Author Topic: Math problem for a few local hams - they couldn't do it  (Read 2140 times)

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Online xrunner

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Math problem for a few local hams - they couldn't do it
« on: October 16, 2019, 11:36:45 pm »
It all started with this simple equation that hams use to calculate wavelength -

λ=c/f

Where -

λ=wavelength in meters
c=speed of light 300,000,000 m/s (normally just rounded up from 299,792,458 m / s
f=frequency in Hz

In ham radio its been simplified by dividing c & f by 10 6 and just using λm=300/f MHz

Simple enough.

In the hf bands there is one frequency that has the same numerical value for both it's frequency and it's wavelength (not the same units of course). It's 17.321 MHz, which has a wavelength of 17.321 meters. I was asking some local hams on the repeater to re-arrange the equation using a little ingenuity so as to be able to simply enter a few keystrokes on a calculator and get the answer - it requires no more information than is in the equation. They didn't already know the answer either. I specifically stated that the actual answer is not what I want because any trained monkey can Google it. No, I want to see how you can get it from the equation directly by doing a little algebra.

It basically reduces to x 2 = 300, therefore x=√300.

They are all (so far) dumbfounded as to how to do it. One guy, when I asked him to try, never even hesitated and just instantly gave up - "I can't do that kind of stuff". No one has solved it.

Remember, these are technical people. Am I naive or is our population losing the ability to do high school math? How is it that hard? Am I being unfair asking this sort of thing of them? I really didn't mean to "show off" I thought they would be able to do it :(

Thoughts?
« Last Edit: October 17, 2019, 04:45:09 pm by xrunner »
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Offline IanB

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Re: Math problem for hams - they couldn't do it
« Reply #1 on: October 16, 2019, 11:44:19 pm »
Remember, these are technical people. Am I naive or is our population losing the ability to do high school math? How is it that hard? Am I being unfair asking this sort of thing of them? I really didn't mean to "show off" I thought they would be able to do it :(

Thoughts?

I don't think you should assume ham radio people are technical people. You should just assume they are people who like playing with radios and talking with other people over the airwaves.

There are certainly some radio enthusiasts who would have no trouble with that problem (I know one). But sadly many people who are not engineers or physicists or something like that have limited math skills.
I'm not an EE--what am I doing here?
 
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Offline soldar

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Re: Math problem for hams - they couldn't do it
« Reply #2 on: October 17, 2019, 12:27:02 am »
It basically reduces to x 2 = 300, therefore x=√300.

The equal sign is overrated.

Things can be equal if they want to, or if they are equal they can be not equal in other ways. Diversity is equality.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline Stray Electron

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Re: Math problem for hams - they couldn't do it
« Reply #3 on: October 17, 2019, 12:47:16 am »
It basically reduces to x 2 = 300, therefore x=√300.

The equal sign is overrated.

Things can be equal if they want to, or if they are equal they can be not equal in other ways. Diversity is equality.

   True New Age thinking!
 

Online xrunner

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Re: Math problem for hams - they couldn't do it
« Reply #4 on: October 17, 2019, 12:54:10 am »
I don't think you should assume ham radio people are technical people. You should just assume they are people who like playing with radios and talking with other people over the airwaves.

Perhaps you are right. It's a formula that hams are taught and use, and they understand how to use it as long as it's got one of the variables already filled in that they need. Oh well ...  :-//

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Offline amyk

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Re: Math problem for hams - they couldn't do it
« Reply #5 on: October 17, 2019, 01:22:53 am »
Throughout the years there has always been a group of hobbyists who never bother to dig deeply and understand things; kit-builders, hams, then the Arduino crowd, now the RPi and its community.
 

Online Circlotron

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Re: Math problem for hams - they couldn't do it
« Reply #6 on: October 17, 2019, 01:41:40 am »
So, is 17.321 metres/MHz the golden ratio of RF?
 
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Offline bob91343

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Re: Math problem for hams - they couldn't do it
« Reply #7 on: October 17, 2019, 02:22:55 am »
Notice that the 17 meter ham band is at 18 MHz, close enough.  If it were the 18 meter band it would be at 17 MHz I guess.  So the square root of 3 is 1.732 and that's the answer.
 

