For the Hams on Board

Posted by: @robo-pi

That would be cool.  I didn't know that you could do that.  I thought you might need some time under your belt between classes.  So I'll prepare for the Extra Class exam and see how far I get.

Well, you could get addicted to DXing, like many of us did!  DX  = long distance.  The game is to make contact with every country in the world.  And prove it by getting a QSL card (the postcard thing.)  Nowadays they do most of that electronically with digitally signed logs matched by computer at the ARRL (American Radio Relay League.)  It's called the DXCC (DX Century Club.)  I had at least one physical card from every country in the world.  Even North Korea!  Some guy from Georgia (the country, not the U.S. state) got in there for a few months and operated in 2002.  I was lucky enough to catch him on the air.  It's the only time it was ever active. 

Anyhow, the ARRL count a lot of non-countries as countries.  For example, Hawaii and Alaska count as separate countries in terms of chasing DX points.  Sable Island is one too.  There are around 330 "things" they consider countries, but I believe the UN only recognizes 175-190 real countries.  The ARRL dropped the country designator around 2000 and started calling them "entities."  Made more sense.

Also, short-wave (HF) propagation depends on the 11-year duration solar cycle.  We're stuck at a prolonged bottom now, and it would be almost impossible to contact long haul stuff even if global politics allowed Hams to operate in every "entity."  However, that's where new blood like yourself would shine.  The technology exists or is being developed that can punch a signal through the white noise that sounds like hissing to the human ear.  I did all mine by audible signals over 25 years, but it'd be neat to re-do it computer to computer using the new algorithms.  Unfortunately, I don't have 25 years left on this planet! LOL

Posted by: @codecage

For what your are planning for robot work, Tech is all that is needed.

That's good to know.  Then if I pass is the Tech class I'll probably just grab it and run.   I get tired easily anymore.  Not sure if I feel like taking two exams in a row anyway.  I'll have to wait and see what I feel like on exam day.   But if Tech is all I need for what I want to do then there's really not much incentive to be taking the General exam.  I'm not into radio, I'm into robotics.  I just want to be able to design dependable radio communications with my robot and not be restricted to just 100mW or WiFi, etc.   So it sounds like Tech Class is all I need then.

@robo-pi

Have you checked out "the guy with the Swiss accent" videos #219 & #220?

I think this would be 30 minutes well spent!

I found it very informative for someone who knows only the very basics of radio transmission theory, despite being the proud owner of SRC & LRC qualifications!

@pugwash,

Thanks Steve.  Those are very good videos.  I actually have a lot of knowledge about how carrier waves and modulation works but I can really appreciate Andreas videos as he really covers the details.  Also it's been a very long time since I actually worked with RF devices.   I was slightly disappointed that he didn't include the 433Mz modules in his final comparison analysis.   Although based on everything he does cover the lower carrier frequency does appear to be best suited for what I would like to do.

He explains the trade-offs between carrier frequency, range, and through-put very well.   Because of the methods of communication I'll be using I have very low through-put requirements.  I'll only need to send a few bytes at a time, and those can even be sent at a very low baud rate.   So this will allow me to take advantage of the lower frequency carrier waves.    And since lower frequencies have a much higher range-to-power ratio going with the 433Mz sounds like a good choice.

The reason I can get by with such low through-put is because the robot will be mostly autonomous.  It will only need to be given a few bytes of information (i.e. commands) and it can take it from there.  The home computer won't need to be monitoring every move the robot makes.   Similarly the robot will only need to return a few bytes of information to inform the home computer its status. 

The only exception to all of this would be if I wanted to have the robot transmit video images back to the home computer.   That would be a nice feature, but not really necessary.   What I might be able to do with a low freq carrier is have the robot send still images that it has pre-processed into GIF graphics.   That way I could get graphical glimpses of what the robot is actually seeing by only having to transmit and receive a few kilobytes.

So these 433Mz modules might just suit my needs.   According to Andreas video the lower frequency of 433Mhz may have the best chance of meeting the range requirements for my project.   So it could  be that I have just accidentally picked up the correct modules for my project.   I have about a dozen pairs of these 433Mz modules so it would be a shame not to use them.   And now it looks like they turned  out to potentially be the best choice after all.   Purely by accident.  When I first bought these I wasn't thinking of anything other than they were cheap. ? But now it looks like they are actually a good choice.  At least for my intended purposes.

Thanks for posting the videos Steve.  Lots of good info in there.  I'll be going back and gleaning over them as I continue to refine this project.

In trying to do something toward my Ham license every day no matter how little, I took some online practice exams.    I took the Tech class license exam first.   The first time I took it I did fail it but only by one question.  I too it a second time (with new questions) that that time I passed with 80%.  I had to guess at some of the answer though.  However, they were educated guesses, I wasn't exactly stabbing in the dark.

