How many channels are there?

I suspect that there is an ID in the digital data stream that will prevent any conflicts for the foreseeable future. 

The information that follows is based on what little information I've found on the transceiver board used in the LC/LC+ remotes.  It appears to be a clone of the nRF24L01+ manufactured by Nordic Semiconductors, the most widely used 2.4GHz transceiver on the market today.  It is possible that the LC/LC+ are using a different data standard and different radio, but the way it works will be pretty much the same no matter what 2.4GHz digital radio they use.  

Anyway, under the assumption that they are using a typical, off the shelf, radio used in thousands of other products,  the radio can be programed to send between 4 and 32 bytes of data in one packet.  It takes only 1 byte of data to send all of the possible information from the remote's controls, (4 bits for 16 speed steps, 1 bit direction and 1 bit for each button.) which leaves at least 3 bytes of information for the engine's address.  If they chose to use 3 byte addresses you could have over 16.7 million unique engine addresses.  

I suspect they chose to send more data than less, seeing as these types of radios make it so easy.  I use 4 byte addresses in my programing with these types of radios, just because I like even numbers and have more data than I know what to do with.  That's over 4 billion possible devices.  

On the other hand, if the programers were especially lazy, the system could be limited to single byte addresses, in which case, you're looking at 256 addresses... or are you?  Actually more like 1536 unique addresses, as the transceivers can be programed to talk on any one of 6 data pipes.  These aren't exactly channels in the normal sense, but can be thought of as such.  

In the 2.4Ghz radio band, devices typically share all of the actual 'channels'  hopping from one to another to find the one with the strongest signal, free of other devices.  This is somewhat difficult these days, considering how much information is flying about on such a tiny band of the radio spectrum.  When you have a moment, thank your microwave oven for that.  

When it comes down to it, think of the possibilities like this; everything that can be done with the Legacy system is done by sending out a number between 0 and 262,144.  thats how many unique, things a legacy system can do.  The radios in LC/LC+ send out at the least, a number between 0 and 4.2 billion, and as much as... well, my calculator errors when I punched it in.  

Short answer, if you sold a lion chief remote for every single locomotive Lionel has made since 1900, then handed one out to every person on the planet, you wouldn't run out of possible addresses.  Digital radios are neat like that.  Now there may be a programed in limit, but it is unlikely to be anything that we'll ever have to worry about.  

JGL

What he said ↑ !

I agree with JGL and GRJ. Much more likely the technology will be obsolete and replaced with something better before any limit becomes a factor.

JohnGaltLine posted:

Short answer, if you sold a lion chief remote for every single locomotive Lionel has made since 1900, then handed one out to every person on the planet, you wouldn't run out of possible addresses.  Digital radios are neat like that.  Now there may be a programed in limit, but it is unlikely to be anything that we'll ever have to worry about.  

JGL

Yes - I understand John Galt Line, Short answer. I also fly model airplanes and belong to two model airplane clubs and the Academy of Model Aeronautics.  We now all fly on the same channel 2.4GHz.  We used to all have to be on a different channel. We had a thing called a channel flag and when I would hang up my channel flag, no other person could fly on that channel.

Now I go to the flying field and turn on my 2.4GHz transmitter first, then the receiver in the aircraft and the aircraft receiver and transmitter are lock together for the entire flight. I just know it works. I have been to several seminars and they have a complex electrical example of why it works, but it is over my pay grade.

There is one more piece of magic to this 2.4GHz transmitters for aircraft. The transmitter that I use can memorize the trim settings for 5 airplanes.  The trim settings are different for each aircraft that I fly. The trim settings keep the plane on a level flight, just like is done on a full size aircraft. 

I set the transmitter for the plane that I am flying, and the servos on the airplane will move to the proper settings.

I have been told, that the combinations of setting within 2.4GHz, could be in the billions, I still do not understand but it works. All AMA Clubs have a safety rule that only 5 airplanes can be in the air at the same time.

