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codecage
(@codecage)
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Joined: 5 years ago
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Topic starter  

Hello everyone.  CodeCage/Steve/N4TTY  here!

Don't be put off by the Topic Title even if you are not an amateur (Ham) radio operator.  All are welcome, but it might be best for the Hams on the forum to keep their mostly Ham radio specific traffic here so those not interested in the topic won't be bothered by the bandwidth we might be using and can ignore the noise on the channel.

73 (a Ham term similar to G'day from those down under), N4TTY

SteveG


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
 

I always wanted to get a Ham Radio license mainly for technical use.   Just to extend the distance that I can remotely control things.   I just read up on it and see that Morris Code is no longer required.  When did they quit that.  I think that was the thing the held me back from getting one years ago.   I could send Morris code, but I had an extremely difficult time trying to decode it when listening to it on the radio.

But now that Morris code is no longer required, perhaps I could get a license.   At 70 years old I'm kind of late.  But as they say, better late then never.   My main reason for wanting it would be to play with radio communications for my robots.  

Question for the Hams out there:

How far can I expect to have radio control over my robot WITHOUT a Ham license?  And what frequencies could I use without a license?

And probably more to the point.  How far could I extend that range if I had a Ham license?

My sole interest is to maintain radio contact with a robot.   It would be small amounts of information.  I'm currently communicating with my robots by just sending a few ASCII coded characters.  I basically "talk" to my robots using short words.   So there's no need for exchanging large amounts of data.   Most of their control is on-board autonomous.  

 

 

 

 

DroneBot Workshop Robotics Engineer
James


   
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(@pugwash)
Sorcerers' Apprentice
Joined: 5 years ago
Posts: 923
 

@robo-pi

Morse Code was named after the American who co-invented the telegraph system, Samuel Morse.

The actual invention of the Morse Code has been attributed to Alfred Vail, another American who was involved in the development of the telegraph system.


   
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Robo Pi
(@robo-pi)
Robotics Engineer
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Posts: 1669
 
Posted by: @robo-pi

Question for the Hams out there:

How far can I expect to have radio control over my robot WITHOUT a Ham license?  And what frequencies could I use without a license?

And probably more to the point.  How far could I extend that range if I had a Ham license?

Just for the record, my questions have already been answered by @ve1dx in this thread:

Wireless Communications

Thanks Paul ? 

DroneBot Workshop Robotics Engineer
James


   
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codecage
(@codecage)
Member Admin
Joined: 5 years ago
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Topic starter  

@robo-pi

Just remember, as always, "Your Mileage May Vary!"

SteveG


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
 
Posted by: @codecage

@robo-pi

Just remember, as always, "Your Mileage May Vary!"

Well Paul didn't actually hand me a schematic or anything that concrete. 

But he did give me information that appears to open up a whole new world of possibilities.  I'm aware that all the "tweaking" is up to me.     But with any luck, I'll soon be able to tweak with official call letters. ? 

Once I get the call letters I'll be back for further instructions. ? 

DroneBot Workshop Robotics Engineer
James


   
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VE1DX
(@ve1dx)
Member
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Posts: 143
 

@robo-pi call letters?  Tisk tisk! ?   It's call sign.  While Ham radio isn't regulated as strongly as it was in years past, you get a call sign like a commercial radio station.  I believe you are in the US, so think of yourself as an amateur version of WCBS or KCBS.  For Hams, it's typically XXNXXX where X are letters and the N is a number.  In general, the fewer letters, the higher the license class.  1X2 and 2X1 calls are almost certainly Extra class.  Like W3AB or NA4A.  In Canada, we all have 2X2 calls or 2X3 calls.  Mine (VE1DX) is an Advanced - (highest level), and you have to be licensed 5 years or more to get a 2-letter suffix.  Every country is somewhat different, except they are always the <some letter(s)><a number><some_letter(s)>format.  In years past, the number generally indicated where you lived (e.g., W1 was northern New England, W2 New york, W3 between New York and Florida, W6 was California, etc.)  However, they relaxed that and people move, so you can find W1s in California and W6s in Maine these days.  You'll likely get a 2X3 as a Technician.  Some people upgrade their license class all the way to Extra and don't change their original call.  It becomes what you are used to. Also, every country has a unique prefix.  VE = Canada.  W,N,A = USA.  F = France, SM = Sweden, etc.