So then I moved onto the General Class exam.  I failed that one with a grade of 57% (you must have at least 74% to pass).   However, after taking the exam they show you which questions you got wrong along with the correct answers.   The questions I got wrong on the G class test were mostly related to rules and regulations, and questions about antenna performance.

All of these results were without having done any studying at all..  So if I'm going this good without studying I imagine I'll do really well after studying.

It's actually fun to take these tests and I'm looking forward to studying.  This brings back a lot of memories when I was younger and first leaning electronics.

I was also cleaning out my attic some more.  I found two Heathkit Oscilloscopes.  An Electronic Switch that is used to turn a single-input oscilloscope into a dual trace scope.  I also found a Semiconductor Curve Tracer that is used in conjunction with the oscilloscope to draw out a graph of the operating characteristics of the semiconductors.   I found a Heathkit vacuum tube voltmeter.   A Heathkit Transistor tester.   And there's a bunch of other stuff up there too.  I can only climb up and down those steps so many times.   The steps to my attic are more like a ladder.  They are extremely steep and great care needs to be taken when trying to carry a heavy old-fashioned oscilloscope down the ladder.  After doing that I'm out of breath and need to go lay down for a bit to recover. ? 

Anyway I just thought I'd report all the fun I'm having here.

@robo-pi

I have been umming and aahing about getting my HAM license for a while now. Not that I really want to get into HAM radio but just for the mental challenge and to say "I've got it!". At 64 years of age, I am just trying to keep my brain agile without having to resort to crossword puzzles etc..

I have sat three different exams in the last twenty years, Short Range, Long Range and German citizenship (a Brexit thing), and have always used the following strategy.

Get hold of the test papers, make a few photocopies, then sit down on the sofa and give them a try. Then I put the results" right answer or wrong answer" in an Excel table to identify which set of questions I was having the most trouble with.

This strategy has successfully got me through all the theory papers.

The Short and Long Range exams were full written answers, but the citizenship exam questions were "vote for Joe" (multiple choice) type questions, and just to make it a little more difficult all three exams were in German. But after almost 40 years here, I speak pretty fluent German.

Anyway, best of luck in your endeavour and I don't doubt we will come back to this topic sometime in the future.

@robo-pi

Insomnia or just burning the candle at both ends??

My moondial says it is about 03:40 in your neck of the woods! ? ? ? 

@robo-pi

If this of interest, I captured these 433MHz signals on SDR and I have been trying to figure out how to build a filter to clean up the signals, ready to decode on my oscilloscope.

If you run this .wav file through Audacity, you can zoom in and take a look at what you may expect when using these modules.

As you suggested in an above post, sending short commands or receiving position data from a robot, the 433MHz would be adequate, but my guess is that they would hardly be suitable for transmitting pictures of even low resolution and with no error checking. But if you do experiment in this direction I would be interested to see the results.

Posted by: @pugwash

I have been umming and aahing about getting my HAM license for a while now. Not that I really want to get into HAM radio but just for the mental challenge and to say "I've got it!". At 64 years of age, I am just trying to keep my brain agile without having to resort to crossword puzzles etc..

Absolutely!  DO IT!  Perhaps we can make an "All Aboard for Ham Radio!" thread and see how many people we can cram onto this train. ? 

You are absolute  right about keeping the brain agile.  I've heard that this is the best  prevention for possible dementia and even Alzheimer's.  Not sure how true the latter is, but exercising the gray matter never hurts.

Most members on here either already have quite a bit of knowledge of electronics, or have a deep desire to learn it.  So they certainly can't go wrong with studying for this exam.  And for some of them the only thing they'll really need to learn on the rules  specific to ham radio as they already know most of the electronics.

I'm in no rush.  I don't plan on taking the exam until mid-winter, and possibly not even until next spring.  So I'll be studying at a relaxed pace to be sure.   However based on the practice exams I've been taking I could probably run out and pass a tech class exam next week if I really wanted to.  This is because I already know the answers to all the electronics questions.  The only questions I have difficulty with are the questions related to Ham Radio rule and band usage, etc.   As well as the specific question on antenna and signal characteristics.  But there doesn't seem to be a lot of those kinds of questions on the Tech class exam.  Those show up in the General Class exam and become quite intense on the Extra Class exam.

The Tech Class exam should really be a piece cake to anyone who already knows electronics.  You could probably miss a couple of the rules questions and still pass.

So yeah, climb on board.  It'll be fun.

Posted by: @pugwash

Insomnia or just burning the candle at both ends??

My moondial says it is about 03:40 in your neck of the woods!  

