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Jorgen

Help me understand how the radio technology works

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A tall order perhaps, but when I search online the explainations are way too technical:huh:

What im wondering about is when I think of radio frequency I think of AM/FM band like 87,5–108 MHz for FM, but that is Mhz and the recievers for RC is of course Ghz.

What does this in reality means? is it the same technology just on a higher frequency or is it nothing like the radiowaves that we use in our radios (for music etc)

 

 

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Well yes they are radio waves (electromagnetic radiation) but at a much higher frequency. And there is a lot more data carried in the signal which is how it can support so many radios being on at the same time and also know which receiver to send the signal to.

Looks like this article is a bit more technical - https://www.rcmodelreviews.com/spreadspectrum01.shtml

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I'm not an expert in radios of any sort, and it isn't really necessary to understand how it works in order to get the best from it, but my rough understanding is as follows:

Older RC radios were 27MHz AM.  That means the signal had a frequency of 27MHz and the signal was sent on the amplitude (or height) of the radio wave.  This was how voice and music was transmitted for years and quality was low but the technology was cheap.  Popular radio stations (broadcasted music and speech) used a different frequency to that of RC radios, although IIRC those "toy grade" walkie talkies that were popular in the 80s also used 27MHz and you could get interference on your RC if the kids across the street were playing Army.

Then there were FM radios.  IIRC these used 27MHz or 40MHz (as well as other frequencies for aircraft) and the signal was carried on the frequency of the wave instead.  This means that 40MHz is not exact - it refers to a range of frequencies for each 'channel' and each channel has a range of frequencies all of its own.  So the exact frequency changes slightly in order to carry the signal.  The FM radio on your kitchen worktop works exactly the same way, but in a different band - 87 - 108MHz.

Modern 2.4GHz radios work in a completely different way.  The basic principle is the same - radio waves are used to carry data - but the technology is very different.  There are many different protocols for 2.4GHz radio systems but essentially they all do the same thing - the transmitter and receiver each have a unique ID on the frequency, and when you bind your Tx to your Rx, you are basically sharing the IDs so they talk to each other and only to each other.  A whole bunch of radios are actually shouting data out at the same time on the 2.4GHz frequency but because all the communication is done with IDs attached, receivers only respond to stuff that is sent specifically for them.  This is more a software thing than the old turning the tuning knob on your kitchen radio or changing the crystal in your old Acoms RC set.

2.4GHz is actually used by pretty much everything wireless - broadband routers, baby monitors, cordless telephones, virtually anything that has that little stubby plastic antenna-on-a-hinge will be 2.4GHz.  Despite that, interference on a 2.4GHz RC radio is rare because of the clever software used for sorting out all the signals.

I hope that helps :)

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57 minutes ago, Mad Ax said:

I'm not an expert in radios of any sort, and it isn't really necessary to understand how it works in order to get the best from it, but my rough understanding is as follows:

Older RC radios were 27MHz AM.  That means the signal had a frequency of 27MHz and the signal was sent on the amplitude (or height) of the radio wave.  This was how voice and music was transmitted for years and quality was low but the technology was cheap.  Popular radio stations (broadcasted music and speech) used a different frequency to that of RC radios, although IIRC those "toy grade" walkie talkies that were popular in the 80s also used 27MHz and you could get interference on your RC if the kids across the street were playing Army.

Then there were FM radios.  IIRC these used 27MHz or 40MHz (as well as other frequencies for aircraft) and the signal was carried on the frequency of the wave instead.  This means that 40MHz is not exact - it refers to a range of frequencies for each 'channel' and each channel has a range of frequencies all of its own.  So the exact frequency changes slightly in order to carry the signal.  The FM radio on your kitchen worktop works exactly the same way, but in a different band - 87 - 108MHz.