My point is before they relaxed the rules, you could get a pretty good idea where a person was just from hearing their call.  A W5 was almost certainly from Texas.  A VE7 from British Columbia, and an SM0 in or near Stockholm.

In terms of tweaking and the like, the Internet is loaded with material on everything Ham radio related.  If you get the 433 MHz modules working, and I'm sure you will, then adding an efficient antenna is going to be easy because there ate tons of resources to read on how to optimize things. Lots of guys are into QRP (low power) and thus getting every bit of RF to squirt out the antenna has been worked on for decades.

One thing that I'd like to know is the exact frequency of those 433 MHz modules.  I sold all my gear, but one can get a frequency counter at a fairly reasonable price.  The receiver module I have has what looks to be a variable inductor on it.  No doubt that's for tweaking the receive frequency.  I don't see a way to adjust the transmit module easily.  I got 4-5 of each online and the first two I tried "talked" to each other, so I didn't pursue it.  If we're going to play with these with more power than 100 milliwatts, I think the rules change.  As Bill says on his web page, we can do it without a license because "They are operated at low power."  I think even 2-3 watts exceeds this.  Also, since they are so cheap, they might have spurious signals or harmonics that would have to be taken into consideration.  But we'll worry about that down the road . . .


   
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Robo Pi
(@robo-pi)
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Posts: 1669
 
Posted by: @ve1dx

call letters? Tisk tisk! ?? It's call sign.

See. I've flunked the Technician Class exam already. ? 

It will most likely be quite a while before I get my license. I'll need to study up for it and see where and when I can go to take the test. It would be nice if I could take it online somehow.

In the meantime I'd like to start playing with my 433Mhz modules and just see what I can do with them. I was playing with them last year but got distracted with frozen pipes in the winter time. And then just never returned to this project.

Here's what I have so far:

Two separate units. Each board has an Arduino UNO to run the show. On the breadboards I have both a transmitter module and a receiver module along with a relay to control which module is powered up. So each board can be either a transmitter or a receiver. On the far right of the breadboard I even have a single 7-segment LED for displaying the results of what I receive. I was planning on just sending digits for the first experiment.

Here are the two boards I currently have for first experiments:

433Mz RF (4)

Here's a closer shot at the breadboard and RF modules.

433Mz RF (6)

I'll need to dig up the schematics I had made for these along with finding the code to see if I can figure out where I had left off.    I think I had everything working electrically.   I was just getting prepared to start working on trying to send some data.   So I'm real close to having this up and running.

 

DroneBot Workshop Robotics Engineer
James


   
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(@pugwash)
Sorcerers' Apprentice
Joined: 5 years ago
Posts: 923
 

@robo-pi

433MHz  modules are extremely limited when it comes to range. I can't remember where I found them but I did come across modules with a reliable range up to one kilometre. But you would have to check the legality situation, but as you seem to live quite remotely I don't really see a problem there!

You might like to check the 433MHz frequency with an SDR. I live in a big city and there is lots of traffic on this frequency, generally just small digital pulses.

Digital transmissions generally have a longer range, something I learned while doing my Short Range Certificate. We were taught that voice communications (156.250 MHZ Channel 16) ship to ship/shore were generally, with the antenna mounted 15 metres above sea level, had a range of about 30 nautical miles, whereas digital communication on a frequency close to the above, using the GMDSS system had a range of about 50 nautical miles, at 1 Watt.

Over and out!

Delta Delta Six One Six Six


   
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(@pugwash)
Sorcerers' Apprentice
Joined: 5 years ago
Posts: 923
 

@robo-pi

This might interest you!

NRF24L01+PA+LNA SMA incl. Antenna Radio Module Long Range 1110m Arduino Raspberry Pi

Costs about 10 bucks on eBay!