I have fatigue problems.   Sometimes during the day I just have no choice but to stop what I'm doing and go lay down.  Sometime I'll fall into a deep sleep and may sleep for as much as 4 hours or more.  Then when I wake back up I find that I can't go back to sleep.  So I just get up and do things while I'm feeling energetic.   So I've given up on trying to keep any sort of normal schedule.   I just get up when I'm feeling energetic and lay down when tiredness hits me.  I've tried fighting against this, but I've found it to be a futile war.  So I've just given into it and although I keep really weird hours I find that it seems to work pretty well.   This way at least I'm awake when I'm up and not fighting fatigue and I'm also not trying to sleep when I'm not tired.  So I just go with the flow.    So yes, you'll often see me up in the wee hours, and missing for large chunks  of the normal working day when I'm sleeping.   It's just totally unpredictable. 

But you could say that I'm burning the candle at both ends as well.  I do try to get as much done as possible when I am feeling good.  So I'm usually doing something constructive every waking moment.   I've  come to value the times when I'm feeling energetic.   But yeah, trying to keep a regular schedule is truly not possible for me.  As much as I want to, when the fatigue hits I have no choice but to go lay down.  If I don't do that I'll literally pass out where I stand.  So there's no fighting it.  Keeping a normal schedule is simply no longer an option.  I think I might have Lyme disease, although I haven't been diagnosed.  But I was bitten by several deer ticks last year.  So I have good reason to suspect that Lyme disease might be the culprit.

Posted by: @pugwash

If this of interest, I captured these 433MHz signals on SDR and I have been trying to figure out how to build a filter to clean up the signals, ready to decode on my oscilloscope.

If you run this .wav file through Audacity, you can zoom in and take a look at what you may expect when using these modules.

Thanks for the .wav file.  I'll need to get a radio receiver here capable of listening to 433Mhz so I can hear what it's being used for in my area.    It would also be nice to be able to hear my own transmitters so I can get an idea of what the signals actually sound like.

With a Ham License the 70cm band actually includes frequencies fro 420Mhz to 450Mhz.  So once I get the Ham License I'll be able to tweak the frequency to possibly use areas of the band that might be quieter in my area.   This is another reason why I would like to have the Amateur radio license.   I'll be legally permitted to technically modify the transmitter frequency, not just the power.

Here's a chart of all the Amateur Radio Bands.

I guess if we're going after the Ham license it wouldn't hurt to know the above chart inside and out.  There will no doubt be questions on the exam concerning which bands are used for what purposes, and what restrictions apply, etc.   So print this chart out and paste it onto your bathroom mirror.  That way, every morning you'll be reminded to study it. ? 

Notice also that everything on the right-hand side of the chart is available for the Tech Class.  So like @codecage mentioned previously in this thread, the Tech Class is really all you need if you want to play around with data transmissions for robotics or remote control.

Lookie what I found in the Attic! ? 

It's an antique signal generator.  It covers both RF and AF.   Including the 433Mhz that I'm interested in.   This will be so cool.   I recall that it was working when stored.  Whether it still works or not is another question.  It believe it was a kit.  Not certain about that.   In any case I'm going to clean it up and see if it works.  If it works I'll clean it up even more with contact cleaner on all the switches etc.  I'm into antiques so this will fit right in with my decor.

I'd probably be hard-pressed to find an antique signal generator like this for FREE.  Or even cheap for that matter. So this is really cool.  I'm really glad I didn't toss this junk out last millennium. 

Lookie! Lookie! Lookie!

My old Virbroplex Morse code key.   I thought I sold that years ago.  Apparently not.

Apparently I have more junk than I thought in the attic.

I must be one of them thar hoarders.  I can never throw anything out.  And quite frankly I'm glad I didn't.

Yet another cool antique find.

I used to have one of these  Along with the matching Transmitter!  Unfortunately I sold them both a very long time ago.  What a BUMMER!  See,.... don't EVER sell anything!  You'll be sorry later. ?  I would love to have this old Ham receiver today.  I remember having a lot of fun listening to this and also trying to copy CW from it.  The white knob in the middle was the BFO and I remember using that to tune in voices.  It worked really slick.  It was a good receiver.   And like I say, I had the matching transmitter too.  And they were both kits that I had assembled and did so very well, if I do say so myself.   So let me go weep that I no longer have these.

Posted by: @pugwash

At 64 years of age, I am just trying to keep my brain agile without having to resort to crossword puzzles etc..

Ah, we're twins!  Same age.  Although the length of time I'll still be 64 I have to now measure in days, not weeks or months.  Agreed that one has to keep the brain working.  Darn entropy and the second law of thermodynamics.  Perhaps we ought to work on an algorithm to disprove and reverse entropy.