Offline james_s

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Re: Math problem for hams - they couldn't do it
« Reply #8 on: October 17, 2019, 02:43:57 am »
Throughout the years there has always been a group of hobbyists who never bother to dig deeply and understand things; kit-builders, hams, then the Arduino crowd, now the RPi and its community.

I think that's overly generalizing, there are people of all skill levels in each of those crowds, it's just that all of these categories lower the barrier of entry which enables people other than the hardcore technical crowd to participate.

I see the exact same thing in the RC airplane community, elitist old guys who look down their noses at anyone who doesn't painstakingly build their planes from balsa sticks, ignoring the fact that the hobby would have likely died out entirely if not for the plethora of inexpensive "foamies" and other nearly ready to fly models one can buy today. The hardcore enthusiasts are still around, they're still free to do their thing, but now a much larger range of people can participate and have fun. Personally I see nothing wrong with this, everyone has different interests in life and I don't think the fact that someone lacks the time, motivation or mental acuity to dig deep into the fundamentals should preclude them from being involved. There's a lot more stuff out there for people to do these days, can't dive deep into all of it.

It's a hobby after all, the whole point is to have fun.
 
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Offline vk6zgo

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Re: Math problem for hams - they couldn't do it
« Reply #9 on: October 17, 2019, 03:13:18 am »
Most US hams use a "magic formula" to give the wavelength in feet, when they are building antennas, so aren't all that familiar with 300/f  where f is MHz, & wavelength in metres, let alone the full version.

The oldtimers knew the real formula, but the "number crunching" was harder to do in your head, so the antenna formula, "half wavelength in feet = 468/f, which you will see in the ARRL publications, & echoed across the Internet was derived.
This includes correction for "end effect", shifting the person using the formula one step further away from the original.

With the proliferation of calculators, both real & "Apps", there is no longer any reason for this "crutch",
but it has become part of the fabric of ham antenna building.

The silly thing is, when you see an Australian ham, born years after metrication in this country, using 468/f, then converting the answer to metres.

 

Offline hamster_nz

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Re: Math problem for hams - they couldn't do it
« Reply #10 on: October 17, 2019, 03:54:48 am »
Although interesting, the answer is of very little impact, other than as a fence post when approximating.

It is a bit like how I know how to calculate celling(log2(x)) as if by magic, and could moan that most programmers only have a intuitive feel for 256, 65,536 and 4,294,967,296

Physicists would put us all to shame, as the rescale and recast things to different basis vectors, so the answer is always "oh, that is just a+b or a*b" hence weird values like MeV for mass.
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Offline thinkfat

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Re: Math problem for hams - they couldn't do it
« Reply #11 on: October 17, 2019, 07:30:18 am »
You're not required to know any algebra for passing a ham radio examination.
You need to learn regulation, lots of, and a little bit of Ohms' Law, but that's about it.
That's about as technical as it gets. Yes, there are very technical people amongst HAMs, and then there's even more who just browse Kenwood or Yaesu catalogs ;)
 

Offline fourfathom

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Re: Math problem for hams - they couldn't do it
« Reply #12 on: October 17, 2019, 07:47:51 am »
You're not required to know any algebra for passing a ham radio examination.
You need to learn regulation, lots of, and a little bit of Ohms' Law, but that's about it.
That's about as technical as it gets. Yes, there are very technical people amongst HAMs, and then there's even more who just browse Kenwood or Yaesu catalogs ;)

That depends on the ham license.  I vaguely recall that about 45 years ago my (USA) Advanced license required some math, and my recently-passed Extra license definitely required some basic RLC vector math.  No algebraic manipulations though.
 

Offline DimitriP

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Re: Math problem for hams - they couldn't do it
« Reply #13 on: October 17, 2019, 07:50:46 am »
Quote
Am I naive

Yes!
Yes
   If three 100  Ohm resistors are connected in parallel, and in series with a 200 Ohm resistor, how many resistors do you have? 
 
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Online BravoV

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Re: Math problem for hams - they couldn't do it
« Reply #14 on: October 17, 2019, 07:59:19 am »
In the old days, I mean really old, that any computer users operators needed to know what a Karnaugh map is.