   
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VE1DX
(@ve1dx)
Member
Joined: 5 years ago
Posts: 143
 

@robo-pi

IMG 3519

It might be your camera angle, but I don't see any antennas on the TX and RX modules.  The ones I got (Amazon) came with a little bag of coiled antennas you had to solder on. In Bill's video, he uses ~ 6-inch pieces of copper wire, which would be more efficient than the coils in the photo above.  Those two "talk" across the room (about 12-14 feet) with whatever their default power is.  They are the things I *think* could be attached to much more efficient antennas.  It's possible a yagi or corner reflector would work with 100-milliwatts for enough distance to send the signal without a license.  It's only little packets of data in short duration bursts.


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
 

This is bringing back a lot of memories because I used to build radios.   The first radio I ever built was a crystal radio.   It amazed me that you could build a radio receiver with such few parts.  I was also interested in radio astronomy and used to listen to radio signals from the sky.  I was quite naive back then hoping to hear ET. ? 

Posted by: @pugwash

433MHz modules are extremely limited when it comes to range. I can't remember where I found them but I did come across modules with a reliable range up to one kilometre. But you would have to check the legality situation, but as you seem to live quite remotely I don't really see a problem there!

That's what I'm thinking.  Because of the remoteness of my local I could probably get away with cheating a little bit and error on the upper side of the power restriction.  I'm a big cheater and was thinking of going as high as 500 mW. ?   A full half watt.   But then again, it wouldn't be fun spending the rest of my life in a jail cell just because I was hoping to build a reliable robot.  So getting the Ham license will not only make things legal, but at that point I could really up the wattage to a few watts without having to worry about being incarcerated for my innocent robot hobby. 

Posted by: @pugwash

Digital transmissions generally have a longer range,

Yes, I'm aware that CW has a far longer range than modulated signals.  But I'm pretty sure I'm already using CW in this set up.   It's just either on or off.  There is no signal modulation.  At least I'm pretty sure that how these modules work.

Posted by: @ve1dx

It might be your camera angle, but I don't see any antennas on the TX and RX modules.

The antennas aren't in the photo.  In fact, I'm not even sure where they are.  I'll probably need to make new ones.    In fact, I was thinking about making antennae separate from the modules and connect them to the modules via coaxial antenna cable.

Before I build my robot radio control, I have another project for these modules.   I have a wood boiler out back and I would like to monitor it from inside the house.  I could just run a cable for that, but I thought that instead of running a physical wire I could just set up two Arduinos with these RF modeules.   One in the stove and one in the house.  Then I could just read things like water temperature and water level without having to go out and check the stove.  I was even thinking of including the ability to operate the stove from inside the house. either by pushing buttons manually, or even having the Arduino control the stove.  I'd especially like to have the stove shut down if it overheats and sound an alarm so I know that something went wrong.  I've had this wood boiler boil over before and it's not fun. 

In fact, it's not actually a "boiler".  It's not supposed to boil.  It's an open system and it's not supposed to go above 180 F.   I could have 185 F or 190 F be the shut down temp.   As long as it doesn't reach 212 F all is well.

Once it starts boiling air bubbles get into the circulating pumps and it becomes a nightmare to get it all sorted back out again.   So that would be a nice first project for my RF experiments.

Posted by: @pugwash

Over and out!

Delta Delta Six One Six Six

Delta detla six one six six
what's your QTH?
I am floating aimlessly
out in outer space

Vee eee one dee ex
can you give me QSL?
I know my signal's reaching you
but is it doing very well?

Shoobie Shoobie Robo Pi
I got my license in the sky
aliens have granted me
the right to be a spy

I'm spying on the earthlings
to see what they have done
Planet Earth is heating up
and getting hotter in the sun

Over over over
I give the airwaves back to you
and now I'm in receiving mode
to hear your signals coming through

DroneBot Workshop Robotics Engineer
James


   
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VE1DX
(@ve1dx)
Member
Joined: 5 years ago
Posts: 143
 

@robo-pi

Posted by: @robo-pi

A full half watt.   But then again, it wouldn't be fun spending the rest of my life in a jail cell just because I was hoping to build a reliable robot.

