users, like the military will not give up anything.
Technically speaking you can tune from 1Hz to GHz frequencies if you have a Software Defined Radio (SDR) typically using an Analogue to Digital Converter (ADC).
Technically 2: antennas are rarely efficient in reception over a wide range.
Commercially: a band limited receiver is cheap. SDR is more expensive.
Because you can't carry enough information on a 1Hz signal. .1% of 85MHz is 85k which is more than enough bandwidth to carry the range of frequencies a human ear can hear.
Also because antennas scale with frequency (c=f*wavelength) so a good antenna for 1Hz communication would be gigantic.
>>8193429
>so a good antenna for 1Hz communication would be gigantic
But it would be fucking memes to have one.
>>8191810
Sub-wavelength antennas are a thing, you know.
>>8191507
>2016
>still listening to AM/FM
>>8192412
The standard IF is 10.7 MHz and for the usual IF=LO-RF mixing scheme the image range of 88..108 MHz would be 109.4..129.4 MHz which was never used for broadcast.
What could be prevented is direct LO interference: To receive 88.1 MHz the LO runs on 98.8 MHz which puts it between two allocated channels. But for this to become a problem you would need to place two sets side by side.