Gary &:

Ah so it is digital 2.4GHz. Thanks!

It's amazing what they can do with that technology. At a model airplane meet I attended last fall there were over 60 small R/C airplanes in the air at once during the mass warbird launch.

2.4 GHZ is interference free because it uses GFSK (frequency shift keying). The transmitter is constantly shifting the transmitted frequency according to a predetermined pattern. The receiver knows the pattern and constantly shifts to the correct frequency. Several pairs of transmitters and receivers can easily simultaneously co-exist in the band with this method.

Gentlemen,

    Interesting stuff!

PCRR/Dave

I was reading the CAB-1LITE manual last night and it said it uses 2.4Ghz also.

The BPRC system I'm using also uses it.

Legacy and the CAB1L use the same frequency out of necessity, they are supposed to be compatible.   However, given the way that you set channels on the Legacy and Legacy Lite, and the fact that WiFi really will step on them, I question if they're using FSK for those.  Note I said "question", I don't really know for sure.

I know the military has used "frequency hopping" for years, don't the RRs use it now in their communications?

Bob Delbridge posted:

I know the military has used "frequency hopping" for years, don't the RRs use it now in their communications?

As a side note, I think it's interesting that the actress Hedy Lamarr is credited with developing the frequency hopping at the beginning of WWII. Her and the man who helped her were inducted into the National Inventors Hall of Fame in 2014. Google it and read her story. It's good reading. Oh, that's Hedy not Hedley.

Yes, Hedy Lamarr did conceive of the frequency hopping concept. The 2.4 GHz band is not used primarily by "essential" users like police, fire, military, etc.  It was set aside for civilian uses including model radio control and has helped to avoid interference common with the lower frequency alloted channels.

How did my thread end up with a Blazing Saddles reference?

BOB WALKER posted:

Yes, Hedy Lamarr did conceive of the frequency hopping concept. The 2.4 GHz band is not used primarily by "essential" users like police, fire, military, etc.  It was set aside for civilian uses including model radio control and has helped to avoid interference common with the lower frequency alloted channels.

I think saying it was 'set aside for civilian uses' is a little... misleading?  It offers the feeling that the FCC intended for everything to be using the 2.4GHz band.  

From my post at the start of the thread.  

JohnGaltLine posted:

When you have a moment, thank your microwave oven for that.  

The 2.4GHz band was left open for public use not in some great effort to provide a useful radio band for the public, but precisely because it was thought of as a useless band for anything important.  Why is it useless?  because the magnetron in your microwave oven broadcasts noise in that band.  You cook your food on 2.450 GHz radio waves.  Thanks to a lot of ingenious folks coming up with solutions the band has been made useable and more than that, the standard for data transmission throughout the world.  Sort of like the government giving the public a patch of swamp land to do what it wants on, and some ingenious folk figuring out how to pump out the water and build disneyland on it.  

As a note, high quality 2.4GHz devices do constant frequency hopping, but most devices don't  Most devices like wireless routers find the channel with the least noise when they are turned on, then stay there until you tell them otherwise.  In most routers you can actually set which channel to use in its settings if you like, but most folks let it pick for you.  

The primary way that devices prevent interference form affecting the transmission of information is not through frequency shifting, but instead through digital transmission with a checksum acknowledgment.  In simplest terms, the transmitter will send the data, then the receiver will send it back.  if the message isn't the same it will be sent again, until it is.  Modern radios do this all by them selves with out the need of the device's processor to worry about it.  You can send the data, and be certain that it will get where it's going, and if it doesn't after some number of tried, only then will it tell the processor that the message failed... but even in this case the device knows the message failed and can try to send it again.  

Edit:  Additional information:  

The simple checksum is built in to simple 2.4GHz transceivers and is what a system like LionChief uses to insure the correct data is received.  Other systems use much more complex systems to insure data is correct.  The advanced systems for error correction have fancy names like Wifi and Bluetooth, and are very, very good at insuring that data is received exactly as it was intended.  

JGL