Online Brumby

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Re: Math problem for hams - they couldn't do it
« Reply #15 on: October 17, 2019, 09:00:23 am »
I've just gotta throw this in here...

300 is just a rough number - like using 22/7 for Pi.  I'd be happier with something like 299.792458
 

Offline magic

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Re: Math problem for hams - they couldn't do it
« Reply #16 on: October 17, 2019, 09:34:00 am »
The equal sign is overrated.

Things can be equal if they want to, or if they are equal they can be not equal in other ways. Diversity is equality.
Spotted the layman :bullshit:

This is a complete nothingburger for any practical application of mathematics and the word "diversity" appears not even once in the article, not sure where you got that from.
Their best chance at achieving any mainstream relevance is a birth of another "new maths" movement in schools which would share the fate of the previous one.
 

Offline bd139

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Re: Math problem for hams - they couldn't do it
« Reply #17 on: October 17, 2019, 10:41:30 am »
Well I wrote a rather lengthy reply to this, got half way through, got distracted by work and accidentally closed the tab. Ooops.  :palm:

I'll keep this a lot more terse. Edit: I failed at that.

I think the cause of this is human apathy and acceptance of incompetence.

At school they teach you all the tools to do this and have done here for the last 50 years. I have never seen any evidence of it sticking past school though. For the average person who doesn't need mathematics to survive, literally three episodes of some shitty soap or drama and the space where logarithms lived is replaced by celebrity ass sizes. dy/dx is probably some rapper's name and simultaneous equations are someone writing E=mc^2 twice.

When someone has spare time and money and takes on a technical hobby that requires some certificate of competence they are greeted with a wall they have to climb. Rather than seeing it as a challenge it becomes an obstacle and they are so used to just being able to walk around obstacles in life, that they don't bother or blow around the issue with money (typical ham: MOAR POWER! into my shitty antenna rather than working out why it's shitty). This causes declining numbers entering the hobby. And because of that they made it easy. Pass percentages here on our multiple choice tests:

Foundation: 73%
Intermediate: 60%
Advanced: 60%

You can get all the mathematics questions wrong and still pass. In fact I suspect that's what happened to a lot of people when I did mine based on the fact that most of them had gone out and bought scientific calculators and were in a right panic because they couldn't use them and didn't know how to rearrange a simple equation from the cheat sheet that comes with the exam paper (yes all the formulas are listed). At best you had to do a simple bit of algebra (rearrange and substitute values in) in the intermediate and advanced papers.

This means the average ham here has an idiot test and then a 60% scrape at worst. A lot of people don't get past foundation still. In fact if I look at the local club there are only two advanced members and they really have zero technical expertise as well. These guys train the next generation. I don't go there now because they are quite defensive over their little cult and when someone new comes in with some technical expertise it's a threat. The threat? Well I built a K2 that actually works unlike one of the G0's who fucked it up :palm:

It's a race to the bottom. We avoid hard things. We accept incompetence. Or we buy our way around it. In some circles there is even social solidarity about mathematical inability.

I don't get humans.
« Last Edit: October 17, 2019, 10:45:44 am by bd139 »
 
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Offline CJay

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Re: Math problem for hams - they couldn't do it
« Reply #18 on: October 17, 2019, 11:32:39 am »
I agree with almost all the comments above to a greater or lesser degree and it frustrates the hell out of me when I see/hear some of the 'wisdom' put about.

But...

I would also point out that there are *many* hams who never could do maths or the technical bits and never wanted to.

A lot of hams have almost zero tech knowledge beyond that required to get their licence and set up a station they bought from a shop so why would they need to know more if they get their kicks from talking to people instead of building gear?

Bear in mind a lot of hams use it for local chatter and 'prepping' for emergencies, one of my regular listens is the Alaska Morning net which is available from a local UK 70CM repeater and they're far from technical.

It's a broad church.
M0UAW
 
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Offline bd139

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Re: Math problem for hams - they couldn't do it
« Reply #19 on: October 17, 2019, 11:48:23 am »
A very good point.

