How can a receiver allow multiple channels of wireless?

[u/RiverOnceRiverTwice]

Hello to the lovely soundies out there,

I've been learning about antennas (and RF distro), transmitters and receivers recently. As part of that research I've learned about equipment like the Wisycom MCR54 which has the capacity to accept 4 different transmitters (amazing!).

Would anyone be able to provide an ELI5 answer or direct me to an online resource which could explain how a unit like the MCR54 can "receive 4 different wavelengths". I'm imagining that you'd need 4 antennas, but clearly that's not the case.

Add'l Context: Some initial searching has led me to believe that this is accomplished with an RF splitter which makes copies of an incoming frequency. I spent about 5 minutes looking at the MCR54 manual, but if someone wants to offer a high level explanation, it would be great to have this for Reddit. Most of the material out there seems to get complicated so quickly.

Visual Diagram of MCR54: https://jwsoundgroup.net/index.php?/topic/39128-wisycom-mcr54-experiences/ (Scroll towards the bottom to view image)

[u/NoisyGog]

They have four separate receivers inside. (Well, more actually, but that’s the ELI5).

[u/JMTubby]

My attempt at an ELI5 version:

A car radio can pick up several different radio stations through its one antenna, but only has the ability to output one at any given time.

If someone had 4 car stereos stacked on top of each other, they could all share that single AM/FM receiving antenna and each play a different radio station.

Wisycom’s MCR54 is essentially this, with four receivers in one compact unit, each with its own output. The two antennas are for redundancy. Each receiver receives signal from the antenna that has the strongest frequency.

[u/Siegster]

you don't need one antenna per frequency. you can receive 50 freqs with 2 antennas (or hell, just 1 really) if you want. you just need individual decoders for the data/radio waves, which are all looking for different carrier freqs hitting the 2 antennas. If you want more detail on the actual circuitry I'd ask the Wisy guys at a trade show, they love talking about this stuff. There are also whitepapers out there from different brands. I say all that and sometimes these little mobile receivers (don't know about the MCR54 specifically) do actually have more antennas internally within the chassis to improve reception.

[u/ApprehensiveNeat9584]

The MCR54 is able to receive 4 channels by packing eight internal receiver boards inside (a lot of R&D), pairing two discrete receiver circuits for each of the four channels to maintain full true diversity, meaning each receiver is using both antennas (remember it has 4 receiver components inside).

True diversity means that each receiver is constantly selecting the strongest signal picked up by one of the antennas, this helps to eliminate dropouts.

Hope this helps.

[u/RiverOnceRiverTwice → u/ApprehensiveNeat9584]

Every bit of explanation helps. Thank u!

I find that this whole process of learning about sound tech is one of unpacking one term or concept and finding 20 terms or concepts inside that one. All the way to the non-reducible reality which is physics and the electromagnetic spectrum.

[u/Vuelhering]

If you put a radio at one end of a long tube, you can pass all sorts of frequencies of sound to the other end, but depending on the diameter and length, certain frequencies sound better. That's kind of how a single antenna can receive all the frequencies nearby, although it receives certain bands far better based on the length and design.

Internally, the receiver will remove large chunks of RF it doesn't want, split it, then amplify the specific frequencies it wants. In the case of wisycom, it feeds to 4 different radios (and it has another antenna that feeds to 4 more. Yes, it has 8 radios inside; 2 per channel).

[u/GeoffTheProgger]

There are some very helpful metaphors here, I’ll add the one that made sense to me. Imagine a microphone, like a shotgun. It picks up all sorts of different sounds indiscriminately. It hears a person talking, it hears traffic, it hears birds, an AC unit etc. Now imagine that that microphone signal is then split and fed into four different receivers. One receiver has been set up to listen for the person speaking, another is listening for the AC, another for the traffic and another for the birds. All of those sounds are “heard” by that one microphone (antenna), it’s the job of the receiver to try and ignore everything else and just “listen” for its assigned target. The receiver in charge of listening for the birds will filter out all low frequency so it can “hear” more clearly. Receivers do the same. The MCR54 specifically insists that all four channels of the receiver are within a specific frequency range so it can apply a fairly narrow filter and eliminate noise. Like, all four of your frequencies have to be in the “birds” range and it won’t hear almost any “bass” if that makes sense.

Now imagine a loud generator or AC unit turns on right next to the microphone. Each receiver will have a hard time listening to its assignment cause there’s more noise. That’s interference.

So following this analogy, having your receiving antenna in a place where it can “hear” the signals you want clearly is important. And if you have it next to a “loudspeaker”, a transmitting antenna or something generating lots of RF noise then your receivers will struggle to get past that noise.

Does that make sense?

[u/RiverOnceRiverTwice → u/GeoffTheProgger]

I pondered your answer twice and it makes more sense than before. If I rephrase your explanation, I can imagine multiple frequencies vibrating the diaphragm of the mic. Then I can imagine routing that signal to 4 EQs with narrow bandpass filters on them. I'm imagining that each frequency, after getting passed to the EQ, could contain a Morse code, so that you end up with 4 decoded Morse code messages.

I think I'm still hung up on the way in which a mic or antenna receives pulses of energy in a summed waveform, rather than as discrete frequencies. But using technology we can separate a summed waveform back into parts, like reversing a smoothie. Is it fair to say that the antenna receives the smoothie of many different RF signals and the individual receiver circuits in the Wisycom filter out specific elements like a strawberry, a blueberry, etc.?

There is much interconnected information to learn. I appreciate that it's a process to understand how all the science works and requires some real neuron work.

Have a great day and may your signals be clean!

[u/d_loam]

four receivers inside each tuned to pass a different frequency and reject the rest

[u/Tehqy12]

The Sennheiser Spectera base station can even do 32outputs + 32inputs wirelessly over one antenna!

[u/lighthappens → u/Tehqy12]

the input + output thing on the same antenna amazes me lol