Modern 2.4GHz radios work in a completely different way.  The basic principle is the same - radio waves are used to carry data - but the technology is very different.  There are many different protocols for 2.4GHz radio systems but essentially they all do the same thing - the transmitter and receiver each have a unique ID on the frequency, and when you bind your Tx to your Rx, you are basically sharing the IDs so they talk to each other and only to each other.  A whole bunch of radios are actually shouting data out at the same time on the 2.4GHz frequency but because all the communication is done with IDs attached, receivers only respond to stuff that is sent specifically for them.  This is more a software thing than the old turning the tuning knob on your kitchen radio or changing the crystal in your old Acoms RC set.

2.4GHz is actually used by pretty much everything wireless - broadband routers, baby monitors, cordless telephones, virtually anything that has that little stubby plastic antenna-on-a-hinge will be 2.4GHz.  Despite that, interference on a 2.4GHz RC radio is rare because of the clever software used for sorting out all the signals.

I hope that helps :)

This is pretty much spot on, but I'm not sure about the early AM radio control stuff. I would say that AM at 27MHz is not possible, AM is typically in the kHz frequency spectrum.

The GHz wireless isn't doing simple multiplexing of the radio signal onto a radio frequency, like FM was. With GHz radios you are essentially creating a mini network with digital packets much like your home wifi, but on a simpler scale. In fact the old WiFi systems were also in the 2.4GHz band, with more modern wifi now moving onto the 5GHz band. The big advantage of GHz radio is that, as Mad Ax said, the data sent out is 'coded' between transmitter and receiver so only those digital packets with the correct ID are decoded.

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14 hours ago, ewant81 said:

I would say that AM at 27MHz is not possible, AM is typically in the kHz frequency spectrum.

Thanks for the correction :) I thought some of my older 27MHz radios from the 80s were AM but I may be completely mis-remembering that.

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12 hours ago, sosidge said:

The old MHz radios do use AM, you haven't misremembered

Yes, I did some googling and I was talking total nonsense. I didn’t know that you could get AM at such high frequency 😳

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@Mad Ax is spot on 

If you’re having fun with older frequencies + vintage cars the more important thing is likely to know where you stand now ?

Trouble is, every country / region tends to differ - two links, UK / EU below:

https://www.ofcom.org.uk/spectrum/radio-spectrum-and-the-law/licence-exempt-radio-use/licence-exempt-devices/Radio-controlled-models

https://www.eurorc.com/page/88/upgrading-the-radio-equipment-of-your-rc-car

Personally, I only run my old stuff with legacy kit at organised revival events, or in the middle of nowhere 

Otherwise, the inelegance of old RC means (in the UK) you’d risk emergency service or marine crossover - and who wants to deny anyone help or pay the fines ?

2.4Ghz obviously solves all that 👍

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13 hours ago, SuperChamp82 said:

@Mad Ax is spot on 

If you’re having fun with older frequencies + vintage cars the more important thing is likely to know where you stand now ?

Trouble is, every country / region tends to differ - two links, UK / EU below:

https://www.ofcom.org.uk/spectrum/radio-spectrum-and-the-law/licence-exempt-radio-use/licence-exempt-devices/Radio-controlled-models

https://www.eurorc.com/page/88/upgrading-the-radio-equipment-of-your-rc-car

Personally, I only run my old stuff with legacy kit at organised revival events, or in the middle of nowhere 

Otherwise, the inelegance of old RC means (in the UK) you’d risk emergency service or marine crossover - and who wants to deny anyone help or pay the fines ?

2.4Ghz obviously solves all that 👍

Good point. A lot of overseas radio equipment was never legal for use in the UK (72 & 75MHz come to mind), probably more of these radios have found there way into the UK because of collectors. You shouldn't be using them!

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3 hours ago, sosidge said:

Good point. A lot of overseas radio equipment was never legal for use in the UK (72 & 75MHz come to mind), probably more of these radios have found there way into the UK because of collectors. You shouldn't be using them!

Yep, this was a big part of the reason I switched to 2.4G for everything. My old Tx/Rx combos were mostly 75MHz but the best one was a 72MHz aircraft set, which had a big "not for surface use" warning that always made me feel a bit guilty every time I used it.

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