Most of the local 2m users here are like that and fair enough. I couldn’t find any common interest with them (other than growing tomatoes) so I packed it in  :-DD
 

Offline imo

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Re: Math problem for hams - they couldn't do it
« Reply #20 on: October 17, 2019, 12:01:12 pm »
I bet you would have gotten a better answer off the repeater asking them what is "the solution of this equation system":
lm = 300 / fmhz
lm = fmhz
:)

PS: in 2018 I was told (in the local hamradio club) there are people wanting to learn Morse, but not interested in getting the ham radio license.. So the motivation of people differs today :)

« Last Edit: October 17, 2019, 12:07:20 pm by imo »
 

Online xrunner

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Re: Math problem for hams - they couldn't do it
« Reply #21 on: October 17, 2019, 12:06:54 pm »
I've just gotta throw this in here...

300 is just a rough number - like using 22/7 for Pi.  I'd be happier with something like 299.792458

Hello Brumby, yea I know and said at the beginning that the actual number is substituted by 300, that's what the ham community uses. If I put in another number (like the actual longer number LOL), it would look even worse to them and I'd have less a chance of getting anyone to try. Besides the principal of solving the equation wouldn't change and you'd just end up with the √299,792,458

Quote
Am I naive

Yes!
Yes

I knew it!

At school they teach you all the tools to do this and have done here for the last 50 years. I have never seen any evidence of it sticking past school though. For the average person who doesn't need mathematics to survive, literally three episodes of some shitty soap or drama and the space where logarithms lived is replaced by celebrity ass sizes. dy/dx is probably some rapper's name and simultaneous equations are someone writing E=mc^2 twice.

I would also point out that there are *many* hams who never could do maths or the technical bits and never wanted to.

See, that's what I assumed, that people had been taught such basic skills even if they didn't particularly like it. I didn't think λ=300/f was in any way so hard to play around with. But, I do have one guy who I asked last week and said he'd try it. I asked the other day if he was still interested in it. He did say he was still thinking about it, so there is still hope. I will give a hint if he gives up and see how it goes from there.

I bet you would have gotten a better answer off the repeater asking them what is "the solution of this linear equation system":
lm = 300 / fmhz
lm = fmhz
:)

Yep - the trick they need to do is realize that those two variables are equal, which is what the description of the problem states "One HF frequency has the same numerical value as it's wavelength". Like I said one guy is still thinking about it ...
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Online Brumby

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Re: Math problem for hams - they couldn't do it
« Reply #22 on: October 17, 2019, 12:59:04 pm »
I've just gotta throw this in here...

300 is just a rough number - like using 22/7 for Pi.  I'd be happier with something like 299.792458

Hello Brumby, yea I know and said at the beginning that the actual number is substituted by 300

 :palm:

Sorry.  That's what I get by skipping down the problem description and not reading properly.

No excuse.
 
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Offline Kjelt

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Re: Math problem for hams - they couldn't do it
« Reply #23 on: October 17, 2019, 02:25:39 pm »
It could well be the noise in your message asking them to solve akjhdsgf ajsdhf98764329587432oriuhqewkjfhqwlkejfhgqoiweuyrqiweuryqoiewuryqw
instead of formulating it clearly and precisely , even better writing it down.

Don't forget that a lot of the problems in math are  not the math it self but the problem description.
Actually it is more language than math what schoolkids get these days which is problematic.

Example of 8 yr old:
Patricia bought a cake and she cut it in 8 pieces and she asked three friends over. How many pieces of cake does everybody get ?

The right answer is it depends how many pieces of cake Patricia is willing to give to her friends, if she wants to share equally or perhaps she gives only one piece each to her friends, eats one her self because she keeps the other four for her brothers and parents.
You can see smoke coming out of teachers ears when you bring it like that but often the problem is not unambiguously formulated. Just try again.
 
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Offline Rascal

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Re: Math problem for hams - they couldn't do it
« Reply #24 on: October 17, 2019, 03:00:25 pm »
A good majority of Hams in the UK use 'plug & play' equipment. No need for math calculations.

I think the Ham culture has changed over the years. Back in my Fathers day it was about building and understanding the equipment, experimenting and testing. Today its easy to pass the exam, and then buy a radio, put a large antenna array on your house and off you go


Paul 

 
 


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