Don't spread this around, but I don't think the FCC (or Industry Canada) have had any inspectors for Amateur Radio in 15-20 years!  ?  When I was active (I gave it up in 2014), there were some bad actors on the air.  Many operators were using heavy-duty profanity and broadcasting (a big no-no) ~2005-2014.  Those us who followed the rules and came from the 1980-2000 era when that would get you a big fine ($10,000 or more) and possibly jail time, were aghast.  But not much ever came of it.  Many operators were running excessive power too.  Not a little over.  I'm talking 5,000-10,000 watts when we were only allowed 1500.  They never were prosecuted.  Before 2000, the FCC and Industry Canada policed Amateur radio heavily.  That all seemed to go away around 2000.  The consensus was that the enforcement resources shifted to cellular networks, cable TV, and other commercial users of the RF spectrum.

About the only way to quickly get in trouble would be to transmit on police, military, emergency, or aircraft frequencies.  Do that, and you might go to jail.  Other than that, after 2000-2005, it seemed whatever "happened in the Ham bands, stayed in the Ham bands."  That was one of the reasons I lost interest.  It was degrading to CB radio, and no one seemed to care.


   
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VE1DX
(@ve1dx)
Member
Joined: 5 years ago
Posts: 143
 
Posted by: @robo-pi

Yes, I'm aware that CW has a far longer range than modulated signals.  But I'm pretty sure I'm already using CW in this set up.   It's just either on or off.  There is no signal modulation.  At least I'm pretty sure that how these modules work.

They use Amplitude Shift Modulation (ASK.)  Kinda like CW, but not quite.  It is on/off and just sends ones and zeros.  Pretty simple.  If the signal is on, it's a one, if it's off, it's a zero.  CW is on/off too, but the length of time it's on and the pattern carries the "intelligence."  Dots and dashes.  r = -.   o = - - - b = -...   so robo = -.  --- -... ---

Those receivers can't decode CW, but they can decode simple ASK.  There are literally dozens of modulation digital schemes that are orders of magnitude more efficient than ASK or CW.  Heavy-duty math involve to encode and decode them, but they can punch through noise louder than they are. 


   
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Robo Pi
(@robo-pi)
Robotics Engineer
Joined: 5 years ago
Posts: 1669
 
Posted by: @ve1dx

Don't spread this around, but I don't think the FCC (or Industry Canada) have had any inspectors for Amateur Radio in 15-20 years! 

I figure that the only way you're going to get into trouble is if your signal is actually interfering with other devices and people start reporting it.  Only then would someone be sent out to investigate the source of the problem.

I'm not sure what a 433Mhz signal would interfere with in my rural area.    Of course if you up the wattage too much you'd be reaching out far beyond your local area.   My ultimate goal for the robot is to have dependable communication up to about 1/4 mile.  But to be dependable the signal will probably need to be strong enough to interfere with things quite a bit further away maybe as much as a mile or two.

I'm thinking the information exchange wouldn't need to be a lot.  It shouldn't need to be a constant stream of data.  The scheme I currently have set up is that the base would send just a couple bytes of info to the robot and then listens for the robot's reply.  The robot would only need to send a single byte back to acknowledge reception of the message.  Then the robot would execute the requested task and only report back to base when the task is completed, or if a problem was encountered.   So the communications would only be a couple of bytes back and forth with possible long delays between them.

Of course if I decide to have the robot send video information back to the base computer that would require the transfer of a ton of data.  But I'm not currently planning on doing that. 

I'm just going to start with these 433Mhz modules for now.  Maybe later, if I get the Tech class license I might look into building a more serious RF connection perhaps on some other frequency entirely.  With the Tech class license I'll have a lot more frequencies to play with.  I could pick one that's best suited to my area.

So getting the Tech class license does sound attractive.  I'd finally be a ham. ? 

 

 

 

DroneBot Workshop Robotics Engineer
James


   
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